You are not logged in.
Saturn C-5 as designed on paper was supposed to lift 127 metric tonnes to LEO, or 45 metric tonnes to trans-Lunar trajectory. Saturn V as built was able to lift 118 metric tonnes to 185km orbit @ 28° inclination, or 47 metric tonnes to trans-Lunar trajectory.
Yep, forgot about that. However, with F-1A's it would have been far closer to 150t to LEO than SLS will ever be. Even as-built, it was an improvement over SLS in terms of initial capability.
SLS: the only configuration able to lift 130t will have 5 SSME, advanced boosters, and an upper stage with a pair of J-2X engines, and fuel tanks with the same diameter as the core stage. They're now talking about only building SLS with 4 SSME, and I don't know if either proposed advanced booster will ever be built, we may only get 5-segment SRBs. All that will significantly reduce lift capacity. And Saturn V as built had reduced lift capacity without compromising number of engines. Be afraid, be very afraid.
This is speculation on my part, but I think that these factors drove the selection of the number of engines for SLS Block I:
- A 4 RS-25 Block I met the required performance target for IOC
- The RS-25 is an expensive engine and a restart of the production line is required to manufacture additional stock, so with existing stocks a flight test program could be completed
I expect that advanced boosters will eventually be developed, but the only option that NASA actually has infrastructure to support the use of is solid.
The J-2X is currently on hold because the engines didn't meet performance expectations, although I expect that the program will be revived when no suitable replacement exists.
Every single post I've made has pounded you into the ground on technical details, we have been over Specific Impulse, power density of solar panels, payload mass fractions, initial mass in LEO. To say I haven't provided any technical argument is THE BIGGEST LIE YET from you.
You've firmly staked your fantasy into the ground, but little else.
The specific impulse numbers that are achievable with SEP are achievable by accelerating V-E-R-Y S-L-O-W-L-Y. So slow that it extends the duration of a manned Mars mission to more than two years and provides for a stay of less than a year on Mars. These numbers come from NASA, Boeing, and every other proposal I've ever seen. Maybe they're all lying because it doesn't support your argument or maybe, just maybe they're trying to tell you something. When higher thrust is utilized to accelerate faster and reduce transit time, the specific impulse drops to numbers that are less than those that would be produced by an advanced NTR.
Your arguing for a massive multi-billion dollar research effort that will replace the current NASA program whole-sale. You need to justify that kind of expenditure by showing that it is superior to any alternative and I've shown that it is markedly inferior instead. Thus your arguing for money to be thrown down a rat-hole and I'm going to oppose that no matter who's backside the money is coming out of.
No, you haven't shown that it's markedly inferior. You've shown that SEP looks better on paper when you use specific impulse numbers that require loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong transit times.
WOW, Boeing actually made a plan on a piece of paper to USE the vehicle that is the current NASA official goal to create. That sure is a lot of unwarranted faith in THEMSELVES to be able to build it don't you think?
It doesn't matter how much faith Boeing has in themselves. Boeing is building a giant gas can for SLS and assembling parts into a rocket. According to ATK, not kbd512 or Impaler or Boeing, 130t without a 5th RS-25 is wishful thinking. If ATK doesn't know how far and how fast their rockets will push the core stage, then I'm going to go way out on a limb and say that no one else does. The SLS core stage doesn't have enough fuel or thrust to put 130t in LEO using current or proposed advanced solid boosters.
The Dynetics liquid boosters would provide enough thrust to put more than 130t in LEO, but according to a NASA engineer working on the redesign of the MLS, there is not room on the pad for the TSM's required for liquid boosters and no facilities have been built to store and pump RP-1 at the pad.
Oh and it's not ready to fly this bloody second either?? Did it ever occur to you that this Boeing plan is perhaps INTENDED FOR THE FUTURE, you know when NASA said they were actually aiming to go to Mars? Now I know your a smoking that Zubrin pipe that says we 'SHOULDA' been on Mars in oh around 1875 or some junk but in the real world things like landing more then 1 ton on Mars and having remotely closed loop life-support are real barriers that can't be glossed over.
You keep throwing that argument in my face about GCNR's, so yeah, I'll throw it back in yours over SLS.
If NASA was permitted to move forward with NTR's and continue use of Saturn V, we'd have been on Mars decades ago. You can call that speculation if you wish, but all of the technology development made it pretty apparent that NASA was serious about the goal.
Let's roll back the clock to 1972 and take stock of where we were more than four decades ago:
* Flight-rated capsule system
* Flight-rated lunar lander, obviously not a Mars lander, but at least it could land somewhere besides Earth
* HLV capable of 130t (150t with F-1A) to LEO
* 1 year out from having a giant Mars transit vehicle, better known as Skylab
* 3 years out from having a flight-rated NTR capable of taking humans to Mars in 6 months or less
Fast forward 45+ years (yes, 45 years because 2 years from now we still won't have a man rated capsule or SLS rocket):
* No flight rated capsule system or manned spacecraft of any kind
* No lander of any kind
* No HLV of any kind
* Russians are nice enough to give us rides to ISS
Seriously you are absolutely insufferable, it takes decades to develop space vehicles and planning and thinking about how to use them before they are ready to use it the only prudent thing to do, one of the biggest problems with SLS is we DON'T have payloads for it, now you want to rule out even THINKING about payloads of 130 mt until the vehicle is their waiting on the launch pad? That is a guaranteed way to never use the capacity created.
I feel the exact same way about you. Your arguments about forward thinking versus what's available right now apply when it favors your arguments but don't apply when it doesn't favor your arguments.
I want to rule out payloads that simply aren't possible with the current SLS architecture, absent many more billions spent and more years of development that entail redesign of the vehicle and/or launch accommodations. You stated that investment in nuclear technology would be some sort of wholesale diversion of funding. Guess what Orion and SLS are right friggin now!?
Orion can't land anywhere but an ocean, it doesn't have the interior volume to carry the provisions required to take astronauts anywhere into deep space, it has already wasted billions of dollars and will waste many more billions if it's permitted to continue to exist, and all the while NASA lacks funding for those systems that it thinks are critical for deep space operations, like closed loop life support and radiation shielding.
No, that would be your desperation speaking, the VASIMIR folks want power at high density, they look at literature on potential solar and nuclear power in terms of theoretical potential and are indifferent as to which ends up providing it. They are not power system experts and can be forgiven for not being well informed about the relative costs to develop these systems or the current state of the art. People who are actually developing Electric propulsion vehicles do not waste time on nuclear fantasies.
Then I guess the people who are working on these technologies are suffering from the same fantastical thinking as I am, because they all seem to say the same thing and it all seems to run counter to what you're saying. That solar panel on your head is baking your brain.
Dose an apples-2-apples comparison frighten you? The fair comparisons are theoretical potentials to theoretical potentials, or current systems to current systems. I've done both and you've been crushed both ways and even the grossly unfair comparison of nuclear theoretical potential to SEP current systems the SEP system is basically tied. I make that intentionally unfair comparison simply to demonstrate how inferior your position is, yet you refuse to see it.
The theoretical specific impulse of a GCNR starts at 3000s and climbs all the way to 6000s. Whether the former or latter most accurately reflects actual performance, transit time is six months or less. The only way your favorite technology achieves that kind of specific impulse, currently or theoretically, is when transit duration is sacrificed.
kb: As usual everything you say is flat out wrong, you have clearly not even read the material and simply have the idea stuck in your head that Nuclear is superior in every way and in every application to "dirty hippy solar", your rantings on Nuclear power not getting used on Earth (which have zero bearing on in-space use) show that your nothing more then a nuclear ideologue who is trying to re-fight that battle in a new territory, one you haven't done the slightest research in.
My statements about use of solar technology, made in the context of human space flight only, have nothing to do with whether I like solar panels and everything to do with the limitations of the technology and what use of the technology requires in the context of human space flight.
If I'm a nuclear ideologue then you're most certainly a solar ideologue. Most of your posts in this thread have started with how stupid I am or how wrong I am, but then fail to provide evidence about why what I proposed won't work or how it's inferior to solar electric technology. If you have any cogent arguments about why what I've proposed won't work, I'd love to know. Apart from lots of adolescent insults, which may be all that you have to offer, you've proven spectacularly incapable of providing anything approaching a technical argument about why nuclear technology is inferior to solar electric technology.
And by the way your '20 years ago' was 1994, any one who could not extrapolate Mores law (which had been roaring along for 20 years already) out another 20 years to reach to obvious conclusion that YES your phone would be hugely more powerful then a server would have been a FLIPPING IDIOT. Just as someone today who has ANY doubt that SEP are going to continue the relentless advances they have made in the last 20 years after the technology come to the west. Conversely people who think a dead technology like NTR, aka trend line of ZERO improvement in 30 years is going to suddenly and for no compelling reason take off would be just as foolish. While you TALK about huge progress potential you show your naked bias by saying you 'hope' SEP advances, while having blind-faith in all things Nuclear.
When there's no development of a technology, it doesn't magically improve. Funny that. Whether or not anyone is working on development of a technology has no bearing on its utility.
I'm not advocating for the replacement of your favorite technology, just the development of a complementary technology that doesn't require an external energy source to function. Wouldn't the fact that I kept writing about development funding for SEP tugs for Mars bound cargo indicate this, or did you ignore those parts of what I wrote because it doesn't support your sophomoric argument about my bias against solar technology?
For specifics, as Terraformer points out you DO NOT TIME FROM LEO TO LMO, your repeated attempts to define this a the goal is blatantly dishonest. You send the mission hardware and/or habitat ship to High Earth Orbit first and then send the crew up to it by a taxi capsule crossing the Radiation belt at speed as has always been done. The crew needs that capsule for return to Earth surface ANYWAYS irregardless of the main propulsion system so it is not a disadvantage vs any other main propulsion system. THAT is what Boeing proposed in the mission concept on the FIRST POST, so your apparent ignorance of this indicates you haven't even read that. Second this proposal has SIGNIFICANTLY reduced SLS launches over NTR DRM5 as I already pointed out to you, again you are simply spewing bullshit when you say that SEP doesn't reduce launch mass.
Van Impe, my solevangelist friend, your repeated attempts to ignore what Boeing has in their presentations is what's blatantly dishonest.
The transit times are in Boeing's presentation and are transit times from/to EML2, not LEO.
Boeing wants to put a 130t SEP tug into LEO. There is no launch vehicle capable of putting something that massive into LEO and short of using liquid boosters (redesigning SLS and redesigning the launch facility accommodations) or addition of another RS-25 to SLS (redesigning SLS), there won't be one in the next 10 to 15 years, either. Read the first part of the previous sentence and let that sink in.
Even if this SEP tug that Boeing wants to build to send humans to Mars was available today, it wouldn't matter because there's no rocket capable of launching it.
The SEP tug, less propellant, could be launched on a F9H. The propellant mass is above current SLS capability. It requires SLS Block IA.
Boeing's proposal requires fewer SLS launches than DRM 5 due to the absence of one cargo mission, use of inflatable heat shields, and refueling of the SEP tug at EML2.
I disagree with Terraformer that gravity assist can reduce transit times to 3 months even from EML1, I think he is confusing gravity assist with oberth-assisted impulsive burns. I've read that three impulsive burns at EM1, Lunar flyby and Earth flyby totaling just 1.2 km/s can send one on a good 6 month transit to Mars, a big savings from doing 4.4 km/s for the same thing from LEO. But 3 months would take considerably more DeltaV then that and I don't think that gravity assists off the Earth itself can be done quickly enough to be useful for human missions (robotic missions needed years of time to do multiple flybys).
Remember HOW LONG YOU TAKE TO REACH EDGE OF EARTH SPHERE OF INFLUENCE IS IRREVERENT TO HELIOCENTRIC TRANSFER TIMES, but climbing the Earth Gravity well is NEARLY ALL OF THE DELTAV of a slowest Holman transfer. We can go slow and efficient inside the Earth Sphere of influence and switch to faster but less efficient propulsion for the Heliocentric transfer once the crew is on board.
I would like to get the crew to Mars in six months or less, as I've previously stated, because I want the crew to spend at least as many days on Mars as they spend in transit to/from Mars. I don't care if it can be done in 3 months or 1 month.
Thus the total DeltaV between 6 months and 8 months transit is VERY small, it is only when you try to go below 3 months that DeltaV starts to get really hard. We can do 6 months with SEP with 5k static ISP and a SEP system (solar and thrusters) totaling just 80 W/kg, or using the 'alpha' spec common in SEP system design which is 12.5 kg/kW. And that is COMPLETELY within current technology, our HALL thrusters and power processing units combined are 2 kg/kw which leaves the Solar a full 10 kg/kw, which is a pathetic 100 W/kg, ROSA array already beats that. And both of these numbers are going to keep improving, but basically we can do a transfer of that duration now if were willing to have a SEP hardware mass of around half the total vehicle mass with payload around 25% using these SANDBAGGED numbers and off the shelf components, that's 'ugly' by SEP standards (but normal by rocket standards) and their is so much potential improvement it would be wasteful to do such a mission now, what will happen is that we will do another decade or two of development and end-up sending vehicles that are 10-20% hardware mass and >50% payload. All the other systems like EDL and life-support are at least that far away from being completed anyways.
We can revisit where we're at with solar technology in another decade or two.
This is Ad-Astra's mission to Mars trajectory plan, applicable to any SEP as they have numbers for fixed and variable ISP
http://www.adastrarocket.com/Andrew-SPESIF-2011.pdf
Forgive me, but did you just post a document where the author recommended the development of advanced nuclear power technology?
Here are the numbers on current alpha and ISP values of thrusters
http://enu.kz/repository/2010/AIAA-2010-6771.pdf
Another document that proposes further investigation of advanced nuclear technology?
Basically where SEP is RIGHT BLOODY NOW, is already competitive with your nonsense Nuclear HIGHEST THEORETICAL POTENTIAL, but SEP has not even scratched the surface of it's theoretical potential. When we start talking highest theoretical potential of SEP the transit times are 1 MONTH, which I pray we don't ever NEED because it's terribly wasteful of payload fraction and we should send more payload to help mitigate radiation and other dangers and in general enhance the surface stay.
You're using an argument about the theoretical potential of SEP against the theoretical potential of NEP or NTR.
I know that chemical, electric, and nuclear thermal propulsion systems all work.
To me, it's a question of what's most suitable for a task, not simply whether or not a particular technology is immediately available.
If you'd have told people 20 years ago that they'd have computers in their pockets that were more powerful than a workstation or server of the times, they'd have told you that that was pure fantasy. Oddly enough, this little technological marvel can be found in the pockets of most working age adults in industrialized countries today.
If we allow the nay-sayers to impede progress because of their short-sightedness, fear, or ego, then technological innovation stagnates and irreplaceable time is lost.
Every study I've seen shows that use of SEP for manned Mars transit vehicles results in the longest transit times, the fewest days spent on Mars, and requires just as many or more launches to implement as NEP or NTR powered transit vehicles. Will improvements in solar panel and thruster technology begin to favor SEP for Mars missions? I certainly hope so, but hope and probability are two entirely different things.
We have another 15 years or so to work on SEP and active radiation shielding to make the transit from LEO to LMO in six months or less or devise a lightweight radiation protection system that permits longer duration flights.
I think nuclear technology provides a redundant and, for certain uses, complementary capability.
With that many moving parts, what could possibly go wrong? More reliable than a Space Shuttle? Probably not. The only accidents that the Space Shuttle encountered were from administrators and engineers ignoring real problems.
Without the ridiculous cross range requirement that necessitated the use of turbojet engines, this project would have been doable, but increasing the count of moving parts only increases complexity and cost. Adding the weight of 28 turbojets only assures that SSTO will be nearly impossible with any useful payload.
SERV would have had slightly better aerodynamics than a refrigerator.
kbd512 wrote:RobertDyck wrote:why?
Why does funding have to be available for SEP tugs or why do we have to kill other programs to fund SEP tugs?
You do realize the SEP is already funded and in development, no other program had to DIE for it because it's costing a pittance compared to what your proposing. The fact that you need to kill SLS and Orion and take it's WHOLE budget to get your Nuclear fantasy off the ground just shows have utterly unrealistic it is. That SLS/Orion money is unfortunately lost to any useful purpose due to congress (not NASA stop harping on them for having their hand forced). But if by some miracle that money were available to redirect to other uses it would better go to the aerocapture, ISPP, life support trinity that was just mentioned as KEY must have technologies.
You keep throwing out this TRL9 term to describe technologies that don't seem to quite measure up to NASA's standard for TRL9 technology.
This is what TRL9 means to NASA:
TRL 9 Actual system "mission proven" through successful mission operations (ground or space): Fully integrated with operational hardware/software systems. Actual system has been thoroughly demonstrated and tested in its operational environment. All documentation completed. Successful operational experience. Sustaining engineering support in place.
VASIMR isn't fully integrated with anything, has never been demonstrated in its operational environment, and there have been no spacecraft propelled with VASIMR technology, successful or otherwise.
We can go to Mars without SEP. That's "nice to have", but not necessary. We need:
- aerocapture
- ISPP
- life supportIn fact, ISPP generally produces methane. SEP doesn't use methane as propellant. So SEP is not required for a human mission to Mars. For the architecture I came up with, a reusable spacecraft travels from ISS to Mars orbit and back. Aerocapture at both ends. Propulsion stage for both ends is initially expendable, but can be replaced by a reusable stage later once technology is available. Whether that is nuclear thermal, nuclear electric, solar electric, or other, is left undefined. However, reusable means we need to harvest propellant from Mars or one of its moons, and deliver that propellant to the reusable stage. That means infrastructure on Mars. That's why no reusable stage for the first mission. Initially, the Mars Ascent Vehicle acts as the TEI stage, so no propellant transfer is required. And return to Earth is entirely ISPP. This required methane/LOX engines.
I've stated before that advanced composite technology would make it possible to have a habitat module that the crew could launch with, transit to/from Mars, and make entry on the outbound/inbound legs. Instead of requiring a piece of tech for this/that/the other, we'd have one PE fabric composite habitat module with carbon foam overwrap (the PE minimizes secondary effects from received radiation, keeps weight comparable to 2219, and the overwrap can withstand a thermal flux equivalent to HRSI), we could use aerocapture combined with propulsive landing, ISRU to refuel for the trip home, and not require a complicated support infrastructure.
This would require two SLS rockets and utilize existing chemical tech. Our explorers don't have the same exploration options available to them that they get with the expedition class missions, but it's far more economical than other plans.
why?
Why does funding have to be available for SEP tugs or why do we have to kill other programs to fund SEP tugs?
True, the version that can lift 130t was to have 5 SSME, and a pair of "advanced boosters", and a full size upper stage with 2 J-2X engines and same tank diameter as the core module. Isn't that "Dark Knight"? What would be the lift capacity be for 5-SSME/2-5SSRM/2-J2X?
Dark Knight is ATK's proposed advanced SRM. Even with better SRM's, SLS won't quite hit the 130t target without 5 RS-25's and ATK is quoted as stating this. However, it gets to between 110t and 120t with the advanced boosters. That's about as good as we're reasonably going to get from SLS.
Orion is not the same as CST-100. Orion has 16.5 feet diameter capsule, CST-100 is 15.0 feet. Orion can carry 6 crew to ISS, CST-100 can carry 7 (ironic). Orion has total launch mass including LAS, ATV-based SM, and fairing of 28.0 metric tonnes; CST-100 is 10t. Orion uses a launch abort rocket like Apollo, CST-100 uses its SM main engines for abort. Orion has an exhaust shield around the capsule to protect from LAS exhaust, CST-100 doesn't need it. Orion SM has a fairing, CST-100 doesn't.
CST-100 is, in certain ways, more capable than our advanced space exploration capsule.
The wheel reinvention thing that NASA likes so much is something that reputable aerospace companies typically avoid if it isn't mandated by nutty government contract requirements.
Could we "throw a bone" to Boeing by letting them keep CST-100 for crew transport to ISS, but kill Orion?
I'd much rather kill Orion than CST-100, but money has to come from somewhere to fund SEP tugs and SLS launches. Honestly, I think both systems need to be killed to free up money for Boeing to develop SEP tugs and produce SLS hardware.
The only way I see one of these capsule systems living a useful life is if the Air Force finds utility in manned space flight capability and assists with funding. NASA is out of money and they're not going to be given more.
They already do. United Launch Alliance (ULA) is a 50:50 joint venture of those two. ULA now owns the former Boeing launch vehicle Delta IV, and the former Lockheed-Martin launch vehicle Atlas V. Boeing has the primary contract for Orion, but Lockheed-Martin is collaborating.
This would be collaboration to produce a real service module for Orion and to produce a cargo variant of Orion for contingency operations. Some of this is related to national insecurity. The government wants NASA to retain manned space flight and cargo delivery capability for military operations independent of any commercial vehicles and launch systems, even though it won't give the agency money to actually use it.
SpaceX and Orbital have begrudgingly been given a seat at the table, but Boeing and Lockheed-Martin are the government's go-to contractors for national security.
I have serious doubts about whether or not ESA will develop the Orion SM in a timely manner.
- When SpaceX produces their Raptor based Rocket it will certainly supplant the SLS, if SpaceX doesn't produce this rocket we are not going to Mars so their is no point in fixating on the launch vehicle other then to specify that it is in a particular size class.
The booster fixation has to do with having a launch vehicle, any launch vehicle, that can actually launch something with the mass that Boeing is proposing.
SpaceX has stated that Raptor and BFR are low on the priorities list. Will it be available 10 years from now? I certainly hope so.
- Again you speak out of an appalling ignorance of SEP, in a variable specific impulse system you can trade off between thrust and ISP, but you can also just add more electric power to get more absolute thrust which keeping your trip times up. 'Low gear' aka high thrust and low ISP for current thrusters is still in the 3000s range which is bloody fantastic compared to NERVA and as good as your pixie-dust coated fantasy of GassCore NTR.
Boeing says that the Isp is in the 2600s range for the type of thrust needed to make the transit in 6 months. They must be appallingly ignorant of SEP capabilities, too.
I'm seeing a pattern here. Everyone who doesn't agree with Impaler is a stupid/ignorant space cadet.
- Actually their is a comparison, the fuel pellet in a nuclear reactor have a heat output 20,000 - 30,000 W/kg Thermal, only 8-15x the theoretical maximum of thin-film-solar. But of course by the time you actually contain them within cladding rods and coolant flows and the like your looking at substantially lower density for the whole thing and these parasitic masses for Nuclear are vastly high then the parasitic mass on solar which is basically a rod or mast to hold the film. What matters is the system level performance, not machismo chest thumping about power density in some tiny portion of the whole system. If you want to look at life-time energy output then Solar is likely to come out ahead because nuclear fuels last less then a year before needing reprocessing while solar systems can operate for decades thus yielding more total energy as they are COLLECTORS rather then fuels and are not limited by their own mass. A NTR is actually even worse then a nuclear power plant because as a high thrust system it operates for only a few MINUTES before it's out of propellent and has to be shutdown with control rods, thus it ultimately imparts LESS energy into it's propellent and wouldn't you know it, LOWER ISP results from lower energy (who would have imagined!!!). When you actually do the math nuclear is pathetic.
If you're going to rant about something, could you at least rant about something that I actually proposed using? I did not, I am not now, nor will I ever advocate using a solid core reactor. Make an argument with applicability to what I advocated using. Gas core reactors don't have fuel cladding, unless you consider the coolant/propellant to be cladding.
A NTR doesn't have to provide thrust all the way to Mars and back. It will still get the crew there in six months or less.
Let's look at some charts to show just how pathetic the energy density of Uranium is:
http://www.cleanenergyinsight.org/inter … omparison/
I'm starting to see what you mean.
http://thebreakthrough.org/index.php/pr … footprints
Yep, it's official, the energy density of those nuclear fuels is absolutely pitiful.
- Again your pathetic concern troll falls flat, if we are assembling a SEP vehicle we won't deploy the panels until were going to depart, or we will simply rotate the panels edge on the atmospheric drag and largely eliminate it. Only when we go to thrust do we need to orient the panel to the sun and incur drag when that angle happens to be broadside to the atmosphere. We can easily calculate the drag force at altitude and know how high we must be to escape the drag, it works out to about 300 km for most SEP system, they would have over a month before orbital decay at that altitude with panels deployed.
You ever think there might have been more than one reason why Boeing wanted to do assembly at a Lagrange point?
- Solar panels on EVERY single object in LEO are struck by debris all the time, including the huge panels on ISS and it has not destroyed it. With modern thin-film solar the damage from such impacts are likely to be even less severe as they just poke clean holes right through it. Their is also no risk of being hit 'in transit' as in actually flying between Earth and Mars, space that hasn't been polluted by humans is in fact mind blowing EMPTY, being hit by meteorites in space is a science-fiction plot device not something that has any statistical likelihood of happening regardless of the size of the vehicle, even in LEO where all that space junk resides it is still fantastically empty. The core vehicle obviously has the same risk of being hit as any other vehicle and is a wash.
Great. Has it degraded the power output of those panels appreciably? Being hit by meteorites is so much science fiction that NASA considers it in the design of their spacecraft and space suits? I guess their just "stupider" than you, as you would put it.
- SEP is good at least to Jupiter before solar power becomes too weak. But even then we either use Nuclear powered electric propulsion or do something like plunge inward toward the sun and burn our propellent rapidly in a Oberth maneuver to slingshot ourselves into the outer solar system and use a ballistic capture at our destination planet (getting back might be tough though). In any case your argument that we need to develop NOW a propulsion system that only going to be used for a trip to Saturn is laughable, Mars is the most aggressive destination currently under consideration for 'next' and it is unquestionably the limit of our technological reach for all the non-propulsive aspects of a mission and or settlement and may even be beyond it. Your simply grasping at straws here to try to come up with something to slander SEP with, you might as well say we should put ALL our money into anti-matter drive so we won't be 'limited' to destinations within the solar-system.
Good for what? For powering small satellites or space tugs that have more mass than Skylab? How am I slandering your favorite technology?
Childish insults aren't arguments for whether or not something will or won't work.
The problem is not the reliability of our launch vehicles or our ability to assemble mission components in orbit. The crushing cost of Orion and SLS does not leave budget for anything else. If NASA is actually serious about going to Mars, something has to go. I would kill the Orion program and focus funding on Dragon.
The breaks:
- With ATK's Dark Knight boosters SLS will peak between 110t and 120t, absent enormously expensive or impractical design changes, that's the maximum capability that we obtain from a 4-SSME/2-5SSRM SLS configuration with evolutionary hardware development
Q: What is the timeline for Dark Knight dev and restart of RS-25D production?
- A SEP tug that comes in at 110t or less has to push an equally heavy cargo to Mars
Q: How much would a SEP tug weigh that just takes the cargo to Mars?
- Orion can't land anywhere but an ocean on Earth
Q: Is there any way to kill this program gracefully that retains the teams and refocuses their work on Dragon development?
- Orion's service module design was so compromised by mass reduction that it's useless for the purpose for which it was originally intended
Q: Can ESA have their team create a methalox descent/ascent engine for Red Dragon, or is this beyond their capability?
- Every single one of these goofy development programs is a total hack job from start to finish and there's no reason to believe that the design of the service module will be completed on time, that SLS will fly with Orion on schedule, or that there will be funding for a manned Orion joy ride around the moon
Q: If there's no money to actually do ARM, can we stop funding it now?
- We need heavy lift to go to Mars, but we don't need an expensive and heavy capsule that can't land on Mars
Things to figure out:
Will NASA connect the dots and determine that it can't simultaneously pay for SLS, Orion, multiple commercial crew providers and still have money left for manned space exploration?
What is the state of development of Red Dragon?
What's the best way to accelerate Red Dragon by directing funding towards development of a methalox engine for propulsive descent/ascent?
Can Boeing kill CST-100 and direct funding towards SEP tugs without massive layoffs?
Can Boeing and Lockheed collaborate on Orion development to keep both Orion and SLS and retain the Boeing people who work on development of manned spacecraft to supply crew/cargo for government/military?
Let's add to that list:
- No artificial gravity can be provided for the crew. 18 months worth of transit time with no artificial gravity if the higher efficiency, lower thrust burns are used. Is this a deal breaker? No.
- The actual tug that Boeing proposes masses 130t. SLS won't throw 130t into LEO without the addition of advanced boosters and a 5th SSME (if the Dynetics liquid boosters that won't fit on the MLS aren't utilized), requiring a complete redesign of the SLS launch vehicle. This is a deal breaker. You either design something that uses 1 SLS launch at it's actual maximum payload capacity that can provide propulsion to Mars and back or don't bother designing it at all.
- The quoted solar panel efficiency is at 1AU. Mars is not 1AU from the sun, thus the massive transfer vehicle.
- Uses Orion, which requires an additional SLS for a gumdrop that can't land anywhere but a terrestrial ocean.
As I've stated before, I have no problem with this technology being utilized for non-human cargo. It only matters that it gets there and if it doesn't, nobody died because we'll have contingency planning in effect to deal with the loss of cargo.
Side Show Bob is quite correct. We're going to try any number of rope tricks because they're conceivably possible, but we're going to ignore the most obvious way of getting from LEO to LMO, which would be direct from LEO to LMO.
kbd512 and Impaler it looks like to me that the disagree to agree comes back to the engine for Nuclear vs Solar if power levels and mass are comperable for each source but not of funding or maturity of readiness.
That said can we get back to the Beoing plan details as to what does not make the grade....please.
From first post:
So whats wrong here?
Certainly:
- These vehicles require a SLS launch of their own because they're so massive and those launches cost more than a STS launch
- Burns that reduce the trip time to 6 months dramatically lower the Isp of the supposedly more efficient electric thrusters
- There is no comparison whatsoever between what a kilo of enriched Uranium yields in energy output and a solar panel that operates at theoretical maximum efficiency; no amount of efficiency improvement is going to make solar technology more efficient than fission or fusion
- The drag produced by these enormous solar panel arrays would bring a SEP tug down in days if we do assembly in LEO or require burning propellant to maintain orbit
- Massive increases in surface area increase the risk of the vehicle being struck by space debris, both in LEO and in transit
- No alternative means we're stuck with a technology that doesn't operate efficiently in places beyond Venus or Mars
Wut? If I have a budget of $2000 to spend, and something comes up that will cost me $500, I don't care if someone else spent $2000 on getting it to that point that it costs me $500; I'm only interested in whether it fits in my budget. If something else comes up that will cost me $2000 for the same capability, then I'm not going to choose that just because it's $2k vs. $2.5k; I'm interested in what it costs *me*.
If the government actually operated in that manner, then this notion of "what it costs me today" would carry water. If we take any technology and only look at "what it cost us today", we'll find that it didn't just cost the $500 we're spending today. We didn't magically get to "today" without the money spent in the "past". It's a false basis for comparison for what something actually costs.
If we spent $10B in the previous five years on a technology and only spend $1 every year thereafter to use a technology, then the technology doesn't magically cost $1 to use unless we also magically get our $10B back.
Sure, I'd like to see a nuclear rocket developed, but at the moment and for the foreseeable future it's politically infeasible. The government won't develop it, the public won't support it, and private companies wouldn't be allowed to develop it even if they want to. So any plan relying on nuclear rockets to work is doomed to failure.
Development of nuclear technology is infeasible because people have convinced themselves it's infeasible. To a person, every single one that complains about what it costs will cheerfully ignore what all other technologies cost to develop and then proclaim it's too expensive. To a person, every single one brings up the specter of death from nuclear radiation, ignores the lethal nuclear radiation that our own star emits, and proclaim that it's too dangerous.
I attribute this behavior to a complete lack of understanding of radiation and an inability to cope with potential dangers like a rational adult. Nuclear technology is one of the favorite, and fanciful, boogeymen that environmentalists like to use to inhibit progress towards their stated goal of "green" energy, whatever that is, and reduction of our carbon footprint.
The e-tards whine about how burning coal destroys the environment, but when we already have a technology that doesn't dump billions of tonnes of CO2 into the environment every year, they completely ignore it and propose construction of solar and wind power plants that only operate in certain conditions, require heavy industry to manufacture components for that also dumps many more tonnes of CO2 into the environment, and naturally the plants costs more money per kW/h than competing technologies. Burning coal dumps more radiation into the environment than nuclear power plants in normal operations.
Are you truly going to stand on this ridiculous sunk-cost fallacy? That all the money spent in the past to develop solar should be added up and used decide if future investment is justified? Will we add up all the money ever spend on Nuclear technology as well? Past costs for every technology are irrelevant, we should only ever look at the future costs and the future additional benefits thouse investments will bring. This is a WELL established principle which better economists they both of us came up with, if you are not capable of understanding it then you have no business making ANY kind of decision involving money PERIOD.
I guess if a dollar spent doesn't equate to a dollar spent in your mind after it has been spent then there's no point in arguing cost with you. I think Congress ascribes to your special kind of economic brilliance.
Frankly your arguments have been one of poorer defenses of NTR that I have seen on this forum. Other NTR proponents at least know something about SEP, and stick to basic NERVA types systems without going into fantasy land Gass-Core stuff. This entire thread has been pearls-before-swine waste of my time as it seems every NTR advocate has a cranium capable of shielding them from not only from deadly neutron radiation but facts and reason as well.
Frankly, you haven't provided any logically consistent arguments for why we should not develop nuclear propulsion technology other than the fact that it will cost money and be difficult.
SEP works well between Venus and Mars. Nuclear power doesn't limit our exploration to that area. Long term thinking here.
Nobody forces you to post here. If it's a waste of your time, you can stop posting whenever you wish.
Fortunately NASA make the right choice in the 1990's to commit to SEP and to drop Nuclear like bag of kittens into a river, we have been on that development track now for 20 years and it's an unstoppable freight train of fruitful development that is not going to stop. Instead it is going to open the solar-system to larger and larger probes and eventually manned missions BLEO. But I expect even THEN dolts on this forum will still be pining their hearts away on Nuclear fantasies.
Pinning your hopes to SEP fantasies won't make the technology any more suitable for expanded manned space exploration, either.
All historical evidence says just the opposite, you are clearly basing your opinion on personal wishes and desires and not actual evidence.
All historical evidence says that technology development costs billions.
If those billions spent lead to a technology that permits us to explore virtually all of our solar system, I consider that a bargain.
NOBODY is working on it BECAUSE it is expensive (AND pointless) not the other way around, think about that for one second, Russia has absolutely no qualms with nuclear technology but they aren't doing it. Instead EVERY MAJOR SPACE AGENCY is putting money into SEP. Do you really think that NASA, ESA, JAXA, Roscosmos are ALL stupider then you?
Then why does NASA have nuclear engineers trying to re-create a nuclear rocket engine? Are they stupider than you?
Site it and give me some kind of estimate.
Do your own searching and your own estimating. I already provided plenty of technical papers that detail how a GCNR would work, experimentation conducted for GCNR research and development, and results. Give your own estimate so I can then attack it and say that it's unrealistic without providing any evidence, which is the only thing you've done up to this point.
As usually you are utterly ignorant of the technology your criticizing. Dawn was launched more then 10 years ago and we have had whole generations of thruster tech between then and now. The NEXT ion thrusters which completed 5 years of endurance testing in 2010 gets 4200s while being having higher thrust:weight. Hall thrusters running on Krypton are hitting ~3000s ranges and will likely start to take over from gridded ion thrusters going forward because their better thrust density and ability to throttle across a wider range of ISP, the ARM mission would likely use them. Also efficiency in a Electric thruster has a meaning different from ISP (in fact it is sloppy to ever use efficiency as a synonym for ISP in regular rockets), it means the percentage of electrical energy converted to kinetic energy and it is around 50-70% for most thrusters and rising as technology improves.
By your own logic a, nuclear rocket engine in a lab is years away from flight testing and may as well be science fiction. So, I'm applying the same logic to your own flawed precepts. Whereupon an engine has flown in space or NASA decides to fund something, the technology leaps into existence and we start counting development dollars. Go fish.
Your 'think is achievable' seems to be nothing more then chopping the first number in half, it's baseless speculation on your part. Your continuing to pretend that NERVA somehow validates Gas-Core, they are RADICALLY different and the Gas Core is orders of magnitude harder. NERVA operates at ~850s ISP and completely in the range of NORMAL ROCKET TEMPERATURES. Gas Core would push material science into unknown territory to contain the temperatures AND pressures to achieve these theoretical numbers, because these numbers assume no barriers imposed by materials being slagged.
What I "think is achievable" is based off of flow experiments, the demonstrated ability of a seeded hydrogen propellant to absorb the thermal flux from the reactor core, and LANL modeling of a reactor core designed to minimize fuel loss while maximizing propellant flow for cooling and propulsive force.
Again your so called thinking here is dead wrong. And as for making fuel it's actually the DOE that's doing that, but it is fuel for RTG, not the stuff that would go into NERVA, these RTG fuels don't get anywhere near that hot.
Have you actually read anything about nuclear rocket engine technology? RTG fuel? What in the world does this have to do with using UF4, UF6, or Am in a GCNR?
The parts of NERVA that are applicable to design of a GCNR are determination of Isp from actual experimentation, the cold flow experiments, the one hot flow experiment, and use of seeded propellants.
Underground might be cheaper then launching, but it won't be CHEAP. You need to have a cavity capable of holding all that exhausted gas which is absolutely huge.
No, it will not be "CHEAP" with capital lettering that you so love. The engines I want to see developed have thrust levels comparable to a RL-10. Go look at some pictures of the salt mines where we store radioactive waste.
Oh brother a sunk-cost fallacy, your really embarrassing yourself now. All costs in the past are GONE, UNRECOVERABLE, IRRELEVANT. We make all decisions on future actions with the world as it currently is as a given, if a million dollar project $2 from completion and and a $1 alternative appears you cancel the incomplete project and save $1. Yes billions have been spent on Solar technology, and millions on electric propulsion, but ALL of thouse costs are both irrelevant now AND in fact thouse costs already payed for themselves a hundred times over in making ALL OUR CURRENT SATELLITES possible which provide services every year valued at over $100 BILLION. All that matters is the MARGINAL costs to get the next generation improvement and the benefits of that next generation vs the marginal costs. This is why these technologies are still being developed, their benefits are huge and the costs are less then the near term benefits. Any alternative propulsion technology is going to need to compare it's full costs vs the marginal costs of improved SEP, this is why Nuclear is never going to happen, it's decades behind and falling further behind every day.
Oh brother, the only money that matters is future money fallacy. Yes, you are embarrassing yourself. Money spent to achieve a capability is not irrelevant. Far better economists than you universally agree on this point. The only logically valid argument you've presented was that our development of nuclear propulsion technology lags behind because we're not putting much funding into it.
No, I just know how to judge technologies rationally.
If we used your rationality for technology development, we'd still be riding around on horses. After all, that new gasoline engine will cost billions to develop and that horse gets you from point A to point B, just like the cars of the early 1900's. You'd fit right in with the current crop of Boeing execs, though.
A solid core NTR could certainly be developed and flight tested sooner than a gas core NTR, but as Impaler pointed out, the payload mass fraction doesn't compare favorably to SEP solutions.
The problems I have with the SEP solutions are as follows:
- Greater number of assembly/deployment and orbital transfer operations
- Orbital transfers take months to accomplish without chemical propellant kick stages (if active radiation shielding can be made sufficiently lightweight, this is less of a problem for a manned vehicle or a solution where the crew is ferried to the transfer vehicle after it's at a Lagrange point, but TRL for active shielding is even lower than it is for gas core reactors; I'm still confident active shielding can be accomplished in another ten years or so)
- Chemical propellant kick stages are required to shorten orbital transfer times (well within our technological capability, but it adds mass to a SEP tug that already requires a SLS launch of its own and reduces overall efficiency)
- Solar panels the size of something a SEP tug would use would undoubtedly increase the chance of collision with space debris (I'd say deployment of the panels prior to reaching a Lagrange point is a mission risk; If a significant portion of an array is damaged or rendered inoperable, there may not be sufficient power to complete an orbital transfer in a timely manner)
- Even if active radiation shielding is available and some measure of artificial gravity can be provided, you're adding months of time in space to the mission without the kick stages
All manned space exploration missions up to now have started in LEO, involved a burn for orbital transfer, and a burn for orbital insertion. Spiraling in/out is a new way of accomplishing orbital transfers, but it obviously works.
How much would a SEP tug that can transfer from LEO to LMO or LLO (even if we have to add kick stages to break orbits), and make the transfer in six months or less weigh?
Is it possible to provide artificial gravity for the crew or would that adversely affect operation of the tug?
Typical space cadet straw-man, I've said it can't be done cheaply and your exaggerating that to 'impossible to achieve at all'. I have said repeatedly that it COULD be done just that it will be gawd awful expensive. Stop trying to put words in my mouth.
Calling people names isn't a form of argument, it's just a personal attack. Could development of a GCNR be expensive? Yes. Will it be dramatically more expensive than any other advanced technology that mankind has developed? If history is any indicator, probably not. It won't be done on feel good funding, though. Let's put it that way.
Again your trying to turn my critique of cost in to a proclamation that the technology cant be developed at all. How can a person be this dishonest?
Your argument is that development of GCNR will be extremely expensive and, as you continue to note, it isn't available right now. The reason it isn't available right now should be fairly obvious. Nobody is working on the technology.
Then site your sources, give me some links to real technical papers.
http://www.osti.gov/scitech/servlets/purl/4017976 <- It can be done
https://archive.org/details/nasa_techdoc_19720013996
http://www.osti.gov/scitech/servlets/purl/5175780
http://deepblue.lib.umich.edu/bitstream … /585_1.pdf <- Don't know if you consider studies to be technical papers or not, but the information in the study was based on actual experimentation with Americium
http://www.researchgate.net/publication … st_reactor
http://books.google.com/books/about/A_F … IDAAAAIAAJ
http://books.google.com/books/about/Sim … vsvLqoOf0C
http://www.researchgate.net/publication … ear_rocket
http://www.researchgate.net/publication … et_concept
http://www.researchgate.net/publication … ded_Risers
http://www.tnw.tudelft.nl/fileadmin/Fac … uwerda.pdf
https://smartech.gatech.edu/bitstream/h … 313_v2.pdf
http://arc.aiaa.org/doi/abs/10.2514/3.2 … alCode=jsr
http://papers.sae.org/929347/ <- Power, not propulsion
http://adsabs.harvard.edu//abs/1988snps.symp..473D <- Mo Powa!
http://alexandria.tue.nl/repository/fre … 620304.pdf
http://www.ans.org/pubs/journals/nt/a_3480
http://www.academia.edu/1705961/Nuclear … Technology
http://www.freepatentsonline.com/3399534.pdf <- Not a technical paper, but a patent for a GCNR from TRW
http://www.inl.gov/technicalpublication … 517271.pdf <- NASA blew some cash on studies of potential fuel candidates for solid core NTR's for Mars DRM 5.0
http://www.inl.gov/technicalpublication … 394162.pdf <- Same as above
https://books.google.com/books?id=Foo-y … or&f=false <- Not a technical paper, but more of a "this is how it could work" paper
https://books.google.com/books?id=aI9Qh … or&f=false <- More of the same
http://www.ebay.com/itm/Gas-Core-Nuclea … 1451583969 <- GCNR Info on eBay!
What part of huge mass killing thrust:weight ratio did you not understand? How dose 'directing' a magnetic field reduce the mass? Are you simply grasping at random words to avoid acknowledging this problem? Do you have even the slightest idea what your talking about?
An enormous magnet is not necessary if you can direct and intensify the magnetic pressure generated. Alvaro Sanchez, from the Autonomous University of Barcelona in Spain has done some ground breaking work in development of this technology.
As usual you couldn't be more wrong, SEP technology has been ongoing for a decade already as part of NASA's Exploration Technology development program, that whole program has a budget of only ~200 million a year and is developing a dozen different things at any one time such as hypersonic decelerators and thouse Sterling RTG you mentioned earlier. Because this is already a know technology that is actively being used by commercial satellites every day the risks for incremental refinement are very low. The Asteroid Redirect vehicle has been budgeted 133 million per year http://optics.org/news/5/3/3 and that is for both the technology and to actually make for the WHOLE vehicle.
Solar panels and SEP technology didn't leap into existence with NASA funding ten years ago. Aerojet-Rocketdyne put the first electric thruster on a spacecraft more than thirty years ago. Many billions of dollars have been invested in solar technology and electric propulsion for spacecraft and rightly so. I see no reason whatsoever to discontinue funding. SEP technology is quite useful if the period of time in space is measured in years and maximum efficiency is more important than how fast you get there. The highest efficiency electric thruster flown to date was, I think, on JPL/NASA's Dawn mission. IIRC, the thruster's efficiency was quoted as being around 3100s.
As for limitations, please elaborate, you seem to have no problem assuming the highest theoretical possibilities of Nuclear propulsion as givens so why don't you apply the same standard to Electric propulsion? You can not seriously be worried about transit times, it has been shown conclusively that SEP can perform a transit to Mars that is comparable to a high thrust system when provided with adequate power.
The highest theoretical limit of efficiency for a gas core NTR was calculated to be around 6000s with a core temperature around 100,000K. I think 3000s is achievable. NTR efficiency centers around how fast you can accelerate the propellant through the core with the thermal flux provided by the fissioning core material. NTR efficiency is not a SWAG on the part of the engineers who were involved with Rover and NERVA, it was determined through actual testing. Whether it is practical to approach the limits of the technology has a lot to do with materials development and the size of the reactor. A reactor the size of a house is obviously a non-starter for space propulsion applications.
Again wrong, no less then wrong your expressing nothing but a blind wish and an appeal to ignorance. We can make very reasonable minimum estimates of cost based on the TRL, the size/energy/mass of the thing we want to develop and basic nature of the technology in question. Nuclear Thermal Rockets as a technology BIG, HIGH ENERGY, HIGH DIFFICULTY. The NERVA has a reasonable TRL 5-6 which is the only factor that isn't bad for it, but even here it is inferior to SEP which is TRL 9. The size, mass and energy density of SEP are all lower then Nuclear propulsion systems, Electric propulsion systems can be tested in vacuum chambers, nuclear rockets aren't going to be tested in the earths atmosphere ever again and would require extensive in-space testing. No honest estimate would put SEP and NTR even remotely in the same ballpark for development costs.
I think a lot of the work performed in NERVA is relevant and applicable to GCNR design and there's no need to reinvent the wheel to prove that we know what we know. NASA is spending what precious little money it does have to try to recreate the fuel elements used in the NERVA engines.
As far as testing is concerned, it can be done underground. The US already stores nuclear waste underground in rather expansive facilities. So long as we're not overly concerned with nuclear waste becoming contaminated with radiation if there's a containment breach, I would perform testing there.
An honest estimate of what a transition from gas powered motor vehicles to electric powered motor vehicles would cost should not ignore the many billions expended to develop internal combustion engines, the billions spent maintaining them, and the billions spent making them more efficient so we're not all choking down the exhaust fumes. Every new technology has up-front costs. Many billions of dollars have already been poured into research for the technologies required to make SEP a reality and it didn't happen in five, ten, or even twenty-five years. The SEP tech doesn't exist in a neat vacuum where only the cost of some small portion of the overall development effort should be considered.
Should we cancel SLS and spend all that money on technology, YES, but not one dime of it on Nuclear propulsion.
Do you work for a company that sells solar panels or electric thrusters?
Just a second ago you were praising the slide-rules, now they seem to be stone knives and bear skins. Our tools are better now yes, but development costs in Aerospace and Nuclear science are still astronomical and a lot of degeneration has occurred much of what they would have accomplished back then would need to be redone.
Did everyone at LANL have their brain fall out of their head recently? I stated that men with far less than what we have to work with today developed nuclear rocket propulsion from scratch. With all of our advanced technology and computational capabilities, are we somehow utterly incapable of creating a fission reactor and flowing hydrogen through it?
They did not have a flight capable system, subsystems were being built and tested but had never been assembled into a finished engine, they were hoping to have a finished engine after several more years of development. I don't see any reason to believe they would not have gotten their with the time and money originally budgeted, but the program was halted many years short of that goal. You seem to be under the false impression that they were one screw turn away from completion.
No, they didn't just have to fuel a rocket and launch it, but to pretend that there was or is some sort of absolute impossibility to picking up where we left off is just silly.
Why must you keep throwing SLS at me as if I am an advocate for it or it is somehow in competition with NTR technology? Dose that fact that just assembling this SLS rocket out of 'off the shelf' shuttle leftovers is in fact costing ungodly amounts of money give you no pause for how expensive right rocket development is? And yet your completely sure that development of Nuclear propulsion with be chump change, and not just solid core but some crazy gass core idea that your convinced is worth it because of some numbers you read off Wikipedia.
Yes, we're spending billions to re-invent Saturn V using inappropriate hardware and the result is a rocket that can't even throw an orbiter into LEO. If we think nothing of spending billions to re-invent what we had four decades ago, in terms of chemical rocket throw capability, then we can damn well spend some money on something that has long term payoff and permits us to explore virtually all of the solar system. Stop with the Wikipedia nonsense. The information I have comes from the papers published by the people who worked on the technology.
Of course it can be contained WITH A HUGE ENOUGH MAGNET, that is the problem! Your not going to control a Gigawatt of plasma with a something that has the kind of mass ratios that we have in the combustion-chamber/nozzle of a chemical engine, a magnetic equivalent is going to be massive and the thrust:weight of the engine is going to tank.
We could use a huge magnet. Or we could use technology that permits us to direct a magnetic field… Muchas gracias, Alvaro.
Now your siting the Manhattan project to me as proof of affordability, have you lost your mind? This is typical space cadet thinking, damn the costs we can do ANYTHING!!!! This is the kind of thinking that has lead to our unending series of space boondoggle, and while you seem to be able to recognize all the other boondoggles like SLS but you have a giant blind-spot for your own boondoggle. I've told you repeatedly that Nuclear rockets are 1) Expensive to develop and 2) don't have the performance to be attractive compared to Electric alternatives. And your response is basically to insist against all evidence that Nuclear rockets will be cheap to develop if we just 'hope' and 'try harder'.
No advanced propulsion technology has ever been "cheap" to develop and this solar electric propulsion that you so love is not an exception to that rule. Many billions of dollars have been invested in the technology and that is the only reason it works as well as it does today. Rather than blowing money on unnecessary make-work projects, like Orion/SLS, I'd rather see NASA actually develop a technology that permits us to explore all of our own solar system, instead of just the parts that are close to the Sun. In finance, it's what you'd call a long term investment. It requires enough wisdom to accept that there will be a tomorrow. Apparently you think it's too difficult or maybe you can only focus on what's right in front of you. I, for one, am quite thankful that those who came before us did not give up simply because a particular problem was difficult or expensive to solve. Few things worthwhile are simple, cheap, or easy. There is such a thing as squandering money and opportunity, though. That is what I believe Orion/SLS are. I have nothing against your precious solar electric technology, but the technology does have limitations and I would like to see development of a complementary technology that does not have those limitations.
I think your problem is that you think COST during development is just another metric of performance that can be beaten into submission by engineering, like needing more speed, more thrust, more what ever. When we hit a snag in the development we will just apply more engineering to 'fix' the cost thing like we would fix any other performance issue. That is not how it works, cost is not something that goes down as you engineer something more, it only goes UP because cost is incurred by engineering. No act of brilliant engineering can un-spend a depleted budget and when your doing cutting edge engineering your going to frequently hit snags that force costs upwards above the original estimate. Costs are more of a floor with the general technology or system architecture setting your best case with reality being considerably above that and a worst case scenario vastly higher. Only after something is DONE being developed can you even hope to start reducing costs, and that is a slow iterative process that's only justified by a high volume of usage to amortize the improvement over.
I believe that you actually have to try to do something before you know how much it's going to cost. Since we're doing nothing of the sort, your guesses about how much development would cost and how long it would take are every bit as imaginary as mine are. I believe that the cost of development would not be outrageous or impossible for NASA to bear, but it would mean that some money squandering programs would have to go.
Exerting yourself in a BALLOON suit is a bad idea but if we do not come up with something much better there will be no point in going to Mars. If exploring Mars will entail people bobbing around like the Stay Puft Marshmallow Man for 6 months we may as well stay home.
Agreed. We're still working on that. I'm not sure we're putting enough money into it, either.
I take it you have not been on a bike recently. Either that or you are incredibly out of shape. Scuba diving can be very strenuous though diver are able to easily carry over an hours worth of air. With the low gravity a much larger life support carried on the vehicle would not be a great encumbrance. As for falling off, that is one of the reasons I suggested the recumbent trike; it is very hard to fall off of.
I walk or drive or fly wherever I'm going these days. I spent most of my childhood riding around on a bike. At 17, I joined the Navy and spent the next six years walking most places and carrying what little I owned. The Navy was anti-carrying-technology, apart from seabags, buses, and aircraft. Everything that could conceivably be hand carried was. I never owned a motor vehicle or a bike until after I left. I'm not saying you can't walk or bike everywhere, but it requires a bit of exertion and our explorers, unfortunately, don't have unlimited oxygen or food supplies.
There's no traffic on Mars, yet, so you don't have to concern yourself by getting flattened by some clown talking on the cell phone in a SUV while you're riding your bike. That's a plus.
The ones who question how effectiveness of are recumbent trike know nothing about the current state of the human powered vehicles in the CONSUMER market. http://www.terratrike.com/ This design could be easily modified for rougher terrain and in 1/6th gravity and almost no air resistance 50 or more miles a day is quite reasonable.
I'm not opposed to the idea of human powered travel, even on another planet, but how do we test all of this? Has anyone used one of these advanced consumer recumbent trikes when it's -100 outside? Whether the vehicle weighs 38% of what it does on Earth or not is of little consequence if you load it down with enough supplies. Have you figured out how are our explorers going to eat, take a dump, or replenish the oxygen for their suits (shouldn't be too hard)? How much would a pressurized HPV weigh? Could you use the HPV as shielding against SPE's?
Because it's lightweight, robust and cheep. You cannot have a passive shield against GCR even with polyethylene, unless you build a spaceship with two meters thick walls.
What you need is only a solar flare protected zone: a double aluminium wall filled with 20-25 cm of water ice is good. Ice it is also a very good heat sink for waste heat and a protection against meteorite puncture.
For CGR protection it will be better something like Boeing's 1500 kg superconductive mini-magnetosphere
If that actually works, it's fantabulous. This is the first such concept I've seen that didn't weigh as much or significantly more than the entire Mars DRM transfer vehicle.
Thanks for the info.
Edited to add content:
If a PE fabric composite is heavy then 25CM of water is surely far heavier.
I don't think I'd want my water supply used as ballistic protection. It'd be pretty tough to live without if it sublimated after an impact penetrated the outer hull.
Exerting yourself in a spacesuit is not a particularly good idea and our space program and the Russian space program has confirmed that.
Riding a bicycle on Earth with no oxygen availability constraints is hard enough. It's also easy enough to fall off and be injured, which is probably not something you want to do on Mars.
The electric vehicles that NASA designs are not race cars, they typically move at a sedate jogging pace or fast walk at maximum speed.
Yes, a large number of people who don't have cars ride bicycles.
A trike on Earth, who is most likely not wearing a space suit, could cover 50 miles a day.
This is a very interesting discussion going on about materials of construction for a spacegoing habitat module. One should note that the requirements are light years apart for a hab that stays in space “forever” vs a hab that must enter atmosphere and land somewhere. Those requirements will likely never be resolved for some centuries yet.
There is no single technology that can make a habitat do all things. However, there are families of products, used in conjunction with each other, that have a synergy to them that makes their combined use suitable for variant requirements.
What I don’t understand is insisting on exposing plastics to vacuum and UV and wild temperature swings where they will degrade at one rate or another. There are some good ones now available that will last a while, but nothing one could construe as “permanent” for any kind of space station-like structure that never lands. Put the plastics on the inside, and put the glass and metals on the outside.
If you read the article, they were thinking of exposing a carbon foam, selected for its light weight and very low thermal conductivity, to the thermal environment, not the PE composite (which, as Rob pointed out, was not really designed for the thermal environment of space). The PE composite forms a pressure hull, but it is inside of a carbon foam overwrap, where the foam can protect it from temperature extremes. The concept is much the same as the dual layer ET foam that both insulates the cryogenic contents of the ET and ablates as aerodynamic heating from drag increases the temperature during STS/SLS ascent. The ET foam is just one example of two different but complementary technologies that make lightweight cryogen gas cans possible.
Based on nothing but existing materials and common sense, I’d suggest a thin aluminum pressure shell surrounded by a thick layer of ordinary pink fiberglass insulation, just like we use in our attics, paper backing and everything. Vacuum won’t hurt glass fiber or paper. Make it quite thick; the nominal commercial batt thickness is 6 inches, double-layer it if you need more.
Why is everyone so fixated on using aluminum? Thin aluminum sheeting is good for not only experiencing the direct effects of high energy ionized particles, but secondary effects from interaction between the ions and the atomic structure of the material they're being driven though.
This needs an over-wrap to protect it from UV. Make that out of simple textile-reinforced mylar (I’d consider using something woven of simple cotton yarns), aluminized on one side. Face the aluminized surface outward, and glue Velcro strips where geometrically appropriate when you fabricate it. Wrap this around your fiberglass layer, and overlap it over itself for securing with the Velcro. Nothing but aluminized mylar faces space and its vacuum and UV, and the mylar part is underneath the aluminum. If this degrades ever so often, it is quite easy to replace, and extremely light and compact to ship. Meteor hole? Stuff some more fiberglass batting into the hole.
Correct. Overwrap required. More stuff made with aluminum?
On the inside is where you arrange your plastic furnishings that can help with radiation shielding effects. Although you’d get even better effects by arranging your water, wastewater and frozen foods as part of your shielding, which things you have to have anyway, although not enough for the whole hab; so just around the designated flare shelter space.
As previously mentioned, NASA has people trying to figure out how to arrange cargo, food, and water to provide shielding.
Inside, these plastics see no UV, no wild temperature swings, and no vacuum. Now you can use any appropriate plastic for any particular detailed purpose, exactly the same way we do down here on Earth. Why make things hard putting plastics outside in space when you don’t need to? (I gotta ask.)
You don't have to and you probably shouldn't.
Whatever you do, do NOT mount anything permanent to the inside of this aluminum pressure shell! Everything must be quickly removable, because you have to reach that shell quickly to patch punctures. There isn’t time for an EVA to do that, and besides, from the inside, the air pressure helps hold and seal your patch. Put your equipment and stores down the core, and put the people and their operating spaces around inside of the pressure shell.
NASA is right there with you, GW.
As for windows, pick a transparency. But add an exterior metal (or composite build-up) shutter that you can operate remotely from the inside. When you’re not using the window, close the shutter. Your transparencies will last a lot longer in a very hostile environment that way. UV and meteoroid impacts are the threats. You can even multi-layer the shutter as metal foils and Kevlar. Just don’t expose the Kevlar to UV, make sure the metal layers cover up all the Kevlar. The shutter doesn’t need to hold pressure, vacuum won’t hurt these materials. If you never put much force on them, then brittleness in the cold is no problem either.
Using metal and poking holes in the pressure hull for windows is not a good idea, but if you're going to do it anyway you might as well be smart about it. Good idea.
(What you would design for an article that lands is quite different.)
More overwrap required.
Zubrin and Baker are engineers. They do know how to design a spacecraft. You are ignoring temperature, strength, mass, stress loads, etc. Aluminum lithium alloy is strong and light weight. It wasn't just for ET, it's also used for the fuselage of the Boeing 777X.
Yes, they're engineers from the 1980's to 1990's. This is 2015. When was the last time they designed a spacecraft? We know they didn't design Apollo and that was the last deep space transfer vehicle NASA flew.
The composites are comparable in mass to NASA's favorite alloy, which is why the researchers even bothered to determine their properties. You're still not getting this "no magic material" concept. Two composites with two different purposes were designed to be used in conjunction with each other. Mass is mass and it doesn't matter where you put it. You can lug additional descent/ascent vehicles with you, or you can use the transfer habitat as a multipurpose vehicle that precludes the requirement for additional vehicles to get to/from Mars and to/from Earth.
For overall mission design and cost, fewer pieces of flight hardware is better. If you asked if I'd like to take two or three different vehicles to go to/from Mars or just one, provided it could satisfy all the mission requirements, I know which option I'd select.
Spacecraft with no windows? I don't think so.
A high-def image isn't good enough?
So your obsession is radiation.
NASA's obsession is with radiation. I could care less if they fry as long as they do it after they complete their exploration mission on Mars.
kbd512 wrote:Dare I ask what would be applicable?
Do you have a different material or set of materials in mind?
I was thinking of just Weldalite, which is aluminum/lithium alloy. That's the same alloy used for the external tank of the Space Shuttle. Robert Zubrin and David Baker used that for Mars Direct. So sticking with the original. But before you posted, I was thinking some more. To expand the habitat to the two deck/story design that I described, really demands lighter materials. The obvious candidate is carbon-fibre/epoxy composite. But the composite your web page describes is Spectra/epoxy. I pointed out temperature limitations, but if protected by multi-layer insulation, it just may work. That's the same insulation as ISS modules, and actually the same as an EMU spacesuit. Hmm.
Why are so many people fixated on using the metal used in the ET? A lightweight gas tank that's used for a few minutes and a long duration deep space habitat have completely different design requirements. There's no economy to be had from using gas tank materials if it leads to the early demise of your crew.
Zubrin and Baker don't know bean dip about radiation. They want to ignore all of it and pretend that the storm shelter to protect against SPE's is all that's required. I have no doubt that the astronauts will get a dose from GCR's because we just don't have anything that can stop particles at those energies, but there's prudent design for that environment and then there's ignoring the problem.
If NASA insists on building their habitat from aluminum, then they can quit going on about the radiation threat because they already know what happens when ions hit thin aluminum cans and they don't need any further data on that. Heck, they had two of their team members who were working on habitat design give a presentation not too far back where they indicated that they were trying to get rid of as much metal in the habitat as they could get away with. The article describes use of two composites that work in conjunction with each other, as previously stated. The ISS modules and EMU are, by NASA's own description, rather poor for stopping particles from SPE's and GCR's.
And use ALON for windows instead of glass. Two reasons: it's 1/4 the thickness of the strongest glass, for the same strength, consequently 1/4 mass. And so impact resistant and so hard that I expect no micrometeoroid pitting. Of course with the same spectrally selective coating as ISS windows, to control UV and IR.
How about we skip windows, irrespective of the rest of the materials selected? I think a camera or camera set is sufficient. There's no reason to compromise the integrity of the habitat any more than absolutely required. If the habitat is rotated to provide artificial gravity, they're not going to be looking at anything that won't make them want to hurl, anyway.
You're still thinking like we're operating in LEO. The environment is different and it's different enough to matter.