August 3rd, 2007

krazy koati

They say our solar system is not alone in space

So you want to land on an asteroid. (That is you, isn't it? It looked like you from a distance, anyway.) Well done. That's the sort of public-spirited ambitious yet practical project we don't have enough of in these troubled times. With that sort of ambition you're sure to get somewhere, in particular, landed on an asteroid, if I have anything to do with it.

The first and most essential thing is to check that you have an asteroid to land on. It had better not be a meteorite, or you're bound to end up in dull arguments with pedantic sorts who insist on important differences between a meteor, a meteoroid, and a meteorite. Even if you surrender and admit it's of critical importance to use exactly the right word for the terms they may not stop, and will continue to harass you for having ever been fool enough to get the terms wrong.

You can try a diversionary maneuver by asking whether it's preferable to say ``Three dollars and twenty-five cents is your change'' or ``Three dollars and twenty-five cents are your change'', and if they don't go for arguing that you can at least be smug that their change was actually four dollars and ten cents and they're out the difference. Better still to avoid the controversy and stick to a word everyone more or less agrees on. If anyone other than me mentions ``minor planets'' poke them.

Let's assume that you're already comfortably near the asteroid. (If you have not then see the earlier article in this series, ``Turning Acronyms In A Wind-Driven Turbine'', which should be ``Tuning'' instead.) Begin with a clean desk and spread a tablecloth neatly across the surface, smoothing any folds as you do.

Inspect the asteroid for distinguishing marks or hazards such as rocky terrain or 30-minute parking spaces. When you are satisfied you have a clear landing spot and that no competing spacecraft are grabbing the same spot turn slowly around so that you are facing directly away from the landing terrain. Extend the landing legs (don't tell me you forgot them!) and back in slowly, confident that the warning beeping cannot be heard in outer space.

Knowing when to stop will be a challenge as it's hard to tell the size of an asteroid, so there's not much way to say when it's one spaceship length behind you, but indicators include the ``ground contact'' light turning on, the legs feeling a sudden sharp resistance, the scouting party sent ahead yelling that you're landing on them, the spaceship going right past through the other side of the asteroid (this is particularly bad as your crew will subtly snicker about you all the way home), or seeing a triumphant victory movie and the credits for all the people who worked on this space program coming up on all computer screens.

Just because you've set down doesn't mean you're done, however. Many asteroids have extremely little gravity, and it could be years before a proper supply chain is established to bring excess gravity from Jupiter there. In the meanwhile make sure your ship does not receive any sudden or shocking news which might make it reflexively jump and drift away, and also discourage your crew from things like synchronized jumping jacks. Synchronized laying still is fine, however. Just to be safe you'll probably want to anchor the landing legs until you're through landing.

It would be lovely if suction cups worked to hold you in place, but they depend on having a vacuum inside normal air pressure and that just doesn't work out in space, which is full of vacuum and short on air pressure. The solution is to cover your suction cups with domes that contain plenty of air. This way the air inside the domes holds the suction cups in place, while the suction cups hold the landing legs that hold the domes in place. Now the only challenge is sending someone out there to lick the ends of your spaceship's suction cups, but you do have to figure how to do some of these things yourself. I still think it looks like you.

Trivia: The Block III ``New'' Rangers, used for Lunar Ranger 7 through 9, had engines with a design of 224 Newtons of thrust, capable of a change of velocity between 0.03 to 60 meters per second. Source: Lunar Impact: A History of Project Ranger, R Cargill Hall, NASA SP-4210.

Currently Reading: Gnarl!, Rudy Rucker.