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GW,
As I said before, STS should only be utilized for missions that require the capability to bring something sizable back. I don't want to actually fly an orbiter if it's not required. The vast majority of missions won't require its unique capabilities. By now you'd think that someone at NASA would learn that once you acquire a capability, you never give it up. If you can ever get it back, it will cost you dearly.
What has the loss of Saturn V cost us in terms of space exploration capability?
The design of SLS made it a spending program, plain and simple. There's no reason whatsoever why it should cost so much, take so long to develop, or not have simply been designed from the outset to have the lift capability that NASA wanted. Unfortunately, government administrators always double down on stupid because having the integrity to admit that you or your staff made a mistake costs you your job.
Rob,
By overhaul do you mean complete redesign? That's what it would take to fly one. There's but a handful of people alive who have any experience with the design. If NASA doesn't permit the contractors to devise some type of impossibly massive craft or issue design requirements that are impossible to meet, it would be simpler to start from scratch and devise a lander with the features you proposed.
SpaceNut,
There is no "fixing" Orion. It's too damn heavy for any launch system we'll have in the near future to send it and a payload that can do something other than carry astronauts into LEO. Ares I and Ares V had to be operated in conjunction with each other to do anything useful. Someone at NASA must have a manual that delineates how to make otherwise simple tasks impossibly complex and expensive. It's either that or entertainment for engineers. Simpletons, like myself, just scratch their heads and wonder what they're smoking. Whatever it is, it must be good.
I presume we're doing this as a "what-if" scenario to determine how much mass we have to stage on the surface of Mars for those inevitable instances where our ECLSS is on the fritz, because that's the only context in which it makes any sense. If you have redundancy for your ECLSS in your transit habitat then unless you completely lose power, in which case everyone dies anyway, the "what-if" is pointless because you can't be resupplied.
I mentioned the mobile exploration architecture because it would seem to make sense to design a mission that permits you to travel to supply caches spread across the surface of Mars if you really distrust your ECLSS engineers that much, scout for potential staging sites for future exploration or settlement activities, and perform field science while you're at it.
I read into what you asked as wanting to know how much mass and in what configurations we'd have to stage it on Mars. The short answer is that not having reliable CL-ECLSS is cost prohibitive. If we wanted to, we spread supplies across the surface of Mars for contingency scenarios. However, you then have to travel to those resupply sites. Would it not make infinitely more sense to have redundancy for your ECLSS, or simply have replacement parts and tested & approved methods of field repair, and use ISRU for collecting oxygen and water rather than trying to ship all of it there?
Are you asking what available upper stage/engine combination could throw 37t to TLI or if there's an upper stage that only weighs ~7t that could throw 37t to TLI? If it's the latter, then there is no upper stage that only weighs ~7t that can throw 37t to TLI.
SLS doesn't have the performance required to throw Orion and a lander to TLI because it wasn't properly designed to begin with.
There's no way to "fix" SLS, short of redesigning the damn thing to be what it was intended to be in the first place. Composite tanks, lighter SRM casings, and using a more energetic propellant for the SRM's may get 115t to LEO or so, but that's where the design tops out at. The 150t to LEO was a requirement that came from multiple studies of what type of throw a heavy lift rocket needed for it to be of utility for a lunar or Mars program. The plan to use 5 or even 6 RS-25's on a 10M core stage wasn't something random that an engineer pulled out of his butt.
Obviously that's not what NASA designed, so launching a capsule and an usable lander to TLI is out of the question.
kbd512, GW Johnson gave answer to you question
SpaceNut, that's just the mass for the consumables and the subsystems that contain them. You have to stuff that into vehicles with enough volume to actually carry all of it, with the largest vehicle in terms of mass and volume being a lander that we currently have no way of getting onto the surface of Mars. If it "only" costs $2.5K/lb, that's $770M in launch costs alone (edit: that's $770M just to get the consumables mass to LEO), using the least expensive launch services provided by SpaceX. As I said before, it's insane.
CL-ECLSS isn't "nice to have", it's mandatory.
I would also include that we would want to account for it breaking down with the initial preload of cargo at the landing site as there will be no second chance if it does. With the data we have predictable out comes for failure of equipment and the resulting increase in the baseline numbers when it does.
I think three CL-ECLSS subsystems are required for the surface habitat. The tech currently in development is efficient enough in terms of mass and volume to make this possible.
If we want mobile surface exploration, then I think we should seriously consider minimal mass and capability ascent vehicles and forgoing emplaced habitats for electric/methalox hybrid Winnebagos. The crew should land in two or perhaps three mobile surface habitats near the ascent vehicle. If all vehicles are functional, then our Martian road warriors start a year long convoy-style road trip across Mars.
Also I think when we talk about human missions to Mars we are talking long stay in my mind and not a sortie flag and foot prints as that will kill any follow up attempts due to cost.
If we do a Mars mission without the tech to sustain our presence there, that's the only mission we'll ever do in our lifetimes. I doubt anyone here wants that, as bad as we all want humans on Mars.
Why are we going to baseline this? A Mars mission without closed loop ECLSS requires slightly insane mass, given current lift capabilities. CL-ECLSS is, more or less, a hard requirement for any realistic Mars mission.
For a crew of four, assuming a 600 day surface stay (or shorter stay and contingency consumables, however you wish to think about it) and 360 day round trip transit time, that's well north of 140t to LEO, never mind the mass required for TMI. We've never landed something with the mass that the surface habitat would require, in consumables alone, for a stay of that length. Why concern ourselves with how much it would weigh?
Once development has been completed, let's fly VPCAR and TSAC aboard ISS and see how well that works.
CL-ECLSS and ISRU make the mission doable from a mass and cost perspective.
To keep ISS resupply and construction commercialized, F9/F9H, Atlas, and D4H should be used. There should be no SLS flights to ISS unless it's delivering a cargo intended to further our manned space exploration objectives.
I think the crew quarters, galley, shower, and head should be in one module and the station keeping system contained within another module. Instead of trying to design a module that can perform all required functions, keep it simple. There's a countdown on these development activities. The solution doesn't have to be perfect in every conceivable way, just functional. Obviously the solar panels need to be upgraded to provide more power for electric thrusters, so that's the first activity to fund.
No, there's no way to support another STS mission. The launch and recovery infrastructure has been destroyed or decommissioned.
If I had my way, all the orbiters would be taken from the museums, the avionics would be upgraded and structural enhancements made to the landing gear, and flight capability restored. From there, the vehicles would simply be stored for future use. Instead of paying lip service to having a contingency flight capability, we'd actually have hardware available for that purpose should the need arise.
There's no point in actually flying an orbiter if other less expensive vehicles are available for the same purpose. STS should be used for high value cargo recovery only.
Exactly, Rob. Orion is an egregiously expensive gimmick that serves no space exploration purpose.
If SLS can't get it's payload to orbit with two stages, its design is also an egregiously expensive gimmick.
We can only afford so many gimmicks and still have funding for the technologies required to get to Mars.
ISS will never serve any broader purpose as long as current ways of doing things prevail.
As long as NASA is applying the scorched earth methodology to the development of space exploration technology, ISS is the next logical thing for them to destroy.
I look forward to the day when ISS is literally transformed into the inferno for taxpayer money that it has always figuratively been.
Let's not waste any more time worrying about how we can salvage something we were never using to its potential to begin with.
Whether sensible or not, out with the "old" and in with the "new".
There was nothing "worn out" about STS except for all the excuses and failures to provide a more economical and capable replacement or complementary capabilities like SLS.
As I've stated in another thread, funds could have been devoted to upgrading the avionics and ECLSS for STS and automated methods for repairing or replacing the STS TPS could have been developed. Congress could have mandated that the components for STS and SLS be manufactured and assembled in one location. Those simple cost saving measures never materialized because there was no economic incentive on the part of the contractors to do so and there's no political support because everyone wants a piece of the pie. There's simply no good reason why a partially reusable spacecraft had to cost so much. It was an entirely contrived aspect of the program. If Congress wanted to dictate something to NASA that made sense, that made all the sense in the world from an economic standpoint.
There's also no reason why ISS should have cost $100B. Something akin to SLS should have been in development with STS, using common hardware. The 5 segment boosters and ATK's proposed Dark Knight boosters contribute very little to the actual performance of SLS, but cost billions to develop. If even the slightest amount of practicality was applied to the SLS development program, a 5 engined core stage would have been developed and a more energetic propellant used in the same basic SRM design utilized by STS.
STS had one capability that capsule systems lack- the ability to return with sizable and heavy cargo. If SLS was not designed to return the expensive RS-25's for refurbishment and reuse, then a STS flight should have accompanied every SLS flight to retrieve the hardware. At $72M a pop, they're too expensive to dump in the ocean after less than ten minutes of use.
If SLS was available to construct ISS with, it would not cost $100B. ISS has been durable enough to remain on orbit for more than a decade. The MDM's on ISS have only been replaced once and upgraded once, that I know of. The Apollo, Saturn V, and Skylab programs incorporated analog and mechanical systems for control purposes. In short, analog and mechanical methods of systems control are heavy and less capable than digital systems.
We've yet to test a high reliability, fault-tolerant closed loop ECLSS subsystem or artificial gravity generation aboard ISS. I'm starting to think that that's never going to happen, so why not bring it down when Russia is ready to take back their station modules to save money and start development work on Skylab II? If it were up to me, I'd bring it down today.
Right now one of the Russian modules is required for station keeping. NASA has been tasked by our president with developing advanced propulsion technology for space exploration. There's no reason why this same technology can't be used on ISS for station keeping. If anything, it reduces the mass of propellant required for station keeping and upgrades its power generation capabilities. If we're going to insist on maintaining ISS, why not do it in as economical fashion as practical and simultaneously test tech required for exploration?
I've never said or thought that anything Russian is bad. In my mind, the Russians are imminently practical and come up with simple ways of doing complicated things that show true ingenuity. However, their internal system of governance has been at odds with ours for decades and that's not likely to change in the future. Unfortunately, that means that we have to come up with ways of making our own tech work if we're not able to rely on them as equal partners in our space exploration endeavors. I would like nothing more than to see both of our nations set aside their differences when it comes to space exploration. Reality says that that might not continue.
If NASA wants to lose ISS rather than come up with ways of making it work using American or European hardware, that's their prerogative. If they can't respond effectively in a timely manner to requirements for station keeping tasks, how could they possibly do something significantly more complicated like mounting a manned mission to Mars? Absolute perfection isn't required for every single task and NASA needs to learn the meaning of "good enough".
NASA had decades to work towards replacement of STS and produced a lot of nothing. A few good ideas, a mountain of bureaucracy, and a dash of propaganda don't amount to an effective and sustainable space exploration program.
Regarding burning the ships, NASA destroyed the STS infrastructure. There was no compelling reason to dismantle all the infrastructure that made STS work, however poorly, especially given the insistence on using STS hardware for SLS. The only way using STS hardware for SLS makes a little bit of sense is if the two programs are operated in conjunction with each other. Unsurprisingly, there's no budget for that because we have make-work projects like ISS to suck funding and we have our prime contractors on cost plus contracts to de-incentivize on-time and within-budget delivery.
Succinctly, if we want to reconfigure ISS to incorporate technologies required for space exploration, like artificial gravity, active radiation shielding, closed loop ECLSS, ROSA and SEP for station keeping, SEP tugs to haul space junk back to ISS, and adding a manufacturing and repair facility to repurpose the space junk, then ISS and commercial space flight programs have a reason to exist. If not, we're just throwing money at ISS maintenance and supply.
Getting rid of the old Russian modules will force us to come up with our own solutions to replace the few capabilities lost when they leave and is a step in the right direction.
Congress isn't interested in a Mars mission. Their interests lie firmly in how much of the federal budget they can win for their districts. If you're interested in a sustainable heavy lift capability, you don't use the most expensive and complicated hardware ever devised to replicate the capability of existing hardware that was intended for that purpose. If SpaceX doesn't come up with a functional equivalent to Saturn V that costs less than SLS to operate, we're not going to Mars within our lifetimes.
Even if we just approach this from the perspective of what would most easily and affordably maintain our ability to commute to ISS, funding three different systems doesn't make any sense. We don't need Cygnus, CST-100, Dragon, and Orion to transport personnel and supplies to ISS. The good ideas need to be separated from economically viable ideas.
The Skylab II concept from Gray Research Inc is the closest thing I've seen to what NASA actually requires for deep space transit. If we weren't spending three billion a year on ISS, we might have enough funding for a next generation space station / deep space transit habitat. If NASA is at all serious about space exploration, it has every incentive to kill ISS funding. However, they're trying to artificially create demand for spacecraft and launch systems where there isn't any by forking over fast sums of money to multiple service providers. At some point, NASA is going to have to prioritize funding if they don't want to be stuck in LEO for the foreseeable future.
After decades of operations conducted at multiple space stations, is there still a lot of critical science work that must be performed at a space station in LEO in order to advance human space flight activities required for a Mars mission?
We could use ISS for closed loop ECLSS experiments, but that's about it. ISS will never be used as a staging point for future manned exploration missions because there's no mission benefits, as far as I am aware, to going to the station first. What would it matter if all partners involved wanted to bring the station down in 2024?
Is ISS merely a destination for astronauts/cosmonauts to go to to maintain the appearance of doing something necessary or relevant for future manned space exploration missions or is the platform critical path for NASA's stated manned space exploration objectives?
In order to gain experience required for future long duration deep space missions, sooner or later we're going to have to actually build and test deep space habitats, radiation mitigation technologies, and advanced propulsion systems. We're not going to do any of that aboard ISS.
With or without international cooperation, ISS is an enormous funding suck and isn't advancing our manned space exploration capabilities. ISS could have been many things, but thus far it has been an orbital construction project and microgravity exposure experiment and little else. If the Russians are serious about further manned space exploration, they likely see ISS in the same light. There's a political component to it, but from a practical perspective maintaining ISS won't advance any manned space exploration objectives.
The only option that's viable for future manned space exploration is to design, built, and test a new class of space exploration habitat capable of long duration missions. This could be viewed as a deep space transit habitat or space station. I guess it all depends on what type of propulsion module is connected to it. Russia is moving on to space exploration and science objectives that are of interest to them and I think we, and our international partners, should do the same. If our space exploration objectives coincide, then cooperation is mutually beneficial.
I think getting rid of the ISS maintenance task is beneficial to all involved. If US and/or foreign companies find benefit in maintaining the space station, that's fine. If the Russians want their modules back, give them their modules back. The future of manned space exploration does not depend on Russian ISS modules.
The more and more I think about, the worse the idea of sending people to Mars in a tiny tin can seems.
As someone who has spent time in small spaces with lots of different people, I can attest that not everyone takes confinement all that well.
Something even bigger than Skylab may be required to keep everyone sane.
That Skylab II concept NASA is floating is looking better every day.
GW,
So, if the multiple O-ring design was an issue with the STS SRM's, have the SLS SRM's switched to using a single O-ring design? If not, then there's no change between STS and SLS, so that's not a valid argument for why STS was "unsafe" (bearing in mind that there's no such thing as "safety" that exists anywhere except between someone's ears).
Regarding avionics upgrades, would it be easier to develop new avionics for an existing vehicle for which there was lots of experience from actual operations or a completely new vehicle with unproven flight characteristics?
I agree that a giant rocket isn't necessary, but it does make some aspects of operations simpler. It made no sense whatsoever to build an expendable launch vehicle using the most expensive reusable hardware ever devised. NASA should have simply declined that Congressional mandate. If Congress wanted to shut down the manned space program, it could have. However, if everyone at NASA stood firm on that position, Congress would also have suffered the backlash from their corporate owners and public opinion. It's just a jobs program at this point. We can sugar coat it any way we like, but it is what it is.
At this juncture, we're going to get a giant rocket whether it's needed or not. Given the length of time SLS has already been in development and the length of time it will be in development before its first flight, I don't think there's any way that it could have been more expensive to simply re-create Saturn V. If we'd done that, we'd have a 130t class rocket as a starting point.
For the asteroid mission to be anything other than a colossal waste of time and money, NASA would need to do three things:
1. Develop a habitat module suitable for deep space transit.
2. Develop a space propulsion system capable of transferring the habitat module in a simple and timely manner.
3. Develop a rocket capable of economically lifting the habitat module and tug to LEO.
Naturally, there's no funding for any of this and no rocket to launch the hardware with. It no longer matters because the money and time have already been wasted.
Here's what "doing it right" involves:
1. Develop a launch system that is actually capable of launching payloads with the mass required for manned deep space exploration, not something that might one day be capable of launching the payloads after many more years of development and billions expended.
2. Develop a space propulsion system capable of taking the crew to the intended target in a reasonable amount of time with minimal operational complexity.
3. Develop a habitat that is durable and fault tolerant enough for long duration missions.
This means that expensive STS hardware designed for refurbishment and reuse, an expensive new capsule system incapable of carrying the supplies required for the transit, and propulsion methods that require months for orbital transfer are unsuitable technologies for meeting these requirements.
The development of a small space capsule system incapable of landing anywhere but a terrestrial ocean was and is completely useless for deep space exploration. Orion has no reason to exist and it never really did. Even its intended use for lunar missions did not require it. There was never any real reason to retire the Space Shuttle. Someone managed to convince NASA management that STS was "unsafe" (as if the entirely fictional human brain construct called "safety" ever existed to begin with).
The criticisms regarding the sustainability of the Apollo and Saturn programs seem to apply to an even greater degree to the Orion and SLS programs. There is simply no way to make the current RS-25's and SRM's economical to use. Using two very different propulsion technologies for the launch vehicle's first stage was, is, and always will be more expensive and more difficult than using a single propulsion technology.
I'm not a fan of the STS program, but it was and is real flight hardware that does not require further development for use. I think its familiarity bred contempt for it, but its replacement is "something new" as opposed to "something required".
There is no way to "fix" the asteroid mission, apart from making it an actual deep space exploration mission that we can't do because we're still not developing the hardware required for the task.
Sometimes you have to admit that you made a mistake. Orion was a mistake in no uncertain terms. SLS was a mistake (the implementation, not the concept of a HLV). These mistakes don't have to consume any more time and money than they already have, but there's no way for anyone in the government to admit to making a mistake without forfeiting their job.
Quaoar wrote:GW Johnson wrote:There's at least two wildly-different versions of gas core, too.
GW
Which are?
I can think of three off the top of my head. Nuclear Saltwater, Nuclear Lightbulb, and Coaxial.
The type of GCNR I had in mind was a coaxial flow open cycle vessel using Americium fissile material and tungsten seeded hydrogen propellant. The reactor would probably have a toroidal core shape to inhibit fuel loss and maximize the propellant's exposure to the thermal flux produced by the core. This complicates flow somewhat but also solves lots of other problems. Ideally, initial models would not require external radiators and thus would be limited to an Isp between 2500s and 3000s. I want to determine how small a reactor could be created to replicate the thrust level of the RL-10 and retain desirable operating characteristics (relatively small quantity of fissile material required for operation, low fissile material loss, modest operating pressure, lightweight moderator, no external radiator required for heat rejection, minimal seeding material required for nozzle cooling).
The tungsten-seeded hydrogen propellant can protect the walls of the containment vessel and nozzle for thermal flux required to achieve an Isp of up to 7000s. With a system that achieves an Isp of up to 3000s, no radiator is necessary. For Isp ranges between 3000s and 6500s, a radiator is required. One of the odd but serendipitous things determined through actual experimentation was that the seed material was only required until the hydrogen was heated to 15,000K, at which point it rapidly became opaque (absorbed radiated photons from the UF6 plasma) at the operating pressures involved. Increasing the operating pressure increased the opacity of the propellant.
Actual experimentation with Americium demonstrated a dramatic reduction in fissile material required to sustain fission. Using UF4 and UF6 for fissile material requires much larger core radii or a more reflective (heavier) moderator. It was determined that there was an optimum moderator thickness of about .46 meters (if using UF6, not Americium). The moderator accounts for a significant portion of the system's mass (unless a higher Isp is desired, at which point radiator mass is a significant portion of the system's mass).
Everything I've read says that this is entirely doable with current materials tech and simply requires funding. If I'm wrong, then I am, but all the scientists who actually did experiments directed towards development of this technology had results that were favorable for continuing development. Then the politicians killed funding.
I advocate for development of NTR tech because it strikes a balance between power and efficiency. If we complete the argument Impaler made in his last post, either more power generation mass or more reaction mass are required to "go faster". The Boeing SEP tug is already at the limit of what a fully evolved SLS booster could lift. If more funding was directed to SEP technology development by canceling costly and redundant capsule systems (Orion and CST-100 immediately come to mind), then perhaps by the time SLS is ready to fly we could have a SEP tug ready to test as well. Impaler shot that idea down.
We can spend money on Cadillac class capsule systems that don't carry the supplies necessary to make a trip to Mars or we can spend money on the propulsion and environmental control tech required to simply get us there and then concern ourselves with how fancy our ISS servicing spacecraft are.
I don't want to wait 20 years for tech to "improve", I want to know what we can do between today and the time SLS is man rated. Why waste time and money playing with space rocks or developing 3 different vehicles to service ISS when we can send a SEP tug and dummy payload to Mars?
I think it's reasonable to want to spend half of your mission time on the objective. I think it's reasonable to want half or more of your mission mass to be payload mass rather than power and propulsion mass. A solid core NTR wouldn't permit that kind of payload fraction, but if a gas core NTR proved feasible then we'd have a much more desirable payload fraction.
NASA spends what little money is allocated for nuclear power and propulsion research trying to re-create the fuel rods for solid core NTR's. Using Uranium fissile material and solid core NTR's are technological dead ends for space exploration. We already know that solid core NTR's using Uranium have undesirable mass fractions and that's not going to change. That is why I proposed development of an Americium fueled gas core reactor. The size and mass of the reactor are dramatically reduced by using Americium as the fissile material.
If, through experimentation, NASA determines that gas core NTR's are not technologically feasible then so be it. At least we'll know what is and is not feasible, rather than focusing on what's easy to do with current technology. I would think that this would be a more productive use of the nuclear engineers and scientists. If no quantum leaps in materials science or nuclear engineering are required, then even if it costs real money to develop into flight hardware, I think it's worth the effort and resources required.
With respect to nuclear propulsion technology programs supplanting existing electrical propulsion technology programs, that should only happen if the new technology provides some sort of required capability that existing technology can't provide and aren't likely to provide with further development. This is unlikely. I think of nuclear propulsion as a complementary technology. If the developmental states of these two technologies were reversed and electrical propulsion tech was developmental and nuclear propulsion tech had 40+ years of development and space flight backing it, I would still want funding for development of electrical propulsion.
The notion that we should only use whatever tech is available right now and completely ignore other propulsion options is ridiculous and demonstrates very narrow minded thinking. Every advanced technology has developmental challenges to overcome. Absent a crystal ball to peer into, I think it's prudent to devote some resources to a range of options.
To their credit, Boeing is actively looking for ways to reduce the cost and weight of the ET. Robotic FSW and spun domes are part of the initial plan and composite tanks and thrust structures are further down the road. Testing on sub scale test articles was completed last year. If testing on full scale test articles goes well, SLS would come really close to the 130t target with advanced solids and the 4 RS-25 core stage.
I'm crossing my fingers and praying to the rocket gods.
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.