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Technology

Spacecraft Launching Maglevs 230

M1000 pointed us over to a recent Wired article regarding NASA picking up maglev technology for launching spacecraft. The reasoning is that the weight-cost of propellant when launching shuttles takes up a high amount of the weight and this would cut down the needs for rocket fuel. Rockets would still be needed for the final launch as the current max maglev speed is 600 MPH. More experiment test models are being worked on now.
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Spacecraft Launching Maglevs

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  • who? Tesla? don't you mean Edison
  • by Anonymous Coward
    What ever Happened to the Guy that Designed those extremely Powerfull Cannons that Canada was experimenting with? They had a couple Low Orbit Launches of Small Projectiles with those things...
  • Ok.. this article doesn't really answer a question of mine .. how tall would you need this thing to be to launch a shuttle? The concept of simply shoving a shuttle a couple of hundred feet into the air then launching with rockets seems weird. I get the feeling I'm not getting the entire gist of this article. Will the maglev simply give the shuttle the initial push into the air where traditional rockets take over? That doesn't seem to SAFE actually .. what if the maglev shoots it up and the rockets don't fire? Ker plunk. Ah well, if it helps commercial spaceflight it's a good thing.

  • I thought Mag-lev has already been used for a train/subway system in Japan?

    Anyone notice the link on slashdot actually has a 'slashdot' directory in the path?

    http://www.wired.com/news/news/slashdot/technolo gy/story/22188.html

    Whereas the news page link is:
    http://www.wired.com/news/technology/0,1282,3184 8,00.html

    Wonder if "Tired" are trying to counter the /. effect.
  • I'll bet Tesla could've answered some of these questions 70-80 years ago.
  • I've always figured that the bigtime use of space wouldn't happen until we had something better than gianormous rockets to get stuff Up. For $75 bucks worth of electricity, a lot of stuff could be sent up everyday. I don't know if people would be hip to being magnetically hurled into space at 6gs for vacations or something but still, it's better than sitting on top of millions of gallons of rocket fuel.
  • Ever since I was a child I've wanted to go into space. I remember reading an article in Wired a few years ago about a company that was planning on offering civilian space cruises. Essentially it was a week for $80K and is supposed to be operational in 2012. Since then I've heard more and more about privatizing the space industry (mostly for turing the launching of satellites over to the private sector) and the possibility that I will be able to do this.

    If this technology works, then a launch into space will only cost $75 plus the repairs involved in the trip. It seems like this will bring this dream even closer.

    That isn't even to mention the increased feaibility of building larger, more habitable space stations. At this cost, sending the materials up will be much cheaper.

    Finally, another great thing this may open is the easy disposal of radioactive waste. With this technology, we may be able to send our waste to Jupiter.

    All and all, I think this is tax money well spent.
  • This is great news. Any way that NASA can streamline their current processes and cut the cost per launch will help us all in the future. So many of our greatest technologies have come from NASA. There was also another wired article (http://www.wired.com/news/news/business/story/219 55.html) that spoke of the privatization of NASA, which I believe is the only hope for one of America's greatest gov't agencies.

    I also predict that out of this very technology may well come the floating cars and skateboards of back to the future fame. :)
    -stax
    /. poster #104543567

  • by Anonymous Coward
    Gerard Bull. He went to work for the Iraqis, building a "supergun" with which they could hit Israel. Israel didn't take too kindly to this, so after a few increasingly blunt warnings, he met with an "unfortunate incident."
  • Back when I was a member of the Chicago Society for Space Settlement (later to be integrated into the larger L5 society), the big thing was Mass Drivers (basically the same technology as Maglev), on the moon, to launch lunar material into space, for construction of space stations, spacecraft, etc.

    This can propel things MUCH faster than 600MPH - I think that the difference is that Maglev is focussed more on a magnetic levitation, to eliminate mechanical drag, but getting to 600MPH does not seem to be much of a boon to me - since the launch vehicle is eventually going to have to reach much faster speeds, thousands of miles per hour - how much would the first 600 save?
    The Mass Driver would have been on the lunar surface, so air friction would have been almost nonexistant, but the models we saw rode on rails, so there was mechanical friction.

    Seems to me they're probably using "Maglev" as a term people who have read Popular Science would be familliar with, but they must be really talking about a Mass Driver.
    The other problem is - accelleration. You wouldn't necessarily want to put a manned vehicle up with this thing, otherwise you'd have to build a VERY long track to stretch the accelleration out over a longer distance to reduce the Gs. Longer track = extreme cost (when you're talking about supercooled magnets and very sensitive sensors, and super-straight track).

    "The number of suckers born each minute doubles every 18 months."
  • by Restil ( 31903 )
    Most of the costs related to space travel is related to the amount of fuel needed to get out of Earth's gravity well. Any small increase in weight requires a large amount of extra fuel, which in turn requires a larger rocket, adding to the weight. ANY reduction in fuel requirements reduces the cost at an exponential rate.

    Other options include using fuel which applies more thrust per mass. Chemical propulsion is very inefficient, but many of the alternatives take advantage of politically unfriendly qualities. Its hard enough to get a nuclear power source into space without half the world complaining about it. If a rocket was propelled by a nuclear reaction, you could bet the complaints would be much louder.

    -Restil
  • by Apuleius ( 6901 ) on Tuesday October 12, 1999 @01:04PM (#1619610) Journal
    Every time your monitor screen goes tie-dye-t-shirt you know it's a launch time.
  • well, the system they talk about in the article accellerates objects at 6g's (6x the force of gravity). i doubt the FAA would allow that to be done to airline passengers (iirc, the average person blacks out at 7g's).

    they could however reduce the acceleration force simply by making the track longer and thus having the object accelerate slower. this solution however introduces more cost, both for the track materials and electricity.

    besides, the main gain of the system described in the article is that they save on the some of the weight of the rocket fuel needed to get them from 0 to whatever the max speed of the maglev system is (600mph here). i doubt enough jet fuel would be saved in the short distance of a runway to offset the cost of the whole system...

    --Siva

    Keyboard not found.
  • what's with this first post mania? it isn't like anyone really *cares*. First of all, the whole 'immortality on a message board' thing isn't true. I personally have my messages arranged highest scoring first, so that I get the most interesting threads, while safely stowing the -1 and 0 posts away at the bottom, in case I need a laugh. Second of all, posting something like 'hey! i've got first post!' is not gonna go over well with the moderators... First Moderator: Hmm, this post says 'Hey! I got first post!' Second Moderator: So do all the other posts... First Moderator: Hmm, -1 to all of them? So your little rating gets shot to hell. Okay, now...on to that article (oh yeah! the article!)... This approach seems exceedingly interesting, but I have a few questions: I assume this won't be used in manned flights? I'm not exactly sure, but isn't 6-G enough to make you black out? Mommy, I don't wanna be an astronaut anymore... Okay, they've got you on this track...now how do they get you from going horizontal (along a track) to vertical (into orbit)? Do they have a steep incline at the end (like a roller coaster? whee! look Houston, no hands!), or is the entire track on an incline? If so, what angle? 45 degrees would be best I suppose...does anyone else care to hazard a guess? Maybe the entire track is vertical, 90 degrees up. Seems like that would take more than 200 kilovolt amps, though. Where are they going to do this, anyway? Personally, I think Cape Canaveral is a really dumb place to launch rockets from. It's at sea level, n'est ce pas? So you have to go through the entire atmosphere...plus all that pesky gravity before you get into orbit. A better place would be in the rockies somewhere (you could turn that place in Florida into a trendy beach resort for government employees on Arbor-Boxing-Skeeball Day Vacation). Not only would the trip to orbit be shorter, but it would be thinner air up there...the only problem might be getting the shuttles up there again; you can't use a ship, you'd have to use trains or trucks (or just land there, which doesn't seem likely). Well, whatever happens, I want a ticket to the first launch =)
  • This will cost a LOT more than $75 per launch. That is just the cost of the electricty to operate the Maglev. There will still be rockets in use, and the fuel requirements will still run into the multi-million dollar range, this will just reduce that figure somewhat.

    -Restil
  • Escape speed is a scalar quantity. As long as you aim something above the horizon and launch it fast enough, it will reach some kind of orbit. Of course flatter trajectories will have to be _somewhat_ faster to account for wind resistance. You could have a maglev track that is very long and nearly flat, and launch your vehicles out over the ocean if you wanted to. Definately interesting stuff.
  • Didn't Arthur C. Clarke have maglev-launched spacecraft in 2001:A Space Odyssey (the book)? Who knows, if NASA gets its act together, we might have this stuff by 2001.
  • He went to work for Iraq designing their "Supergun". He was murdered a short time later.
    ^. .^
  • Since all the acceleration (0-600mph) would have to happen while the craft was moving along the linear track, it wouldn't be too good for anything living. (unless you had a really long track)

    A friend of mine had an idea to buy old missile silos out in the plains and use them to launch capsules w/ people in them to ~20k feet, then fly to a destination from there. Just turn the silos into giant inductive coils. No problem.

    Except, just as above, all the acceleration would have to happen before the capsule left the silo. The only thing left inside the capsule would be a greasy skeleton and lot of red goo.

    But it might be a great way of delivering payloads that can withstand a lot of g's. Too bad a lot of the instruments on satellites are almost as delicate as a human being.
  • I've read (where I forget) that rocket launches release a lot of atmospheric pollutants. I don't remember if it destroys the ozone layer, or causes global warming. Of course, generating electricity isn't a pollution free process either.
  • I believe these cannons used conventional explosives for propellants.
  • My reading of the article is that the track is used for "launch assist", meaning that it doesn't totally replace the rockets. It just means that the fuel needed to achieve escape velocity is considerably reduced.

    Does anyone have more exact info on this? The article doesn't go into detail about how much of the actual fuel is replaced by this technology. It does mention a 20 percent reduction in the overall mass of the rocket, but what does that translate into? Anyone know?

  • by Daffy Duck ( 17350 ) on Tuesday October 12, 1999 @01:13PM (#1619621) Homepage
    The article doesn't mention it, but last year Lawrence Livermore National Labs wrote [llnl.gov] about a maglev system with a passive track, saying there were plans to test it for use in rocket launches. I'm a huge fan of this "Inductrack" system, but I haven't seen any mention of it in months. Does anyone know if this is the system they're using?

    The article says the concept was tested in England, so I doubt it's the same technology, but hope springs eternal.

  • Escape velocity is seven miles per second or 25,200 miles per hour. I ve often wondered if it's possible to use the same construction techniques that were used to build the "Chunnel" across the English Channel to build a LONG undersea tunnel with it s mouth at the surface.

    Then, using a combination of magnetic acceleration and pneumatic pressure, accelerate a
    payload to escape velocity without ANY rocket fuel.

    Of course the thing would be hugely expensive to build. But once built, throwing payloads
    into space would be cheap, cheap, cheap.

    (A variation of this was used by the lunar revolutionaries in _The_Moon_is_a_Harsh_Mistress_.)

    It would seem that the exit velocity of this device is only limited by it's length. (Okay,
    length, air resistance, and C.)

    trichard

    p.s. Someone do the math to see how long this tunnel would have to be to accelerate
    an object from rest to 7mps at 1G, 2G and 5G's.

  • "Electricity is both inexpensive and environmentally safe"

    Is it really more environmentally sound than burning rocket fuel? Isn't a lot of electricity still produced by burning coal? Seems to me we're far from having "environmentally safe" electricity.

    I don't debate the value of the technique - any reduction in weight is incredibly helpful during such a launch. I just don't like the fact that this guy's claiming environmental superiority. Sure, there's less pollution at the launch site, but there's still pollution at the plant...
  • I don't have the maglev gun performance numbers handy, but I doubt this technology will make a *practical* space launch vehicle. For one thing, imagine the infrastructure involved with building a maglev rail on the side of a decent-size mountain (to get the altitude and structural strength required to launch a cargo-bearing craft). Plus, you still have to have a rocket for the rest of the way up.

    OTOH, there exist propulsion technologies that require minimal to no infrastructure and are probably safer (think of the poor safety people having to deal with rocket fuel being propelled at Mach 1 (~600 MPH) up the side of a damn mountain! ;-).:

    Linear Aerospike engines (what the X-33 will use). Basically they optimize rocket performance for any given altitude, making for a far more efficient launch, and enabling Single-Stage-To-Orbit (SSTO) vehicles that are lighter and smaller.

    Aerial Rocket Refueling [rocketplane.com]. Also known as "Black Horse" [mit.edu]Technology which is far crazier than the aerospike and far less safe, but it'll probably be cheaper if it gets off the ground (pun not intended).

    Alternative SSTOs like that rotor-rocket (the name of the company escapes me) and the McDonnel Douglas (I guess Boeing now) Delta Clipper.

    ICBMs... didn't the Russians recently launched a LEO off a damn silo? ;-)....

    Maglevs are cool, but IMHO rail-guns will be a lot more useful for what the Army *really* wants them for: high-speed anti-armor projectiles, as in tank canons... guess with those Lithium Polymer batteries, they might be able to pull that off ;-)...

  • I'm not exactly sure, but isn't 6-G enough to make you black out?

    A human being in good health will black out somewhere between 9 and 11 Gs. At least that's what they say about fighter pilots.
  • iirc, the average person blacks out around 7g's. space shuttle astronauts are subjected to 3g's during takeoff, which most people can take fairly easily (think amusement parks).

    regarding the angle of the track, thats the question i was left with after reading the article. as someone else mentioned, it is possible to penetrate the atmosphere at any positive angle above the horizon (provided there are no obstructions). i would think the system wouldnt work straight up b/c the object would no longer be levitating above the track, it would be next to it (unless they surround it with track sections, which seems a bit impractical).

    as for Cape Canaveral, i believe one of the considerations in choosing that location is that its close to a large body of water (2 if you count the gulf of mexico). they jetison the Solid Rocket Boosters after 2 minutes of flight, and they are later picked up by ship. obviously you wouldnt want to just drop those over land. the other thing to consider is, if they have to scrub the launch, they dont want to be jetisoning the SRB's or the big fuel tank (cant remember what its called) over land and have it drop on a populated area.

    hope i didnt babble to much...

    --Siva

    Keyboard not found.
  • That's a good point, especially if you consider than most nuclear reactors in north america are growing old and there isn't the political will to build more nuclear reactors. When those reactors retire, guess what they're going to be replaced with, natural gas/coal/etc reactors. So much for Kyoto.
  • The closer to the equator, the better. Launch to the east at the equator and you pick up about 1000 miles per hour from the rotation of the Earth.

    Escape velocity is just one big vector sum, you know.
  • Is it just me? Somehow I can't help but visualize something that looks a lot like Gerry Anderson's Fireball XL5 [ed.ac.uk] - a rocket-aided launch of an aerodynimcally-shaped spacecraft from a track (although the track would have to be a bit more vertical).

    Maybe somebody could start designing a prototype of Captain Steve Zodiac's space scooter as well.

    --

  • I think the reason for florida is that if something goes really wrong, the debris won't land on people. It would land in the ocean.

    Bah, accidents dont happen very often (only once so far).. I agree with you.. The money is worth the people. :)
  • hmm...i do recall that about fighter pilots, but i was thinking 7 for "average" people, since fighter pilots do have a bit more training. plus, iirc, they also have a system in their flight suits that helps force blood back up to their head (well, i know it helps improve circulation somehow...).

    --Siva

    Keyboard not found.
  • thats a good point too actually. i would think theyd have to insulate the object's (be it plane or spacecraft) electronics systems from the magnetic field...here's where my electrical physics knowledge ends however...

    --Siva

    Keyboard not found.
  • It is a lot more friendly to the environment than burning rocket fuel :)
  • but are those Gs sitting, or laying down. iirc, you can take a lot more if you are laying down (now hard to do with spacecraft)
  • I thought a "rail-gun" was something different, something like an aluminum slug used as propellant, by being vaporized by a high intensity microwave source, otherwise fairly similar to a standard "gun". . .

    Or do I have my technologies mixed up?

    "The number of suckers born each minute doubles every 18 months."
  • I did a little math, and I hope the numbers aren't totally off here... The Space Shuttle, accelerating at about 3gs, takes about 50 seconds to reach 600 miles per hour. The SSMEs (Space Shuttle Main Engines) consume over 1,000 lbs of fuel each second, so by getting rid of that first 50 seconds worth of fuel, you can put an extra 50,000lbs of cargo into orbit.

    These numbers apply to the Space Shuttle itself, which is only rated to carry 55,000 lbs of cargo in any case, so think about how important that first 600mph is first and imagine what it could do for a spacecraft designed to take advantage of it. In the case of the Space Shuttle, it would theoretically double the cargo weight capacity (if there were only enough volume to take advantage of that).

    Using magnetic assist is an excellent idea. I would like to see the day when a launching track goes up the side of Mt. Kilimanjaro and can toss cargo and ships into orbit almost unassisted.
  • Seems to me they're probably using "Maglev" as a term people who have read Popular Science would be familliar with, but they must be really talking about a Mass Driver.

    No, They're talking about using magnetic levitation, a linear motor.

    Further, given that they are talking about trying to supply power only to small portions of the track at a time, I would guess they are trying to cut down costs for a really long track. As far as I understand the technology (and some of you physics guys can help me out here, 'cause its been a while since I looked at it) all the really expenisve bits (i.e. used for cooling) can go into the vehicle, and the track can be just turned off and on in time. The track both suspends and propels the vehicle.

    The reall problem is shielding any human passanger from the magnetic fields that are going to be in the area. The shielding is gona be heavy. But There was at least one human usable maglev at an airport in england, so it is doable.

    locust

  • I just did the math to see how long this tunnel has to be... I'm not to familiar with miles, but I've used 1 mile = 1609 meters To sccelerate an object from 0 to 7 miles/s, at 1G would take a 4013 miles long tunnel (with no air resistance). 2G: 1003 miles, and 5G: 159 miles. Stian
  • The problem that I see with this is what happens if the rocket misfires. The object that they're trying to launch has already been lifted x feet off the ground. This seems like a recipe for disaster to me.
  • 6Gs is pretty extreme but for trained pilots/astronauts laying on their backs it shouldn't be an issue, its only going to be for a few seconds. Fighter pilots experience blackouts and tunnel vision during high G maneuvers but part of that is due to G forces pulling blood down into their legs and away from the brain. With the seating position in the shuttle or other launch vehicle blood rushing to the head is going to be more of a problem than blood rushing to the lower extremities. Top fuel dragsters are now routinely pulling 0 to 300 in under 5 seconds at 5Gs and the drivers are not yet experiencing blackouts.

    As far as launching from Florida, its a velocity issue. You must accelerate to something like 17,000Mph to achieve orbit, at the equator you pick up 1000Mph free from rotational velocity. Florida is closer to the equator and thus gets more of that free velocity than a launch site further north would.

  • Actually, the proposed launch mechanism saves fuel and reduces pollution. This is because an ordinary rocket wastes a lot of energy accelerating its own fuel; if you can reduce the amount of fuel that's on the rocket, you can get away with considerably less fuel total. Less fuel = less pollution. (This doesn't even violate TANSTAAFL, because the ordinary rocket effectively buys two lunches only to vomit one.)

    Furthermore, as bad as coal may be, I tend to suspect that rocket fuel is worse on an environmental impact per joule basis. Unless you're dealing with reeeeealy high-sulfur coal...

  • I wonder: if that tunnel was constructed, would there be a problem with the magnets? Would there be any un-for-seen variations within Earth's own magnetosphere that would cause the payload to slow down? I'm definitely not an expert, but I'm just curious about this project.

    Rajiv Varma
  • The article doesn't go into detail about how much of the actual fuel is replaced by this technology. It does mention a 20 percent reduction in the overall mass of the rocket, but what does that translate into?

    Most rockets are huge canisters of fuel with a teensy little area to hold people and cargo. Doing multiple stages helps, but you're still talking about a vehicle that's mostly fuel. So it's probably a 20% (or some number remarkably close) reduction in fuel with a corresponding 20% reduction in bits of rocket to hold fuel. Or maybe it's a 21% reduction in fuel and a 15% reduction of the rest of the rocket. Either way, the fuel reduction and the overall mass reduction won't be too far apart.
  • #1 unanswered question: How long a track are we talking about?

    please pardon my imperial units, IANARS*

    600mph = 880 feet per second

    6g = 32fps^2 * 6 = 186fps^2

    dig out HP-15c...

    time on rail is 880/186, 4.7 seconds

    distance = 1/2 acceleration * time^2 = 1/2 * 186 * 4.7^2 = 2000 feet!

    Well thats a little extreme for something that wants to point up in the air. How about if we squish the astronauts to 9gs? (The computers can fly until they become concious again.)

    acceleration is 288fps^2, time on rail is 2.8 seconds, rail length is 1100 feet. Still fairly long.

    I'm just guessing here, but if you lay the track flat you will lose the initial energy gains to air resistance in the longer atmospheric journey. This isn't going to be any wimpy tower either, multiply the shuttle mass by 9 to get the load on the 110 story tall tower, be sure to plan for lots of vibration. For those of you calculating along, the shuttle is about 2000 tons at lift off. You can probably deduct 20% of course for the savings of this system.

    Maybe for non-human, sturdy payloads and outrageous accelerations this can work out.

    #2 Unasnwered question: Why linear induction?

    Assuming a preliminary kinetic boost is a winner, why linear induction? Aircraft carriers seem happy with steam catapults. How about conventional electric motors on a carriage? I'm reasonably sure these are more efficient for a given price if they can do the job.

    IANARS = I am not a rocket scientist

  • Getting to LEO is hard .... you have to get above the atmosphere then go sideways real fast.

    Don't start building that big accelerator in the basement just yet ....

    Most rockets that launch go straight up to get out of the atmosphere as quickly as possible (drag is the killer - taking off on an angle is a sure way to waste valuble energy) then take a roughly 90 degree turn to put them selves into orbit.

    Since it stays on the ground all this does is does is give the payload a helping hand getting out of the atmosphere ... it doesn't help it get into LEO (you still need reaction mass for that) - you aren't ever going to be shot off a big railgun directly into orbit (unless you have something to catch you up there).

  • by Anonymous Coward on Tuesday October 12, 1999 @01:45PM (#1619650)
    You can read about Dr. Gerland Bull here [std.com].

    How it works

    • Take a long tube, a gun barrel, around 100 or more meters long.
    • put a rocket in the gun.
    • Fire the rocket, and as it passes along the barrell detonate additional charges behind it keeping the pressure in the barrell approximately what it was when the main charges were fired.
    • result: hypervelocity projectiles from a relatively low-tech gun
    • Fast enough to get things into orbit for under $1 per pound, around 1/10000th of current launch prices.
    • Successful prototypes were built, but never orbital ones.
    His personal story
    • He designed large guns in Canada.
    • They cut his funding and he went independent
    • People didn't take his stuff seriously.
    • He freelanced for unpopular nations (China, Iraq)
    • He did some work on scud missiles and somebody, probably mossad, killed him.

    What got built

    • In tests, a 36m gun reached 1/3 of escape velocity
    • The Iraqi "Supergun" was built by Bull and had a 1500 mile range if used for ground-to-ground, but only in one direction
    • It was actually intended as a prototype of a satalite launch system.
    • AARC most of the parts were made by companies who usually make oil well drilling equipment. It's low tech.
    Thoughts on the technology
    • Fuel-air or conventional propellents are much more efficient for vehicle launch than electicity, and don't let anybody tell you different without hard numbers to back them up.
    • For a space station, 90% of the mass you need could be thrown up into orbit out of a cannon and nobody would care. The peaches might bruised but that's about it.
    • It's not about manned space flight or astronomy, it's about engineering, so why would NASA care?
    If I was in the position of backing a launch technology for unmanned cargo launch, this would be it. Everything else is a poor second best, IMHO.
  • er...maybe im forgetting something from physics class (not surprising considering how many i slept through), but doesnt the mass of the object work into the equation somewhere? i seem to remember F = ma among other things.....

    ah hell with it...

    --Siva

    Keyboard not found.
  • At that point you could basically toss boxes of cargo into space, no need for elaborate packaging, just make it aerodynamic, strap it onto the "maggun" on mt. kilimanjaro and thoomp, its in orbit.
  • Wouldn't this technology (slow/speedup?) the Earth's rotation in time?

    I mean, I understand that near equatorial conventional launches do the same thing and that maybe the atmospheric effects of burning tons of fuel isn't all that great but changing the Earth's rotational speed would cause some pretty drastic weather and climate changes, right?

    So, I guess I'm wondering if this is more, less, or equally harmful to the Earth? If it's less, do we make them start using the technology in the opposite direction to offset the changes?

    Hrm...
  • by dutky ( 20510 ) on Tuesday October 12, 1999 @01:47PM (#1619654) Homepage Journal
    Has anyone bothered to do the required math for this before posting about how you couldn't launch people with this thing without turning them into raspberry jam? A little bit of calculation shows that a 1km long track, accelerating the payload at 4g for a little over six and a half seconds will get the payload up to the maximum stated velocity at the end of the track (actually about 100 meters short of the end, but what's a hundred meters between friends?) A human can easily withstand a force of 4g for six or seven seconds.

    The track could run essentially parallel to the surface of the earth for most of its length, since it doesn't matter too much what direction your velocity is in, so long as your path doesn't intersect the ground or a mountain or somesuch.

    As for how much this would help you: you would be getting about 5% of your required velocity for low earth orbit without the need for onboard reaction mass. The amount of reaction mass you consume during takeoff is something like inverse exponentail (or maybe inverse log. In either case, there are a bunch of constant factors thrown in) so that most of the fuel is used early on. A 5% savings in reaction mass during the first part of takeoff may be worth a lot more (like 20%) in the total amount of fuel needed.

    What I'd like to know is where this maximum velocity comes from. I assume that it has to do with wind resistance at sea level, or somesuch, but I'd like to know for certain.

    - Jeff Dutky
  • > Distance = 1/2 acceleration * time^2 = 1/2 * 186 * 4.7^2 = 2000 feet!

    > Well thats a little extreme for something that wants to point up in the air.

    well maybe not - just build it up the side a mountain somewhere - higher is better! (less air resistance) so is close to the equator - Kilamanjaro (sp?) would probably make a cool space port

  • Weel, not in this case. The question was, how long the tunnel
    has to be, given acceleration 1G, 2G or 5G.
    You use F=ma to find out how great the force
    working on the object is, when it's has an acceleration of ??m/s^2.
    1G = 9.81 m/s^2

    -Stian
  • by RebornData ( 25811 ) on Tuesday October 12, 1999 @01:54PM (#1619657)
    The problem with air resistance is not that it would merely slow your launch vehicle down. The problem is that your spacecraft would be doing a killer impression of the Stay-Puft Marshmallow Man long before it got into orbit.

    Shielding works OK for re-entry vehicles when you've got a nice, thin upper atmosphere to slow you down before you get to the thick stuff. Something tells me that surviving orbital velocities near sea-level is going to require something more substantial than ceramic tiles.
  • I think it might launch off like Superman: The Escape over at Six Flags Magic Mountain. It uses magnets to rocket off to 100 MPH (world's fastest "coaster") and curves up so you go up to 450 some odd feet. Here's [thrillride.com] some pictures. Except in the space shuttle's case, it wouldn't stop. Once it reached it's top speed, it would fire it's rockets and go on up. And if the rockets failed, it would just follow the track back down. BTW, that ride is a lot of fun : )
  • Oh come on!

    This so-called news was old hat when the NewScientist did a feature on it about 10 years ago

    The main gist was that the newer surface mount ICs would survive with relatively little modification - but no humans/live multicellular organisms above that of a flea would survive. Not that that is a particular problem if you are launching another sat.

    Mind you I think that the biggest snag was successfully evacuating the cannon to avoid those ultra-mach type problems the fluid mechanics guys (and gals!) really like to get their teeth into.

    One final comment - if you think that Concorde was loud.....

    Slainte mhath

    Torcuill

  • Presumably they could use some kind of shielding around the launch device to prevent enormous magnetic fields from screwing with peoples' monitors... if that would happen, which it wouldn't. Remember that if they were doing this from Cape Canaveral, where they do now, they're miles from where anyone lives, so even the biggest magnetic field we could produce would still have a negligable effect at that distance. Unless they set off a nuke, or something... love those EMPs!

    --- Dirtside
  • First, it would take a long time to slow the earth's rotation any appreciable amount. You probably have more to worry about from the tidal drag of the moon than from this.

    Second, the environmental effect of rocket exhaust is minimal, since most rockets used for orbital launch are liquid fueld (Oxy-Hydrogen or Oxy-Hydrozene) and the result of the reaction is almost entirely water vapor.

    Finally, you would likely use the linear accelerator in a west to east direction, in order to get a little extra push from the earth's rotation. On the flip side, returning payloads probably want to land in the east to west direction so that the earth's rotation silghtly reduces their touchdown velocity. Some of what you would loose in takeoff you could get back on landing. (similar problems are addressed by A.C. Clarke when he talks about rotating 'sky-hooks', which would stand to loose sizable fractions of their rorational energy to the accelerated and decelerated payloads)

    (The 'little extra push' is actually equal to about 1000 mph in either direction at the equator, so it is far from negligible. It would put your actual takeoff velocity at about 10% of LEO velocity)

    - Jeff Dutky
    • You do not want to be doing escape velocity at sealevel. The thermal equivalent is deep ultraviolet and the area loading is in the crumbling-diamonds range. The 600 MPH limit is probably aerodynamic. Max Q.
    • An absurdly huge amount of fuel goes into getting up to Mach One; something like 50%. 600 MPH isn't bad at all.
    • Nine Gs is the limit for fighter pilots sitting more or less upright (actually about 30 degrees from upright.) Lying down on your back in NASA fashion makes for much higher limits.
    • The biggest payoff would be if they could get up to ramjet speeds using a local nuclear plant. Or the Grid at off-peak times, keeping in mind that when a shuttle launches it briefly matches the power output of the entire US electrical generation industry. Still, dragging a launch vehicle up to ramjet speeds would allow ditching most of the LOX, and that's two-thirds of the fuel load.
  • Much better than a tunnel would be a rail going up a mountain side. The difference is that at the top of a reasonalby high mountain, air resistance is about half of the ocean level.
  • If you assume that there is no friction or air resistance, then you can use (Vfinal)^2=(Voriginal)^2+2*acceleration*distance Vfinal being 7miles/sec (11401.4208 m/s) Voriginal being 0 Acceleration: 1G=9.8m/s^2 2G=19.6m/s^2 5G=49m/s^2 Solve for s s -> 6.632265115238399e6 m (~4561mi) @ 1G s -> 3.3161325576191996e6 m (~2281mi) @ 2G s -> 1.3264530230476798e6 m (~820mi) @ 5G So, as you can see the tunnel would have to be insanely long to get anything into space _assuming_ your number of 7 miles/sec. is correct.
  • They're not planning to use this thing to launch the shuttle. I suppose some future manned craft might use it but not the shuttle.

    The idea is to get the vehicle from 0 to 600 mph without using any fuel on the vehicle. Less fuel to carry means the craft can be either carry more cargo or be smaller, either way it reduces $$$/kg to orbit.

    It's just like a multi-stage rocket, which is simply two or more rockets stacked on top of each other. In this case the "first stage" is a fixed maglev rail which can be reused. What happens on current rockets if the second stage doesn't light up after the first is through? Time for a swim. Not really much different.
  • The obvious solution for blackout in fighter pilots would be to genetically engineer a supplementary brain somewhere in their knees, where it would be protected from trauma by the kneecap and suppied of nutrients by the big leg arteries.

  • Furthermore, as bad as coal may be, I tend to suspect that rocket fuel is worse on an environmental impact per joule basis. Unless you're dealing with reeeeealy high-sulfur coal...

    Nope, they use hydrogen and oxygen as fuel, the exhast is steam.
    Cheers,

    Rick Kirkland
  • According to common sense going from 1g to 2 would be half of the 1 g number. What formula did you use. Check my Physics post (sorry about the formatting in it) and check my math, Mathematica 4.0 did it, so I think its right.
  • no its due to Florida's closeness to equator...

    take off from higher latitude and you have to factor in many more variables into your launch window
    We are all in the gutter, but some of us are looking at the stars --Oscar Wilde
  • I did a little math, and I hope the numbers aren't totally off here... The Space Shuttle, accelerating at about 3gs, takes about 50 seconds to reach 600 miles per hour. The SSMEs (Space Shuttle Main Engines) consume over 1,000 lbs of fuel each second, so by getting rid of that first 50 seconds worth of fuel, you can put an extra 50,000lbs of cargo into orbit.

    Ah, but those 55,000lb of fuel are partly used to put the 55,000lb of fuel in the air as it is. It is also burnt up before the space shuttle exits the atmosphere. If that 55,000lb of fuel was cargo then the shuttle would be carrying 55,000lb extra for the entirity of its journey, not just the first 60 seconds, so the actual amount extra that the Space Shuttle could carry would be considerably lower.

    These numbers apply to the Space Shuttle itself, which is only rated to carry 55,000 lbs of cargo in any case, so think about how important that first 600mph is first and imagine what it could do for a spacecraft designed to take advantage of it. In the case of the Space Shuttle, it would theoretically double the cargo weight capacity (if there were only enough volume to take advantage of that).

    Using magnetic assist is an excellent idea. I would like to see the day when a launching track goes up the side of Mt. Kilimanjaro and can toss cargo and ships into orbit almost unassisted.

    I wonder how the Tanzanians would react to this :), why not somewhere in te alps of the rockies instead ;-)

    --

  • Please kindly note that the fuel is currently
    the least expensive part of a rocket launch;
    the infrastructure costs and labor costs are
    a whole lot more.
  • You bet, but the power they produce is measured in "kilovolt-amps" rather than kilowatts.
  • what about the computers inside the shuttle? How are they going to shield those from the shear strength of the magnetic field that would be needed to bounce that thing into space?
  • Listing a few things the author missed:
    1. This concept is very old. It goes back beyond the British HOTOL aerospaceplane and all the way back to the Antipodal Bomber concept of Werner Von Braun in the 40's. Attributing it to NASA today just shows how backwards NASA is, and how clueless journalists are.
    2. Sewing machines and electric drills do not use induction motors. They use universal motors. Completely different technology. Again, clueless journalists.
    I could go on, but it's late, I'm tired...
    --
    Deja Moo: The feeling that
  • Just wait until you see the intricate mechanisms used to get the crew from the preparation building to the ship's cabin. Lots of hydraulics, whirring around on cables, that kind of thing. ;)

    (the whole space program would get a lot easier if they'd just hire Captain Scarlet)
  • Ultimately, yes. But before it becomes a problem, we tell Chris Reeves to ignore Marlon Brando and circle the Earth really quickly.
  • by jafac ( 1449 )
    Disney's MGM Studios has a ride called "Rock-n-Rollercoaster", I rode it, and they said it pulled about 3.8 Gs. It goes from 0-60 in 2.5 seconds (you do the math, I'm too lazy). It runs on rails like any other rollercoaster, but it's powered by a linear magnetic motor, that is, pretty much the same as maglev, only there's no levitation. No big hill climb. No big drop. Kind of sacriligeous as far as rollercoasters go, but then that kick at the start. Man! So I'd have to say, 3.8 Gs was a lot for me, especially in a plastic rollercoaster seat that was a tad too small, but I felt I could have taken a lot more.
    6? ehhhhh, I don't know. . . maybe. 9? definately not.

    "The number of suckers born each minute doubles every 18 months."
  • 600 mph is 1000 km/hr, or about 280 m/s.

    The length of a track needed to accelerate from 0 to v is equal to v^2/2a, where a is the acceleration. One G of acceleration is about 10 m/s^2. Thus, the length of the track needed is about 3.9 kilometers divided by the number of Gs.

    According to NASA, the Shuttle accelerates no faster than 3 Gs [nasa.gov], so we'd need a 1.3 km track, or about 4300 feet. For comparison, the Shuttle requires 2500 feet [nasa.gov]. (That figure's at the very end of the document I linked to.)

    So, the track you'd need is long, but not outrageously long.

  • The article doesn't go into detail about how much of the actual fuel is replaced by this technology. It does mention a 20 percent reduction in the overall mass of the rocket, but what does that translate into? Anyone know?

    Quite simply it just means that it would require approx 20% less fuel [not quite exactly 20% off the fuel itself, since some of that mass savings is in the container/systems for that extra fuel]. So they can use the savings to either make the craft smaller [thereby saving even MORE mass/fuel] or they can use the savings to allow the craft to hold more cargo/passengers with less fuel.

    That's how I see it anyway... It's a great idea that is long overdue. We need much more research in makeing launches cheaper/safer if I'm going to be able to live out my dream of going into space.:)

    Ender

  • A friend of mine had an idea to buy old missile silos out in the plains and use them to launch capsules w/ people in them to ~20k feet, then fly to a destination from there. Just turn the silos into giant inductive coils. No problem.

    Actually, there is a problem there. Solenoids and other magnetic field carriers take time to build in strength and time to discharge.

    If you ignored that charge/discharge time (lets imagine its 0), since solenoids pull objects towards their center, it would only make sense to have the solenoid on for the first half of the capsule's journey through the solenoid. If it was on for the second half (ie remained on), the capsule would actually be slowed down as it was pulled towards the center of the solenoid. It would bounce back and forth a little and then just remain motionless at the center.

    Now if you turned the solenoid off (assuming discharge time of 0) after the capsule reaches the half-way mark, it would continue on its merry way at whatever velocity the capsule had reached by the mid-point of the solenoid.

    Now, in reality, if the solenoid is large enough to exert more than one g on a 1 ton capsule (a reasonable estimate for your purpose), its going to take a very large magnetic field. The larger the field is, the longer it takes to build. The longer it takes to build, the longer it takes to die. So, if your capsule is in the bottom of this silo and the magnetic field is turned on, by the time it reaches the center of the solenoid, its moving at a good pace. Now the power is turned off and the magnetic field slowly diapates. Because it wasn't instantaneous, the capsule is slowed down by the remaining force drawing it towards the center of the solenoid. By the time the capsule reaches the end of the coil, its velocity is back to 0 and gravity takes over, bringing it back to the bottom of your silo.

    So, there has to be a solution, you say. The solution is mag-lev. Use a whole long line of MUCH SMALLER magnetic field sources in sequence. This allows for a very short charge and discharge time, allowing the capsule to remain in motion.

    This of course would present a problem for your silo idea, unless you were able to build a track into the air above the silo.

    I actually looked into this way back in high school when a friend of mine and I came up with an idea for a solenoid-fired BB gun. We figured that the only way to get the BB up to speed is to use a long line of solenoids. I think it would have worked.. but we were never able to build it due to a lack of experience with electrical timing circuits.

    -molo

    p.s.: sorry for the lack of quantitative stuff here.. someone have a physics book around?

  • 1G=9.8m/s This is true for a constant radius from the center of the earth, but remember gravity is some constant * the inverse of the radius. This is NOT a linear equation, but an integral as gravity decreases from 9.8m/s to whatever gravity is as you reach final altitude... someone wanna do the math... I sure don't.
  • It seems to me that both the x000 mile tunnel, or a ?? mile track up the side of a mountain would both be pretty much ruined by the first tectonic activity in the area.
  • err sorry its "some constant * the inverse of the radius squared"
  • i doubt enough jet fuel would be saved in the short distance of a runway to offset the cost of the whole system...
    With a 600 MPH boost, the rocket can cut off its engines with 600 MPH less of delta-V. It can also save on "gravity losses" because it could start with a faster climb and start flying horizontally sooner.

    This wouldn't be useful on something like the Space Scuttle (pun intended) because the stack cannot handle 6 G's. Something like a re-designed X-33 (Venture Star) could do it. And I suspect that NASA is suggesting it now because the X-33's design compromises have added so much weight that it can't carry a payload to orbit without several hundred MPH of head start.

    Somebody, Congress, please boot the idiot NASA managers who selected the X-33 proposal and hire the guys who designed the DC-X; if we'd just continued with the DC-Y we'd have an orbital test vehicle by now! Oh, I forgot, the program was too cheap and didn't have enough slush to generate your campaign donations! Silly me!
    --
    Deja Moo: The feeling that

  • Nope.

    (1) distance = v(0) + 0.5 * a * t^2
    (2) v(final) = v(0) + a * t
    From (1) and (2) we find:
    distance (given v(0)= 0) = v(final)^2/(2*a)

    a= g = 9.81 m/s^2

    -Stian
  • by cybercuzco ( 100904 ) on Tuesday October 12, 1999 @02:21PM (#1619691) Homepage Journal
    The official nasa press release for this mag-lev system can be found here [nasa.gov] This system does use the Inductrack system mentiones earlier, which has several advantages over other forms of mas driver, which this essentially is. The inductrack system is bacically coils of ordinary wire surrounding some sort of ferrous core. The article above mentions that each section of track weighs over 500lbs wich is due laregly to the huge chunk of iron in the center of the coil of wire. This reduces cost and complexety many times. You dont need any cooling apparatus, you dont need any expensive magnets, and its very scalable. To make the track longer just ad a section of track. This is a very promising technology, it could really pave the way for cheap access to space. Heres hoping that nasa will continue to develop it.

    There is one problem though, that is, there might be a speed limit associated with it. As the craft accelerates, a larger magnetic field needs to be generated to continue the acceleration, this means more current through the coils of wire. Eventually the wire will overheat and short out or simply melt. Previously a speed limit of 600 mph was mentioned, this seems plausible, but id need more data. Also, if the speed can max out at around say mach 10 (about 6000 mph) then scramjets can be used in place of rockets. Scramjets are much more eifficient than rockets since they burn oxygen in the air, resulting in a further reduction in weight of fuel and a commensurate increase in payload capacity.

  • They use a long flat "runway" that curves up at the end.

    In other words, you pick up a lot of speed on the ground, then you hit a ramp, *whoosh*.
  • its easy to isolate something from a magnetic field if the field is know, just build a faraday cage around whatever electronice you want to protect. iirc, most desktops are shielded but laptops arent due to weight considerations.

  • It's true that the external tank contains liquid hydrogen and oxygen. But the initial thrust, the part that the maglev would be replacing or supplementing, is largely provided by the solid rocket boosters, or SRBs.

    From NASA's website [nasa.gov]:

    The two SRBs provide 71.4 percent of the thrust at lift- off and during first-stage ascent.

    (snip)

    The propellant mixture in each SRB motor consists of an ammonium perchlorate (oxidizer, 69.6 percent by weight), aluminum (fuel, 16 percent), iron oxide (a catalyst, 0.4 percent), a polymer (a binder that holds the mixture together, 12.04 percent), and an epoxy curing agent (1.96 percent).

    Now, if that mixture combusts to steam, I'll eat it.
  • Otherwise, you're talking about spacecraft use to launch maglevs. Which seems kinda silly.

  • Sorry, I thought you might be getting a couple concepts mixed. As for commercial aircraft, you're right:many of them already require more space to land than to take off so it's doubtful that saving them 35 seconds or so of acceleration would be worth the cost of adding catapult gear to either the airports or airplanes.
    --
    Deja Moo: The feeling that
  • Since it's on a track, it's reasonably close to the ground, and I guess they don't want to go supersonic that close. Probably the energy required rises steeply there, not to mention strutural strengthening. I imagine sonic booms reflecting off the ground can make for some nasty buffeting.

    --
  • by SpinyNorman ( 33776 ) on Tuesday October 12, 1999 @03:18PM (#1619722)
    Escape velocity may be 7 miles/sec (25,200 mph), but the shuttle doesn't completely escape Earth's gravity - it goes into orbit. The shuttle's orbital velocity is 17,000 mph.
  • www.apollosaturn.com

    First stage engine cutoff occurred at 147,000 feet. Thrust increased from 7,648,000 pounds at sea level to approximately 9,160,000 pounds at cutoff. When rockets burn in dense air, they are not nearly as efficient as burning in thin air or a vacuum. That's one big reason for launching from 35,000 feet on an airplane.

    Thin air also means less drag. 69 seconds into flight the Saturn V experienced maximum aerodynamic pressure, which was 460,000 pounds of drag force. The first stage engines burned for 135.5 seconds.

    OK, I was unable to determine how fast the rocket is moving at MECO. But, it says that the first stage separates at an altitude of 205,000 feet, and it coasts upwards to an altitude of 366,000 feet before it falls back into the ocean. It doesn't burn up, but it actually impacts the ocean 350 miles downrange.

    So, how fast would something have to go if it were to coast up for 161,000 feet?

    Well, 161000 feet is 49072.8 meters. The relevant formula is v^2=2*9.8m/s*h. Solving the equation shows that the first stage was moving at the vertical speed of 981 meters per second. This is the same as 2194 miles per hour, or about 3 times the speed of sound at sea level. This says nothing of the horizontal speed, which would mean that the rocket would have been moving even faster than I calculated. Air resistance is ignored for these equations.

    It looks like the Saturn V could have gotten a 33% boost if it was launched from an airplane at 600 MPH just from the speed of the plane.

    Another 15% or so would have come from the increase in rocket efficiency in thinner air.

    And *that* is why Pegasus is a good idea.

  • by KFury ( 19522 ) on Tuesday October 12, 1999 @05:52PM (#1619761) Homepage
    So say you somehow got past all the other problems of melting while exiting the atmosphere or creating an all-metal probe so the killer g-forces wouldn't be a problem, all you've done is make something that could launch a projectile.

    Without creating a gun that could reach close to escape velocity, you could only achieve orbit by performing an OMS burn at the apogee, in other words, circularize the orbit so the probe doesn't just crash down ala Newton.

    The problem here is thaqt the size of the OMS burn needed is directly proportional to how vertical the launch was. If you shoot straight up, you need a strong enough burn to accellerate the craft to orbital speeds (17Kmph) which is a lot of fuel and kind of wrecks the point. Also, the lower the metal-nonmetal ratio, the less acceleration there will be on the craft.

    So you have to launch at an angle, slicing through a serious cut of atmosphere to make for a projectile moving closer to paralelling the orbit it's trying to get into. This would of course mean a huge slowdown from drag.

    So either way, you're toast, unless you're building a gun powerful enough to launch something so fast that even after the parachute that is Earth's atmosphere, it's still going 7 miles per second (and I'd LOVE to see one of these going up. The plasma trail would be quite a sight!) or you've got a gun that's really good at throwing rocks at other people. Metal rocks, mind you. I wouldn't even want to think of the implications of trying to construct a nuclear (or even worse, a biological) weapon that could survive those g-forces and remain intact and functioning.

    Makes Pegasus and moon bases seem simple...

    www.fury.com [fury.com]

  • by coyote-san ( 38515 ) on Tuesday October 12, 1999 @06:31PM (#1619774)
    As an aside, max-Q changes with the altitude of your launch. Depending upon far more factors than I am competent to analyze it might make sense to move launch sites from Florida (good equatorial boost) to Colorado (smaller boost, but launch track at 8000'-10000') except for the small problem of dropping empty tanks on Kansas.

    But if we did that, Washington might not hear about it for a month.

    (That's my obJamesBond reference, from _Diamonds are Forever_. Nobody should talk about this stuff without references to diamond encrusted laser spacecraft and bikini-clad starlets.)

    But back to the serious stuff, I know that I only have about 85% of the air density from sea level at just over 5000'. I definitely feel it when I'm down in that thick soup at sea level! At 10000' the air density drops to 70% of sea level.

    From a launch perspective, a rail in Mexico looks *very* good. (15,000' altoplane?, perhaps 60% of sea level?) It would also give you a good equatorial boost. Unfortunately there's the problems of politics, power (Colorado launch sites could tap into the Western US power grid), and launch techs ill from altitude sickness. Still, with NAFTA it's something to consider if it significantly cuts the cost-to-orbit.

    Finally, a quick sanity check is the shuttle's SRBs. I don't recall the exact numbers but I thought they were dropped at something like 6 miles altitude/mach 3. In terms of the total trip to LEO it's fairly modest, but it's crucial because of the high cost of lifting fuel for the later stages. A maglev track in the mountains may be enough to get you 30-40% of the way to where the SRBs are dropped, when using the current shuttle stack!
  • 90 degree turn? If I took off from a horizontal position and kept going in a straight line (not curving with the earth) I would eventually reach outerspace anyways. Not doing the math, but I'd be willing to bet that you'd only have to travel through maby .30 more atmosphere, but considering most of your acceleration could be done without gravitational hinderance, this could end up being a cost saver. Anyone care to do the math? Accually I'll try then repost my findings :)
  • Hmm, I can't seem to find the highth of our atmosphere. But anyways the equation would be
    (Radius from center of earth to edge of atmosphere)^2 - (Radius of Earth)^2 = (distance from earths surface to atmosphere taking horizontal path)^2

    So I know the mean radius of the earth is 6371 km
    I know the terrestrial atmospher is 8.5 km high
    this is where most of our power is lost, but in all honestly is only a fraction of the total distance, which I can't find the figure right now too :(
    so
    6379.5^2 - 6371^2 ~= 329 km
    square root that and you get
    hmmmm WOW. heeh did the numbers as I typed it. so that would increase the distance by almost 40 fold, though I notice if I assume a highth much greater, like 100km the difference decreases to about 10 fold. Hmm guess these numbers are not acceptable, nevermind then. If my basic formula is wrong someone please tell me, I'm just drawing a right triangle, with the two sides, 1 being from center to surface (at takeoff point) and other from takeoff to ecscape of atmosphere, and hyp being from center to excape point. But then you have to subtract the fact that you won't really be leaving the track for many km so that could almost be subtracted. Many I could only imagine the building cost... hey why not just an elevator tower going straight to outerspace :)
  • The last time I watched a shuttle launch, I remember the velocity indicator reading something like 25K mph. It doesn't seem like maglev speeds of 600 mph would accomplish much

    Well, imagine for a moment that the ship is 1/10th or less of its current weight. It takes a WHOLE LOT less force to 50 tons into orbit than to put 500 tons... I think with the correpsonding reduction in spacecraft size this is a feasible propulsion method. Most likely a 5 mile track with 3 miles straight to build up speed, and then a ramp that shot it straight up... Probably wouldn't want to use it for manned flight just yet, but it would rock for launching space station parts, and satellites, and anything else that could handle the pressure.

    Kintanon
  • > Distance = 1/2 acceleration * time^2 = 1/2 * 186 * 4.7^2 = 2000 feet!
    > Well thats a little extreme for something that wants to point up in the air.

    well maybe not - just build it up the side a mountain somewhere - higher is better! (less air resistance) so is close to the equator - Kilamanjaro (sp?) would probably make a cool space port



    Ummm, 2000 feet is only a conventional 20 story building. We have those all over the place. I'm sure NASA can build one that won't fall over when they shoot a 1000ton rocket up the side of it.

    Kintanon
  • Oops, Someone shoot me. 2000 feet = 200 story building, ok that is a little tall.>:)

    Kintanon
  • DC-X just used old rockets, same as all other american space vehicles.
    And that's because DC-X was an atmospheric test vehicle, designed and constructed specifically to prove some of the tricker parts of the DC-1 design (namely, the "flip over" transition from nose-first gliding flight to tail-first powered flight for landing). It used off-the-shelf RL-10 motors because developing new motors was not necessary and thus not part of the charter. Either DC-Y or DC-1 could have switched to an aerospike motor without changing the basic design.
    The only advantage it had was it could take of and land vertically and move sideways - I dread to think of the fuel cost involved.
    The fuel cost wasn't very much; the vehicle would have been mostly empty tanks by the time it landed. And it had other, very substantial advantages:
    1. It did not have to glide to a landing. This allows considerably more flexibility in the aerodynamics.
    2. It did not have to land horizontally. This is advantageous in two ways:
      • There is no requirement to transition from powered flight to gliding flight in order to land; the spacecraft always lands under power, so it can make an emergency landing as soon as it gets rid of enough fuel to avoid collapsing the gear.
      • Any flat patch of ground will do for an emergency landing site; no runway is required.
    About the only thing the X-33 has going for it is that it behaves more like the Space Scuttle. Unfortunately, this similarity also appears to include development cost and schedule.
    X-33 uses new engines, new materials, etc. Yes it takes longer to develop, yes it cost more and YES it is worth it.
    Our current engines appear to be sufficient to build a much cheaper replacement for the Scuttle, and on a much faster schedule than X-33. In the mean time we are stuck with a vehicle designed in the 70's whose performance is a fraction of what was promised (65,000 lbs to orbit is only a dream) and requires a standing army of over 10,000 maintenance personnel to keep it flying. Worse, we cannot build any more and if we lose even one vehicle it will force other programs (like ISS) to be radically scaled back or even scrapped. Last, the engine technology of X-33 could be applied to a VTVL with little difficulty; however, with a going DC-1 program it would be forced to prove its worth instead of being locked in as part of "the only game in town". You can't escape the conclusion that the X-33 program is more about generating lots of money for contractors than making a cost-effective launch vehicle.
    --
    Deja Moo: The feeling that

There's no sense in being precise when you don't even know what you're talking about. -- John von Neumann

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