Magnetic Space Launches 301
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...
Re:Used up in the cost to get the electricity, tho (Score:5, Insightful)
Re:Maybe MagLev will save us yet! (Score:2, Insightful)
I don't know the exact cost/[pound|kilo] to get something into orbit, however reduced weight means less cost and less energy needed per launch. Seems like a win/win situation to me.
Re:Going to acceleration or height? (Score:5, Insightful)
The same could be said for New York City. The devil is in the details, my friend. Folks thought the Shuttle would open up cheap access to space, since we'd get to reuse the orbiters. Ha ha.
[To avoid dangerously high acceleration, manned flights] will be launched off of a gradually ascending slope spanning a couple of kilometers.
Sorry, but that's still way too short. To achieve a minimum orbital velocity in a 2-kilometer run, you'd have to accelerate at a little more than 1500 gees. Splat.
Even with a 100-kilometer ramp, you'd be dealing with an average acceleration greater than 31 gees. It appears that, as far as space projects go, this will only ever be useful as an initial-stage boost, or for boosting raw materials into space for orbital construction projects.
Of course, it would still make a nice high-tech catapult for lobbing massive conventional weapons hundreds of miles, but of course no one in the Pentagon is thinking of THAT possibility...
Re:Used up in the cost to get the electricity, tho (Score:2, Insightful)
Now, if they can use solar energy to fire that baby... That would be the shiznit!
What about EM rail to pass lower atmosphere? (Score:2, Insightful)
If you look at am EM rail as something not to completely launch a vehicle into orbit, but to clear the dense portion of the lower atmosphere (and maybe give it enough velocity to save fuel on acceleration), doesn't it make more sense? That is, an EM rail as part of a greater delivery system, and not the whole delivery system?
A few points to make... (Score:3, Insightful)
They want to reduce the fuel needed. Meaning the launch vehicles will have to do some thrust by themselves, but not nearly as much.
Also, some people have noted that g-forces would be a problem. Not likely, if we angle the vehicle at a 45-degree starting angle we drastically reduce the ammount of g-forces needed.
Another point, the maglev system is frictionless. The LV is at no time during the launch touching the track. You've seen bullet-trains, right? Same consept. This further reduces the work needed to launch a vehicle.
I do see this system working. It will probably be 10 years or so, but it will work.
Re:Going to acceleration or height? (Score:3, Insightful)
Maglev might be able to give these devices a good shove before the rockets kick in and might therefore save substantial amounts of fuel (and fuel saved is weight saved, which then saves even more fuel on the way to orbit).
Re:Used up in the cost to get the electricity, tho (Score:3, Insightful)
Re:Cost per what? (Score:2, Insightful)
The reality is that the English units make more sense to you and I simply because that's what we've been raised with. They are no more or less sensical than metric units. Yes, I'm more comfortable with arbitrary measurements in the English system - I know my handspan is 10". I know one of my knuckles is roughly 1". I know how far a mile is, how big a gallon is, and how heavy 10 pounds is.
But to say that 1 kilometer, or 1 liter, or 1 kilogram is obviously not as simple to understand just shows how short sighted you are. If you'd been raised in a country that had transitioned to these measurements decades ago then you'd be wondering what the hell is up with these silly english units.
And yes, the only time it really matters is when you start doing conversions. You don't have to do them? That's nice. Not planning on doing much cooking are you? Because scaling recipes would sure as hell be easier to do with metric than English. Or doing reasonable conversions in any kind of construction (length of wood, sq ft->sq yd vs sq meter, etc). And I'm not even going to get into doing scientific calculations.
Oh, and before someone whines that metric doesn't make sense unless you convert to a metric time system, get a clue. The time system already has a fairly consistant base - base 60. There isn't a single English system that has anything even vaguely consistent. Besides which, once you get to seconds everyone starts using them as a metric baseline - milliseconds, nanoseconds, megaseconds, etc.
As a counterpoint, however, I do wish people would stop bringing up inane English units like bushel, league, hectares, etc. These units aren't used in anything but the same specialized fields that they were originally invented for. The only units that are in common usage are inches, feet, yards, miles (length); ounces, pounds, tons (weight); and teaspoons, tablespoons, ounces, cups, pints, quarts, gallons (volume - yes, this is the single most fucked up system of the bunch).
Folks, you're not getting it (Score:5, Insightful)
You don't build a magrail to give your spacecraft orbital velocity. Of course that's silly, for the reasons given above. You use it to give you some small PART of your velocity. This is extremely beneficial.
The crucial insight is that each bit of fuel you use for some stage of the flight needs to be lifted be even more fuel in the previous stage. Think backwards from orbit and it will make sense.
Say you have a 100-kilo satellite you want to accelerate at a constant rate for some period of time. For the last second of your flight, you need to burn, say, 10 kilos of fuel. That means the second before that, you need enough fuel to accelerate 110 kilos, 100 Kg of spacecraft plus the 10 Kg of fuel you'll need in the next second. So you'll need 11 kilos of fuel for the second-to-last second of acceleration. The second before that, you need 12.1 kilos. and before that, about 15 kilos. If you know anything about exponentials, you can then imagine how much fuel you need for the FIRST few seconds of the flight.
(This is not actually quite how spacecraft usually work, but it illustrates the general point nicely)
Over 90% of the fuel you are carrying is used just to lift the rest of the fuel that is burned later on, and a huge fraction of it is burned in just the first few seconds. And of course each kilo of fuel you carry requires a larger spacecraft to hold it, which in turn weighs more, which in turn requires even more fuel. So, if you can use a 10km or 100km rail to get your first few seconds of acceleration, you save a huge amount of fuel. This means a smaller spacecraft, which in turn means even LESS fuel carried.
The power burned by the railgun/mass driver/maglev whatever may actually be more expensive in raw form than rocket fuel (i.e. kerosene, in Russian rockets, which is less expensive per joule than electricity. US rockets use liquid hydrogen, which costs a bundle because you have to use vast amounts of electricity to cool it.), but it doesn't exponentially increase in magnitude as you head down the rail, because it's transmitted through wires rather than carried as mass in the spacecraft. Every second, you only need the same amount of electricity you used the previous second.
The same is true of chemical-powered ram and shock cannons, where fuel filling a cylindrical pipe is combusted behind the accelerating spacecraft travelling through the pipe. (not recommended for human payloads).
Furthermore, if your spacecraft has wings, this may give you yet another benefit. The shuttle has wings, but launches straight up, meaning for the ascent they are just dead weight requiring a huge, exponentially-scaled mass of fuel to lift. But on an almost-horizontal launching system, the wings can provide lift, and thereby actually be useful on the ascent stage. This of course is made easier if the vehicle already has significant velocity before it even lights its engines.
This whole system may not be a panacea; I'm skeptical too. But it probably is worth looking into, because it may help and doesn't require any technologies that don't yet exist. (unlike skyhooks/beanstalks or other strangenesses)