Reusable Space Vehicle, part 2

After watching SpaceShipOne on TV this morning, I was thinking again about my electromagnetic double-barreled space gun which captures the energy of a returning craft to launch the next one. Obviously, since a hotel on the moon is my ultimate goal, the gun needs to be able to fire its projectile at what is for all intents and purposes escape velocity, plus extra for the loss due to drag the first few miles of flight. Since the acceleration would have to be moderate in deference to my squishy guests, I knew that to get up to that kind of speed would take a launcher several kilometers long.

But how long? Well, this morning I did the math. Escape velocity is about 11100 m/s. We’ll shoot for 12000 m/s to give us a little cushion. Plus, it makes the math easier. OK, the first warning bells started to go off when I realized that in the last second of the launch the capsule would need almost 12 Km of launcher. Uh, oh.

Get out your shovels, boys and girls, because to get the capsule up to target velocity at the only moderately-stressful acceleration of 40m/s/s would take 300 seconds, or five minutes. In that time the capsule would travel 1800 Km, almost 1/4 of the diameter of the Earth.

The electrogun could still be used for an initial boost for a ship which also carried its own rockets to allow it to claw up out of the gravity well, and indeed several people have already thought of that. (I have not seen any design that recaptures the energy on return, however.) A gun with much greater acceleration and a shorter barrel could also be used to launch non-squishy payloads.

It’s also worth noting that it would take only a tiny fraction of the energy to needed achieve escape velocity to match the feat of SpaceShipOne, so I’ll still happily accept any large donations to make my dream a reality. In the meantime, I’m back to rooting for the Space Elevator boys to deliver my hotel guests.

8 thoughts on “Reusable Space Vehicle, part 2

  1. m&m’s may not seem squishy, but to get the gun barrel down to a “manageable” length of 18km, the acceleration would be 4000 m/s/s, or about 400 g’s. I think that would squish even the sturdiest of m&m’s.

    It does, however, suggest a possible answer to why there was a watermelon in a hydraulic press at the Banzai Institute.

  2. Did you see the designer and pilot of SpaceShipOne on Leno tonight?

    You get the designer, with Isaac Asimov sideburns, and the pilot, 63 years old with thick glasses — his age keeps him from having a commercial pilot’s licence even though otherwise he’s in great shape. These guys just plain look like what happens to the high-school super-geek 40 years later. Yet they took their little rocket to outer space, and they did it without any major problems. They made it look easy.

  3. I notice according to the Albuquerque Journal, the Truth or Consequences airport is going to get a MAJOR renovation. I had thought this X Prize stuff was happening at White Sands — but no, that’s only a temporary arrangement. The X Prize guys plan to fly out of T or C.

    Talk about cool. Lots of cities have international airports, and Houston goes so far as to have an intercontinental one, but T or C will have the first interplanetary airport.

    We’ve always laughed about the T or C airport signs, featuring a silouhette of a jetliner, for what’s really a tiny airstrip in the desert for Cessnas and cropdusters, and occasionally Ted Turner’s private jet. What a hoot if the sign remains inaccurate, but for the opposite reason — what’s flying there is way cooler than jetliners.

    Speaking of pictorial signs, did anyone ever figure out the penguin on a unicycle?

  4. Mojave, where SpaceShipOne launched is, I understand, a licensed spaceport. T or C probably is also. I invite submissions of what the sign should look like. I will publish all suggestions.

    Unless a Canadian highway department rep weighs in, we will never know about the unicycle squirrel juggler.

  5. Speaking of squirrels, Leno just replayed a clip of Dubya expressing his feelings about modern technology — I can’t say it’s an exact quote, since I didn’t tape it, but it was something like, “It’s amazing the technology we have nowadays, where a camera can tell the difference between a squirrel and a bomb.”

    Hmmmm….. maybe THAT’S why nobody ever found any WMDs in Iraq — we should have been looking at the squirrels!

  6. Since I’m still curious about the sign, I went to Alberta’s driver’s license manual, which can be found at http://www.trans.gov.ab.ca/Content/doctype45/production/basicdrivershandbook.pdf

    and discovered that whereas New Mexico has a mere 32-page booklet for prospective driver’s-license applicants, Alberta has a 161-page book. I didn’t find the sign you saw, but I found enough information that I would guess the sign is about using caution while riding a motorcycle (or maybe with loads prone to shifting), as the road surface is bumpy. (BTW, I really got a hoot out of the “trucks entering from the right” sign illustrated on Page 33.)

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