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NASA Looks At Railgun-Like Rocket Launcher
coondoggie writes "NASA is looking hard at a way to blast spacecraft horizontally down an electrified track or gas-powered sled and into space, hitting speeds of about Mach 10. The craft would then return and land on a runway by the launch site."
Space is not up, it's all over, we're on a sphere.
You can go to your right and ignore gravity completely to reach space.
-- This space for lease, low setup fee, inquire within!
That space is up.
Up is relative. Space is away.
The higher the technology, the sharper that two-edged sword.
That space is up.
You see, they'll fire the spacecraft horizontally and it'll fly really really fast until it falls off the World into orbit.
RIP America
July 4, 1776 - September 11, 2001
so basically the trick is to fall down and miss?
the preceding post was not spell checked... suck it.
After all the hype that we've been hearing over the years about rail-guns and seeing a few military and hobbyist demos on video sites, this one piece of near-former sci-fi may be finally coming to fruition as a usable approach. It's a great example of the sort of thing that had to wait for technological improvements and refinements, rather than a fundamental scientific or technological breakthrough, and is the convergence of several technologies. I'm encouraged to see more progress on such things which seems to have in recent years been eclipsed by information technology's faster cycles and overhyping in media (and I say this as someone who makes his living as a software engineer).
"Politicians and diapers must be changed often, and for the same reason."
Ah, Heinlein, may you never cease to spin.
Anyway, the other think to consider (especially for things like laser-based launches) is that the current "spit out a ton of speed really quickly and then coast your way to orbit" approach really sucks. Even a slow nice steady boost will get you to orbit without needing to hit escape velocity.
You're special forces then? That's great! I just love your olympics!
And even Mach 10 isn't enough, orbital velocity is close to Mach 25. You cannot run at that speed inside the atmosphere, there's no material that could withstand the heat.
I've seen a much better idea proposed. Put that electric accelerator track in orbit. The energy needed to reach orbital altitude is much less than the energy needed to accelerate to orbital speed.
One could launch the spacecraft vertically to an interception with the accelerator track, then it would catch the track and get the needed horizontal speed while already outside the atmosphere.
"Fall down and miss" is orbital dynamics at is most basic.
Is buying a Harley Davidson as your first motorcycle since you were 16 at age 49 a midlife crisis issue?
Even a slow nice steady boost will get you to orbit without needing to hit escape velocity.
Well, sure, you could do at a walking pace ... if you had the reaction mass.
The higher the technology, the sharper that two-edged sword.
Why would they do this at sea level? This should be done somewhere in the American West, at altitude. At 10K feet there is a heck of a lot less air resistance. Could be done on one of the Air Force ranges for sonic boom sake.
Ah, Heinlein, may you never cease to spin
Yes, Heinlein used this tech as a centerpiece enabling technology for Moon->Earth grain shipments (and as a kinetic weapon used against Earth once the rebellion started..."throwing rice") from a lunar penal colony in his superb science fiction novel "The Moon Is A Harsh Mistress". I highly recommend the story. Heinlein was amazing at predicting tech & science advances far, far ahead of any of his contemporaries.
In the above Heinlein novel, a rail launcher for Earth was proposed for several possible locations. These proposed locations shared certain characteristics, among them was elevation/altitude at the launcher exit point.
NASA could do a lot worse than taking some more inspiration (IIRC he's generally credited with the concept of communications satellites) from such an intellect.
Strat
Progressivism (aka US 'Liberalism'): Ideas so good they need a police/surveillance-state to enforce.
There are a number of reasons why rail guns are more attractive than a "steady boost".
First, we don't have anything that gives a steady boost for any reasonable amount of time at a reasonable amount of force. Rockets just don't last very long in the overall scheme of things, and laser-based propulsion systems don't have enough force to launch any appreciable payload (yet).
Second, rail guns don't require you to accelerate fuel in order to keep on accelerating. This puts an effective limit on rockets, and anything the rail gun adds pushes out our capacity based on the fuel limit.
Third, the higher/faster you're going before you start using conventional rockets will reduce fuel requirements, increase payload, or increase orbit. This is somewhat related to the second item, but not entirely. Conventional rockets require you to bring your fuel with you, which reduces payload capacity, and this compounds with the effects of being deeper in the gravity well.
Sure I'm paranoid, but am I paranoid enough?
You don't need escape velocity to orbit. (but yeah, even that velocity is higher than mach 10)
Everyone is banging their head over trying to hit Mach 10 on the track.
TFS and everyone else is misunderstanding the proposal.
The current idea is for the sled on the track to accelerate a scramjet up to about 600mph, then the scramjet lifts off, flies up to altitude and at about mach 10, releases a rocket which boosts the payload into orbit.
Sled (reusable) on the ground = 1st Stage
Scramjet (reusable) in the atmosphere = 2nd Stage
Booster Rocket in space = 3rd Stage
All extensions of more or less current technology.
And as you tread the halls of sanity, You feel so glad to be, Unable to go beyond. I have a message, From another time..
im pretty sure mach 25 is orbital velocity. which would make mach 6 a bit over 20% of the speed needed. which is more than 6%.
Ouch, hope your physics teacher doesn't see your post. If E=1/2 * m * v**2, the ratio boils down to (mach6)**2 / (mach25)**2 which works out to 36/625 which works out to 5.76 percent. The energy required to gain altitude does matter, if you're going up a couple hundred miles. If it didn't, elevators wouldn't need motors. You are correct that the velocity is where most of the energy goes, and I didn't bother to verify the math, but its vaguely around the remaining 0.24 percent figure.
My point still stands, an idealized orbital rocket at mach 6 and 60kft has only burned about 6% of its total fuel.
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
Yes, you've verified the staging equations, but you're still better off with a traditional, simple, ultra reliable first stage. The absolutely cheapest thing about orbital rocket launchers is the propellants, everything from R+D to launch support costs more. "Saving fuel" is a profoundly false economy for orbital launchers. A great way to spend billions to save millions (or less).
Also first stage is arguably the most phase of flight. A terrible place to "innovate".
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger