Clark Lindsey has been live blogging the Augustine Commission hearings in DC. Just keep scrolling. Little editorializing other than a “sigh…” when John Shannon disses reusability.
[Thursday morning update]
Alan Boyle has a summary and link round up of yesterday’s festivities.
[Update a few minutes later]
A couple days ago, I noted my hope that the Augustine Commission wouldn’t just look at alternative launch architectures, but rather take a big-picture, systems approach, and look at exploration architectures overall (which I assume that Jeff Greason was trying to do with his depot question to the DIRECT team). That means reexamining all of the assumptions, including what the lunar lander would look like. Jon Goff has some thoughts today.
[Late morning update]
A day-after summary from Jeff Foust.
I caught part of it. The Direct guy, when asked “who’s on your team?” would’ve done better by saying “I can give you a partial list, but some contributors asked to remain anonymous” instead of the answer he gave.
Glad to see Clark’s summary.
The way I would have worded the answer is:
The people of DIRECT include an array of engineers and accountants from the very same divisions doing the analysis for Constellation. With the strong antipathy we’ve experienced from the higher levels within NASA, most of our adherents would wish to remain anonymous. We can certainly get you in contact with them indirectly, and some might come forward upon request, but they’d prefer to remain anonymous. The numbers should stand on their own.
The one missing line IMNSHO was “Jupiter does not -require- a depot. Our Lunar and Mars missions do rely upon using two launches to fill the Earth Departure Stage with propellant in orbit. This would be facilitated by a depot, be we absolutely do not require it, and it is not anywhere on our critical path.”
Not only does Jupiter not require a depot, but if a depot exists, there is no requirement for Jupiter.
The DIRECT spokesman, when asked by Mr. Greason (XCOR) about prop depot and EELV, replied that DIRECT could offer a larger payload volume.
Can’t the existing EELV’s (or their growth versions) offer a larger payload volume than they do now? Wouldn’t that be an upgrade option to the payload fairing and the mounting hardware within the payload volume? I assume the vibrational coupling of a larger (dry) payload with the Delta IV / Atlas V’s would differ from the existing environment.
Anyone?
It is understandable the DIRECT people would mention volume since it is one of their strong points. On the other hand it is a red herring. If you want large habitation volume, use inflatables. If you’re worried about instability of the Altair, then don’t use a damned cryogenic lander, use a horizontal lander, use a crasher stage, have the EDS do the LOI and well as the TLI or use L1/LLO depots. If you want large telescopes, then unfortunately you don’t have the budget. It’s no use spending tons of money on a large launcher when you don’t have the money to launch any payloads on it.
The DIRECT people claim one of their strong points is that they don’t put depots on the critical path to the moon, although they failed to emphasise that in yesterday’s presentation. The problem with that is that they do put the moon on the critical path to depots (and by extension commercial development of space), which would mean it could easily take 20 years before those depots are developed. It also puts the moon on the critical path activity beyond LEO.
None of this is necessary. It is possible to have depots soon without putting cryogenic depots on the critical path to the moon and it is possible to go beyond LEO sooner (MEO, GEO, L1/L2, NEOs) and with smaller yearly budgets. I’ll again plug my old favourite of hypergolics depots. In LEO they would support tugs and make resupply more efficient, at L1 or in LLO they could support simpler and safer landers and reusable shuttles with only slightly higher IMLEO. They would therefore be an immediately useful asset, as well as precursors to more advanced cryogenic depots.
Work on cryogenic depots should also start immediately, in parallel and not on the critical path. Jon Goff’s suggestion of having NASA work with industry to define open standards for depot interfaces, funding some research and committing itself to buying propellant on orbit and then getting out of they way is an excellent one. Similarly, there should be a strategic plan for the development of other advanced technologies such as aerobraking, ISRU, SEP.
I’ll again plug my old favourite of hypergolics depots.
Well, its already up there, and a tanker is also operational. Those are called the ISS and Progress.
So why ISNT anyone using them ?
What do you mean why isn’t anyone using them? They are being used. It’s true they aren’t being used to refuel tugs. I believe they should be. ISS is probably not very useful as a depot, but there is no reason a depot couldn’t be kept at a safe distance in the same orbit. Also note that ESA plans a hypergolic lander and is considering an L1/LLO hypergolics depot.
Do you see any fundamental technical reasons why they aren’t being used to refuel tugs or other spacecraft?
There’s very little you can do with excess payload volume other than carry hydrogen. One of the dirty secrets of Shuttle-C was that it was hard to actually utilize efficiently, because its volume capacity and lift capacity weren’t well matched with typical payload densities. If you lifted with full capacity, you probably had to carry a lot of water, or ballast. If you lifted as much typical hardware as payload as it could carry (at ten to twenty thousand dollars a pound) the lanch would be worth a billion for payload alone. Where were we going to get the money to really use such a thing? This is a problem with using Ares V for large science missions as well. The payloads would be unaffordable (and a huge risk when put up on a single launch).
The DIRECT people claim one of their strong points is that they don’t put depots on the critical path to the moon, although they failed to emphasise that in yesterday’s presentation.
And one of their weak points is that it puts a single new expensive (though probably less so than Ares) launch system on the critical path to the moon. This does not make for a robust architecture.
If you lifted with full capacity, you probably had to carry a lot of water, or ballast.
Or dense propellant. To make sense of the combined volume and payload you could use a mix of fluffy cargo and dense propellant. I’m opposed to an SDLV, but if we ended up with one, that might be one of the more sensible ways to use it.
Another way to use the massive payload of an SDLV is to use it to launch crew to higher-energy staging points. My long term favourite was L1, but lately I’ve come to think GEO and MEO aren’t so bad either. They are less efficient energetically, but they allow for easier reuse of spacecraft than LEO. Propulsive braking to GEO or even MEO is feasible, even with hypergolics. And MEO/GEO staging takes away NASA’s lifeboat argument, since MEO/GEO rendez-vous can still be reasonably described as EOR. Technically this is also true for L1 rendez-vous, but the >=3 day trip leaves the door open to the lifeboat argument. Another advantage of a higher-energy staging point is that you would need a smaller EDS, which means even Shuttle-C could perhaps be used to do EOR-LOR should NASA insist on that.
I guess the other argument for volume is the hydrogen tanks. They would be quite ‘fluffy’ and hard to make inflatable.
Im not a fan of HLVs at all either, but i dont think that the case could be made that fillilng the payload volume with something useful would be too expensive. For planetary probes, the solution is pretty simple : build them small as they do now ( with relaxed weight margins of course), just build more copies. Marginal cost of extra copy of hardware should be pretty low.
For orbiters, bigger solar panels for more power, more stationkeeping propellant, neither too expensive.
Asteroids are ideal for this: there are so many of them, they are very interesting scientifically and potentially for ISRU as well. And having a common ground segment also helps.
Can’t the existing EELV’s (or their growth versions) offer a larger payload volume than they do now?
I think I’ve read upgraded EELVs could have 7m fairings. Of course, 5m is pretty darn big as it is.
Yes, Boeing, at least, looked at a lot of EELV derivatives with wider fairings.
With a ‘basic cylinder’ tank shape, you wouldn’t necessarily need a whole fairing, just an aerodynamic cap for the pointy end and an adapter for the back end of the payload…