Comments on: Random Thoughts: Risk, Orbital Rendezvous, and Depots

By: Martijn Meijering

Martijn Meijering — Mon, 19 Oct 2009 22:20:33 +0000

I wonder if that individual agreed with plans to scuttle said station at the earliest opportunity, which is even more messed up.

By: john hare

john hare — Mon, 19 Oct 2009 22:18:29 +0000

On ARocket the other day one of the participants in the fiasco said roughly, “We have a space station, so what if it is 15 years late and $72B over budget, that doesn’t matter because we have a space station.” As long as anybody involved can make a statement like that, seriously as far as I could tell, you have a situation that will not close.

By: Martijn Meijering

Martijn Meijering — Mon, 19 Oct 2009 22:06:08 +0000

Another good thing to keep in mind is that keeping something off the critical path doesn’t necessarily mean delaying its development. It can also mean using something else as a backup. Preferably something that already exists so it doesn’t eat up too much development money. Another solution would be to find something else to do until the risky thing is developed. Say keeping the ISS alive indefinitely and migrating to commercial crew taxis. But whatever you do, make sure you develop the new technology and perhaps some competing ideas.

Constellation is an example of what not to do. To avoid putting cryogenic propellant transfer on the critical path (wise in my opinion) they develop something new which likely takes a whole of lot more money and is much less useful and even downright harmful to commercial development of space. That’s taking one problem and replacing it with a bigger one. But of course the reasons given by Constellation are just rationalisations, pretexts to keep the Shuttle workforce alive and to keep NASA in the launch business.

By: Andrew Swallow

Andrew Swallow — Wed, 10 Jun 2009 01:33:06 +0000

A propellant depot can help send probes to Mars and other planets plus satellites to GEO. This means that the design of the depot, tug, refuelling tanker and interface can be debugged whilst the Ares V/Jupiter are still being developed. The depot would then be at Technology Readiness Level (TRL) 9 when manned space flight needs them.

The next major problem is getting private investors interested. A COTS-PD may help.

By: Adam Greenwood

Adam Greenwood — Tue, 09 Jun 2009 15:40:32 +0000

Adam; I think you misunderstood the article. NASA has not “justified” propellant depot, they have in fact rejected them as being “too risky” to put into the development path for the Return-to-the-Moon program. At least so far. Jon’s argument is that Propellant Depot(s) are LESS technically risky than risky options that NASA has taken BEFORE to get to the Moon.

No, my point is that if there really was no technical risk associated with the development of Ares/Orion then there was no point in NASA being in charge of developing them.

By: Adam Greenwood

Adam Greenwood — Tue, 09 Jun 2009 15:38:14 +0000

In the aftermath of the Iraq invasion and in the run-up to the stimulus, a commentator, I think it was Megan McArdle, admitted that her support of the Iraq invasion had been flawed because her case for it relied on the Administration doing exactly the right thing. But in reality the Administration will always err, so her case was flawed. Liberal economists, she pointed out, were doing the same thing with the TARP and the stimulus package and the CO2 cap-and-trade bill. They were countering objections by saying, ‘yes, but if we do this and this and this just right, then we can thread the needle and get around that objection.’ But in politics this and this and this never happen. You never thread the needle. A program isn’t worth doing unless it has big margins. Orion/Ares didn’t and doesn’t.

On the flip side, in business its almost always the secondary revenue streams that make or break you. Just as you don’t want a project where everything has to go right to succeed, you do want a project that can succeed in multiple ways. That’s where you really cash in. As Orion/Ares has developed, its role has become more and more limited. A propellant depot, on the other hand, by nature would enable lots of different kind of capabilities. Its not a luxury buy, its an investment. Its infrastructure.

By: MG

MG — Mon, 08 Jun 2009 18:52:19 +0000

“temporary storage container”

Heh. That Jon is a sly one, isn’t he?

By: Jonathan Goff

Jonathan Goff — Mon, 08 Jun 2009 13:38:36 +0000

Nels,
I was being a little bit coy about the LOX/LH2 transfer. The transfers I was referring to involve transferring liquid through a series of valves and pumps into a “temporary storage container”…..

….where they sit for a couple of milliseconds until the flames vaporize them and then they leak out this venturi thingy and vent harmlessly into space….

Seriously though, engines are far more susceptible to damage from getting gas bubbles and other things, and require far more rapid transfers than you need for propellant tanking. The fact that they can make that work, reliably on demand, is a strong argument that “cryogenic propellant transfer” is a lot more mature than most people realize. The only two things that a relight doesn’t demonstrate are a) the cryogenic fluid coupling (which we have decades of experience doing on the ground where you have to deal with dust, humidity freezing, and liquifying air), and b) holding the propellants in a settled state during the transfer.

~Jon

By: Nels Anderson

Nels Anderson — Mon, 08 Jun 2009 08:50:52 +0000

Jon,

You mention that hundreds of flights of the Centaur, S-IVB and Delta IV upper stage have demonstrated “even fluid transfer.” How and when has this been done? I was aware that transfer of non-cryogens was routine but not that cryogens had ever been transferred in space.

By: Eric Goldstein

Eric Goldstein — Sun, 07 Jun 2009 22:19:01 +0000

Jon, your post made me look for more details. I was unfamiliar with part of the LOR decision recounted here:
http://oea.larc.nasa.gov/PAIS/Rendezvous.html Perhaps many veteran space buffs already know all the details recounted and more, but the last few paragraphs of the link tell a great story about going around the normal chain-of-command that I hadn’t heard before.