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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."
That space is up.
Up is relative. Space is away.
The higher the technology, the sharper that two-edged sword.
Well, I believe this critter was up and at it in the 70's at Princeton: http://en.wikipedia.org/wiki/Gerard_K._O'Neill
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
Sorry, but 10x roller coaster speeds isn't close to Mach 10.
NASA is on to something interesting here. It would seem that MagLev is required (no wheels can handle that speed), and it would be interesting to see what kind of acceleration they can get out of LIM's. Rocket propulsion seems a waste in this application. It might help bullet-train technology, and we can get some new spin-off inventions from NASA.
I need trepanation like I need a hole in the head.
so basically the trick is to fall down and miss?
the preceding post was not spell checked... suck it.
You're being facetious, but that's exactly what would happen.
General Relativity: Space-time tells matter where to go; Matter tells space-time what shape to be.
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!
... in which case Newton's Laws would adequately describe the reasons why your ultra-expensive orbital mass driver is now an ultra-expensive meteor shower.
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
Once ignited, Mach 10 wouldn't be outrageous for a Scramjet.
Well, that seems a bit optimistic for a device that has been successfully flown, what, twice? Its kind of like planning the Boeing 777 the day after the wright brothers first flight.
The real killer with all these "hybrid" lifter designs is they are all ignorant of the virtually unknown 666 rule.
The 666 rule is that Mach 6 (which is tricky for an air breathing aircraft) at 60000 feet (again, tricky) is a whopping 6% of the way to orbit.
So, if, in your wildest dreams, you can simultaneously achieve mach 6 at 60Kft, which would be quite the noteworthy achievement, you've still got 94% of the way to go.
Alternately, you could take the required second stage, and make the fuel tank at least 6% bigger and skip all this air breathing foolishness.
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
"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?
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.
IIRC he's generally credited with the concept of communications satellites
Nope. That was Arthur C. Clarke, another of the grand masters of hard science-fiction.
The higher the technology, the sharper that two-edged sword.
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?
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..
Yeah but going mach 10 at ground level isn't exactly rainbows and ponies either...
True, but you do have the potential to turn ponies into rainbows...
If brevity is the soul of wit, then how does one explain Twitter?
before gravity takes control.
As the GP said, gravity is a conservative force. It is ALWAYS in control. Right now, gravity from distance stars is pulling us in their direction--the force is infinitestimal but present nonetheless. It is an extreme colloquialism to say that when you throw a ball up in the air gravity "takes control" when it starts to fall down, never mind that gravity caused the slowing of its ascent as well. Same as in orbits.
"Coasting into orbit," in your colloquial usage, simply means cutting the engines at a lower altitude than the final orbital altitude. To pull it off, you have to be going faster than orbital velocity at the lower altitude so that after your engine is cut off, some of your kinetic energy is transferred to potential energy, and you slow down while still going up until you reach the final orbit. This is no doubt used for small portions of most flights. But the GP's point is correct; anyone who understands Newtonian physics will be able to tell whether and what orbit you will reach once you cut your engines, thus no one ever bothers to talk about "coasting".
The only difference with a railgun-only launch system is you reach the maximum velocity at ground level and spend the *entire* trip to orbit "coasting." This is not what NASA is proposing. They will use the railgun only as the first stage, followed by scramjets and an orbital-insertion rocket engine, which is a much more realistic proposal.
When you cut off your engines, you *are* in orbit. There is no "final" orbit to go to from there. The only question is, does your orbit intersect the Earth or not :-)
There is great potential for energy savings, which would mean higher payloads and/or less expensive flights.
You want higher payloads, find a rocket that works, and make it bigger.
As for less expense, I take it you believe most of the cost of the space shuttle program is liquid H2? If so, you are horribly misinformed. If, by some utter miracle, the shuttle could be operated on flying unicorns instead of solid boosters and H2/O2, calculate the delta cost in the shuttle program. I think you'll be surprised how many decimal places you'll need to use.
Liquid H2 costs about a buck a pound in the quantities NASA uses. (We'd pay closer to two bucks a pound). The entire shuttle tank holds about a quarter million pounds of liq H2. No math phd required to figure that filling the fuel tank costs about a quarter mil. A similar level of math is required to multiply that by about 130 shuttle flights to get a lifetime program cost of a whopping 30 million or so. Wikipedia claims the total cost of the shuttle program from "I gotta idea" to end of program is about 175 Billion. So, liquid H2 fuel cost works out to 30 / 175000 * 100 = about 0.02 percent of total project cost. "Saving fuel" is simply irrelevant.
So, if we risk the lives of every crewman using a new non-man rated engine and/or delay the vehicle program by decades to develop and deploy the amazing fuel free flying unicorn engine system, we will save a whopping two hundredths of a percent of total program cost. Or rephrased, for the R+D to pay for itself, we need the total cost of R+D and deployment to remain below two hundredths of a percent of program cost.
Two hundredths of a percent of project cost is about what you budget for developing and deploying the HR diversity training, or perhaps company funded picnics. Not a realistic budget factor for a new primary propulsion system.
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
and laser-based propulsion systems don't have enough force to launch any appreciable payload (yet).
And they never will. Lasers will NEVER be able to push anything into orbit, period. E=MC2. If you make E big enough to push a payload into orbit, your E ends up turning into M. Lasers only a bit more powerful than what we have now will end up creating matter in their pumping chambers and halting their output. The top few lasers on the planet are pretty close to the maximum power lasers can attain before spontaneously creating mass from the light they make. What may work, however is using a laser to beam power to the "solar" cells at the bottom of a space elevator and using that power to inch up the elevator cable.