NASA Looks At Railgun-Like Rocket Launcher 231
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."
Well, this is not a (Score:3, Interesting)
NASA still cannot do simple math. (Score:2, Interesting)
"...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:Finally... (Score:1, Interesting)
No. Sorry to disappoint all the folks who just don't get it, but this is not going to be a railgun. As a software engineer, your confusion on this is certainly excusable -- after all, even SF and video games, by and large, seem determined to make sure nobody understands what a railgun is.
At present, railguns suck -- even the Navy's version (the only thing close to being productized) is anticipated to need rail replacement/rebuild every dozen shots or so at first, with the hope that they can improve on that once it's operational. That's entirely feasible for a weapon that fires what's essentially a metal slug (perhaps a few hundred or thousand dollars) with range, accuracy, and damage on par with a $500,000 cruise missile; the money saved more than allows for having a bunch of replacement rails (only a few feet long) on hand, and replacing them can be done fairly quickly. They suck, it's just that cruise missiles suck even more.
But on a miles-long track, replacing or refinishing the rails is an insanely slow and expensive undertaking -- not that it's completely infeasible (after all, rockets, short of SSTO, suck pretty hard too), but you'd have a hard time solidly beating rocket launch rates and costs, and with the enormous capital outlay to build the launch ramp, you've gotta be sure you can undercut the competition and make it back. No, the reason it's called "railgun-like" in TFT, and "an electrified track" in TFS, rather than simply a railgun, is because it's going to be a linear induction motor or similar (in fact, probably a LIM to get up to Mach ~2, then a scramjet the rest of the way), not a linear homopolar motor, or (as the LHM with a projectile-armature is commonly known) railgun.
Oh, and FWIW, another quite interesting launch-ramp concept is the BFG [tbfg.org]'s ram accelerator concept -- IMHO the most promising of the various alternative-launch-schemes-with-websites (aka crazy bastards looking for VC). Highly recommended reading for alternative launch geeks, especially those with enough sense to realize they won't see a geosynch space elevator in their lifetime...
Re:Let's hope NASA is better at math than TFA (Score:2, Interesting)
Re:Finally... (Score:3, Interesting)
Nope, this piece of "near former sci-fi" is just as far from fruition as it ever was.
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:Well, this is not a (Score:3, Interesting)
NOT A Railgun (Score:1, Interesting)
TFA title is wrong. Bad journalism. Sensationalist title. This is not a railgun, this is a linear induction motor. Yes, they're right, they are used for amusement rides.
Re:NASA still cannot do simple math. (Score:4, Interesting)
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:Well, this is not a (Score:3, Interesting)
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.
Re:Put the railgun in orbit (Score:2, Interesting)