Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?
Space Science

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...
This discussion has been archived. No new comments can be posted.

Magnetic Space Launches

Comments Filter:
  • weird i just saw this on a discovery documentary like 5 minutes ago... neat
  • Although this technology is by far a better way to get payloads into space, all the energy used to create sufficient electricity to do so would make this method of launch just as costly as the previous. Mag/Lev is an excellent suggestion, after we make more breakthroughs in superconductivity and emf it will become a spectacular solution.
    • by AtariDatacenter ( 31657 ) on Friday January 04, 2002 @05:13AM (#2784088)
      Well, I don't think the *cost* of energy (in terms of dollars) really is the issue here. It is the amount of onboard fuel which displaces the amount of cargo you can take into orbit. And since fuel has weight, the more fuel you add, the more fuel you need to achieve orbit. So, earth-based electricity vs. vehicle based fuel really would be a plus.
      • by LadyLucky ( 546115 ) on Friday January 04, 2002 @06:07AM (#2784216) Homepage
        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.

        • I didn't think they launched rockets exactly vertically. To get the orbital speed right, they go off at an angle - possibly after goign straight up for the most dense part of the atmosphere. I suppose for geostationary sattelites they don't need quite the rotation (and they need to go further up). Easier to explain with a picture, but no can do here.

          This is why they like to launch from near the equator and always orbit in the same direction as the earth - you get a substantial boost (900 miles an hour according to Monty Python).
        • Definitely doesn't need to be vertical - you're out of half the atmosphere in 7 miles, out of over 99% of the atmosphere by 50 miles high, and by that point the velocity you need to get to orbit needs to be horizontal, not vertical; you still need some vertical thrust to counteract gravity of course, the main point is there's an optimal thrust/weight ratio beyond the atmosphere that is also associated with a specific curved trajectory, far from vertical...
    • Touche... The amount of coal to be burned to produce the electricity required may (notice I did say may) offset the environmental savings.
      Now, if they can use solar energy to fire that baby... That would be the shiznit!

    • all the energy used to create sufficient electricity to do so would make this method of launch just as costly as the previous

      Well, not exactly. In a traditional launch, the initial thrust has to get the mass of the payload PLUS a whole LOT of fuel moving. But as the fuel burns, each pound (or ounce, or whatever unit you want) of fuel adds more actual acceleration than the last pound did, because it has the same thrust but less mass that it has to push. The efficiency of the energy spent can be calculated by taking the integral of how much thrust is produced as the mass it needs to push decreases. As the launch progresses, each ounce of fuel has more effect (in the goal of accelerating the rest of the fuel and the payload) than the previous one did.

      In the mag-lev case, the mass of the object being launched starts out MUCH MUCH smaller than in a traditional case, and the entire object stays at that smaller mass. By the time the object has reached its target velocity, (I'm simplifying the math a little here) the total energy spent has been mass(final) times velocity squared, instead of the of integral of the mass(inital to final) times velocity squared (mass and time being our changing variables). It'd make more sense if I could figure a way to show mathematic equations in html ;), but if you've had some calculus it should make sense. Much less energy is actually used to get a given amount of mass to a given velocity.

      Obviously, it still requires energy, but not nearly the amount of energy for a traditional launch. Likely (at this point in the development of the technology) the mag-lev launch would still require some fuel burn at the end, to get the vehicle from the post-mag-lev velocity to an orbital velocity, and to get it up to the right height, but a lot of energy would already have been saved.

      In a nutshell, for emphasis: the vast majority of the energy required to launch something into orbit is used at the beginning of the launch, and mag-lev technology would be able to reduce the initial launch sequence's energy dramatically.

      • In a nutshell, for emphasis: the vast majority of the energy required to launch something into orbit is used at the beginning of the launch, and mag-lev technology would be able to reduce the initial launch sequence's energy dramatically.

        In a nutshell for emphasis: Your analysis, and others repeating the same thing, ignore one simple fact: Mag launching is *very inefficient*. It's unclear that there will be any cost savings, LH2 and LOX are fairly cheap, even reducing their costs by 50% won't affect launch costs much. Just because the energy (fuel) required in the vehicle proper is lower does not mean the total energy requirements in the system are lower.
  • by AtariDatacenter ( 31657 ) on Friday January 04, 2002 @05:11AM (#2784086)
    I'm wondering how much of the benefits of this is in the acceleration/speed they hope to achieve in a small space, versus the height they want to reach. I'm an idiot on the subject, admittedly (who's an expert, anyhow?), but which is more unrealistic, building an EM rail that reaches near orbit, or trying to accelerate 100s of tons verticaly to reach a high speed? (I'm still going to assume that they'll use rockets to reach orbit, and not 100% rely on the rail for the energy.)
    • In theory they hope to use this to totally replace rocket launches as it would be

      A. Safer
      - all equipment on ground easy to maintain and in case of a failed launch or problem the rail would still result in a partial launch - meaning the pilot could presumably guide the plane/wahtever to a landing.
      - No need to carry volatile chemicals

      B. Cheaper since, once agian, everything is on the ground - no need for throwaway boosters, etc Indeed once you pay for the construction all that is left is electricity and maintence.

      C. The plan isn't to accelerate them vertically as the G forces would kill a man to obtain earth orbit you have to have a speed of (I think) 25 Km/Sec which would, in a vertical launch scenario of say a 1000 meter tower, result in way over the 9-10 G's a human can survie. Instead they will be launched off of a gradually ascending slope spanning a couple of kilometers.

      However, and this is a big iffy, in all honesty this technology will go nowhere without superconducting materials to use in the rail. Without these existing, or any future, non-superconducting material cannot hope to maintain the power output/magnetic field necassary to propel an object to Earth Orbit or Near Earth Orbit (NEO).
      • by Tsar ( 536185 ) on Friday January 04, 2002 @05:42AM (#2784147) Homepage Journal
        [O]nce you pay for the construction all that is left is electricity and maintence.

        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...
        • by Rogerborg ( 306625 ) on Friday January 04, 2002 @06:32AM (#2784268) Homepage
          • To achieve a minimum orbital velocity in a 2-kilometer run, you'd have to accelerate at a little more than 1500 gees.

          Yup. And for a more manageable 10g, you'd need a 315km run to reach geosynchronous velocity. Of course, you'd also burn to a crisp in the atmosphere ;-)

          The advantage of railgun / rocket sled launches is in getting you some of the way up to orbital velocity, but there's still a good long way to go. Basically, you can't reach orbital velocity while still inside the atmosphere, so you have to carry a bunch of fuel up with you whichever way you cut it.

          Here's some handy dandy info for those who want to have a play with the numbers and have forgotten their Newtonian stuff:

          Geosynchronous orbit is at 42,245m, which requires an orbital velocity of 7869m/s. Gravity is 9.81m/s^2

          Distance = half of acceleration times time squared (s = 0.5 * a * t^2) and velocity equals acceleration times time, so time equals velocity divided by acceleration (v = a * t, t = v / a)

          If you know the speed that you want and the acceleration that you can tolerate, this gives you:

          s = 0.5 * v^2 / a (e.g. for 7869m/s and 98.1m/s^2, s = 0.5 * 7869 * 7869 / 98.1 = 315602m = 315km)

          Or, if you know the distance you have and speed that you want, and want to know the acceleration you need:

          a = 0.5 * v^2 / s (e.g. for 7869m/s and a 2km run, a = 0.5 * 7869 * 7869 / 2000 = 15480 m/s^2 or about 1578g!)

        • Of course, it would still make a nice high-tech catapult for lobbing massive conventional weapons hundreds of miles

          Hmmmm - I think I'd start to ask questions when I notice my neighbor building a giant maglev rail on a mountain pointing at me. Nothing is so suspicious as somebody constructing a gun that can only point at your head. ;-)
      • A. Safer - all equipment on ground easy to maintain and in case of a failed launch or problem the rail would still result in a partial launch - meaning the pilot could presumably guide the plane/wahtever to a landing.

        Maybe, maybe not. What if it tosses it fast enough to come off the rail, but not fast enough to maintain (gliding) flight? No safe landing!

        - No need to carry volatile chemicals

        Sorry, no. Maglev launched vehicles are going to have to carry significant amounts of fuel to boost themselves into orbit. Otherwise they'll pay an incredible penalty in heat sheilding to overcome the atmospheric heating at launch. (And it will be in different places mostly than that required for reentry, so no saving there.)

        B. Cheaper since, once agian, everything is on the ground - no need for throwaway boosters, etc Indeed once you pay for the construction all that is left is electricity and maintence.

        Maybe, maybe not. You have to get the launch rate up high enough to amortize the cost.
    • Traditional rockets tend to burn up to one quarter of their overall fuel reserves before they lift the first inches off the ground/out the silo.

      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).

    Just turn the thing into a giant "Tower of Terror" to raise funds ;)

    -- Dan =)
  • by Tsar ( 536185 ) on Friday January 04, 2002 @05:22AM (#2784106) Homepage Journal
    let's hope that the Navy research gets us a step closer to not burning all that Oxygen and Hydrogen to get to space...

    Yes, we must reduce emissions of deadly Dihydrogen Monoxide []! It's already filling our rivers, streams and oceans, and has been found even in the ice of Antarctica! The time to act is now, people! Before our wells are full of this dangerous chemical!
    • I think you're missing a very important detail. If the shuttle/ship/whatever doesn't need to carry the fuel necessary to get it into orbit then you've just removed a LOT of added weight. Think of how much weight SRBs add, let alone the liquid fuel tank.
      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.
      • by Tsar ( 536185 ) on Friday January 04, 2002 @05:54AM (#2784188) Homepage Journal
        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.
        • Hmm. Too braindead to do the calculation, but do you get a win if you have a circular track? You can go round that, accelerating away and then either let go (wheeee!) or bank off onto a straightening bit.

          Anyone care to do some sums on circumference, centripetel (sp?) force (oooh ooh centrigugal/centripetal flame war please) and other interesting numbers?
        • Those are interesting calculations. Now try this. If you just want to replace the first stage, then how long does the track need to be? Assume that the launch starts off horizontal, and then bends through an arc to over 45% toward vertical. And that you are replacing only the first stage. How long does the track need to be? How high should you try to go? Would Pikes Peak be a good launch site?
        • To compensate for drag in the atmosphere you need a muzzle exit velocity aroun 10-11 km/s. You'll still need a rocket on board to circularize your orbit less you come back down into the atmospher on the same parabola that you left. You can use this rocket to help you escape though and leave the the
          muzzle at a lower velocity. A 30 km launcher could accelerate cargo to 11 km/sec at 4000 gees, and could accelerate a rocket with people to 1.5 km/sec at 8 gees and save a lot of fuel for the rocket.

          Of course, an even better solution is to build your mag lev accelerator into a loop like a particle accelerator... then you can accelerate at whatever rate you want :)
        • by IdahoEv ( 195056 ) on Friday January 04, 2002 @01:51PM (#2786268) Homepage
          Few people here seem to understand the crucial issue. A couple do, but their posts haven't been modded up... here's another try.

          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)
          • oh yeah, that's another thing - once the vehicle gets to a certain speed via maglev, you might actually be able to use ramjet engines, which need to be travelling at supersonic speeds just to be lit. This would save on oxidizer.

            However, there's no real reason ramjets can't be used in space launches now. . .
          • simply calculating back from orbit means you can never have enough fuel to lift the fuel you just added, ad infinitum

            You have to factor in the fact that your craft gets lighter as you ascend - because it is shedding fuel when it burns it.
        • well, even with that "muzzle velocity" of 7814m/sec, you'll still need supplemental rocket propulsion to keep the craft going at that speed until it clears the atmosphere, and all that drag.

          Plus, at low altitudes, 7814m/sec is going to vaporize your vehicle very quickly - unless you add a heat-shield. Obviously, 3112 G's is going to mean an unmanned launch. Even 15 G's is pretty unrealistic. So you have to add a heat shield for launch, when you don't intend to even have a recovery.
          That's not an optimal design.

          Even in an unmanned vehicle - 3112 G's is pretty unrealistic. We CAN build a vehicle that could withstand it, but it would probably need so much reinforcement that there'd be less room for cargo - plus, your cargo would now have to be engineered to withstand 3112 Gs.

          So really, you have to accellerate magnetically to some speed, probably subsonic, enough to get the vehicle airborne, perhaps a few thousand feet, and THEN ignite rockets. At altitude, air friction won't be as bad an obstacle (nor will the sound barrier).

          I've read (on slashdot, years ago, so don't quote me on this) that the majority of rocket thrust is spent lofting more rocket fuel up through the lower and much thicker few miles of the atmosphere. Clear that barrier, and there's a significant savings already. You can't do entirely without rockets, nor would it be wise to try.
  • If I remember a while back, I could have sworn I saw some sort of launch system in either a computer animation demonstration or in a game itself.

    This idea would be interesting to apply into space as there is very little friction in space to slow things down. Why not make an addon on to the IIS to launch vehicles to Mars or Venus via this launch method? If the track was long enough it could go faster than convention rocketry. And in fact, less fuel would be needed on the vehicle since the mag-lev was the device that launched it.
  • The article mentions that you can use a mag-lev system to vastly increase the velocity of an aircraft. But on a carrier, it's also necessary to slow the aircraft down very quickly for a landing. Mag-lev is suited to this task as well - by turning the magnets "backwards," it is possible to reverse the direction of the track.

    By using mag-lev for both takeoffs and landings, the Navy could presumably have takeoffs and landings on the same boat very close to each other, without the complexity of the current mechanical system. But, of course, mag-levs are useless for landings from spacee, since spacecraft usually don't have wings - and those that do can just use parachutes for losing speed.

  • by flacco ( 324089 ) on Friday January 04, 2002 @05:48AM (#2784169)
    Would this result in lighter ICBM's with no vulnerable, sluggish launch phase and no heat signature during launch?

    Though I guess you'd have a hell of an "electro-magnetic signature".

    • Funny you should mention that...
      An American scientist during the 80s (I can't remember his name, but there have been shows about him and his work on Discovery and TLC) thought about creating a massive artillery piece for launching satellites into orbit. The artillery "barrel" would be almost half a mile long, and it would be a large facility. The US wasn't interested in it, and the scientist, very interested in promoting the tech, went to other countries to promote it. Eventually ended up in Iraq selling the tech to Saddam, where it actually started getting built. It was one of the "weapons of mass destruction" destroyed during the gulf war.

      I don't think the idea was ever put into actual practice, but if you can lob a several ton shell across countries, you might be able to change the trajectory such that the satellite cuts through the ionisphere (sp?) and can obtain a stable orbit.
      • I believe you are refering to Gerrald Bull (sp?). He was a Canadian who was murdered in Belgium IIRC. The rumours at the time pointed very heavily towards the Mossad and much less so at the CIA. Check out the following for more info: ht m n. htm
      • An American scientist during the 80s (I can't remember his name, but there have been shows about him and his work on Discovery and TLC) thought about creating a massive artillery piece for launching satellites into orbit.

        Turns out that the gun required to launch a useful payload required barrels made from unobtanium and quite long. By the time you added boosters to the payload to cut down on gun size, and move it into something buildable, you didn't save any money and created a very payload hostile launch enviroment. (I.E. pointless)
  • by Rogerborg ( 306625 ) on Friday January 04, 2002 @06:05AM (#2784211) Homepage
    • NASA hopes to drive down the cost of rocket departures from $10,000 per pound to $1,000 per pound

    Whoa there, son. Y'all from the future? Let's use units we all understand: what's that work out to in bushels of cotton per hectare?

    Hmmm, I can't help but think that if we ceased habitually using stone age units of measurement, then we might be able to stop pounding Mars with "landers" ;-)

    • Using Pounds is a way for NASA to save money...

      As Pounds is a measure of weight rather than mass, the cost goes down as the weight reduces as the payload goes into orbit.

      If you used Kilograms then you would be measuring mass which stays fixed, hence no cost savings ;-)

      (Top Tip - Always buy a 2.2 Pounds of moon rock, never 1 Kilogram - You will get about 6 times as much rock due to the lower gravity on the moon)
    • Pounds (of force and mass) are great units for working with rocket equations because you can "cheat" on your units and use specific impulse (measured in seconds... sort of) instead of using exhaust velocity. I also find it makes it easier to use gees as your unit of accel. than using m/s^2 with kg of mass and newtons of force.

      Metric is great fun for calculating electrical problems (IMHO), but English is better for rocketry. In adv. physics, just pick whatever strange units (like measuring velocity in %c) make the equations come out easy then convert back when you are done. Units of measure are just a tool, no need to be a zealot about them.
  • Based on what I've read so far, it really isn't realistic to expect something like the space shuttle to be placed into orbit 100% from an EM rail. However, I'd go back to those other unconventional designs, like a helicopter or a jet being used as a launch vehicle for something designed to go into orbit. Those are being pushed because the benefit is that they clear the lower, dense atmosphere, which is where a lot of fuel is said to be spent.

    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?
  • by Daniel Wood ( 531906 ) on Friday January 04, 2002 @06:13AM (#2784228) Homepage Journal
    Hopefully, we can reduce the weight of the fuel and oxidizer that's needed to be carried on board the vehicle and that will decrease the size of the vehicle," said NASA scientist Kenneth House. "So hopefully, we could get more payload into space with less of the fuel."

    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.

  • let's hope that the Navy research gets us a step closer to not burning all that Oxygen and Hydrogen to get to space...

    ...We wouldn't want all the resulting water vapor polluting our atmosphere, and our poor mother earth.

    • We wouldn't want all the resulting water vapor polluting our atmosphere, and our poor mother earth.

      Little known fact: H20 is a greenhouse gas. It's not nearly as bad as CO2, but it can contribute to warming the planet. Of course, I seriously doubt that shuttle launches contribute materially to any kind of warming. We don't launch them very often, and the atmosphere is big. It's just that the idea of "water-vapor pollution" might not be as far-fetched as you make it out to be.

      On the other hand, lots of water vapor should also cause more cloud formation, which raises the albedo and should lower the average temperature. There are days that I think that climate science is even more dismal than economics...

      • I did know that particular fact... and I agree, there isn't much a shuttle launch adds, considering all the power plants out there that dump their steam right into the atmosphere right after it goes through the turbines.

        My uncle was a NASA engineer who built devices to study the ozone layer and the greenhouse effect. His team's opinions were a bit different than the doomsayers regarding the greenhouse effect. Mainly, that the Earth cycles through periods of greenhousing followed by glaciation, and that we are on a warming trend anyway.

        The amount of greenhouse gases emitted by humans is comparatively low compared to some natural sources like volcanic eruptions.

        Interestingly enough, the Mt. Pinnatubo eruption in the early '90s (was 91 or 92,..) spilled more CO2 into the air than people could imagine, but the dust it spilled into the air lowered the average temperature of the northern hemisphere about .5 degrees for almost a year.

        It was very noticable, too. We had snow in August, which is normally our hottest month here. (Normally hits near 100 degrees.) There was basically no summer that year.

        If lowering the Earth's temperature by .5 degrees has that effect, I would welcome a few more degrees increase! I'd like the safety margin. I really hate the cold!
  • by nsample ( 261457 ) <nsample AT stanford DOT edu> on Friday January 04, 2002 @07:00AM (#2784321) Homepage
    This makes me feel REALLY old, but the EML technology research has been going on for over 20 years. I recall the 1990 High School CX debate topic very well and spent most of the year debating EML launchers (prototyped on Sandia National Labs railgun). We spent the summer in the library in New Mexico visiting Sandia and UNM to research our cases. They were already launching coffee can-sized payloads at that time.

    Some of the EML experiments from the late 80s and early 90s were visited at a 95 IEEE pulsed power conference: here []. Of course, it's been a HOT topic since pre-85, when the first IEEE pulsed power conference was held.

    We've been at the brink of maglev space launches for the alst 20 decades. Maybe it'll happen tomorrow. Probably not. There's basically no money in this sort of solution for defense contractors, so it generally languishes in congressional committees when it comes time to fund...

    Oh well. It would be cheaper, cleaner, safer, and a whole helluva lot more fun at parties... but the same issues applied 20 years ago as today: it doesn't get funded b/c it's a public works-type solution to space. There's no money for Lockheed in something like that.
    • Remember - in 2001 - A space yawdezze (book, not movie), Clarke predicted (or at least for literary purposes), that by 1999 we would be using Magnetic Launching. Remember - Floyd was impressed that they were using the power of an entire nuclear bomb's energy output simply to launch him into space. I forget how long clarke speculated the track would have to be, but he was only going to the space station.

      What we need now are some nice scifi devices such as Inertial Dampeners, Transporters, and bigass klingon battle cruisers.
    • We've been at the brink of maglev space launches for the alst 20 decades.

      And for pretty much the same reasons as we've been on the brink of fusion power for about the same length of time... Mainly that there are enourmous practical engineering and economic problems between viewgraphs and working hardware. It's not entirely clear that any money will be saved in the near (10-15 yrs) term between the current systems and a maglev system.

      The bulk of our current infrastructure has long since been amortized; to replace it with a new system will be tremendously expensive. (Hence the focus of CATS on minimizing infrastructure requirements.) Hardware costs are (mistakenly) believed to dominate launch costs, but the real cost in current generation systems is in payroll. (Again most CATS efforts seek to minimize the costs of preparing the vehicle (ELV) or turn around (RLV).) The trick to reducing space access costs is to reduce life cycle costs, and maglev does just the opposite by introducing a enormous R&D and capital construction costs right at the front end, especially if not accompnied by changes to other parts of the overall system.
  • a payload the size of most smaller sattelites or even a resupply module for the ISS could easily be flung into space with a railgun. The technology is proven, doesnt require special superconductors, and they have plenty of linear space at the cape to build a launch facility. The only thing they would need is a massive amount of electrical energy... like their own power plant.

    In fact they were going to build such a launch system back in the 80's... I remember seeing it in a Pop-Sci magazine when I was in highschool.
  • Magnets schmagnets, lets just tie a long rope to the space station and we can climb up, like in gym class.
  • Great idea to save some fuel.

    Give the spacecraft a push, so you can wait until a certain hight before you turn on the rockets.

    This is great if the rockets then actually ignite. Otherwise you would look kind of silly just throwing a spacecraft high into the air and then just watching as it drops :-)

    By the way - to all those posts discussing geo-stationary orbit and earth escape velocity. You dont need to go all that way :-) The space station is orbiting in approximately 400 km, and it is much cheaper to go there.


    • A manned shuttle would have wings, and would be able to glide or power back to a landing strip. Or, if it were a vertical lander, it could do a really fancy tail swing maneuver and touch down with rockets on.

      An unmanned wingless craft could be permitted to go splash in the ocean.
    • That's one of the advantages of conventional launches with liquid-fueled engines. You can start and test the engines for proper operation before you commit to a launch by releasing clamps or blowing bolts to release the launch vehicle from the pad.
  • silly magnets (Score:2, Interesting)

    by buzban ( 227721 )
    I'm glad that maglev technology is finally being applied to something worthwhile. I'm getting really tired of seeing all the maglev rail transportation projects that never go anywhere (figuratively and literally)... :
  • Pardon my naivety but if a speed of over 7000 metres/sec is needed to achieve orbit, wouldn't the craft burn up?
    And wouldn't it have to be going much faster than that off the launch track in order to be at 7000 m/s as it leaves the atmosphere?
    It would be better to use the maglev to achieve the velocity necessary to cause a ramjet (or is it scram?) to ignite so as not to require the assistance of conventional jets, rockets and B52s to launch them.
  • I'm sure this was one of the technologies that you get in Sid Meyer's Alpha Centauri - so it must be workable!
  • by ( 216696 ) <> on Friday January 04, 2002 @10:53AM (#2785045) Homepage Journal
    Imagine a cable running from the top of a 50 km tower into geo-stationary Earth orbit. Travelling on the cable is made through electromagnetic propulsion. Nasa is considering a 50 years timeframe for the space elevator [] to become real.

    Maybe I'll go in space after all.
  • by dar ( 15755 )
    How odd that we just had a Heinlein poll and no one has yet mentioned that this sort of launcher was described in "The Moon is a Harsh Mistress" quite some time ago.

  • There are more people looking at this for space launch than just a handful of guys in Huntsville launching model airplanes. And a lot more than $30,000 is being spent on it. These guys just did a little better PR (perhaps the fact that Huntsville is a short drive from CNN's facilities in Atlanta helped). Surely you don't expect CNN to have the latest (or even accurate) aerospace news, do you? Do they do an accurate job reporting about software? Go spend the money on (or find a library that has) a subscription to Aviation Leak and Space Technology, Janes, or better yet Journal of Spacecraft and Rockets if you really want to know what is happening.

    U. of Washington EM Propulsion google cache [] (the original is either down or has been pulled for security reasons)

    Gun Launched Satellites JH-APL [] (.pdf file)
  • Magic Mountain, in Valencia, California. I believe it is the Superman ride. It launches a pretty massive set of roller coaster cars from 0 to 100mph at about 2 Gs. I'm not sure why the designers chose this method, but it is a great proof of concept.

    To me, the best use of this kind of launcher would be to get an orbiter up to ramjet speeds, say 500 mph, then let it fly on ramjet power up to a tanker. I'd have the ship fully fueled with LOX, but with almost empty fuel tanks, so that it could be lighter and easier to get off the ground. Once fully fueled, use the ramjet to get to 100,000 ft and Mach 3 or so. From that altitude and speed, single-stage-to-orbit is remarkably easier than it is from the ground. You can use full-expansion engine bells to get good specific impulse, and going from Mach 3 to Mach 25 is significantly delta-V than 0 to Mach 25.

  • Yes, NASA is always chronically underfunded for it's intended missions, but fortunately they aren't the only ones working on it. The military invests a lot of money in R&D, including pretty far-out projects (thanks to DARPA), and there's a long, long list of technology transfers. So if the Navy develops this one for carriers, it won't be long before someone applies it to space.
  • Here's some simple physics to show why this idea is great. If a force acts between two bodies, one of mass M1 (the spacecraft) and one of mass M2 (the exhaust gas, or in this case, the earth and launcher), then the energy efficiency of the process is M2 / (M1 + M2). In other words, the more massive the launcher, the more efficient the launch. (For physicists in the audience, I will get into detail if you wish.)

    Consider a gas-exhaust rocket. Say that the rocket has a mass of 1000 kg and the fuel has a total mass of 100 kg (don't know if it's realistic, just an example). The efficiency of this process (neglecting heat losses) is 100 / (1000 + 100) = 0.091 = 9.1%. Now, consider the earth/launcher system, with enormous mass compared to the spacecraft. The efficiency of this process is M2 / (M1 + M2) where M2 is a huge number compared to M1. This efficiency is close to 1, or 100%!

    What this means is that the vast majority of the energy you put in ends up accelerating the craft. This is opposed to the gas-exhaust system where only 9% of the energy goes into the spacecraft -- the remainder is carried away in the exhaust kinetic energy.

  • If we ever hope to build large space stations, then cutting the cost of earth launch to $1,000 per pound won't cut it. On the other hand, this technology on the Moon, perhaps with solar cells providing the electrical power, would allow for very cheap transfer of lunar material, refined or not, to points earthward. That could be Earth orbit or L4 or L5.
  • My father is the John Cole quoted in the CNN article and it's his office that is managing the maglev (among a lot of much more interesting projects), so I am familiar with this particular project. No one at NASA want's to use maglev as the only method for putting anything into orbit, but rather as a launch assist for chemical rockets. You would be amazed at the weight savings just by accelerating a rocket to 500MPH before using onboard fuel. Also, another point missed by most is that while maglev has been around a while, one of the main problems has been power availablity. For an operational system, you will need 3-6 Megawatt's in 6 seconds. To solve that problem (they don't think they could get a large nuclear power plant just for this thing) they are thinking about using VERY large flywheels to slowly spin up and store the energy until launch. And funding is next to nill. The army was kind enough to donate a few model airplains for the test rig. I used to have some MPEG's of this, if I find the URL, I'll post them. For further perusing and some nice pics, try l and John Cole Jr.

"my terminal is a lethal teaspoon." -- Patricia O Tuama