Cuddihy's Cut

Cuddihy's Cut on the events of the day....

Monday, February 13, 2006


Wow, my first serious post gets linked to! Lesson: trackback works.

Thanks to all who offered well wishes. Even though this is a (as may be expected) hectic week, strangely enough I have more free time than usual. I mean, I budgeted it that way when we set the wedding date, but somehow I expected to be more behind anyway. hmm.

Rand's right that some of the assumptions I made for the numbers doom the architecture from the start--nobody would seriously consider a fully reusable lunar architecture at this stage. I ran it out of curiousity to find out 'why not,' and there's many little things that can be done to trim the propellant requirements.

But that's part of the conclusion I drew from the exercise--it suggests that a lunar (or any kind of deep space) sustainable architecture is probably not a near term thing, even after you get launch costs down an order of magnitude from current prices. When you get down to it, there are some hard facts of rocket science and economics, having to do with delta v, mass ratio, launch rate, and market.

There's an excellent paper on the Colony Fund website by Transterrestrial musing's own Sam Dinkin, David Livingston, and John Jurist that is a detailed discussion of a lot of those considerations. In fact it's titled "When Rocket Science meets the Dismal Science."

For NASA, the problem is worsened because they have to meet not just the realities of the technology and marketplace (as a customer, not provider), but also the political reality of convincing Congressmen that their architecture is worth paying for. I don't think Congress is ready to fund an architecture that requires an alternative market to spring up in order to be feasible. It would be like funding ARPAnet in the 70's because of potential tax revenue. Congress just isn't that clairvoyant.

update 10:38 PM

The link to the Dinkin paper goes to the correct paper, but the title appears to have changed some time recently from "When Rocket Science Meets the Dismal Science" to "When Physics, Economics, and Reality Collide" . I'm not sure when that changed, as I have the same paged saved on my hard drive with the old name at home. Either way, it's a good read.

Welcome to Competent Management

Keith Cowing seems to think that competently managing a large beaureacracy involves extreme deference to any random manager who has a different opinion than the top management.

This isn't a one time freak-out by Cowing: every time someone at NASA gets canned or transferred for refusing to follow orders, Cowing posts it as crushing of dissent, as if the courage to speak out against job realingment is of the same importance as shuttle safety.

The truth is, if you are a manager, people like Scott Hubbard are who you pray you never have working for you. People who put the security of their individual fiefdom above the overall mission. That is exactly how NASA has gone in circles for decades. Thousands of individually well-intentioned people, each trying to maintain their own particular niche without regard to the overall picture.

Yet when a competent manager comes in and starts organizing the beaureacracy to actually accomplish a task, people like Hubbard (and Cowing) throw up so many roadblocks that it's very tough to accomplish anything.

The truth is this: as a NASA civil servant, you do NOT have the right to your job. You do not have the right to pursue whatever space science tickles your fancy. Just because you work for the federal government does NOT give you the right to blow off top management and obstruct every effort that you do not happen to agree with.

Griffen laid out a plan, asked Hubbard to implement it for the good of the entire VSE (which in reality should be more important than the maintenance of the NASA beaureacracy.) Hubbard refused, so Griffen had to put in someone who would actually 'kowtow' to the actual plan.

I respect Keith Cowing a great deal, and his news reporting has had an overall extremely positive effect on NASA over the last 8 years. But I wish he would allow Griffen to organize NASA in a competent way without complaining whenever some golden cow has to be melted down to a productive purpose.

Sunday, February 12, 2006

Lunar Architecture

Okay, evidently Blogger lets you post pictures now, so I'm more willing to spend some time blogging

I'm just starting this out (again), and I'm getting married next weekend to an awesome babe, so don't expect too much this week. (ha. nobody will read this for months if ever.)

Here's a start:

Over at Selenian Bookdocks Jon Goff posted an idea that piqued my interest: an entirely reusable LEO-->Moon-->LEO architecture, using depots in LEO and L1. The interesting thing to me was the idea of using propulsive braking for the return--even when it costs you Ginormous amounts of fuel.

I did a little excel check and found that, although it's physically possible, it's kind of nuts: for example, using LOX/Ker (Is 340s), with a bare-bones module of 7 tons, and a payload-to-drymass fraction of 0.17 (slightly better than any existing rocket), you need 223 metric tons of propellant at L1 to fuel your 40 ton LM.

Lets say you brought that propellant to L1 in a reusable LEO-L1 transporter that drops off 10 tons at a time, and uses aerobraking to get into LEO. that's 22 trips. Plus one additional trip to bring the lunar module. 23. And each of those trips is going to cost you 264 mT propellant in LEO. That's 6077 mT of propellant you need in LEO, just to accomplish one lunar mission.

One thing most depot-advocates argue for is that cheaper launchers with higher launch rates will lower the cost/lb to orbit. It becomes clear why they have to argue that if you actually run the numbers. At 6077 mT of payload, even if you use the (currently) hypothetical Falcon 9, at 9.3 mT to LEO, you need 653 Falcon 9s ($27 mil a pop, $17 bil total).

It's not hard to see why even CEV proposals that use L1 stayed away from depending on reusability .

That doesn't mean the resuability architecture idea should be thrown away, however.