Magnetic Space Launches

DiZNoG writes "This CNN article discusses NASA experimenting with the idea of using Mag-Lev technology to launch payloads into space. Mentioned in the article is that the U.S. Navy is working on the technology for it's aircraft carriers to launch fighters. Unfortunately the NASA project is horribly underfunded ($30,000) for research. Cool technology, let's hope that the Navy research gets us a step closer to not burning all that Oxygen and Hydrogen to get to space...

Comments

Re:Perhaps a silly question?

[Jherico]

But why not have a rocket take off that drags a string behind it? And, say, take the string to the moon.

I'm not positive, but I'm pretty sure that no material has the tensile strength to hold its own weight all the way to the moon. If you held a 5 foot string, it weighs practically nothing. If you dug a 100 mile hold and held a 100 mile string that was dangling down it it would rip your arm off. If you suspended it from something stronger than you, the string would just break under its own weight.

Plus you can't anchor a string to the earth and the moon. The earth rotates much faster than the moon orbits. If you attached it to just the earth it would only line up with the moon once a day, and it would be going so fast as it passed it you would be smashed into the moon. By the same token if you attached it to the moon, it would fly around the earth every 24 hours, meaning it would be blazingly fast, about 350 mph. Bad rope burn if you try to grab it.

However, it might be possible to build a 'string' that is strong enough to simply lead into orbit. Anchor one end to the earth, and the other to a large mass slightly outside geosync orbit, which is still way way closer than the moon. Then you can climb the string all the way to the mass and be flung away from the earth. At any rate we still don't have strong enough string. Yet.

Re:Maybe MagLev will save us yet!

[Tsar]

I think you're missing a very important detail -- I was making a joke. But let's go ahead and apply this to the shuttle. Here's how far you have to make your acceleration track in order to reach 7,814 m/sec (minimum orbital velocity) at various G-forces:

3112 gees ............ 1.0 km
100 gees ............ 31.1 km
15 gees ............ 207.5 km
8 gees (comfy?) .... 389.0 km

Think about how long you watch a shuttle launch, and that it's accelerating for that entire time. It takes a long, long track to pull this off. Better to build short, fast ones and use them for launching construction materials into orbit.

Re:Used up in the cost to get the electricity, tho

[LadyLucky]

IIRC, the terminal velocity of a rocket is (to a first approximation) the product of the logarithm of the ratios of the total mass (including fuel) and the payload mass, and the exhaust velocity. This means you nead TONS of fuel to boost a small payload, especially given Earth's escape velocity of 11 km/sec.

The advantage here would be that you dont need to burn fuel to make the fuel move. You dont need to add extra weight to get started. Im not an expert, but i assume that the basic idea would be gather speed (not even necessarily vertically to begin with), and then launch it vertically. It needs to be vertical to escape the drag of the atmosphere as quickly as possible.

Re:Cost per what?

[armb]

> I'm either 5'11" (say, roughly 6') tall or 180.34cm. Now, which of those gives you a better mental picture of how tall I am?

The one you are more used to of course. That doesn't make it better in any objective sense.

I'm about 190cm (say, a handswidth under 2m), or 0.009 furlongs, or 0.3 rods, or 0.09 chains. Which of those gives a better mental picture?

Incidentally are you really 5'11" to within 1/200th of an inch? If not, the apparent accuracy of the ".34" you quote is completely bogus.

> Does metric even have "dry volume" measurements?

Yes of course. Cubic metres. Same as wet volume, since a volume doesn't actually change depending whether its contents are wet or dry. The dimensions of volume are length^3, so the SI unit for volume is (unit for length)^3.