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."

Comments

Well, this is not a

[ScrewMaster]

new idea, exactly, but I guess it's good to see NASA looking at other possibilities. There are many. I remember MIT doing work on alternate launch technologies back in the seventies, if not earlier. The mass driver was one (a giant electromagnetic linear accelerator) although the idea was kicked around in science-fiction long before that. My current favorite is a possibly-reusable rocket whose reaction mass is water, using heat energy provided by ground-based lasers. You could launch things into orbit all day long with a setup like that. Probably need a dedicated nuclear power plant to run the thing.

Re:Well, this is not a

[pixelpusher220]

Yeah but going mach 10 at ground level isn't exactly rainbows and ponies either...

Re:Well, this is not a

[dwinks616]

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.

NASA still cannot do simple math.

[drcheap]

"...hitting speeds of about Mach 10."

"Starr noted that electric tracks catapult rollercoaster riders daily at theme parks. But those tracks call for speeds of 60 mph -- enough to thrill riders, but not nearly fast enough to launch something into space. The launcher would need to reach at least 10 times that speed over the course of two miles in Starr's proposal."

Mach 10 = 600mph ???

Re:NASA still cannot do simple math.

[vlm]

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.

Re:Let's hope NASA is better at math than TFA

[movrev]

Accelerating up to supersonic speeds on a maglev track is quite problematic from a controls/stability perspective. The generated shock waves will bounce off of the ground/track creating some interesting ground effects which will mess up the launch unless properly controlled. I'm sure their proposal is to get the sled up to about Mach 1, at which point they'll be able to take off with a ramjet engine. Once they reach around Mach 5 in the atmosphere, they could transition into a scramjet configuration which can theoretically allow them to reach orbital speeds. This specific problem has been in NASA's mind for a number of years now. I used to work on this precise thing in collaboration with them around 5 years ago.

Re:Finally...

[DerekLyons]

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.

Nope, this piece of "near former sci-fi" is just as far from fruition as it ever was.
 

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.

It's a great example of people not learning from the past and re-inventing the square wheel because now they have the tech to make carbon fiber square wheels instead of those old fashioned wooden ones.
 
But they're still square wheels.
 
The basic problem with a railgun is that it give only a fraction of the velocity required - and it does so only in one plane. (Orbital velocity has both a horizontal and a vertical component, railguns provide velocity only in the horizontal, cannons only in the vertical.) So you end up still needing a substantial rocket stage in order to provide the missing velocity - but now that rocket stage needs to be reinforced (thus increasing parasitic mass) in order to stand the stresses of being handled (while fueled) horizontally and of having to maneuver while still deep in the atmosphere[1] and insulated against structural heating from friction due to it's high speed low in the atmosphere... You end up not gaining anything over the conventional approach.
 
Railguns don't work because we lack some wonder technology for the gun - they don't work because the structural sums don't add up for the booster. Any materials improvement that you could apply to a railgun boosted launcher, you can also apply to a conventional launcher, which still leaves the railgun launcher trailing in performance and cost.
 
Railguns and a host of other alternative launch schemes look so simple and obvious that people simply cannot convince themselves that they don't work. So, they keep throwing money and tech at the problem convinced that this time it will work, it's so simple it just has to work. So NASA will waste a couple of hundred million dollars dicking around with the new gun - and then they'll discover the problem of booster design (again). And just like the last dozen times they've done this, the project will quietly be dropped.
 
Until the next time someone comes up with a PowerPoint presentation showing how this time it will be different.

[1] If you ever watch a rocket launch, you'll notice it goes more-or-less straight up for a couple of miles before starting to pitch over - there's a reason for that.

Re:Put the railgun in orbit

[dwinks616]

The point of having it evacuated is to avoid air resistance. Every last bit of energy lost to air resistance is energy gained in heat.