Mike Mealling over at RocketForge has added to his shwag offerings. In particular the Apollo LEM mug is cool, though the Skylab Mousepad is also quite geek-chic. I'm hoping he'll add an RL-10 mug (hint).

I'm a big fan of the RL-10, since it's as close to the realizing the ideal of evolvable design as any spaceflight gadget that I'm aware of, having been in use since 1963, with continuous upgrades and improvements since then. It's also the engine that was used (in yet another variant) on the DC-X, which is enough to earn it a spot in space history even without the large number of variants. I suspect that there are Russian engines which come close to the RL-10 in realizing evolvable design, but none pop immediately to mind (a reflection of ignorance more than anything else).

I'd be interested to hear of other candidates for best realized evolvable design in space hardware. Bear in mind that by "realized evolvable design" I mean not just design that is capable of incremental improvement, but design which has actually undergone substantial incremental improvement, or which has spawned a large number of useful variants. Soyuz is one obvious candidate. I suspect that there are Russian spacesuit designs which also meet the criteria for realized evolvable design.

This post honestly started out as just a pointer to the new RocketForge mug, but obviously I'm in a bit of a rambling frame of mind. For more on why you too should be a fan of the RL-10, check out the relevant collection of archived Usenet posts on Yarchive.

NASA has a new book out called Taming Liquid Hydrogen about the Centaur development. You should read it.

Dr. Day - thanks for the pointer. I'll look into it.

Dr. Case, no need to call me Dr. Day.

Here's a link that mentions it:

http://collectspace.com/ubb/Forum9/HTML/000369.html

It sells for $28 and you can buy it from the NASA Information Center. I highly recommend it. I read a draft version and offered the authors some help. The draft was quite good. They went into a lot of the problems of using this exotic fuel.

Dr. Case, no need to call me Dr. Day.

OK, but you've got to promise to stop calling me Dr. Case :-)

I appreciate the pointer. I'm going to buy the book. Looks like an interesting read.

You can call me Squiggums...

One complaint that I have heard about the Centaur book is that it is light on the details of the modifications made to the Centaur over the years. Although I have forgotten what the book says, I vaguely remember a lack of info on how Centaur evolved after its first decade or so. This is not that surprising, as it became primarily an industry effort rather than a NASA effort, and it is much harder for a historian to get access to industry records.

(My own interest has been the Agena upper stage and I have very little information on the technical changes made to the vehicle after the mid-1960s, for this and classification reasons.)

Although few people realize it, the Centaur development was a major controversy at the time, mired in some nasty bureaucratic infighting among other things. Today we accept it as simply another piece of well-worn hardware. But it was not easy to design.

It is also worth noting that the Soviets gave up on high energy stages at this time and did not pick them up again until the latter 1960s. This proved to be a big problem for them. Although their N-1 rocket was more powerful than the Saturn V, the real advantage for the Saturn was its powerful upper stages and its lightweight payload design. There were even independent experts in the mid-1960s who recognized that this was likely to give the Americans the advantage in the race to the moon compared to the Soviets.

Just a nit, but the RL10 isn't hyphenated.

A great book that details the development of the RL10 among other things, is "Advanced Engine Development at Pratt & Whitney" by Dick Mulready, ISBN 0-7680-0664-3.

Regarding evolved rocket hardware, I believe the RD-180, RD-170 family of rocket engines by Energomash has pedigree that goes back to the dawn of the space age.

Robert - Thanks for the pointer. I'll be buying it in the near future. I'm also looking for references on some of the more oddball things that have been tried with the RL10 (lack of hyphenation noted) like flourine, FLOX, and propane. I've seen some coverage in NASA SP-4044 (which covers early use of LH2), but I'm particularly interested in details of the use of propane in expander cycle engines.

Please check out the sites about...