The Next Generation of Human Spaceflight

[Brian H]

The fuels in the SSTS tanks are hydrogen and oxygen. Vent them for a little bit and they are gone.

Yes, the solid boosters that fall away may be toxic, but the Main Tank (liquid H and O) is not.

[TDPerk]

I wonder if the person was talking about the OMS or another thruster. UDMH and nitrotex are not pleasant company.

[Skipjack]

The fuels in the SSTS tanks are hydrogen and oxygen. Vent them for a little bit and they are gone.

Yes, this is true. Someone once put together a good analysis on why reusing the ETs as "wet" stations is not such a good idea. I have to look this up again.

[hanelyp]

The fuels in the SSTS tanks are hydrogen and oxygen. Vent them for a little bit and they are gone.

If you're build a pressurized volume for humans, you like oxygen, and hydrogen is only a problem in combustible concentrations. Some deep sea breathing mixes use a bit of hydrogen.

[zapkitty]

There's also the idea of using the tanks to build space stations, which was put forward by space enthusiasts since the 1990s. I've never seen a good argument as to why it couldn't be done.

Simple.

Foam shedding.

Next question?

The tank is pretty much carried into orbit anyway, is pretty much airtight, and doesn't seem to suffer much structural damage from launch or ascent (apart from shedding some foam insulation - but that doesn't compromise the metal substructure for reuse in orbit).

Nope. It creates massive debris clouds... and as the foam is not designed for vacuum you have a gift that will keep on giving for generations to come.

Once upon a time it was a given that the ET would be taken to orbit and reused... so much so that art and stories about such reuse abound.

But in reality the ET is optimized for its current purpose and cannot be realigned to a different purpose more cheaply than simply lofting the equivalent or greater volume as a payload on the LV using the ET.

As this has been hashed out extensively in other forums the following recap is offered simply to save time... it might seem dogmatic but it's just the situation as it currently stands:

Again: It's cheaper and quicker to loft an equivalent volume, even in sections that must be assembled (which option, BTW, everyone hates with current spacesuits and operational limitations), than it is to redesign the foam/ET for reuse.

People immediately try to think of ways around this problem but no one has stumbled upon a workable solution yet. Some of the more common ideas follow:

The tank cannot fly without the foam or a similar level of insulation that must be just as effective, just as light and just as (relatively) cheap. The LV would literally blow up as evaporating hydrogen cavitates in the SSME turbopumps.

You can't reformulate the foam... at least not more cheaply than simply redesigning the tank... which is not simple or cheap and such a redesign would greatly impact the performance of the LV regardless.

You can't physically restrain the foam with a special coating or a high-tech stocking... at least not without violating the cost, complexity and performance requirements.

That's where it stands... and as Obama presides over the gutting of yet another government program and gifts the proceeds to our lords and masters, that's where it will end.

The commercial people had the right idea... but basically NASA was the only thing standing between them and the insatiable demands of the oligarchy. An awful lot of commercial supporters are in for a shock when not only is the NASA LV money not redirected to them but the money they'd already been promised is taken away as well.

[djolds1]

It's true that a young private company headed by a space nut who doesn't prioritize profits tends to be more efficient than a half-century-old government bureaucracy. But there are things the government can do that a private, for-profit company simply cannot attempt.

Governmental agencies have official power and regulatory advantages, yes.

NASA has spent the last five years or so heroically attempting to realize an abominably bad rocket design that was imposed on them from above by an egotistical administrator and his hand-picked cronies. The engineers in the trenches are not to blame for this - remember, it was mostly those same engineers that were behind DIRECT...

True.

It is also notable that NASA did not have rocket design experience when it started Ares I. SpaceX, on the other hand, was composed largely of the best and brightest across the industry, and lots of them did have such experience. And they still screwed up numerous times (something I think NASA should be a little less afraid of, BTW). NASA should do a lot better the second time around, especially since the rocket they're trying to design will make a lot more sense this time...

SpaceX is young enough to still have an Apollo style mission-oriented mentality. NASA is a mature governmental bureaucracy, concerned with self-preservation and dominated by the Iron Law of Bureaucracy. If it survives, SpaceX itself will, in time, become just another megacorp. Senses of mission are fleeting.

Also, Dragon doesn't have a service module... probably shouldn't be the bulk of the expense, but still...

I thought one could be attached if desired?

It is certainly reasonable to maintain that NASA should be gotten out of the launch business, and I'm not completely sure I disagree. But killing the whole thing?

NACA was killed after a 43 year run. Why does NASA deserve institutional immortality? It is long past having served its purpose.

The problems with NASA are starting to shake out. Griffin and a number of his cronies are gone, and MSFC is using their brand-new buzzword - "affordability" - as if no one's ever heard of it before. This is a really stupid time to start talking about killing it.

Fadwords come and go. The Space Shuttle was praised as the harbinger of affordable space travel. FORTY YEARS AGO. How many "fool me twices" does a bureaucracy get?

$300M to develop a super heavy!? I don't think you people fully understand the disparity in scale between what SpaceX has done and what is required for SLS.

Possible.

Elon Musk has stated that SpaceX could build a super heavy lifter for $2.5B in development funds and $300M/flight (Jim on nasaspaceflight.com, an EELV man with a reputation for almost never being wrong, refers to these as "fantasy numbers"). This does not include an upper stage upgrade, which is necessary if you want an EDS.

ULA seems to believe that they could build Atlas V Phase II for about $3B. This does not appear to include the upper stage (ACES-41, also known as EELV Phase I), which they price at about $3.5B. It also does not include man-rating and support for human spaceflight. Per-flight costs have been estimated at several hundred million a pop, though that may be pessimistic...

Numbers seem reasonable. A bit inflated for my tastes, but then I've less problem with risk and bare-bones LCLV architectures than do bureaucrats and politicians.

NASA should be able to come up with a Shuttle-derived super heavy for around $8-10B, including all the necessary support for human spaceflight, and also including sustainment and modification costs for the systems and infrastructure being carried over.

Inflate 3x.

Sure, SpaceX would probably be cheaper, more efficient. But not by an order of magnitude or anything.

Enough. 3x cheaper is 33% of NASA's costs.

For NASA to change its operating mode radically enough to use either Atlas V Phase II or the super heavy Falcon, it would have to spend between $3B and $11B in reorientation costs (Augustine, quoting NASA's estimate). As a result, it is conceivable that going with SpaceX could be more expensive overall than going with SDLV, even now.

You assume an intact NASA here.

On the other hand, Elon seems to think that the most logical place to launch his super heavy from is LC-39, so maybe the cost of reorientation wouldn't be all that huge - but his project would have to bear the cost of sustaining LC-39, which I doubt is in the estimate...

A slimmed down FAA/ Office of Civil Space Launch can manage that. Full-on NASA not required.

And, of course, this success means nothing regarding ISS sustainment and resupply through 2012, except that the situation isn't even worse than we thought. (Which is good, because the situation was already pretty dire.) It's too late for Shuttle to continue, and Dragon cannot fill the gap. Nor can any of the other resupply craft; all of them combined, including Dragon, were supposed to act as additional capacity on top of the core Shuttle support. Griffin didn't care, of course...

All spilled milk now. Eat the gap period and move on. What is the optimum end state on the other side of the uncomfortable tunnel?

Dragon can carry, according to Elon, about 3.5 mT of useful cargo to the ISS. Or seven astronauts, but the most that will likely switch out at one time is three or four, so it's not ultimately all that different from Shuttle in that respect (Shuttle needs four guys with fresh training to fly it, so it can usually only rotate three). Speaking solely in terms of pressurized cargo, one Shuttle+MPLM is roughly the equal of two and a half Dragons. The crew capability is another Dragon. Not to mention that Shuttle can carry more than an extra Dragon's worth of unpressurized cargo on the same flight as that MPLM. Shuttle would fly about five or six times per year in full swing; five Shuttles is 23 Dragons. Who here thinks Dragon will fly 18 COTS cargo flights and five crewed flights in 2012?

Irrelevant. In the current and coming decade+'s fiscal environment, lower cost for "luxury" programs like space is critical. PERIOD. If those lower costs also enable some additional indulgences (aka scientific missions) at the margins, so much the better.

My point is, yes, SpaceX is really great, but certain people need to adjust their contrast knobs so the details don't get flattened to black and white...

After my initial quick skim of your post, I was going to congratulate you to taking me to task for lapses in reasoning. But after a detailed read, I see nothing that has done so.

Yes NASA is sunk cost, but much of that sunk cost can be retained while jettisoning the chaff. NASA has served its purpose, and the chance to rescue the failed Shuttle architecture into a productive SDLV seems to have passed, despite the fine ideas of the DIRECT people. Time to reassess, economize, kill a zombie that is now a restraint living off past glories, and retrench to BDBs plus capsules out of SpaceX, ULA, Boeing, etc.

[djolds1]

What makes you think a Shuttle-derived heavy lifter would have anywhere near the baggage STS does? I've seen an estimate that says Jupiter would need about 1/3 the workforce of Shuttle; most of the work is related to the orbiter. Not to mention that even STS has seen substantial efficiency improvements over the last decade or so...

Scale up SpaceX to deal with a BFR and you're probably talking the same ballpark. Even trying to scale up to being able to launch dozens of Falcon 9s per year would dramatically increase SpaceX's workforce.

True. Which is why I originally suggested splitting part of NASA off to FAA - let it run the civil launchport infrastructure. No different from government funded roads. But get it OUT of the launcher design game. I did NOT mean to imply that SpaceX should or can do everything.

I know Shuttle is suboptimal, and I know SDLV is technically suboptimal. But (a) they aren't nearly as suboptimal as people tend to think, and (b) sometimes better is the enemy of good. And right now, it looks like SDLV is what Congress will fund.

Fair enough.

[GW Johnson]

I had been working on ways and means to do Mars exploration without a heavy-lift rocket. Think I found a way to do it. I wrote it up and posted it over at http://exrocketman.blogspot.com. Enjoy.

[GIThruster]

Link's not working, GW. Why not repost the entire bit here? Would be fascinating to look at.

[zapkitty]

Link's not working, GW. Why not repost the entire bit here? Would be fascinating to look at.

It works. Just omit the trailing period that he accidentally included:

http://exrocketman.blogspot.com

[GW Johnson]

I see the problem. Try this

http://exrocketman.blogspot.com

Now that I've done this, I will return to cheaper access to LEO for a while. The post for the Mars mission on "exrocketman" is for Dec 20 2010.

[GIThruster]

Fascinating stuff, GW. Had to skim some but will give it another read tomorrow. Couple questions:

I had never heard the open gas core could reach 6,000 Isp. You sure this is accurate and do you have a source? Sounds high to me.

If you have a 6,000 Isp gas core engine, why not use it on the landers as well? Why not use it for everything outside LEO? Would it leave significant radiation contamination at a landing site or disperse at thousands of miles/hour? What sort of radiation levels are we talking about with an open core?

[djolds1]

Fascinating stuff, GW. Had to skim some but will give it another read tomorrow. Couple questions:

I had never heard the open gas core could reach 6,000 Isp. You sure this is accurate and do you have a source? Sounds high to me.

Winchell Chung cites 5100 seconds Isp for NTR-Gas/Open 2nd Gen:

http://www.projectrho.com/rocket/enginelist.php

[GIThruster]

Yeah, I'd seen 5,000 Isp figures before but not 6,000. GW's plan needs 6,000 if I understand him correctly.

[GW Johnson]

My 6000 sec figure dates from some old mission studies from about 1969 or 1970, about the time containment and gas fission controllability were being verified in bench tests. They did understand two limits, but these were very fuzzy. One was a cooling limit: heavy radiator necessary above 2000-2500 sec Isp. This radiator reduces engine system thrust/weight below 1. Not suitable except as orbit propulsion. The upper limit was even fuzzier: some sort of transparency to radiation meant the engine might suddenly vaporize if you pushed it too hard. This was thought to be about 10,000 sec Isp, but was very poorly known for sure.

There were a whole bunch of different studies for missions to Mars about that time. The one with a 6000 sec gas core option that I saw was single stage orbit-to-orbit 4 million lb departure weight, 6-12 men as crew, fast trip to Mars (45 days one-way, I think it was). The corresponding solid core single-stage vehicle was slower, and 12 million lb, as I recall. Chemical vehicles were that heavy or larger, and multi-stage throwaway designs. You got only the crew return capsules back. With the nukes, you at least had the option to reuse the vehicle.

The nuke rockets were joint NASA AEC things under Project Rover. Solid core tests were done from 1959 through the last one in 1973, I think it was. By 1973, they had pretty well worked the bugs out of NERVA, although its T/W was less than desirable. Radiologically, the plume had been cleaned up pretty well. Rover was killed by NASA when Nixon killed Apollo and all manned flight outside LEO, that second being something not well remembered today.

There were also gas core design studies and experiments being performed as part of Rover. Just not actual engine tests. These were more scientific bench tests of feasibility. It actually looked pretty good for the open cycle gas core design, right up to termination in 1972. They were then about two years from doing their very first gas core engine test artiicle, with the 15 year interval from 1972 to a planned Mars mission in 1987 to "get it right".

The "other" gas core design was the "nuclear lightbulb". This featured zero plume radiation, but was limited by temperature of the lightbulb material to about 1300 sec Isp or so. It was projected to have much better T/W than NERVA, and so was being considered for Earth surface launch application. NERVA was only useful as an upper stage engine, such as for doubling the payload of a Saturn-5. But, at 0.38 gee on Mars, NERVA is "good enough", and requires no real development, just re-creation.

I don't generally like designing missions around a technology that is undeveloped, but gas core is really attractive, if it can be done. The old data said it looked likely that it could be done. The proper sequence here is to develop a first-article gas core engine to requirements from a paper Mars mission, then design a real Mars mission around what you get from your tests. My purpose with the study posted on "exrocketman" is to show that this is attractive enough to warrant a real gas core nuke rocket project.

We're going to need something better than chemical if we really want to send men to Mars.