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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.
kbd512: Which plastic are you thinking of? What is its embrittlement temperature? How does it withstand vacuum?
I'll let the people doing the work provide the explanation:
If NASA makes a deep space habitat out of aluminum, given their understanding of the radiation environment, then they can stop with all the radiation danger hoopla.
The researchers who think an aluminum can is a good deep space habitat probably haven't been exposed to too many SPE's.
A habitat of that volume would certainly provide more storage.
Astronauts of the Sea. Shipped direct to Mars in fantastic plastic.
kbd512: I'm rejecting your 'counter examples' because they are not remotely good for a basis of comparison. A Sterling RTG is the combination of two VERY old and simple technologies operating at low power density, not to mention it is a physically small device (completely incapable of doing any of the propulsion work we have been describing) which lowers development costs further. The idea that this device development cost would in ANYWAY be predictive of something like a NTR or god-forbid the GasCore NTR is appallingly dishonest. You might as well have pulled out a home smoke-detector and told me because it contains radioactive Americium that it proves Nuclear technology is cheap.
I don't think any example would be satisfactory to you, short of a lightweight reactor falling from the sky and into a thrust structure of a Mars bound vessel. The premise in your argument was that any nuclear reactor requires billions to develop and decades of research. The NTR's produced in the 60's and 70's were created by men who didn't have access to a calculator, but with all our technological advantages and materials science advances, we're grossly incapable of creating a nuclear reactor for use in a spacecraft? Why? Because you say so?
I am again going to call BS on the 3000s - 6000s ISP for your GCNTR, thouse are pie in the sky theoretical limits that assume no heat transfer to the engine itself. Our current rockets engines and nozzles are already at the very limits of material science to not melt from the heat of the exhaust, the solid core NTR has thouse same limits plus the limits of it's core material melting, all the ISP gain of the NTR is from the use of pure Hydrogen propellent, the temperatures are the same as current rockets. The Gas core would get around the core material limits but you still need a chamber to hold pressure and a nozzle to create thrust thouse things have walls and that wall is made of metal, so no higher temperature or ISP is possible.
Yes, without a magnetic nozzle a gas core reactor would slag the nozzle and slag the containment vessel. What's the exhaust temperature like for VASIMR? I've seen those things slag the instruments mounted behind them in seconds, but somehow the nozzle and device remain in one piece after literally thousands of firings.
Unless you start talking about magnetically contained Plasmas, at which point your engine is going to require huge magnets and starts to look like a Tokamak, dose this sound even remotely cheap to develop to you?
So now you're comparing a reactor operating at tens of thousands of degrees to a fusion reactor operating at tens of millions of degrees?
Stop throwing around these nonsense theoretical numbers off Wikipedia and telling me they are 'doable', no one has a clue how to build gas-core your describing or what kind of performance it would actually have after countless engineering compromises that would inevitably be necessary. As far as I'm concerned it's like telling me the ISP of antimatter, and for all that herculean development work your ISP is no better then SEP is getting RIGHT NOW.
The numbers come from the papers published by the group working on the reactors. Since, as you stated, we don't have any gas core reactors, what type of engineering compromises are you referring to? The herculean development effort was from a group of men far fewer in number than we have working on SLS. We're going to spend billions to develop a chemical rocket that can't put a payload into orbit that weighs as much as a Space Shuttle. Somehow that's Jim Crack dandy, but spending the money on a nuclear reactor is a waste of time and money?
And would everyone stop with the conspiratorial BS that some cabal of government/aerospace have been intentionally stopping us from going to Mars, your channeling some Zubrin really hard here. Their are absolutely VAST technological gulfs between us and Mars and limited funding to overcome these challenges, statements like 'we could have been on Mars in 1980' are pure crank nonsense on par with Moon-landing-Hoax stuff.
What else do you attribute the complete lack of progress in space exploration for that past four decades to? You're worried about how much a gas core reactor costs or how long it takes to develop? The companies that NASA likes to do business with have literally expended tens of billions of dollars and I can't seem to find a single article of flight hardware designed for manned space exploration that's been produced in that time, unless one counts doing donuts around the Earth as manned space exploration.
Yes, if work had continued on NTR's (because the hardware was all but flight capable by the time El Presidente decided to pull the funding) and Saturn V wasn't dumped (because it was too expensive, whereas the far more costly Space Shuttle was affordable) we'd have had flight hardware capable of going to Mars. All manned space exploration stopped when the Apollo, Saturn, and NTR programs were cancelled. Everything that's followed has been about making someone a lot of money. In short, we now have a bureaucracy to doll out funding for pet projects, stroke egos, and provide the appearance of doing something while not actually accomplishing any space exploration.
Boeing and others want to find as many ways to not accomplish a Mars landing as possible. It keeps the millers milling and the money flowing. If you're on a cost plus contract, you have no economic incentive to deliver anything on-time and within budget.
There's landing on Mars and then there's building lunar bases (not landing on Mars), building orbital propellant depots in LEO/LLO/LMO (also not landing on Mars), and playing with space rocks (something that's completely unrelated to landing on Mars).
All of the so-called precursor missions are synonyms for "not going to Mars".
There are real problems with a Mars landing and then there are contrived problems. If we busy NASA with enough tasks that don't directly solve the problems with getting to/from and landing/living on Mars, then there won't be funding for the technology to make the landing possible.
kbd - I think you misunderstood my point. What we don't have info on is how well people perform when put into mass-adjusted suits on a low G body like Mars or the Moon after prolonged exposure to zero G (we know they recover well on Earth, and we can probably hazard a guess they will perform quite will with special suits to simulate gravity on Mars or Moon). So you need the preceding phase of zero G to simulate the journey to Mars. That's why I argue for an analogue mission to the Moon - which is only 3 or 4 days away (so a rescue mission could be mounted).
I was trying to make the point that I don't want to "experiment" with whether or not humans bounce back like flubber after we've gone to the trouble and expense of transporting them to Mars. I advocated for the use of a 1G rotating habitat, better known as a wheel, that would take them to their destination in perfect operating condition. If there was any need for them to immediately leave their spacecraft to go somewhere else, as may be the case if they had a hard landing that damaged the spacecraft, then absent any other injuries they would be in good physical condition and more likely to succeed in the attempt.
It's called risk reduction. We could leave the astronauts in microgravity for six months and they would indeed survive the trip and there's no question in my mind about that. However, I want the crew to be fully functional from the moment they land and I don't want them passing out during any moderate to high G entry that may be required (hopefully high G deceleration is not required, but the Mars EDL program is not far enough along for the types of payloads we're talking about to know with any certainty) to assist with deceleration from orbit.
Robert, the EML2 point has the significant advantage of lower delta-V requirements since it's pretty much at the edge of the Earth-Moon system, gravitationally, and also has ready 24/7 access to the Moon and/or Earth for gravitational slingshots. It does make sense to have a space station there, more sense in fact than LEO.
Of course direct to Mars or LEO rendezvous makes far more sense for early missions to Mars. In the long term an EML2 station makes sense, but right now it's just pork.
How are we going to use solar power for anything if we park a space station, orbital transfer vehicle, or any other type of spacecraft in the shade when it requires sunlight to operate?
I said that solar panel technology can be developed to high power density for modest costs, not that building the whole tug is that cheap or that the cost of launch it into LEO is cheap. This means it is pointless to try to develop nuclear POWER systems for use in inner solar-system space, solar already crushes them even the proposed Sterling RTG concepts which is what I think your talking about from LANL, that kind of system is only 4x the power of RTG's and while it would be nice past Jupiter on a probe or on planetary surfaces, but it is inferior as an in-space power source.
You stated that nuclear technology requires spending inordinate amounts of time and money to produce a result. I provided a direct counter example that demonstrated that people who were more interested in producing an efficient piece of hardware that was not insanely expensive of complicated to produce could, and in point of fact, did produce a piece of hardware without requiring an inordinate amount of funding. The LANL reactor is a fission reactor, designed for spacecraft, that produces more power, weighs less than the RTG technology it replaces, and there's nothing terribly complicated about it.
Every time I point out a flaw in a nuclear system you seem to jump to something else with out regard for it it is an engine or a power source or even the slightest concern for scaling or for the TRL. You've jumped now between no less then three different technologies that only the Nuclear word in common and are trying to treat them as one thing that somehow has all of the superlatives of each but none of the downsides, it's like some crazy tag-team wrestling match against team Nuclear.
In what way? By providing counter-examples? By stating that nuclear technology is not impossible science fiction technology? Yes, nuclear technology has downsides. Every technology does. So what?
You know very well that our launch vehicle costs are completely separate from our TMI vehicle development and fabrication costs so don't try to bring in any hysterics about what SLS or any other launch vehicle costs (and yes SLS costs too much), all the Initial mass on the ground costs huge money to become IMLEO, we will use the best launch vehicle we can find in the end. The lower the launch vehicle cost the less we should spend on expensive TMI stages.
Launch costs always have to be factored into the cost of actually using any given piece of technology in space. Claiming that launch costs aren't a part of the implementation cost is intellectually dishonest. If the number of required launches didn't matter, then we'd just stick with using chemical propellant rockets because that technology is available today and has been available for decades.
If you want to go by DRM 5 then you need to actually look at what kind of payload fraction the NTR stage actually gives, it's 300 mt of NTR stages (at 875–950s ISP, not one bit of downgrading from NERVA) to push 60 mt of habitat LEO->LMO->LEO. As I said earlier SEP are looking at stage masses COMPARABLE to the payload, not 5x larger, and when I say they need a bit more propellent to do a return leg that is not with refueling at Mars, that's just another ~50% more propellent at outset so you end up with a stage that is between 1.5 -2 times the size of the payload. This simply crushes NTR which required 9 SLS launches in DRM 5, the new Boeing plan is 5-6 AND brings most hardware back to LEO for reuse so each subsequent mission is even fewer SLS launches, by your own standard NTR is what is stupid if you even take a cursory glance at the numbers.
I have never advocated using solid core NTR's, but I was pointing out that the technology doesn't require kick stages to get out of LEO or back to LEO (since we're trying to get rid of that inefficient chemical propulsion technology and replace it with something better), the solid core NTR technology gives your transfer vehicle a round-trip transit time of around 12 months, and yes, I was confusing what I advocated using when I was making the comparison about mass. I made a huge mistake in the comparison. In my mind I substituted a gas core reactor's efficiency and required propellant mass for a solid core reactor's efficiency and propellant mass, because using an inefficient design is just stupid. You're right, you're right, you're right. Did I mention that you're right? Well, guess what? You're right.
If a gas core reactor is three times as efficient or better, and we know how efficient a given reactor core design will be at accelerating our propellant based on research conducted decades ago that determined how specific heat affected mass flow required to achieve a given level of thrust, then our gas core reactor will provide a specific impulse ranging from 3000s (doable) to 6000s (possible, but considerable materials development required).
If we triple our efficiency, then our propellant mass shrinks appropriately. We're still left with a heavy reactor due to shielding requirements, so what can we do about that? Well, the core cross section of a reactor fueled with Americium instead of Uranium Hexafluoride or Uranium Tetrafluoride can be reduced between 60% and 70%, depending on design, and still produce the same specific heat.
No massive radiators were or are necessary for NTR's. The heat is transferred to the propellant. Still less efficient than a Hall thruster? Obviously, but there is no spiraling out because the thrust generated is much higher, no kick stages or refueling of kick stages is required (and reverting back to chemical rocket technology to transfer orbits reduces the overall efficiency of the transfer vehicle), no massive and delicate solar arrays to fly through a shooting gallery with, and you get there as fast as a conventional rocket will reasonably take you (about six months). Since you keep talking about Zubrin, I will finally channel Side Show Bob here, "Lift and throw."
When Boeing, or anyone else for that matter, has a SEP tug that can transfer orbits without reverting back to using chemical rocket technology, capable of pushing a payload of equivalent mass as a chemical or NTR powered rocket in the same time frame, while requiring the same number or fewer heavy lift launches, then you'll have a technology that's superior to NTR technology. I don't think such a vehicle exists, but I'd love to be proven wrong.
For crying out loud, a GCNR is a science fiction engine, TRL of 1, you have NO BLOODY CLUE what it's power density would be of IF it could even be built, or what mass it would be and what launch vehicle it would need, you might as well be talking about the power density of anti-matter. Solar technology is mature and scalable the engineering to make the array level power density higher is just engineering of deployment structures and trusses the theoretical limits are what the cells alone would produce, this is dirt simple engineering compared to any kind of nuclear system. The ROSA array was developed with a NASA grant for a few MILLION dollars, the power density is 200-400 W/kg at the wing level according to the manufacturer. Their difference in the nearness and cost to get more power and more power density from solar vs nuclear is just staggering, the nuclear stuff is Billions of dollars and decades vs millions and a few years for solar, how are people so grossly misinformed, who is spreading all this garbage?
I was going to stop talking about this, but given your insistence on this nonsensical idea that everything that hasn't fallen into our laps must necessarily cost billions or take decades…
LANL designed, built, and tested a reactor, yes a real working nuclear reactor, for small spacecraft power in less then a year and for less than a million dollars. I'm certain that if we had involved some defense contractors we could make the project cost billions and last for decades… Kinda like STS and SLS.
By your logic a SEP tug is science fiction because it's never been built. We DO HAVE A BLOODY CLUE about what the power density would be because real research was funded by the same organization funding SEP technology because at one point in time in this country real people were really interested in going to Mars. You want to talk about spreading garbage? That's garbage.
We can have a SEP tug for a few million dollars? In what universe? Certainly not this one because the SLS launch it requires is forecasted to cost billions, never mind the fact that SLS has never flown, which also makes it science fiction by your logic.
Nobody has ever built an anti-matter rocket engine. We have videos of the nuclear rocket engines developed in the 1960's and 1970's. I guess if you didn't see it with your own eyes then it never existed.
I'm talking about actual hardware that's either exists now or is about to come out of the lab, if your going to talk science fiction nuclear systems then I'll come back with Fusion powered Magnetoplasmadynamic thrusters that could theoretically put a Megawatt of power through a device the size of a 5 gallon bucket and produce 200 N, and these things have actually been made and operated in labs.
As long as you're talking about nonsense, by all means, keep going.
SEP tug stages, solar + thrusters + propellent + tank are expected to be about the same or LESS mass then the payload and will move the payload from LEO to LMO with a stop at L2 if you wish, add a bit more propellent and you can move your payload BACK to LEO/L2. They beat NTR in payload fraction even for the simplest TMI in which the payload has to make a direct (dangerous) entry to Mars atmosphere, but the SEP can give you soooo much more, a parking orbit without a heat-shield, return to Earth and then reusability of both the tug AND the payload. Will the SEP tug need Heavy-lift? If your monolithic payload already needs heavy-lift then it would be stupid not to use it for lifting the stage too, EVERY TMI stage ever proposed have been comparable in mass to the payload it pushes through TMI so it has commonality with the launch vehicle that puts the payload in LEO, the question is how MANY TMI stages you need, SEP has by far the best ratio at 1:1 with the potential for 1:2 if we can get into the 20-30k ISP ranges.
So this SEP tug weighs about as much as the payload it's pushing or perhaps a little less, takes just as long to get to where it's going as any NTR powered vehicle would, and requires additional propellant to make it back to LEO, but somehow that's cheaper and more efficient? NASA's Mars DRM 5 proposed the use of conventional solid core NTR's, downrated the efficiency of the engine of the exact type they wanted to use had demonstrated, and the transit vehicle was designed to go from LEO to LMO to LEO without refueling. Oh, and from my perspective it would be stupid to require the use of more heavy lift rockets that cost well north of a billion dollars per launch.
Assuming Russia's plan has the size I calculated from their image, total size is 105,800 square metres. An American football field is 120.0 yards × 53.3 yards or 6400 square yards = 5,351.215104 square metres. So the solar array area is 19.77 American football fields.
Yes, but our solar tech is better than their solar tech.
Maybe Impaler can tell us how big a vehicle we're talking about to move the mass of the tug and a 110t payload from L1/L2 to Mars.
I don't recall seeing exactly how much area Boeing envisioned for their SEP tug or what the mass would be, but perhaps I didn't read carefully enough. I've gone through various proposals from Boeing, NASA, ESA, and others. All of the SEP powered transfer vehicle proposals I've seen are fairly substantial and require heavy lift.
I don't give two hoots about using chemical, solar electric, nuclear electric, or nuclear thermal to get to Mars. There are problems and benefits associated with each solution. I've already stated the reasons why I think nuclear propulsion, done the right way and with the right tech, is preferable and won't belabor the point any further.
I just want to figure out what our chances of shooting ourselves in the foot are with whatever tech we use to get there.
If we fly a vehicle with a large enough surface area through as much space as we're going to cover to make the transit, we're bound to hit something along the way. If we use SEP, will the damage be catastrophic or does it merely degrade performance? I'm curious to know what our options are for damage control to maintain a powered transfer when that happens.
Is there a way to deploy a lesser portion of the total surface area of the solar panels to move the tug away from what little remains of Earth's atmosphere in LEO? These solar arrays have substantial surface area, so I presume that's been factored into their design.
I have reservations about the size of these things and how delicate they are, but if it works reliably then it serves the requirement and removes another reason for NASA to stall the mission.
It is possible, although never demonstrated that the tech can scale up, as Impaler has noted, but my understanding is that even in LEO the Space Shuttle was and ISS is routinely peppered with debris.
What happens if one of these arrays or the truss supporting it is hit with something the size of a marble?
I would presume that the likelihood of simply damaging a panel is far higher than damaging a support structure, but is any of that been baked into the hardware design and mission planning?
I know what the Technology Readiness level of NTR is and it only a 5-6, it was NOT completed because completion would be involve demonstration of a system in space to achieve TRL of 8 a 'flight qualified system'. SEP is already a 9.
The performance of the NERVA system is simply obsolete now, the mass sent through TMI is only 50% more then a chemical booster, that's not even worth investing in even if SEP did not exist.
So NASA is spending what little funding it puts into nuclear propulsion to re-create a solid core reactor that isn't worth the investment. Makes perfect sense.
SEP mission durations can be as short as any chemical mission, stop repeating this garbage based on unmanned probes. When we send robots to Mars chemical we send them as SLOW as possible for efficiency and for any single impulse event that is Holman transfer with is 8 months at most, low-thrust systems are capable of even slower and more efficient non-Holman trajectory but this is a WIDER RANGE that is being utilized. The only limit to speed is power density and the near term Solar power density that is already in the development pipeline will allow transits of comparable duration to any high thrust systems. The LEO to Mars period is not what we care about either, it is the High Earth Orbit To Mars that matters, the SEP vehicle goes to High orbit alone and then the crew take a fast Taxi of a few days to dock with it, THEN the relevant human mission duration begins. You know this so stop throwing out blatantly dishonest comparisons.
I've never had any problem with the length of the mission, but the throw to LEO for the proposed chemical solutions and the type of SEP vehicles being proposed is substantial. If we can afford heavier throws, I'd put the money into the payload.
And you are blatantly wrong on Free return trajectory, thouse do NOT last 6 months and they occur incredibly infrequently, like once every decade, the total duration is space is close to two years and the radiation dose would be terrible. They are not a remotely practical for a mission to Mars that intends to land, only Tito's crazy flyby mission is aiming to for that trajectory.
I have no idea why so much is made of the free return trajectory nonsense. Once you get to Mars you're not coming home for awhile.
For GRC protection Mars atmosphere is NOTHING, literally less shielding in it then the aluminum of the spacecraft you rode in. The Martian GROUND shields half a hemisphere and cuts your GCR dosage in half but that is it. If you want to shield yourself on Mars you need to get under neither several meters of regolith which is certainly possible but by no means trivial. Something like half of the total GCR dosage you get on a Mars mission is radiation on the surface because of the long 500 day surface stay, getting to Mars fast is not the ONLY solution to the radiation problem though every person with a 'fast' propulsion system to sell you pretends that it is.
You accept the radiation dose, don't do the mission, or put far more funding into lowering the incredible mass of the proposed active shielding. I think it's a solution in search of a problem. Short of burying the habitats and limiting surface stays, I don't see any other feasible solutions.
Your information is woefully out of date, Solar easily exceeds Nuclear power density in the Inner solar system (for in-space power, planetary surfaces are a very different environment), you need to be somewhere past Jupiter for Nuclear to be superior now. NASA is developing 300+ W/kg Solar arrays and theoretical limits are in the 1000 W/kg range. Nuclear systems simply can't reach that power density because they are thermal and need massive radiators and a whole working-fluid/turbine systems. This is what people ignore about Nuclear, they look at the mass of a core and ignore the rest of the system which is 90% of the mass and it's this part of the system which faces fundamental Carnot efficiency limits that give us little hope of a breakthrough improvement.
Are solar panels near that kW/kg threshold yet? Because that's where GCNR's operate at.
The heat has to go somewhere, but generally you want to convert that heat to power or heat propellant. If you start radiating the thermal energy from the reactor into space, you reduce efficiency.
A single Falcon 9 can lift an entire GCNR. The type of SEP transfer vehicle that Boeing wants to build to go to Mars with would require a SLS launch of its own.
Yes that's how long it would take with NO SUPPORT at all, the commercial and small funding deep-space probes Electric propulsion and solar panels would give us human-flight capable systems in that kind of time-frame. IF we actually invested heavily in developing it then that could be considerably faster. This is in contrast to nuclear systems which are moving at a rate of zero with zero funding. NASA should put it's money on accelerating something that is not completely dependent upon NASA, just like NASA should buy commercial launch rockets rather then build boondoggles that it is the only customer for.
I never said that NASA shouldn't pour money into the technology. I firmly believe that the benefits are worth the development funding.
No the technology has never been competitive with Solar for power, or with Big Dumb Boosters for propulsion, the 'politics' stuff is a BS excuse that Nuclear proponents have used for decades to nurse their failure and bitterness. I should hardly be surprised this sentiment is rampant on these forums considering Zubrin himself is absolutely dripping in this kind of resentment for politicians and half-concealed self-flattery "If only they had listened to ME we would be on Mars now!".
A failure of what? The people who developed nuclear power and propulsion for NASA didn't fail at anything. You can't fail at what you're never given a chance to attempt.
Resent politicians for acting like politicians? I think a good number of them can be pretty short-sighted but I don't resent them.
If funding for the space nuclear power and propulsion development effort had continued, we'd have visited Mars in the early 1980's, long before Zubrin ever started his rants about how we could go to Mars "DIRECT". That's all history, though, and I don't really care that much about the past since it can't be changed. Just because we wasted a lot of development funding in the past doesn't mean we have to continue to do so.
Double standard much, where are the 10 MW space based nuclear reactors ready to launch? Our largest Arrays is the ROSA from Deployable Space System at 63 m^3, a dozen of these would be used to create a MegaROSA system of 750 m^3 and 300 kw, less then one order of magnitude short of the football field in area and enough power for things like Asteroid Redirect, so actually not that far off. The ROSA arrays are set to become the new industry standard on commercial satellites too.
It's hard to develop a program when funding is pulled or never made available.
You 'accept' an error if you think nuclear systems are higher power density then solar. And everyone in the SEP system field acknowledges that the power density of the energy source is the Primary determinant of the overall vehicles performance because the mass of thrusters hardware is minimal and scales very well, and the propellent fractions are already wonderfully low, so low that we would generally want to trade that back for higher thrust and shorter duration, which requires more power. So yes it is all about the power source density.
I accept that gas core reactors have power densities that are at the theoretical limits of solar technology and don't have the limitations of solar technology. We keep going round and round on this point. The tech hasn't been developed because it hasn't been funded. I think solar tech is great and we could conceivably use it to explore the inner solar system, but that's about it.
Astronauts CAN WALK after returning from the ISS, as I said it is a myth that people are crippled by 6 months of zero-G, that kind of stuff only happened a decade ago when we did not have the present exercise schedules. It is a solved problem, the Astronauts will need 3 days of safety recuperation on the surface because of adjustment of the shape of the eye that makes vision blurry, this is the ONLY current restriction that Astronauts have now upon returning to Earth, they can't drive vehicles for 3 days after returning to 1 G, we would thus not expect them to make any EVA's for comparable period on Mars. They will be walking around in the Habitat just fine for thouse 3 days waiting to get out on the surface.
Bone decalcification doesn't disappear in three days and not all of the eye problems disappear in three days, either. If the astronauts don't have to go anywhere after they land then that may be fine. Alternatively you could simply avoid the situation altogether with artificial gravity. I have a feeling that if artificial gravity is a costly or insurmountable engineering challenge that lots of other aspects of the program would prevent us from moving forward.
I don't know what the solution to radiation is either, active magnetic based shielding is just one of many ideas that may not work. I just know that the solution is NOT passive Mass of ANY kind, their is hardly any difference between aluminum and liquid hydrogen (the best shielding) when it comes to stopping GCR, you would need a 200 tons of Aluminum and 100 tons of Hydrogen, both are equally unfeasible even if the later is half as much.
Active shielding for GCR mitigation isn't a critical technology for a Mars mission and that's the point I've tried to make. The better materials are for shielding from SPE's, not GCR's. I have no idea how a 400t-1600t active radiation shielding system would play into the SLS cost-per-launch equation, but I'm guessing it wouldn't be too helpful.
I doubt anyone is going to send people to Mars without an analogue mission to the moon. I agree with Impaler that AG is likely to prove a very expensive diversion in terms of both money and time.
Flying a transit habitat around the moon for six months won't tell us anything that we don't already know about microgravity.
AG is too expensive or complicated whereas active radiation shielding is some sort of requirement for a Mars mission? The tech for effective particle shields to deflect protons with gigavolt energies or better is guaranteed to be far more expensive and heavier than AG. All the concepts I've seen had impressive power requirements. Are we going to power the propulsion system with our solar panels or use it to deflect radiation?
If we stop using soda cans for habitats, that'd be a good first step towards reducing radiation exposure. There are lots of better materials for absorbing radiation than aluminum.
With respect to AG, humans weren't designed for microgravity environments and there's no getting around that. Microgravity poses actual health problems and just because someone is ambulatory doesn't mean the effects aren't real or lasting. All we need is for someone's corneas to be adversely affected on the surface of Mars to put all the ridiculous hand wringing about the effects of radiation into context.
We can establish how people will react by taking them to the Moon first in lunar orbit for 6 months, until landing on the lunar surface, where they can work in 1G weighted suits and their health can be assessed. The Mars habitat can be tested at the same time.
We already have plenty of data to discern the health effects of microgravity and radiation. We don't need any more human guinea pigs to tell us what we already know.
I think they will be able to cope. But we have to test it first without taking them to Mars would be my view.
I don't want to find out how well the crew fares when they're tens of millions of miles from home.
kbd512: Your critique of SEP is completely baseless. You seem to think that the technology can only work at small scale. That is where it is currently being used because that is the size of our unmanned systems like satellites and probes, the performance of the SEP is currently being used to reduce the size of the launch rocket and add multiple destinations/lifespan to satellites because this is most cost effective first utilization. But that has nothing to do with what scale it CAN operate at, it's like saying in 1945 that Rockets would never scale to bigger then a V2 because that's all that had been done so far.
Solar technology isn't even close to nuclear technology in terms of power density. If putting weight in LEO weren't a problem, SEP would be an enabling technology. However, reality being what it is, it's awfully expensive to put anything into orbit.
The only limiting factor to SEP scaling is the Solar, and we have a 40 year history of higher and higher power availability on every type of space vehicle. Electric propulsion systems and Solar arrays gain higher power-to-weight ratios as they scale up. This scaling up is not a simple as just making a bigger tank of fuel and a bigger rocket engine, we have to do significant redesign and optimization of lots of hardware but the direction has always consistently been towards a higher performance system that has positive scaling factors. It is just a matter of time and clustering of large numbers of solar arrays and electric thrusters into a single vehicle to create something that reach the size and pushing-capacity to move human spaceflight level masses.
And that might happen… In another 20 years or so.
I'm all for Technology development, and NASA badly needs to be allowed to redirect all that 'launch vehicle' boondoggle money into tech as the Obama administration tried to do. But I disagree on all of the things you've point at as worthy of development, the current crop of tech that NASA is looking at such as Mars EDL, and mitigating propellent boil-off are the best choices, they just don't have the budget to do more then the top few choices, and slowly at that. All of the technologies your asking for are on the other hand dead-ends or unnecessary and wouldn't in my opinion be deserving of any development funding.
Artificial gravity is a dead end? For who? Certainly not the astronauts.
Nuclear propulsion and power are politically unpopular. The technology works.
Nuclear rockets have always been pie-in-the-sky, they are impossible to develop incrementally on the ground due to radiation release, the ISP they offer is no longer remotely attractive compared to what a SEP system can offer right now, their is zero reason to invest in this technology and that's exactly what is being invested in it a big zero. I don't know why this forum is full of people who feel in love with Nuclear propulsion 20 years ago and never reconsidered that the mighty N might not be the ultimate solution to everything in space (I know the Hollywood movies certainly give this impression), but your ALL chasing a phantom that will never see the light of day.
Whereas those spacecraft with solar arrays the size of football fields are awaiting the next launch? Yeah, right.
I don't love nuclear propulsion, but I accept that splitting atoms produces more power than using photons to excite electrons. You seem to equate the efficiency of an electric propulsion system with the means of providing the electricity to it.
Artificial gravity sounds nice, but we have enough ISS experience to send people up for 6 months and have them come down into Earth gravity and be good to go in a few days, they are not cripples as some people like to exaggerate. In other words we can get to Mars in ISS derived habs and just recuperate for a tiny fraction of the surface stay time upon landing in lander/habitat, a trivial operational constraint that allows us to dispense with all the engineering of spinning stuff.
That's just what I want. A group of astronauts who can't walk without fainting after they've landed on another planet thirty million miles from Earth. All the engineering of spinning a wheel is too complicated? Wow. Maybe we should just be content here on Earth.
Radiation shielding against Solar Flares is basically a solved problem, we use a modest water tank 'storm shelter', every proposed Mars transit vehicle has included this for decades now and no one expects it to be a problem to built it or do it and it hardly adds any mass to the vehicle given crew water needs, this radiation presents NO barrier to NASA. Cosmic Rays are the radiation that is currently the show stopper and which NASA has no solution for because their is NO passive shielding solution short hundreds of g/cm^3 which is far beyond our mass budgets. Either we will find some kind of active shielding in space, discover that the dosages are less damaging then previously thought based on animal studies, focus on getting underground on Mars so the crew only gets the in-Space dosage, or just raise the chance of death threshold for astronauts. Radiation deserves study but we should absolutely NOT be down-selecting to 'passive shielding' at this time.
When I was speaking about better passive radiation shielding, I meant using better habitat materials than aluminum cans. Some of the mass estimates for active radiation shielding exceed the entire mass estimates for Mars DRM's, so without knowing which particular tech you're referencing, I'll leave it at that.
Sure Boeing is a contractor that is in it for profit and will not expend any profit to make a smaller portion but that is how Space x is different as its not a contractor. Also true that shuttle not flying should have been a savings but all that money was poured into SLS. Of course we do know that Nuclear power is a vital part for any manned space exploration as we have seen the numbers for a solar powered mission amass beyond even sls capability for a surface useage without adding in more launchers, that are very expensive to begin with. Then you have the proliferation of nuclear in space as a fear factor and unless its a cooperation mission then it would be fore shadowed as a military platforms use.
SpaceX is a current NASA contractor that provides supplies to ISS and launch services.
I think retirement of the Space Shuttle was a mistake and the creation of the Orion capsule was certainly a mistake. The lack of meaningful development of the launch hardware over the STS program's thirty year history was a more profound mistake. If SLS actually becomes flight capable, each flight will dump many hundreds of millions of dollars of hardware into the ocean after a few minutes of use.
If the orbiters retrieved the SLS RS-25's for future flights, an orbital manufacturing module at ISS repurposed the alloys and foam in the ET's into spacecraft shells, and SEP tugs trucked ET's and other discarded rocket parts back to ISS, then we'd have a sustainable space exploration program. The entire point of STS was to have a space truck capable of delivering/retrieving cargo and execution of complex orbital assembly and repair operations. Now that STS finally has a mission that justifies its cost, it has been retired. How else could defense contractors bilk many more billions out of NASA by providing an even more expensive and unsustainable solution?
There's nothing wrong with using STS and SLS hardware in conjunction with each other, but using either system on its own doesn't make a lot of sense. A consolidation of facilities and better program oversight are required if NASA wants a sustainable space exploration solution. There's no reasonable explanation as to why STS and SLS have to cost so much. It's an entirely contrived situation that NASA could correct at any time.
Your last supposition is why I so desperately want a gas core reactor developed. It has little military utility apart from providing power and propulsion, but it's utility for manned space exploration as both an energy dense power source and an integral part of an efficient propulsion system can't be understated. So far, it's the most efficient method of power production we've come up with that actually works for the intended purpose.
I think SEP is fabulous and there's every reason to continue development of the technology for satellite propulsion. The technology miniaturizes well and it's an enabler for unmanned space exploration and lower cost commercial satellites for research purposes. It's simply not realistic for manned space exploration.
Until such time as fusion reactors, anti-matter, and/or so-called anti-gravity devices are available, GCNR's provide the most realistic solution to the problems of power and propulsion for manned space exploration.
Similarly, any manned space exploration program needs to include hardware to generate an artificial 1G environment for astronauts to live in during transit and no other alternative is a suitable substitute.
There's only three enabling technologies required for deep space exploration that we don't already have:
- gas core nuclear reactor
- rotating artificial gravity habitat module
- effective passive radiation shielding
We need to seriously push the TRL on all of those technologies and the only way to do it is to cut funding to programs that don't enable deep space exploration. Ending the Orion program and ARM is a good start.
JCO,
Boeing isn't planning anything for Mars that doesn't involve expenditure of inordinate amounts of funding with little or no result so as to keep the gravy train rolling along.
You only have to listen to their leadership for five minutes to realize that they're not interested in doing anything more than using existing technology to maximize profits. You'll not see anything new from them as long as that kind of thinking permeates management.
Sadly, Mr. Musk is one of only a handful of corporate executives who seems to have a genuine personal interest in a manned Mars exploration program and a willingness to direct the resources of his company towards that goal.
The Asteroid Retrieval Mission that NASA is currently wasting tax money on is the inevitable result of not having a goal oriented program focus, no manned space exploration capability, and no money to fund development of systems that would provide that capability.
You can think of SLS and Orion as being akin to stimulus and shovel-ready jobs, which is to say that both programs blow mad money (SLS and Orion on much smaller scale, thankfully), have not produced any result other than what we already knew they would produce (lots of money up in smoke and plenty of hot air), and then the hard vacuum that follows the inevitable failure where there is neither the funding to continue manned space exploration nor the availability of mission hardware.
Let's talk about where the rubber meets the roads for a minute.
NASA has had a period of more than four decades where no manned space exploration of any kind has taken place, unless one considers watching the health of astronauts and other lab animals slowly deteriorate in microgravity aboard various space stations to be space exploration. While the effects of microgravity is a useful data point, there's virtually no chance of that information ever being pertinent to any manned space exploration because any real effort at manned space exploration would include artificial gravity, a technology that has received virtually no funding up to this point.
The period of time where something like SLS would have been useful would have been the thirty years that STS was in operation. No Space Shuttle has flown in the past four years and it's unlikely that the Space Shuttle will ever fly again. The major problems with STS were entirely within management of the program and not overwhelming deficiencies in the flight hardware. In other words, the crushing cost of STS and SLS has everything to do with having facilities scattered across the United States, man-power intensive ways of correcting simple problems that machines could correct for far less money, and layer upon layer of bureaucratic management that has a lot of nothing to do with execution of operations.
Once upon a time, there was absolutely nothing about Mars exploration, apart from the landers, that had to be created from scratch. However, after the lunar landings were completed the space nuclear power and propulsion program was immediately defunded and so no flight hardware was created. Chemical, NEP, and SEP are all quaint ideas for manned space exploration, but all of them require technology that no longer exists (NEP), was never developed (NEP), or is impractical (Chemical, SEP).
Nuclear power is a virtual requirement for any meaningful manned space exploration, but there's no money for that because of SLS and Orion and all the billions wasted on cancelled programs designed to develop the capability that SLS is supposed to provide.
SEP is an extremely useful technology that is practical for smaller unmanned spacecraft. NASA is actively funding the program in a meaningful way, as it should. However, the technology doesn't scale.
NEP could be useful for larger unmanned spacecraft, but use in manned spacecraft requires GCNR's to achieve the power density required for viability.
NTR is presently the only technology reasonably capable of providing propulsion for manned space exploration missions but there's little more than feel good funding being provided to this program.
Now let's relate all of this to Boeing's master Mars technology plan.
In a nutshell, all of the current proposals rely on technologies that either cost an inordinate amount for the capability provided, don't exist, or don't scale to the levels required for a manned Mars exploration program.
I like the capability that SLS provides, but there's nothing about Boeing's heavy lift rocket that should take 10 years to develop or require tens of billions of dollars. Simply put, the rocket costs too much, has an inferior payload capacity in comparison to Saturn V, and has taken too long to develop. Saturn V was designed, built, and flown in less time using entirely new hardware by men who had nothing but slide rules, pencils, and paper.
If we gave one year's worth of Orion/SLS funding to Mr. Musk, we'd have both a heavy lift rocket of comparable or better capability to Saturn V and a capsule system capable of landing on another planet in about two or three years.
I like SEP and I think we should continue to develop the technology, but it's not an enabler for a manned Mars mission. The SEP solution requires the same number of SLS flights or perhaps 1 less, dependent upon the specifics of the solution. The trade-off is a couple hundred extra days in space and NASA is already whining about how long it takes to go to Mars because of radiation and the entirely avoidable effects of microgravity that it has never tried to counteract with artificial gravity.
So, all-in-all, it's more pie-in-the-sky from a company that's busy riding the gravy train.
If you have a couple billion dollars worth of flight hardware riding on your prudent decision making, suspend all disbelief. Don't take a wild guess at whether or not something could be a problem. If you know something struck your spacecraft because you have a video of it, no further evidence should be necessary to warrant an inspection. There's just no excuse for that.
For the love of all that's holy, if the manufacturer of a product tells you there's a problem with it then pay attention. If you don't understand, ask questions. Some part of that has to be incorporated into Critical Thinking 101, a class that's apparently not taken often enough or not taught widely enough.
The risk assessment for a rocket flies even in the face of the shuttle as after columbia was destroyed astronauts were ready to fly the Hubble rescue mission even without a chance of a safe haven if it had recieved damage.
As for the SRB resonance with fuel burn think changing the harmonic by creating a fret ( think Guitar) inside the chamber for the pitch to change to as the fuel burns. Had a sliding sleeve inside that moves up or down the walls of the chamber to make the change...
This is a good example of why America needs more than one launch system and more than one spacecraft ready to go at all times.
HST cost the taxpayers billions, more than the cost of an orbiter and STS launch combined. That's too much money to throw away because some rinky dink part failed, however spectacularly.
The TPS should be inspected on any spacecraft, irrespective of whether or not it was hit by anything, before reentry. Columbia was not an example of how fragile or dangerous STS was, but rather how arrogant the engineers who were running operations could be. If the TPS of a spacecraft is damaged, a small unmanned rocket with tools and parts should have been ready to go to fix it on orbit.
Whereupon Dragon is man rated, NASA should have a Dragon/Falcon 9 as a back up to any Orion mission. If we're sticking with the requirement for triple redundancy in manned space flight systems, perhaps a second Dragon should be ready to go at ISS. If that hundred billion dollar space station buys us anything, it really ought to include the ability to fix minor problems with damaged spacecraft.
If you do the math on the efficiency of LOX/LH2 and APCP, or pretty much anything else, it all looks remarkably similar to LOX/RP-1 in the end.
Chemical rocket technology is extremely limited and no amount of cleverness is going to significantly improve efficiency or thrust-to-weight beyond what's already been achieved.
The complication of high pressure turbo machinery and fabrication of parts from exotic alloys more or less guarantees that any rocket using that type of technology is going to be prohibitively expensive.
A large, pressure fed rocket is simply too inexpensive and not enough of an engineering challenge to interest NASA or its contractors. If a rocket only costs a few million to fabricate, doesn't require much in the way of technology to fabricate, and can be launched anywhere there's water, that's never something you'll see them do because there won't be hundreds of millions in profits from cost plus contracts.
The F-1 was a remarkable achievement for its day, but there are simpler and more cost effective options for heavy lift. Nobody is even trying because there's not enough money in it. FYI, F-1B boosters for SLS are never going to happen because the MLS would have to be redesigned, there's no room for the TSM's on the pad, and the attendant storage tanks, pipes, and pumps for the RP-1 would have to be built.
If the spectacular reduction in parts count and less expensive methods of fabricating the major assemblies make the F-1B inexpensive enough, there might still be a market for the engine, irrespective of whether or not SLS uses it.
There's this problem that's infected the thinking of virtually everyone at NASA with any authority to do anything and, to an even greater extent, the contractors that NASA uses.
I call the problem technosis. Yes, I just made that up.
Technosis is characterized by a burning desire to create magnificently complicated systems that take technology to and often times over the bleeding edge. Though the system may be perfectly designed to do whatever task it's designed to do, it will fail spectacularly if someone so much as farts in the wrong direction. The notion that every solution to a simple problem has to embody perfection or demonstrate an absurd degree of technical complexity is just stupid.
Let's use Orion as an example. When it was designed, nobody knew exactly how much it would weigh, but they did know that it would be pretty hefty for a capsule. Instead of waiting until the craft was somewhere near a baseline design, development of Ares I proceeded absent sufficiently detailed information about the weight of the capsule. What was the predictable result? The capsule's service module had to be redesigned to the point that it was useless for its originally intended purpose, the upper stage of the Ares I had to be redesigned to save weight and increase performance, and at the end of the day a lot of money was spent without result.
The precious launch abort system that everyone is purring about weighs north of 7t. That capsule couldn't possibly use the extra propellant for more dV, could it? I have another term I use for the abort system- dead weight. The rocket either works or it doesn't.
Let's fast forward to the best part. Now that Ares I has been cancelled, NASA intends to launch Orion on SLS, a rocket that's even more complicated than Ares I. It's projected to have flight costs in excess of a billion dollars per launch. In other words, Orion/SLS will be every bit as affordable and sustainable as STS. If the primary problem with STS was the cost of operations, anyone care to hazard a guess as to where our "new" manned space program is headed?