Transterrestrial Musings

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Boeing has unveiled a radical redesign of NASA's plan to return to the lunar surface: save weight (and money) by saving gas for a sub-orbital fill-'er-up, then shoot 15 times more material to the moon. Can the space agency jive with private space to get the new propellant depot off the ground?

Huh?

Posted by I am unclear on the concept at September 24, 2007 07:58 PM

Hey, I only write 'em. I don't edit them.

Posted by Rand Simberg at September 24, 2007 08:20 PM

Of course it doesn't save any "gas". It would take at least as much fuel to launch, fill, and visit the propellant depot as it would to pack it all in one trip.

But hey, for those who naive enough to think that the US "won" in Anbar or that Iran and Iraq aren't allies...

Posted by at September 24, 2007 08:26 PM

I would think the savings would come in the fact that the propellant does not have to go up in a vehicle that is rated as safe for humans. Who knows, by the time they're ready to go we may even be able to contract out someone to take a suborbital up and release a bit of fuel into the correct orbit where they can be recovered and used later. Assuming the fuel doesn't bleed off too easily.

Having a fuel depot would also remove the need for aerobraking for orbital craft thus saving on heat shield issues that have been somewhat problematic of late.

Posted by rjschwarz at September 24, 2007 09:33 PM

"but land just 18 tons of weight on the moon—only two tons of which aren’t the lander itself. "
----------
Don't you mean to say that only two tons _are_ the lander itself? It reads like you've got a 16 ton lander with two tons of fuel. Maybe I'm dense but that does not seem right.

Posted by Stewart at September 24, 2007 10:03 PM

Of course it doesn't save any "gas". It would take at least as much fuel to launch, fill, and visit the propellant depot as it would to pack it all in one trip.

Assuming they can do this, then you can carry smaller tanks and hence less weight in the launch vehicle. Sure you need more mass overall, but the vehicles seperately can have better performance (higher ration of cargo to gross, fueled mass) since they don't need reaction mass to reach orbit directly.

Posted by Karl Hallowell at September 24, 2007 10:34 PM

Of course it doesn't save any "gas". It would take at least as much fuel to launch, fill, and visit the propellant depot as it would to pack it all in one trip.

Posted by Karl Hallowell at September 24, 2007 10:34 PM

Sure you need more mass overall, but the vehicles separately can have better performance (higher ration of cargo to gross, fueled mass) since they don't need reaction mass to reach orbit directly.

They already don't need reaction mass to reach orbit directly. Only the orbit stage has to reach orbit.

Besides, performance would take a hit because the flight path has to match the specific orbit of the depot. And they would have to launch docking hardware and the hardware of the depot itself.

Of course people who are not naive should realize that bad ideas are sometimes good --- for Boeing.

Posted by at September 24, 2007 10:51 PM

Sorry, I think my web browser flaked out. Didn't do anything (eg, didn't load a new page) so I thought I hadn't clicked submit.

Posted by Karl Hallowell at September 24, 2007 10:51 PM

I think the depot idea is much better on many levels.

Rand make a perfect point in his article. Since the payload going to the depot is cheap (and while dangerous, not fragile like satellites or moon-bound equipment), we can get it into space with cheaper launches on cheaper vehicles.

We also will probably get a lot of operational benefit. There might only be a few moon missions to begin with, but there could well be hundreds of earth to depot trips. If somebody designs and builds a good, cheap, reusable earth-to-orbit ship to get fuel to the depot, and flies the thing hundreds of times, the cost per flight is going to get lower and lower.

My engineering gut likes the idea too. Rather than making a gargantuan everything-gets-launched-in-a-big-rocket approach, we are modularizing the problem. Instead of "how do we get to the moon and back, carrying everything with us the whole way, including all necessary propellent," we have (1) how do we get the fuel depot up and running, (2) how do we cheaply fill up the fuel depot, (3) how do we get the to-the-moon equipment into orbit, (4) how do we refuel the to-the-moon equipment from the depot, (5) how do we now get from earth orbit to the moon and back (much easier than from earth surface to moon surface and back), (6) how do we get back down to earth surface from earth orbit. This suggest another obvious possibility which would be to set up a fuel depot in lunar orbit as well. All of these individual problems are much easier to solve than the original big problem. And now that the problems are broken down, each is separately amenable to competition and market forces.

I think it might actually take "less gas" as well. The ships adding fuel to the depot do not have to lift the mass and propellent necessary to take themselves to the moon, so those ships are lighter and simpler than the earth-surface-to-moon-surface ship.

But "more gas" or "less gas" is irrelevant. Propellant is actually quite cheap compared to everything else--design and operation cost. It would be much easier to design and operate all these smaller systems which don't have to do as much. Consider an analogy. What if you had to design one vehicle to do everything? Commuter car, cross country cargo hauler, off road vehicle, sporty fun driving, refrigerated cargo, dangerous liquid cargo, tow truck... you'd end up with an unuseable behemoth. We have semi trailer trucks for one thing, small cars for another, SUVs for another, pickups, sports cars, motorcycles, etc. The fuel depot allows us to have different space vehicles suited for different purposes, rather than trying to make a single system which does everything. We'd have ships and missions to put up the depot, ships and missions to deliver fuel to the depot, ships and missions to get the moon stuff into orbit, ships and missions to get the moon stuff from earth orbit to lunar orbit, ships and missions to get from lunar orbit to lunar surface--and all things could be suited to their particular purpose, rather than having to do everything.

I could probably come up with more, but one last point seems worth making. The fuel depot is the path to an increased future in space. It would be immediately useful for other things. It would also be very useful for future things. It would also drive a lot of competition to develop cheap earth-orbit access, an absolute necessity if we are ever to really get into space permanently. If we do a one-shot moon mission again, we'll once again be left with nothing after the huzzahs die down.

Posted by Jeff Mauldin at September 25, 2007 03:08 AM

So who do I write to get the fuel depot idea picked over the previous design? And how do we sell this idea to congress and the public so NASA has to buy in?

Posted by Jeff Mauldin at September 25, 2007 03:09 AM

>>>>>So who do I write to get the fuel depot idea picked over the previous design? And how do we sell this idea to congress and the public so NASA has to buy in?

One nit with your phrasing.
When you force a decision on people, they tend to counter react to that concept, making it as difficult as possible to implememnt.

How do we create a situation in which NASA wants to buy in? That would make a big difference though it may seem like a small thing to most.

Posted by john hare at September 25, 2007 04:00 AM

Why store hydrogen in the depot? It's bulky and boils off quickly. You have to have the big tanks in the exploration hardware for it anyway. And it's light and constitutes only one seventh of the total propellants mass. All this means it can be sent up when the exploration hardware travels up and never has to leave a tank. It doesn't make much of a mass penalty.

It's the LOX that you want to store on a depot. 6/7 of propellant mass, denser than water, doesn't boil off as easily as hydrogen.

Posted by mz at September 25, 2007 04:39 AM

Of course it doesn't save any "gas". It would take at least as much fuel to launch, fill, and visit the propellant depot as it would to pack it all in one trip.

But hey, for those who naive enough to think that the US "won" in Anbar or that Iran and Iraq aren't allies...

I see that our latest anonymous idiot is as clueless about orbital mechanics as he is about foreign policy. If you can deliver fifteen times as much cargo for less than twice as much propellant, then of course you have "saved gas."

Posted by Rand Simberg at September 25, 2007 06:18 AM

Don't you mean to say that only two tons _are_ the lander itself? It reads like you've got a 16 ton lander with two tons of fuel. Maybe I'm dense but that does not seem right.

No. You have a lander with sixteen tons, most of which is the propellant for the ascent stage, and two tons of which is the payload to be delivered to the lunar surface.

Posted by Rand Simberg at September 25, 2007 07:00 AM

"Rather than making a gargantuan everything-gets-launched-in-a-big-rocket approach"

It seems a BDB might be ideal for something like this if the Sea Dragon concept would play out.

Posted by Mike Puckett at September 25, 2007 07:29 AM

If you can deliver fifteen times as much cargo for less than twice as much propellant, then of course you have "saved gas."

It is true that the more cargo they plan to send to the moon, the less propellant they can use per pound of cargo. That is true in various ways with or without a propellant depot. But of course it doesn't save gas or money or any other resource in total; instead it expands the mission.

The propellant depot expands the mission in a way that is particularly favorable to Boeing. Since the VSE is a colossal bridge to nowhere, an early launch of a propellant depot amounts to erecting the first pylon.

The important thing to remember is that Boeing is a giant and ambitious government contractor. If you're a libertarian, you should suspicious of its plans. But if you're a neolibertarian... Well, it seems that neolibertarianism is to libertarianism as NeoPets are to pets.

Posted by at September 25, 2007 07:48 AM

" ",

Your mask has slipped.

The benefit of a propellant depot is that it delinks expensive, mission critical hardware from a custom launcher.

Consider. IF a lunar lander has to transport all its propellant into LEO, then its structure has to accomodate all the launch loads (acceleration, vibration, acoustic, thermal, etc) applied to that propellant.

If it then loads propellant at an orbiting depot, it faces much more benign loading conditions.

Lighter, more robust structure.

Better mission reliability.

Higher launch rate of smaller rockets to amortize fixed costs.

Don't take my word for it. Read the entire AIAA paper the Direct Launch folks have written. I have. It articulates well the value of propellant depots.

Now, just because you are FUBAR on this topic doesn't necessarily imply that you are FUBAR on Iraq. However, it is reasonable to infer that you are using common "reasoning" patterns in both. From that inference, your writings on Iraq are suspect.

Nice job, though. You simultaneously undercut your credibility on space exploration AND warfare.

Best wishes,

Posted by MG at September 25, 2007 08:26 AM

This I agree with. Create a depot and let the free market determine who can get the fuel up there at the lowest cost.

My opinion is that a genuine RLV would make a lousy un-crewed fuel tanker.

The RLV itself will be a high value item, therefore even if the system is not man-rated, redundancies to safeguard the RLV asset will be necessary and that will add mass and cost. Plus, any mass that comes back down would be pure parasitic weight.

Instead, think Bic pen. Put fuel tanks intended for depot delivery on top of ultra-disposable rockets having the lowest dry mass feasible.

RS-68s "cost" about $12 million each (per nasaspaceflight) based on current D-IV flight rates. If a private sector disposable fuel tanker used 3 of them for a first stage and if one tanker flew each day that would be over 1000 RS-68s consumed each year. The efficiencies of mass production would drive down the per unit cost of each RS-68 quite considerably.

Same thing with the fuel tanker tankage. Building LH2 fuel tanks capable of multiple flights to LEO strikes me as a expensive proposition. Start making giant tanks on an assembly line and the cost per unit falls through the floor.

So, how much "value" is captured by returning engines that will cost far less than $10 million each?

Heh! Even a pair of ATK RSRMs made fully disposable with plastic casings (to increase the fuel/dry mass ratio) could be useful as well.

= = =

Of course, the market should pick the winner(s), not NASA or Congress or blogs. I'm just saying that a stripped down bared bones BIG launcher that traded reliability for low cost would be a contender for being one of the winners.

Posted by Bill White at September 25, 2007 08:41 AM

MG,

I happen to think that a bare-bones Jupiter would make an awesome fuel tanker. If we double our consumption of RS-68s and standard ETs the price per unit should fall considerably.

Not even taking into account stuff that could be stripped off the fuel tanker version of Jupiter because the payload is inherently low value.

This Democrat LOVES the DirectLauncher, V2.0.

= = =

Using L point architectures is another terrific aspect of all this. Create EML-1 and/or EML-2 depots for lunar LOX.

Posted by Bill White at September 25, 2007 08:49 AM

The benefit of a propellant depot is that it delinks expensive, mission critical hardware from a custom launcher.

But the drawback of a propellant depot is that links the expensive, mission critical hardware to other hardware for refueling in space. Since that has never been done before, it is particularly easy for Boeing to low-ball its cost.

Besides, the claim wasn't just that a propellant depot would save money (which it won't); the claim was that it would save fuel. Basic physics shows that it doesn't save fuel, except as a pretext to upscale the mission and thus use less fuel per pound of luggage.

You simultaneously undercut your credibility on space exploration AND warfare.

Rest assured that both the VSE and the Iraq war will unravel in 2009. Space exploration will survive in some form, and so will anti-terrorism, but they won't look anything like what we have now. Right the prediction down right now, wait a hear and a half, and you'll see.

Posted by at September 25, 2007 08:54 AM

Bill,
I actually think an RLV would be a great vehicle for fueling orbital propellant depots. For an economic RLV you want *lots* of flights. The more flights you have in a given time, the cheaper an RLV will be per flight. In spite of all that "parasitic mass", etc. Propellant depots are just about the only market other than flying people/light cargo to orbit that I think really has the potential to drive hundreds or thousands of RLV flights per year.

~Jon

Posted by Jonathan Goff at September 25, 2007 09:00 AM

Mz,
Storing the hydrogen can make sense as well. Boiloff doesn't have to be fast with proper tank insulation design. It's tricky, but not very heavy or expensive once you've worked out the design. And being able to provide both fuel and oxidizer makes the depot more useful. Eventually, you'd want to branch out into other relevant fuels: kerosene, methane, maybe even some of the nasty hypergols, etc.

The reason you provide hydrogen isn't because it's efficient from an engineering standpoint, but because you can make money doing so. :-)

~Jon

Posted by Jonathan Goff at September 25, 2007 09:03 AM

Jon -

I predict Boeing will look to hedge against both approaches. Then, the market can decide.

On the political side, if someone in the private sector looks to deploy a fuel tanker based on Zenit should NASA refuse to buy the delivered fuel?

Posted by Bill White at September 25, 2007 09:13 AM

"Rest assured that both the VSE and the Iraq war will unravel in 2009. ... Right the prediction down right now, wait a hear and a half, and you'll see."

Are you serious? What does "unravel" look like?

And why should I "rest assured" about a prediction that can't be evaluated for 18 months, and then, when I can, there is no adverse consequence for someone who posts as " "?

It requires a suspension of disbelief. With respect, I don't buy it. (courtesy of Clinton and Lantos)

PS: Spell check betrayed you. The verb is "write", not "right".

Posted by MG at September 25, 2007 09:36 AM

On hydrogen boiloff-

Boiled-off hydrogen is still cold enough to circulate around the LOX tanks and drop your LOX boiloff rate to zero. Then the LH2 can be reacted with some LOX to produce water, another heavy consumable that you need to bring along anyway. So you deliver a little heavy on the LH2, then tank up with LOX, LH2 and water.

Posted by Tom at September 25, 2007 09:39 AM

On hydrogen boiloff-

Posted by Tom at September 25, 2007 09:39 AM

On hydrogen boiloff-

Posted by Tom at September 25, 2007 09:39 AM

On hydrogen boiloff-

(sorry about the multiple posts...delete some if necessary)

Posted by Tom at September 25, 2007 09:40 AM

I like the fuel depot idea because it decouples the mission from the implementation. Just as a gas station here on earth can refuel mopeds, motorcycles, cars, SUVs, RVs, trucks, and so on, an orbiting fuel depot could fuel moon missions, asteroid missions, Mars missions, and indeed pretty much any mission beyond low earth orbit. For that matter, such a depot, when combined with a fleet of space tugs, could provide the propellant necessary for station-keeping for lots of satellites currently in orbit, thus extending their usable lifespans manyfold.

Posted by Ed Minchau at September 25, 2007 10:20 AM

Bill,
I think the key here is making sure that any propellant depot developed is *commercially* operated. I'm not sure how much say NASA really has on where the propellants came from if they're buying from a commercial depot. You would still have to try and pick the right orbit to maximize the number of potential suppliers (and customers--once the capability exists with an anchor tenant, NASA isn't going to be the only one interested), but there should be no problem buying internationally and selling internationally.

~Jon

Posted by Jonathan Goff at September 25, 2007 10:50 AM

Jon, with a just-LOX depot you'd get 86% of the benefit with 27% of the trouble. (mass vs volume)
And that's not taking into account the boiloff problems! You don't get any volume benefit from the depot since the exploration hardware has to have big enough tanks to hold the stuff anyway.

You can launch the EDS and LSAM with the few tons of hydrogen included just fine on a Delta IV Heavy or similar. Each on its own of course. About 15 t of LH2 in total. No reason to bother with the depot for such small loads. It's almost the same flying with an empty tank as if the tank is filled with hydrogen. 70 kg per cubic meter.

Posted by mz at September 25, 2007 12:48 PM

mz,
I may be doing my BOTE calculation wrong, but I'm getting closer to 25mT of hydrogen for the EDS/LSAM. That actually matters a bit. More importantly, what I'm *really* interested in isn't the VSE implications of a propellant depot, but the commercial implications. For many commercial concepts, being able to tank up both propellants has real advantages, particularly for reusable systems.

While LOX gets you most of the benefit as far as VSE is concerned, being able to store LH2 or LCH4 is also very beneficial.

And as for the LH2 boiloff issues...all I can say is that I know of some pretty interesting potential solutions that are being investigated...

~Jon

Posted by Jonathan Goff at September 25, 2007 01:09 PM

As a pilot program, LOX-only would perhaps make sense.
Relatively easy to store for long periods, and can supply various upper stages.
Makes interface specifications for tankers way easier as well.

Depending on actual demand, supplying hydrogen, methane, propane and so on, perhaps with different tanker interface specs could follow.

Posted by kert at September 25, 2007 01:14 PM

Whoa, 25 t (mT means millitesla) of hydrogen would mean 7*25 t = 175 tonnes of LOX/LH2 propellants in total. What are you launching??

I think the Ares V has less than 150 t (perhaps 120-130 t) performance to LEO and even that has the dry masses and the hypergolic LSAM ascent stage. And Orion won't carry hydrogen. So 105 t would be a closer guess for the mass of LOX/LH2 propellants yielding 15 t of LH2.

Posted by mz at September 25, 2007 01:23 PM

One analogy that might help sell this idea is another Boeing product: the B-52. The B-52 cannot even launch with a full fuel load - not when it is carrying a full bomb load, anyhow, which is the only time it really matters.

On a mission, the B-52 takes off with a full bomb load and only a small amount of fuel. It then makes rendezvous with one or more KC-x tankers (another Boeing product, at least originally), take on however much fuel it needs, fly across the globe to bomb the begeezus out of whoever has been unlucky enough to gain our attention, and then return to base.

Without the tankers, the B-52 is next to worthless. To follow the NASA mission pattern to date, the B-52 would have to launch with all its fuel and, therefore, drop little more than a few hand grenades on its target.

Hope this helps convince your more hawkish readers. Your extremely more hawkish readers may wish to take a B-52 and bomb NASA out of existence, thereby clearing the way for more and profitable use of space.

Posted by John K Berntson at September 25, 2007 01:35 PM

The benefit of a propellant depot is that it delinks expensive, mission critical hardware from a custom launcher.

We know a custom launcher is very expensive. Plenty of history demonstrating that. As I see it, the only point to your first paragraph is that no one has done a fuel depo yet. Once it's done and we understand the problems far better, then your concern is addressed.

My point on suborbital refueling is off the mark since Boeing isn't actually proposing to do this.

It would require somewhat more propellant overall to refuel in orbit and then head to the Moon than to go directly to the Moon. I recall the latter requires less delta v though I don't know how much less.

Glancing through Rand's article and the comments in this thread, I don't see anyone actually proposing that an orbital propellant depot will use less fuel (especially when you include boil off), but rather that the missions that launch lunar vehicles are more efficient and the overall program is cheaper. You get more of yourt original mass fraction to the Moon. But that's only for the launches that go to the Moon.

So to summarize, you would have a number of launches service the depot. Then some launches, perhaps on a DIRECT, would take up lunar landing vehicles which refuel at the depot. The delta v from LEO to landing on the Moon is less than 6 km/s, so you get a good mass fraction.

Posted by Karl Hallowell at September 25, 2007 02:27 PM

It would require somewhat more propellant overall to refuel in orbit and then head to the Moon than to go directly to the Moon.

That's kind of irrelevant, since NASA has no plans to go directly to the moon. They have to stop in LEO and tag up with the Orion anyway. So there's very little propellant penalty for stopping at a depot at the same time, and topping up the tanks.

Posted by Rand Simberg at September 25, 2007 02:34 PM

A propellant depot, in addition to providing the benefits described earlier, is also an essential step toward the sustained exploitation of extraterrestrial material for propellant production. Any such scheme must involve the production and storage of propellant, followed by its transfer into the vehicles.

If NASA does abandon the ESAS as currently conceived and moves toward something like this, then maybe the horse really can learn how to sing.

Posted by Paul Dietz at September 25, 2007 02:57 PM

Really dumb idea.

- With dozens of fuel deliveries, using as you say, "low reliability rockets" from a variety of sources, the chance of something going catestrophically wrong increases significantly. Plus each fueling launch would inject debris into LEO.

- We're talking about LOX and LH, which are not the most forgiving substances on Earth, much less in orbit. Pumping and transfering these in zero gee hasn't been tried on a large scale and if something goes wrong the fuel station blows up.

- In A Very Big Way.

- Ignoring for the moment the impact on NASA operations, the debris field would be the largest ever injected into LEO. The force of the blast would scatter it widely and close any number of launch windows, perhaps all of them.

If you're going to build a fuel dump in space at least put it on the Moon, where if it blows up it comes back "down" afterwards. Either land to refuel or shuttle fuel in limited quantities into lunar orbit, where even if a robotic shuttle blows it won't take out half the satellites in LEO.

Posted by Orion at September 25, 2007 03:04 PM

If NASA does abandon the ESAS as currently conceived and moves toward something like this, then maybe the horse really can learn how to sing.

Well, yes, Paul, but somehow, I don't think that would have made it past the editors at Popular Mechanics.

Of course, that's why I have a blog, and comments section...

Posted by Rand Simberg at September 25, 2007 03:08 PM

Really dumb idea.

That was a really dumb comment, "Orion."

Do you work for ATK, by any chance?

Posted by Rand Simberg at September 25, 2007 03:10 PM

Orion: your objections seem obtuse. Of course with many launches, the chances of launches failing goes up. The key is you don't care, you just schedule more.

As for the depot blowing up: what is the energy driving this? You don't store the hydrogen and oxygen in the same tank, or even in close proximity, necessarily. The pressure in the tanks need not be terribly high either.

The best objection would be that of collisions during rendevous, but we have experience with avoiding that. If required, you have the third parties send up standardized propellant tanks that are collected by an OTV to be brought to the depot.

Posted by Paul Dietz at September 25, 2007 03:12 PM

This whole architecture leads me to wonder: once the depot is in place, is there any benefit in sending up a new lunar lander with each mission? Why not just build a cycling shuttle that never lands on either body, carries its own lander(s), and transfer cargo from your initial launch vehicle to the shuttle. Would that be a worthwhile approach?

Posted by Jason Bontrager at September 25, 2007 03:24 PM

Wow! I'm the first person to say this.

One of the problems of an orbital fuel depot is boiloff. Fine - launch a big tank of water, and generate the propellants on site as required - or, presumably, slightly before. Less fuel loss to evaporation, less dangerous materials in the launch vehicle, and of course to make this work you have to have significant power generation in orbit - which has advantages that nobody here will need spelling out.

Posted by Fletcher Christian at September 25, 2007 05:07 PM

There's a reason you're the first to suggest it, because you haven't checked your power requirements for water splitting. 100kW buys you kg/hour (I think it's 2.2), and you still have to cool it. I've run the numbers.

Posted by Tom at September 25, 2007 05:40 PM

I hope Boeing will consider launching a small prototype regardless of whether NASA changes course during the next months or not (perhaps we'll get Direct for christmas after all ^_^).

It shouldn't be too hard to justify towards shareholders since it would likely establish/strenghten the case for a profitable future business venture as well as improve some of their present ones.

Kudos to Boeing either way, together with LM and NG it looks like these aren't quite the brontosauri one could have thought but rather nimble raptors.

Posted by Habitat Hermit at September 25, 2007 05:42 PM

"Are you serious? What does "unravel" look like?"

In 2009, it looks like President Thompson kicking ass and taking names. Unravel is unravel for Iran and co.

I predict it here and now, write it down and worship my mad hero/analyist skillz' in 18 months!

Posted by Jack Ryan at September 25, 2007 06:06 PM

There is a more detailed proposal written in 2006, dealing with many issues raised here:
http://users.tkk.fi/~tmaja/flex/flex.htm

If an individual launch has a success probability of 98%, you have 14 launches and 2 spares, the probability of more than 2 failing of the 14 is 0.00246 or 0.25%. So spare launches can make it so "failure is an option". The orbital depot architecture is extremely flexible, if it is wanted to be.

And you can switch to modest payload high flight rate and more reliable RLV:s if it is useful.

Posted by mz at September 26, 2007 04:41 AM

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
since PM seems have "locked" the article comments upload, I've posted it on HS:
http://www.hobbyspace.com/nucleus/index.php?itemid=4596
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Posted by gm at September 26, 2007 08:19 AM

In 2009, it looks like President Thompson kicking ass and taking names.

If you're really a talented prognosticator, you can make big bucks with this forecast on Intrade. You can buy Fred Thompson for 9 cents on the dollar.

Meanwhile I have to revise my take on the propellant depot proposal. I had described it as a possible big-money project for Boeing that would also keep the VSE alive. But what it actually looks like now is some creative science fiction from Dallas Bienhoff, who happens to work at Boeing. It's almost realistic --- if NASA wanted it badly enough, they might be able to build something like it. But almost is not good enough; probably neither Boeing nor NASA will ever put muscle behind it. (I'll give it this much credit, it's not as stupid as a space elevator.)

For that matter, at a higher level the whole VSE looks like that. It looks like it will almost happen, but not really.

Posted by at September 26, 2007 08:40 AM

Orion: your objections seem obtuse.

Only if you're dense as lead.

Of course with many launches, the chances of launches failing goes up. The key is you don't care, you just schedule more.

Consequences, old boy: consequences. If the fuel shuttle blows up on the pad you don't really care - as long as it's not YOUR pad, that is. If it blows up in midflight and debris rains down on your car you care quite a bit. More seriously, if the "low reliability" tanker fails in flight you care because at the very least you have to keep track of the hulk for however long it takes to fall out of orbit and burn up. If it explodes the tracking problem increases exponentially. And if it goes while docked to the fuel depot the whole place goes up with it.

As for the depot blowing up: what is the energy driving this? You don't store the hydrogen and oxygen in the same tank, or even in close proximity, necessarily.

You don't have to mix propellants for these to be dangerous. It was an LOX tank that blew up in Apollo 13's SM, crippled the ship, and nearly killed the crew if you'll recall. That was a VERY SMALL TANK, relatively speaking; only used to power their primary fuel cells.

The pressure in the tanks need not be terribly high either.

If you can afford very, very, large tanks I suppose not. There's certainly no size restriction on what you can build in orbit, just on the cost. I will bet though that Boeing is proposing cyrogenic storage and cryogenic liquids are dangerous and tricky to handle on the ground, much moreso in the extreme conditions of space.

Perhaps I am being obtuse. The LEO environment is INCREDIBLY FRAGILE with regards to space travel: It wouldn't take very much to shut it down completely to us. Space Shuttles have returned from orbit with dings and gouges from little more than paint chips flying around up there; left over from decades-old launches. Our satellites burn a lot of reaction mass dodging launch debris right now. We've improved our procedures and greatly reduced the junk cast off per launch but even so the debris density is increasing. Even if nothing goes wrong the dozens or even hundreds of tanker launches to Boeing's fuel depot would compound the problem.

If something does go wrong it goes catestrophically wrong. We have industrial accidents with fuel tanks all the time on the ground. 1-2 blow up every year or so. Afterwards we can send in crews to collect and haul away the wreckage. In Space There Is No Cleanup: the debris would be scattered over a hundred thousand square miles. We need to be very, very, careful with what we put in LEO because screwing up even once could lose LEO to us forever.

Posted by Orion at September 26, 2007 09:59 AM

Orion,

In LEO, there is a very good cleanup mechanism. It is called "atmosphere". Residence times in LEO depend upon the objects ballistic coefficient and its orbital parameters.

Most LEO mission failures occur prior to orbital insertion. Propellant delivery missions would have a higher proportion of such failures, because the payload is inert.

Posted by MG at September 26, 2007 10:11 AM

>>>>>So who do I write to get the fuel depot idea picked over the previous design? And how do we sell this idea to congress and the public so NASA has to buy in?

>>>>>One nit with your phrasing.
When you force a decision on people, they tend to counter react to that concept, making it as difficult as possible to implememnt.

>>>>>How do we create a situation in which NASA wants to buy in? That would make a big difference though it may seem like a small thing to most.

You're right. So who do I write and what do I do to convince my wife the designer coat makes her look fat?

Posted by at September 26, 2007 01:41 PM

Ironically, while orbital propellant transfer will fix the current NASA architectures poor to non-existent ‘mission’ mass margin it also makes the Ares-V unnecessary at the same time.

In addition, site access and anytime return is driven by the propellant Orion has on board so shortfalls form Ares-I can’t be fixed with additional ‘mission’ mass available under a propellant transfer scenario with or without the Ares-V.

As we showed in our AIAA Space 2007 paper a true direct derivative of STS will result in an upper stage with more than enough empty volume in orbit (refilled by the propellant depot) to place over 90mT on a Trans-Lunar Injection Trajectory.

Because any STS derivative will have a high fixed cost the number of launches per year doesn’t significantly affect the total expenses per year. As such biasing the launches towards propellant depot refills won’t alter the yearly cost significantly. It ultimately comes down to what the available budget is for all the expensive spacecraft need for the mission not the cheap propellant or adjusting the amount of unused (but paid for) launches out of KSC.

In the end the higher development cost needed for the Ares-V 25% lift capability increase over the Jupiter-232 (Ares-III) is unnecessary altogether for a multitude of reasons. A propellant depot just makes the Ares-V even less necessary than it already is.

Posted by Stephen Metschan at September 26, 2007 04:17 PM

In LEO, there is a very good cleanup mechanism. It is called "atmosphere".

http://en.wikipedia.org/wiki/Image:Debris-GEO1280.jpg

Posted by Orion at September 26, 2007 09:42 PM

>>>>You're right. So who do I write and what do I do to convince my wife the designer coat makes her look fat?

If you phrase the question like that, then accept that you have lost already. If I knew how to control womens' (or mens')spending habits, I would make enough money off the book to finance my own space ship.

In my experience though, concentrating on the negative (makes you look fat) is slightly more disaster prone than using a positive like, this other one makes you look thinner.

In the space context also, concentrating on the negatives can be counterproductive. Forcing an organization to do something will produce less results than persuading the same group. If you can convince them that it was their idea, it will be even more likely to happen.

Posted by john hare at September 27, 2007 03:01 AM

Okay, Orion, you win...

the non sequitur prize.

Congratulations.

Posted by MG at September 27, 2007 07:19 AM

Okay, Orion, you win...

the non sequitur prize.

You claimed there's no problem with orbital debris in LEO: a picture is worth 1000 words.

My position is that unless something absolutely, positively, needs to be in LEO we shouldn't put it there because there's just too much risk to the space program; yours seems to be "Gee This Is a Nifty Idea (tm) So Let's Do It!" NASA will of course weigh the risks against rewards and weigh in somewhere between the two extremes. Let's leave it at that.

Posted by at September 27, 2007 10:27 AM

" ",

Kindly do me the courtesy of referring to what I actually write, and please do NOT put words into my mouth. I expect that sort of thing from an adolescent, not an adult.

I did not say there is no problem with LEO debris.
Orbital debris is a problem. In LEO, the atmosphere reduces orbital debris by removing energy from their orbits. Do you believe otherwise?

Your policy position about the use of LEO is very cute, albeit naive and misguided.

The biggest threat to the "space program" is government control over access to and uses of space. Orbital debris is a well-understood problem, with well-understood solutions.

Posted by MG at September 27, 2007 02:38 PM

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