Comments on: Additional AV-017 Flight Experiment Information

By: PrairieKirk

PrairieKirk — Wed, 12 Jan 2011 04:12:29 +0000

Well, it’s been a year now…, and I don’t know if this comment will even be accepted this far on.

But thought I should let you all know that the links to the “published some information” and “presentation” in Jon’s 12 Jan 2010 post have gone dead.

Anyone have a URL for where the papers might still be found?

By: Robert Wallace

Robert Wallace — Sat, 17 Apr 2010 05:24:34 +0000

This is fantastic. I pondered years ago what the Air Force’s take on space-based refueling depots was — but I was thinking on the Moon and in lunar orbit — following extraction from hoped for lunar ice deposits at the poles. Everything I have had a chance to read here all makes sense — and would make a great focus topic for a high school-level aerospace Science Technology Engineering and Math (STEM) Education enrichment module. You have all your physics principles present, numerous chemistry topics, tons of engineering analysis problems, and plenty of math required in your various trade-off analyses. NASA is kicking-off a Summer of Innovation Project in 2010 and the STEM content of Orbiting Refueling Depot Engineering offers a fantastic “vehicle” for integrated STEM knowledge transfer. Any thoughts gentlemen?

By: Jonathan Goff

Jonathan Goff — Wed, 20 Jan 2010 15:41:37 +0000

Nels,
You could possibly do that, but with a decent sunshade, that’s no longer your biggest source of heat flow into the tanks–your electronics deck is. Cooling the connections between the hot and cold stuff is a better use of the GH2′s remaining heat capacity. Plus, you generally want to use that GH2 (that’s now quite a bit warmer) in a warm-gas RCS jet for stationkeeping purposes. If you send it out through the sunshield, it’s a lot harder to do that.

~Jon

By: Nels Anderson

Nels Anderson — Wed, 20 Jan 2010 08:10:41 +0000

Final reference to “GO2″ should read “GH2″.

By: Nels Anderson

Nels Anderson — Wed, 20 Jan 2010 07:58:49 +0000

Yeah, you’re right–no GO2 to play with. But come to think of it, because of GH2′s high heat capacity, even after it’s warmed up to LO2 temperatures it still makes a better coolant than does GO2. So, how about cooling the sunshade with the GH2 *after* it’s cooled the LO2? GH2 is probably friendlier to sunshade materials too. And if you want to use warmed up GO2 for propulsion, the additional heating may be useful.

By: Jonathan Goff

Jonathan Goff — Tue, 19 Jan 2010 15:40:34 +0000

Nels,
They may be concerned about ITAR issues when it comes to discussing technologies like this (even though they really have absolutely nothing to do with missiles or how you would do weapons, ITAR still hangs over our head). But I agree, those are good questions that I would like to see answers to. I imagine that you might be able to back some of that info out if you tried hard enough, by looking at previous papers, estimating hydrazine reserves, trying to look up the thrust specs of their hydrazine thrusters, etc. But it would be cool just to have that published in a paper later this year. We’ll see.

As for using GO2 to cool the sunshield…if you’re using the GH2 to cool the LO2, there isn’t going to be a lot (or any) GO2 to use for a sunshield…

~Jon

By: Nels Anderson

Nels Anderson — Tue, 19 Jan 2010 11:47:40 +0000

I see what you mean about ULA taking a don’t-rock-the-boat stance: the written piece never mentions depots or anything like them.

The first questions that arise in my mind are about the *numbers*: how low was the acceleration in the low-g test? How long did the slosh observed in that mode last? What was the rotation rate in solid-body mode? How long were these modes used?

Although it’s not directly relevant to depots, I wonder whether the successful MRS test might indicate that the RL10 could conceivably be ignited on a two-phase mixture (the original J-2S was supposed to be able to do this). Is it significant that LO2 was depleted before LH2, i.e., would depleting LH2 first be risky?

About the chill-down test, why is pulsed LH2 a new technique, if pulsed LO2 has been around for years?

Gotta love the RL10: world’s first hydrogen engine, still going strong forty years on.

Re the above discussion of using evaporate to chill the sunshade, chilling the sunshade with GO2 seems like it might be a good idea. Surely the best use of GH2, however, is to chill the LO2. That way every joule of heat absorbed by the GH2 is a joule extracted from propellants.

By: Jonathan Goff

Jonathan Goff — Mon, 18 Jan 2010 16:07:21 +0000

Neil,
My guess is not until the President has set his exploration agenda, and Congress decided what to do about it. ULA unfortunately has to answer to Boeing an LM, and I think both of them are very much in a “don’t-rock-the-boat” mentality. If ULA were a “free-man” so-to-speak, I bet they’d be speaking up more, but ultimately, they have to answer to their shareholders, who in this case don’t necessarily have only ULA’s interests in mind.

It’d be sweet if at some point ULA could free itself from those constraints, but I doubt it’ll happen.

~Jon

By: Neil H.

Neil H. — Mon, 18 Jan 2010 00:12:56 +0000

Jon, any ideas on whether there will be a press release or anything on this sometime? It’d be nice for propellant depots to get more publicity.

By: A_M_Swallow

A_M_Swallow — Thu, 14 Jan 2010 03:55:05 +0000

Propellant depots will not be considered a tested technology until a satellite has been fuelled and sent to lunar orbit, geostationary orbit or possibly a planet.