Nasa Flip-Flops on SLS vs Fuel Depots? Well, Maybe
Nasawatch has a headline that says “NASA Studies Show Cheaper Alternatives to SLS.” Well, yes, and no. Click on the article and it takes you to Spaceref where we learn that this comes from a press release by Rep. Dana Rohrabacher! Yeah great source. Like we should really care what a politician says.
The Nasa source is supposedly a real fuel depot study, linked here, dated last July 21. This looks like an updated version of some of the same study charts that showed SLS to be the best choice over a year ago. You can actually do things cheaper with fuel depots, but the flip side is you actually have to develop and own some fuel depots, and you still have the logistics and manufacturing turntimes to build more vehicles if you have no SLS. Click the link and read to the end where it talks about the necessary conditions to use depots. (and don’t pay attention to politicians!)
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Space depots within cis-lunar space really only make sense for commercial operations to the Earth-Moon Lagrange points and to the lunar surface and really requires a substantial amount of traffic to those destinations in order to be economically viable.
NASA’s primary focus should be on deploying gas stations on the Moon by exploiting the Moons polar ice resources.
You must have clicked on the wrong link. The only connection to Rohrabacher is that he had previously requested that NASA release their fuel depot study results. They have not but Spaceref has obtained this overview presentation anyway.
The presentation is from this past July, not a year ago. If you actually read this presentation, it shows clearly that a deep space architecture based on fuel depots and commercial launchers saves “tens of billions” over the SLS. It would also be more flexible and robust since there are multiple redundant space transports available. Furthermore, missions to an NEO and to the Moon would happen much sooner.
Yes, the cryogenic fuel depots have to be demonstrated but they are not some distant technology but one nearly at hand. With Centaur experience and ground tests, the only thing left is in-orbit demos. The funding needed to get them into operation is a tiny fraction of the cost of the SLS.
The presentation addresses the HEFT objections to fuel depot/comm’l launchers on page 66. HEFT said there were launcher capacity constraints. The presentation explains that the industry in fact is operating currently at under-capacity and could quickly ramp up. “Additional capacity is a ‘feature’, not a ‘bug’ for US launch industry”.
I’ll note that there are also synergistic effects that would benefit the whole space industry. The combination of higher launch rates and competition would lower the cost of space access for everyone.
Your instant dismissal of results that show the overwhelming advantages of a low cost alternative to the SLS is symptomatic of a NASA/aerospace industry culture that has become pathologically antagonistic to anything that doesn’t look like Apollo.
“….has become pathologically antagonistic to anything that doesn’t look like Apollo.”
This has nothing remotely to do with the Apollo program, its about maintaining a monopoly for shareholders.
Clark-
I saw both the July PowerPoint, and a previous one from last year that was different. I don’t think Spaceref got the previous one.
Based on the difference between the 2, the July version is a bit more positive towards the depot option, but there are still logistics and complexity issues.
I don’t care either way. If the powers want depots, I hope they get funded and do them!
@Clark Lindsey
Traveling to an asteroid or to Mars using either an HLV or propellant depots is going to require a technological breakthrough in radiation shielding in order to protect astronaut’s brains from several months of brain damaging exposure to heavy nuclei. Other wise, several hundred tonnes of mass shielding is going to be required. Such enormous mass requirements for manned interplanetary journeys could not be reasonably conducted with chemical rockets and will probably have to wait until the age of nuclear rockets or titanic light sails.
I should also note that HLVs are actually inherently compatible with fuel depots since they can launch large amounts of fuel into orbit per tonne much cheaper than small launch vehicles can.
What did you expect out of NASAwatch? It’s like the Fox News of space blogs.
@Clark Lindsey
The amount of fuel which a crew capsule needs to reach escape velocity is very high, especially if you assume a smaller launch vehicle. That alone demands enough fuel to fill an upper stage, so not much is saved by using propellant depots. That’s before you get into issues like powering a compressor and a cooling unit to store cryofuels in space, or how to conduct a fluid transfer in space. Then, of course, there’s transporting the fuel into space and getting it to the propellant depot. Very quickly, you see why a legacy approach is favored; we know that it works and it doesn’t require a whole bunch of extra spaceborne devices which likely have high hidden costs.
@Marcel
In theory, you could use an electromagnetic shield or water to stop the nuclei from causing too much damage to the crew. Of course, electromagnetic shielding requires a lot of power (though a few nuclear thermocouples could probably do the job with little extra space) and a water shield is both heavy and needs a lot of extra plumbing to work.
Astro_student:
Bite your tonque, guy! You’re slandering a very good web site. NASAwatch has had a nice long run, it’s got knowledable reporters and people posting comments that aren’t too blatantly Republican or Democratic political operatives, it’s reasonably on top of current news. This is worthy of praise — and if you’ll take a good look at some of the other space “news” sites, I think you’ll come to appreciate what Keith Cowling has accomplished.
When was the last time Keith Cowing ever said anything constructive about NASA on his website? For that matter, when was the last time he ever showed the engineers any respect? Most of the time, he presents a very one-sided account of the agency and shills for SpaceX. That’s why I started reading Paul Spudis’ blog; he usually is spot on and doesn’t promote all of the NASA bashing that seems to permeate NASAwatch.
Yes, most of the other space “news” sites are pretty dry, but that’s because the media seems to treat science and engineering like magic. It doesn’t help that most media outlets have downsized their science reporting.
Astronautics Student: “When was the last time Keith Cowing ever said anything constructive about NASA on his website?”
Maybe back in 2002. Cowling really seems to have liked Sean O’Keefe. The Aministrators since …. not so much … and that colors things. We’re not talking about Reuters here or the BBC. Cowling’s got OnOrbit and SpaceRef for straight news coverage; NASAwatch focuses more on space agency politics and public relations, and it’s seldom neutral, because Keith has very inflated ideas of how NASA ought to be publicising itself. I don’t think he much cares about the actual day-to-day mechanics of designing and building rockets.
None the less, NASA is a product of politics — and publicity, and inside-the-Beltway gossip, and “spin” — as much it is of engineering, which makes NASAwatch a web site well worth attention.
@Astronautics Student:
– There have been some recent advances in cryocoolers that may make fuel depots quite feasible.
– Fluid transfer in space is not an obstacle. The ISS has the equipment in place and is routinely refueled by Progress and (possibly) the ATV. It’s built into the Russian docking adaptor. Cryo prop transfer has some temperature concerns, but no real breakthrough is needed.
– developing fuel depots and transfer as a routine operation has effects on more than BEO operations.
– launchers for fuel can be cheaper, as they don’t need to be human-rated and can use trajectories and g-loads that a human transport can’t use.
You can always count Astronautics Student to worship at the alter of Constellation, and other failed programs.
And you can always count on Ferris Valyn to exaggerate and spin worse than a bored Fox News reporter
@ANON
-It’s one thing to develop a precusor technology, it is quite another to actually implement it and stay within the laws of physics.
-I am talking specifically about cryo fluid transfer, where temperature issues are far from the only concern.
-It’s not just a matter of they type of rocket you need, it’s the payload you are flying. We are, after all, talking about an entire stage’s worth of fuel that needs to get into space. That’s expensive no matter what angle you approach it from, and unless you can greatly reduce the fuel required for escape, sending a bunch of rocket fuel to a propellant depot consumes just as much (if not more) energy than a traditional heavy lift vehicle.
At least Cowing uses his real name. Who are you?
Go nuclear.
@Werner:
You first, sweetheart.