Wednesday, October 31, 2007

Surprising Simplicity in the Biggest Engine Ever Made

Last Christmas, my wife's present to me was a trip to Space Camp as part of their three day adult program. In all honesty, it was a lot of fun. Space Camp is directly adjacent to and has free access to the U.S. Space & Rocket Center, which has a museum and a rocket garden filled with various rockets and their assorted hardware bits. Saturn V F-1 engines are about as ubiquitous there as doorstops. Which got me to investigating the various components that make up an F-1 engine, the biggest single combustion chamber engine ever made. I was surprised to discover that the F-1 is comparatively simple. A single turbine, fed with a fuel rich mixture from the LOX and RP-1 lines, spins a single shaft which drives two large pumps (one for LOX and one for RP-1) which look not very different than the centrifugal pumps used in swimming pool plumbing. The exhaust from the turbine is sent out the at bottom of the regeneratively cooled engine bell. This is done, I assume, to film cool the last 8 feet or so of the engine bell, which isn't cooled regeneratively.

The SSME by comparison, is a nightmare out of necessity. This is mostly because pumping liquid hydrogen up to pressure is particularly non-trivial, and requires a multitude of turbines and pumps to operate. As a result, the thrust to weight ratio of the SSME is substantially lower (73.12) than the F-1's (94.07) even with the obvious differences in maximum available Isp of their different fuel mixtures. NOTE: figures provided by It makes one wonder if the improvements in Isp
have really been worth it.


Space Camp was a worthwhile vacation. I recommend it to other space geeks everywhere. Yeah, it's camp, with its obligatory camp food, but at least they have a salad bar and you get to hang out with a lot of similarly minded people.

Frustration in New Mexico

October was also the month of the X-Prize Cup, which featured Armadillo Aerospace's attempt to win the Northrup Grumman Lunar Lander Challenge. I won't go into detail here, but sadly the LLC prizes are still up for grabs. Armadillo Aerospace(AA) got remarkably close to winning the LLC 1 challenge, but was ultimately stymied by engine problems, especially a hard start which shattered their engine's graphite nozzle and pretty much put the kibosh on further flights at the challenge. The details of AA's trials and tribulations can be found here. The entrepreneurial space industry is still young. There is still much learning to be done and it suffers a bit from a paucity of flight hardware. In almost all cases, flight hardware consists of single flight article per team with limited spares. As the industry matures, this will undoubtedly change, although right now teams would benefit from a series of standard issue engines or at least open-source style standard designs. ITAR probably wouldn't allow that, but on the other hand, who in their right mind would build an ICBM with reusable LOX-alcohol engines?

By the way, the Northrup Grumman Lunar Lander Challenge patch at the top of the post is courtesy of the X-prize Foundation. Thanks Sarah!

Tuesday, October 30, 2007


Last December I questioned the practice of retracting and extending the ISS's solar arrays as though they were mini-blinds, and it appears as though those concerns were well founded. Honestly, I am not gloating over this recent turn of events. It saddens me that this has occurred, but I can't say I'm surprised. Discussion around the office has brought up the notion that it might've been a good idea to disconnect the solar panels from the station entirely and move them off to the side while adding the new modules and what have you. Naturally moving them off to the side would mean attaching them to the station via a "stiff piece of rope". A stiff piece of rope in this case might be something along the lines of an extremely long carbon fiber tent pole or similar. I have a few more observations that I will make in other entries this month and next.

Thursday, October 04, 2007

Happy 50th Birthday, Space Age!

I can't imagine there are any space-blogs or websites that aren't covering Sputnik 1 today, so therefore I must as well. Sputnik was launched 50 years ago today on October 4th, 1957, not counting time zones and date line differences. The 58cm/22.8inch aluminum sphere sporting 4 whip antennas weighed 83.6kg/183.9lb, transmitted a continuous stream of beeps on 20 and 40 MHz for 23 days, and was lofted by an R-7 rocket. The R-7 was actually designed as a heavy lift ICBM, but with the lighter payload, it was able to make orbit. Also of interest is that the R-7 (undoubtedly a somewhat modernized version) is still the launch vehicle for the Soyuz and Progress spacecraft we know and love today. Not a bad run for a launch vehicle.

One concern I have in the news coverage of the Sputnik launch is that many keep saying Sputnik was the size of a basketball, which isn't exactly true. A regulation basketball has a circumference of 36 inches, or about 11.5 inches in diameter. This would make Sputnik almost exactly twice the diameter of a basketball. Is this quibbling? Yeah maybe.

Back in 1997, astronauts on the MIR space station tossed a miniature Sputnik that was the size of a basketball out the airlock in commemoration of the 40th anniversary of the Sputnik launch. That story may be found here. At any rate, happy birthday space age!