Slashdot Mirror
Spacecraft Launching Maglevs
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.
who? Tesla? don't you mean Edison
Maglev takoff 747's would be cool too. And for short trips, you could to a magnetic slingshot of a small fueless glider.
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...
(for those who don't know, Gerald Bull designed a system for just this kind of launch, but rather than maglev it used conventional propellants. Estimates said launches would cost $0.50 / lb). Nasa ignored it and Bull went abroad to design super cannons for the Iraquis with effective ranges of 1500 miles.
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?
o gy/story/22188.html
4 8,00.html
/. effect.
Anyone notice the link on slashdot actually has a 'slashdot' directory in the path?
http://www.wired.com/news/news/slashdot/technol
Whereas the news page link is:
http://www.wired.com/news/technology/0,1282,318
Wonder if "Tired" are trying to counter the
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.
-no broken link
I also predict that out of this very technology may well come the floating cars and skateboards of back to the future fame. :)
/. poster #104543567
-stax
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.
Josh
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."
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
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
Play with my webcams and lights here
Every time your monitor screen goes tie-dye-t-shirt you know it's a launch time.
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 =)
Then again, I could be wrong.
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.
-- Veni, vidi, dormivi
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.
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...
/* The beatings will continue until morale improves. */
Injured software engineer wins against Mattel!
Now all we have to do is gather up all the WinDoze boxes, strap 'em on and, phwooosh! Off they go! :) "The path of least resistance is what makes both men and rivers crooked" - Anon Y. Mous
And then he was mysteriously murdered. .^
^.
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.
Keyboard not found.
Press F1 to continue.
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.
-?-
Maybe somebody could start designing a prototype of Captain Steve Zodiac's space scooter as well.
--
It is a lot more friendly to the environment than burning rocket fuel :)
roughly equivalent to the energy in 2,000 100-watt light bulbs
who knew that light bulbs were energy sources
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.
I browse with my threshold at 2 so I can't read my own comments :-)
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...
--
Do I look like I speak for my employer?
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
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).
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 storyWhat 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.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...
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
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 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
-- NSY - SY OOT - Doric signs on local shop doors.
Saturn V holds the all-time speed/distance record.
Lacking <sarcasm> tags,
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.
The best way to accelerate a windows box is at 9.8 meters per second square.
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.
"Be nice, veer left, and never stop thinking" Iain Banks - Walking On Glass
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
Satellites can be placed in orbit at much lower velocities than terran escape velocity.
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.
The best way to accelerate a windows box is at 9.8 meters per second square.
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?
- 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.
- 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
Time is Nature's way of keeping everything from happening at once... the bitch.
railgun the thing into space!
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."
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
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, so we'd need a 1.3 km track, or about 4300 feet. For comparison, the Shuttle requires 2500 feet. (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.
--
Do I look like I speak for my employer?
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?
Using your sig line to advertise for friends is lame.
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.
Intolerant people should be shot.
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
Time is Nature's way of keeping everything from happening at once... the bitch.
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.
From NASA's website:
Now, if that mixture combusts to steam, I'll eat it.--
Do I look like I speak for my employer?
Rockets don't work well at sea level, you have to make terrible compromises to get a rocket with a typical bell-shaped nozzle to go from ground to orbit. The Aerospike nozzles that Lockheed is trying to use on their X-34 should eliminate this problem, but they are unproven (to put it mildly).
But ramjets make perfect first stages! Powerful, simple, light, fuel efficient (compared to [only!] rockets) and well-understood.
thad
I love Mondays. On a Monday, anything is possible.
The comment I just posted below has to do with the Space Shuttle. The various conventional rockets use different propellants of varying environmental friendliness (for which I have no data on hand). But a lot of the big rockets use some sort of solid rocket boosters, probably with a propellant similar to that in the Shuttle's SRBs.
--
Do I look like I speak for my employer?
I thought he was shot in the head.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
>>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.
Well, SOME rocket motors use hydrogen and oxygen. The Space Shuttle's liquid fuel main engines do, but what do you think the solid fuel booster they strap on to the main tank uses? In fact, most rockets don't use hydrogen and Oxygen. The ones derived from ICBMs don't because they have to stay fueled for months at a time, and hydrogen and oxygen evaporate too quickly. All rockets have a fuel and an oxydizer - in solid rockets these are combined into a ready to ignite solid. These are frequently some pretty nasty things. In other liquid fueled rockets,things like nitric acid, flourine, nitrogen tetroxide and others can be oxidizers, with fuels like kerosene, hydrazine, alcohol hydyne, and others.
Cheers
Eric Geyer
I for one am still wondering when Cedar Point is gonna start putting catapults from decommissioned aircraft carriers into their roller coasters.
New, next summer: Ride the F-16 coaster, complete with catapult takeoff!
As for NASA, I agree. That'd be a hell of a way to give a serious kick to a rocket. Heat is cheap, especially nuclear heat. Can you just see a nuke-powered steam catapult, solid fuel rockets, and NASA engineers, in close proximity to one another? That's a disaster waiting to happen, but it sure would be funny to watch.
And since everyone keeps asking: You start firing the rockets BEFORE you hit the catapult. Let 'em burn for a second or two, no big deal. Then once you know they're working properly, you hit the BRS and set things into motion.
>>"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 guess the argument is the same as electric cars vs gas cars. With electric cars, all the pollution of the energy generation is located in a single source where the pollution is more easily captured and treated. (This does not take into account the pollution caused by the batteries, of course) The gas powered car must carry its pollution control apparatus with it, and the pollutants are less easily caputured. In addition, there are many, many small mechanisms that must be kept in correct working order, rather than one large one.
In a rocket launch, much of the energy is spent overcoming air resistance in the lower parts of the athmosphere. If you could launch from high in the air, or use a ground-based propulsion system to get the launch vehicle started, you could make a smaller and cheaper vehicle.
Cheers
Eric
I can just see the next tragedy for the American space program:
The Degauss Button
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
Time is Nature's way of keeping everything from happening at once... the bitch.
i'm no expert but i understood a faraday cage had to be earthed? that would raise a whole new snarl of engineering difficulties i would have thought. Maglev with earth strap trailing behind at 600mph
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.
--
Infuriate left and right
Two words: Heat shielding.
The space shuttle gets to hit the thinnest parts of the atmosphere first. And you still need to avoid certain re-entry angles...
The track-length problem is pretty easy (1/2 v^2 = a * d), but I would like to ask-
What kind of materials could withstand escape velocity, straight up, at 14,494 ft? The straight up is to simplify the problem (less time in nasty thick atmosphere), the 14,494 ft is the height of Mount Whitney, (CA), tallest mountain in the continental US.
I ask this problem 'cause it requires knowledge of aerodynamics, pressure variation with altitude, heat dissipation, and more stuff I don't know... Mt. Whitney I found via search engine, the rest sounds like work...
But at a guess, this 'almost-best-case' unassisted lift off will still fry 'ya, even with modern ceramics....rockets will probably be used for some time yet, even if we have assisted launch systems that work.
It's impossible to shoot completely dumb cargoes into space, without an orbital correction they'll end up in an eliptical orbit that intersects with the Earth someplace. All cargo would still need a small rocket to circularize the orbit once it gets way up there. But yes, this would still be a big win. And it'd help reduce the unemployment problem in Tanzenia.
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.
It makes sense to have an L-shaped ramp where a vehicle can be thrust vertically, then be curved into an upward motion. Applying a constant force to the object in linear motion translates into a direct bearing on how high it will go. However, doing the same vertically requires that enough energy be input to counteract gravity first.
Cool! Ride a rail gun right into orbit!
And for only $75 worth of electricity? (obviously not counting rocket fuel) That's awesome!
--
grappler
Vidi, Vici, Veni
Given that 515 km/h (that's 320 mph for the metric impaired, more than HALF the speed of an airliner) has been achieved with a STOCK train (okay, souped-up with bigger wheels and a faster gearing), moving people around is a pretty lame use for maglev.
No, really, launching shit in space is really a much better use for all that high technology...
-- ----------------------------------------------
Vive le logiciel... Libre!!!
What happens if you abort the launch before the rocket ignites? You've basically got a manned artillery shell...
(I'm sure they'd a way around this, but however they do it, it would be a hell of a show.)
MSK
The escape velocity of earth is mach23, which is about 16200mph.
Obviously 600mph wouldnt be enough to fling you out of orbit (the current world landspeed record is just over the speed of sound, which is 700some mph), but it's enough to decrease the amount of fuel needed to get you out of orbit. Since the mass of the object (shuttle in this case) doesnt necessitate huge costs to get it moving using a maglev launch system you can get the thing in the air at almost mach1 for, as they said, about $100. Once in the air, you have the option of either using one of those new super turbines to get it up to about mach4 or just cut on the jets. In either case, the fuel needed is lowered by some amount. As the fuel for the first 600mph isnt required you also dont need fuel to boost that fuel up, so it decreases a little more.
The maglev thing isnt (yet anyway) an alternative to chemical rockets (or any other booster system) but it's a way to decrease costs per launch.
Dreamweaver
"If a man hasn't discovered something he will die for, he isn't fit to live" -- MLK, Jr.
man calm down, build it somewhere where there's not a lot of quakes. jeez lets just get the ball rolling on this!
its a friggin' magnetic track, you get up to about 103 miles an hour and then your weightless for a few seconds, it kicks ass!
I may be wrong, but, when starting a body from rest, like on a launch pad, don't you need a significant amount of energy just to start out? And even if this is not so, I've watched how long a rocket spends not moving after its engines have started, just building up the Newtons to push to rocket up. This wasted energy/ rocket fuel/weight can just be removed.
USA-Democracy is 270 million YESes and NOes a day, not one every four years.
Although saddam is definitely a bad boy, although harvard trained and from a christian-hearted family, I've always wondered whether or not destroying Bull's technology for launching communications and intelligence satelites might have been additional economic cause for that war.
Moving the mass horizontally is one thing, getting to start going up is another. Yes, achieving escape velocity at 100 feet above sea level will do it, I don't think the pilots or hapless bystanders would enjoy it too much.
The energy consumption will go up immensely when vertical motion is applied. Any help in getting the beastie moving is good. But as has been mentioned most aren't practical for human travel.
Even non-human/biological payloads would have to be designed to withstand 10's even 1000's of G's of acceleration.
One launch concept sort of alluded to is the Ram Accelerator. A big tube is filled with combustible gases. Then a projectile is launched at sonic velocities. The compression waves coming off of the projectile ignite the gases and further accelerate the body. The side effect is the several 100's/1000's of G's of acceleration on the body.
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
Kevin Fox
I remember reading about something like this in a book by Marshall Savage (How to Colonize the Galaxy in 8 Steps or something like that.)
The idea was to accelerate a launch vehicle down a mag-track and up the side of a mountain. When the capsule emerged, the rest of the propulsion force would come from large, earth-bound lasers vaporizing a block of super-frozen ice on the back of the capsule and expelling it out a rear nozzle.
While I'm not sure about the strength of the actual science behind this idea, it sounded pretty interesting. More info about it is probably available at Savage's site (http://www.fmf.org).
Does anyone remember Heinlein's book? It explains a lot of the forum questions in a highly entertaining novel that has much else to recommend it.
Besides the Cyborg spaceships, the moon has a 3g official catapult of 100km in length, and a 10g 30km one which is used for the moon independence movement.
And when they try politicing on earth, they try to sell the catapult idea to every government on the planet.
Useful features.
Equatorial location.
High altitude.
E/W orientation.
Long slope.
Several mountains that fit this description were mentioned in the book.
I'm excited. A 350km catapult pushing at 20G (only inanimate cargo) was proposed for earth.
-- perl -e'print pack"H*","6e656d6f406d38792e6f7267"'
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!
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
I can't remember enough physics to figure out whether it is the magnetic flux density or the derivative thereof which is leads to the force. Basically, you have to dump a shitload of current into the the thing from some big capacitors, which gives both I and dI/dt big.
Maglev is completely different. AFAICR, Maglev is what you get if you "straighten out" the cylindrical interface between coils and magnets in the rotor of an electric motor, making them planar.
-- open source? sounds like the real book --
If it were merely a matter of being close to the equator, they could have put the launch site near Miami or Brownsville, Texas, both of which are further south than Canaveral. But they didn't.
From a Kennedy Space Center page about the Space Shuttle:
If the launch site was in Miami, the available launch angles would be greatly reduced, as any launches angled to the south would risk dropping a SRB onto the Bahamas. Likewise, basing the launches in Brownsville would risk dropping shuttle bits along the entire US Gulf Coast, Florida, the Yucatan, and Cuba.
But then again, I could be wrong.
Could i have the same thing metric measures.
95% of us would then understand !
And remember : NASA lost MArs Surveyor because english/metric system mix.
English measures is like latin : no more used by living beeings ; )
X-33 uses new engines, new materials, etc. Yes it takes longer to develop, yes it cost more and YES it is worth it.
Oh and as a side note there is a better (I have heard) space craft out there - the Russian space shuttle was meant to be a big improvement on the american one (Russia always was very good with rocket design, just bankrupt and ineptly led :)
The article says it'll only cost $75 worth of electricity to get a vehicle into orbit! Are they crazy?
Suppose a moderately sized satellite massing 1 metric tonne:
mass m = 10e3 kg
Escape Velocity v = 11.179e3 m/s
Kinetic Energy E = (mv^2)/2 = 6.2e10 J
In the UK electricity is available to industry for, oh, I don't know, about 5 pence per kiloWatt-hour. Given that the yanks get everything cheaper than we do, lets say they pay 5 cents per kiloWatt-hour:
1 kW/h = 3.6e6 J
Kinetic energy of escape velocity measured in kW/h:
6.2e10 J / 3.6e6 J = 1.7e4
Cost of energy: 1.7e4 * $0.05 = $850
Damn! well it's not $75 for the whole journey but insertion into low earth orbit doesn't mean going the whole way. And it's still phenomenally cheap. Who'd a thunk it?
Now that's the way to get construction materials for a space station up there...
Consciousness is not what it thinks it is
Thought exists only as an abstraction
If the arguement is about simply putting things into space for less cash, y'all might be interested to read about the British space program (obit 1970, one successful orbital payload delivery). They used a propellant of Kerosene and Hydrogen Peroxide, and launched things for a tiny, tiny fraction of the cost of an equivalent NASA launch. The project was abandonned when the government "couldn't see a practical purpose" for a Space Program. Black Arrow was just one of a set of rockets produced using the same tech.
You can read about it here.
Isn't it bogus to claim that using a "mag-lev"/"railgun"/whatever technology would save money? Maybe it's just me, but it would seem that this would take an absolutely enormous amount of energy to accelerate a multiple-ton spacecraft out of this thing. Isn't a big gun, like someone else suggested, a better idea? Problem with guns though, is that the spacecraft itself needs SOME sort of propellent or it won't be able to manoeuver (however you spell that).
It's 10 PM. Do you know if you're un-American?
About 15 years ago I read about a commercial satellite-launching company that wanted to provide the initial acceleration through buoyancy. They proposed to extend the rocket shell below the engines and drop the rocket (upright) 100 meters down into the ocean (near the equator). To launch, they would blow air into this bottom chamber and FLOAT the rocket to the surface. When it emerged, the bottom tube would be jettisoned and the engines ignited.
Everything should be made as simple as possible, but no simpler. -Albert Einstein
Lol, been there in June ;) :)
I think they would try to sell every bit of it.
At least they would love the PR
Now techies would have yet another reason to do the Kilimanjaro!
--
People using html in email should be shot.
- It did not have to glide to a landing. This allows considerably more flexibility in the aerodynamics.
- 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. 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
Time is Nature's way of keeping everything from happening at once... the bitch.
I worked on a study of a hypervelocity gun launcher to get payloads into orbit. Muzzle velocity optimizes at 5500 m/s for 600 kg projectile delivering 100 kg net to orbit per trip. Peak acceleration is 100 g's, which is not a problem for what we were delivering - propellant.
The gun uses hydrogen gas at 3000 psi flowed though a heat exhange bed then into the barrel.
Hydrogen, being the lightest gas, gives you the
highest muzzle velocity.
System development cost is about $80 million,
and can support 1 launch per day. So throughput
is 36 tons per year, or about 1/4 of the Shuttle
launch capacity.
A gun exists at Livermore Laboratory firing 5 kg at 4 km/s. It cost about $ 3M to build. We figured a couple of prototypes would be needed: 25 kg @ 4.5 km/s and 120 kg @ 5.0 km/s, to work out the bugs before going to the full scale gun. Prototypes would cost about $10M and $30M.
The problem w/ escape velocity at sea level is...
...one of your own making. The article doesn't mention anything about reaching escape velocity at sea level. It talks about reaching a speed of 600 mph at which point conventional rockets take over.
Bottom line: it's a LOT easier to go from 600mph to escape velocity than it is to go from 0mph to escape velocity.
**>>BELCH
The article says it'll only cost $75 worth of electricity to get a vehicle into orbit! Are they crazy?
It doesn't say that *anywhere* in the article. It says it'll cost $75 to accelerate the vehicle to 600mph.
**>>BELCH
Can't you just put the works in a tube and suck the air out? Of course you'd have to stop up the end and open it at the right time (or make the stopper disposable that the craft could break through... Would the inrushing air at the time of opening negate the effects of accelleration through a near-vacuum? Could fans (or something) be placed near the end to maintain some kind of decreased pressure within the tube? Perhaps simply heating the last 50 meters or so of the tube would be enough of a plug?
Work is for people who lack the imagination to play.
Heh, aren't mountains formed by tectonic events? Doesn't that imply that areas around mountains are inherently unsuitable for large scale interconnected building projects?
Work is for people who lack the imagination to play.