You are not logged in.
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.
Not required, and annoying. Your descriptions of those materials is overblown. I really don't see an applicaiton for either. Research is good, but neither appear to be truly applicable.
Dare I ask what would be applicable?
Do you have a different material or set of materials in mind?
kbd512 wrote:There's only one way to find out how well a material holds up over time. Last time I checked, we still had a rather large orbital facility to test it at.
Damn good idea. Bigelow Aerospace wants to add a small module that can be carried in a Dragon CRS trunk. Good idea. Even if it isn't used, just to test the material.
I'm saying PE can't be used for pressure containment, or restraint. You could stack sheets against the walls as radiation shielding. Polypropylene could be used for the same purpose. For radiation shielding, it's about the same. I read a NASA article that claimed PP could better withstand polymer degradation from radiation. But realize this doesn't replace the aluminum can, just add to it.
Ok, you want me to read the whole thing. Oh! They want to use UHMWPE, also known as Spectra. That's different. Same ratio of carbon to hydrogen, so same radiation shielding, but much stronger. Composite 1 is Spectra with resin. Still not comfortable with the idea of spacecraft pressure shell made of this stuff. Spectra 1000 is only rated for +100°C to -150°C. Spectra 1000 becomes embrittled below -150°C; but spacecraft exterior in LEO has to endure +121°C to -156°C, so that's really pushing it. Do they want to replace Nextel in the ballistic sandwich for TransHab? You can't replace a soft fabric with a rigid composite; it can't deploy.
Good grief, man. Reading required. The test articles were two composites, used in conjunction with each other, to cover the gamut of protection problems that a habitat module would encounter, from transit to reentry. Both composites are solid materials, so to speak. The spectra composite material is inside a carbon foam overwrap. The spectra composite provides radiation protection and atmospheric containment. The carbon foam provides thermal protection equivalent to the Space Shuttle HRSI tiles and has an impact resistant coating applied to provide high velocity impact protection.
Nothing's perfect, but this solution uses materials with complementary properties that are lightweight and efficient for their intended functions. If there's something better available, I'm sure we'll hear about it.
Here's some actual REAL research on what NERVA cost and how long it would have taken to complete, THIS is what you base your cost estimates on if you have a shred of honesty and it confirms everything I've been saying.
It doesn't confirm anything other than what you want it to confirm. As I stated before, these men were designing things with slide rules and precious little knowledge of nuclear power. We had only detonated the first nuclear weapon fifteen years prior to the start of the program. This is 2015, not 1960. We have better technology at our disposal now. We're not starting from scratch.
"During FY 1970, NERVA moved into a phase of detailed design and hardware fabrication. The goal now was not further research, but rather the development of a flight-qualified engine with 75,000 pounds of thrust, at a cost of $860 million over a period of eight to nine years. The program received $88 million in FY 1970 and $85 million in FY 1971, with the funds coming jointly from NASA and the Atomic Energy Commission."
After you falsely claimed that we were nowhere near having flight capable nuclear propulsion hardware in the early 1980's, you provide an excerpt stating that the R&D phase of the project was over and they were busy with the development of flight hardware. I'm perplexed.
$860 million 1970's dollars is $5.25 BILLION in today's dollars. And that was just the lowest end NERVA rocket which is not even worth going back too, if you go for anything more advanced like this Gass-core nonsense it would be at least 10 times more, their is nothing but a vague notion of what this core would look like, no actual engineering AT ALL and nothing that could put any reasonable upper limit on development costs, it would be an absolutely unbounded development effort and we do not have infinite money to throw at problems.
We're going to launch SLS rockets that have already cost significantly more money to develop that use a good number of existing elements of the previous man rated launch system, but you're whining about what NERVA cost? The GCNR has had multiple studies of every aspect of the design, including CFD modeling to determine what the best shape of the core would be to reduce fuel loss, maximize the cross section of the propellant heated by core, and best use of the propellant for heat transfer.
Yes I am going to compare the Magnetic confinement needs of the GassCore NTR to a Tokamak even if they are hugely different in temperature. Because your nozzle just as slagged at 10 degrees above it's melting temperature as it is at 10 million degrees above. And your talking about an absolutely huge amount of mass and power transfer through these engines, hundreds of Megawatts possibly Gigawatts, your either going to be completely isolated from that kind of heat flux or your going to instantly melt. Any kind of low-thrust engine like a VASIMIR or a Lorentz force based thrusters is moving GRAMS of material per second and they need active cooling, they can get away with it because it's an all electric system, all heat and all plasma confinement is by microwaves and magnets respectively, hot stuff never comes into contact with cold stuff.
Complete isolation. That's the general idea. Power level ranges between 5 and 10 GW. If a plasma that's tens of millions of degrees can be contained, is there a specific reason why a plasma that's tens of thousands of degrees can't be contained?
It should be plain enough that 'Engineering compromises' are the add-ons, losses of performance, cost over-runs that inevitably result when you move from theoretical engineering to REAL engineering and testing of a real system. No pie-in-the-sky piece of engineering survives contact with the physical world just as no battle plan survives contact with the enemy. You must be beyond naive to look at piece of theoretical potential based engineering and think that full potential is what your going to get at the end of development effort, the more speculative the concept the shorter of the goal it will fall.
If you were to tell a Marine from 2MARDIV in August of 45, having seen three years of combat, that a single bomb smaller than a car could destroy an entire city, he'd have laughed his rear end off. Around the second week of September, he required no further convincing. Sometimes you have to suspend a little disbelief that something is possible. You make it seem as if we could spend a trillion dollars over 50 years and have nothing to show for it. You've made so many arguments that are so far out of proportion to reality that it's laughable.
Since you left out the best part of the article, I'll include it here:
This decision ended a longstanding NASA policy of developing advanced [425] engines well before there was need for them. The agency had contracted with Rocketdyne to build the F-1 as early as January 1959, over two years before Kennedy called for Apollo. Development of the J-2 dated to September 1960. The demise of NERVA meant that nobody would be flying to Mars, perhaps not even within our lifetimes. <- [Edited] This is what the loss of the Saturn and space nuclear propulsion program means in a context that everyone here should be able to understand.
So you don't know. The linked article talks about fundamental research. Although research is good, this material is far from ready. You realize one goal of any spacecraft design is reduced weight. Once you do that, you reduce radiation shielding. And the article talks about polyethylene. This article gives some data on high density polyethylene. It states embrittlement at -180°F, which is about -117.78°C. LEO experiences wide temperature swings. The Canadian Space Agency website says a spacesuit must handle +120°C to -150°C. Wikipedia says +250°F (+121°C) to -249°F (-156°C). I guess it depends if you round to Celsius or Fahrenheit. Either way it doesn't sound like polyethylene will provide structural strength to hold air pressure.
You did read the part of the article about the second composite, right? I am not aware of any thneed material that's all things to all people at all times. The second composite was developed to provide thermal and ballistic protection. PE fabrics are not going to survive a reentry or even withstand the thermal flux of space very well, but it's about as good a material for passive radiation shielding that a spacecraft could realistically use.
TransHab uses more advanced polymers. But they're light, not optimized for radiation shielding. Kevlar is an advanced form of Nylon, containing chlorine. Nomex also contains chlorine. Nextel is alumina-boria-silica. Initially, TransHab provides more protection against micrometeoroids than aluminum alloy. However, I have to ask how it will stand up over time.
TransHab has Multi-Layer Insulation on the outside, which is the same thermal insulation as ISS. That consists of the aluminized Mylar, with Kapton backing. Dacron fabric keeps the Mylar layers separate. I believe the outer most fabric is Orthofabric, the same as EMU spacesuits. That is a double layer plane weave of PTFE fabric facing, with Nomex backing, and every 3/8" two thread of Nomex are replaced with Kevlar.
NASA: Multi-Layer Insulation
There's only one way to find out how well a material holds up over time. Last time I checked, we still had a rather large orbital facility to test it at.
The lunar mission outpost topics of the past did talk of a hydrogenated plastic to be one of the protective elements but from what irc was it was 6 inches thick making it not pratical for a complete vehicle but as a shelter area it would be more preferable to use it for with those specifications of need.
This was an attempt to create a technology set that covered everything from deep space operations to reentry into the Earth's atmosphere. A purpose built deep space habitat need not utilize all aspects of the materials solution provided, but perhaps a multi-function habitat that makes use of all these technologies could service all mission requirements. If we drop the launch abort system requirements, our intrepid explorers could conceivably launch in their transfer habitat, use the habitat to transfer to go to/from Mars (assuming a methalox propulsion module that can take advantage of ISRU is included), and then reenter Earth's atmosphere after they've completed their mission.
Anyway, that's the juice. Worth the squeeze? Not sure.