Optimal location for rail/sled catapult launcher.

[Biscuit]

A discussion in the 'single stage to orbit' thread got me to thinking.

... I put this into the 'Addon Requests' as I think this would be a good addon launcher / base ... if I can find the time I may even attempt it someday myself ...

I know I had read in one of my scifi novels in the past about a rail launch system to give a ship an initial boost to get it on it's way.

Some google searching didn't turn up a lot, and I can't find much on it here in the forums.

Some plans have been looked at in the past, but info is scarce.

Anyway, my idea is basically a sled riding a rail running up the side of a mountain. Something like the Hyperion SSTO plan http://www.astronautix.com/lvs/hypnssto.htm

The sled would probably be riding multiple rails (don't know that maglev could hold 200+ tons off the rails) ... propulsion for the sled would probably best be performed by basically a linear magnetic motor along the rail ... I'm sure the base/launcher system would probably have to have a dedicated nuclear power plant to provide the power needed.

Location, not sure, but Kilimanjaro seems the best so far. A few kilometers of runup to gain some momentum, then a swoop up the slope to release the 'payload' at about 5.8 km altitude (according to Google's terrain map) at a high subsonic velocity ... could possibly be ramped up for even greater speed, haven't figured out the math yet. Lot's of things to work out ... power consumption, stability, maxQ, not to mention the undertaking such a real-world project would be in a remote location.

A few quick runs with an empty XR5 took anywhere from 14% - 20% of the fuel to reach that altitude and speed on realistic settings, but I admit I wasn't trying real hard ... even assuming it only taking 10% of the fuel, that was flying it empty. Loading the bay up with a heavy payload would use much more.

The launch base done as a vessel so that it could 'attach' and release it's payload from the sled, it would be at least a few kilometers long.

Not sure of the real world practicality, but I can't get this image of an XR5 being catapulted up the side of a mountain and released. I would love to have a system like this.

Any thoughts on a better location? Would this be something worth pursuing?

... sorry for the ramble on this one ...

:huh:

 

[Sherrif of Nottingham]

Yeah, I've heard of these systems... though if a mag'lev' can pull 200+ tons across rails, wouldn't it be able to lift them off the rails enough to remove the friction?

I did almost fail physics, but still... lolz

 

[2552]

You could try the Lunar Mass Driver addon

[ame="http://www.orbithangar.com/searchid.php?ID=620"]Lunar Mass Driver, release 3[/ame]

 

[loading]

http://www.launchloop.com/

This is not exactly what you are thinking of, but something similar.

Its an 3000 Km acceleration track 80 km above the Pacific.
As stated in the documents it is able to get 5 tons to orbital speed using current tech.

 

[Notebook]

Here's an early version...

N.

 

[Biscuit]

The 'Lunar Mass Driver' was roughly what I was thinking ... that style of launcher running to and up the side of Kilimanjaro.

 

[Salamander]

with the bend upward just short of the ejection end, wouldn't that cause centrifugal forces beyond good and evil?

 

[Biscuit]

with the bend upward just short of the ejection end, wouldn't that cause centrifugal forces beyond good and evil?

Not sure. Definitely wouldn't do to slam the crew with enough G force to cause them to black out just before flinging them into the air. Ooops! :rofl:

 

[GregBurch]

This always seemed like a cool idea to me when I was a kid, but now I'm not so sure. The amount of energy and altitude you're getting from the catapult just isn't that great, compared to what you can do with a flyback reusable first stage. The engineering and risk cost/benefit doesn't strike me as positively as it did 40 years ago.

Now on the moon or other airless body, a mag-catapult's energy benefits are a whole 'nuther story ...

 

[pete.dakota]

There was a similar discussion on M6 about a rocket-sled/maglev based return to Earth launch system on the Moon. I'm trying to find the thread using Google, but with no luck.

As for your idea; considering research, construction, power and maintenance costs for the whole system, it probably wouldn't be any less economically-efficient to launch the payload on a conventional, staged rocket (which, in theory, should be cheaper and more accessible in the future).

Also, if the track was to be placed up the side of Kilimanjaro (which I hope it isn't- it's very pretty), the launch azimuth (and so, orbit inclination) window would be very small- as the track would be fixed. This is extremely impracticable for commercial launch system.

 

[Biscuit]

...
As for your idea; considering research, construction, power and maintenance costs for the whole system, it probably wouldn't be any less economically-efficient to launch the payload on a conventional, staged rocket (which, in theory, should be cheaper and more accessible in the future).

Also, if the track was to be placed up the side of Kilimanjaro (which I hope it isn't- it's very pretty), the launch azimuth (and so, orbit inclination) window would be very small- as the track would be fixed. This is extremely impracticable for commercial launch system.

Probably impractical economically speaking, and it's probably childhood remembrances of Heinlein novels coming back out, but it just seems like a really cool idea.

Some off-the-cuff calculations ... if the radius of the curve is around 4 km (should be doable to roughly match the slope, the start of the rail would be at around 4km altitude to begin with) you should be able to get a release at approx 5.7 km altitude, with an airspeed of around 270 m/sec at a pitch of about 50 degrees at just over a 2G load. An unladen sparrow ... er, I mean, in an empty Vanguard the best I've been able to do is use 12% of the fuel to get to that altitude/speed from the KSC runway.

At 4 Gs a launch speed of around mach 1.2 should be achievable, but realistically I don't know what the shockwave rebounding from the mountainside would do ... definately wouldn't want to be trying to hike up a trail while that thing came by at that speed.

It probably would have to have it's own dedicated nuclear power plant to provide enough power, and a regular runway/pad to bring in supplies and ships for launch.

Anyway, it's a nice thought experiment to play with until I get some modeling skills under my belt.

The inclination is low, only just over 3 degrees, but that could be pretty useful for stuff headed to an equatorial or geosynchronous orbit.

 

[tblaxland]

It probably would have to have it's own dedicated nuclear power plant to provide enough power

I don't think that this would be a practical proposition, given that this thing would be operating at a very low duty cycle. To illustrate this point, I have done some back-of-the-envelope calcs myself.

Say your launch velocity is 300m/s and you get there at an acceleration of 3g, ie, 30m/s/s and your are launch a 25t DeltaGlider. The energy added to your vessel would be E = 0.5mv2 = 1125MJ. You could add a bit to that for drag losses but they would be fairly small over the time frame we are considering here compared to the kinetic energy added to the vehicle. The acceleration time would be 300/30 = 10s. Average power use during the launch would then be 1125MJ/10s = 112.5MW (fairly small in nuclear power plant terms). The biggest problem is that this power is only required for 10s - the rest of the time your powerplant would have to either turn down its output (not easy for any large scale power station, let alone a nuclear one) or divert it to the grid (not really satisfactory because other generators would have to take the slack during launches). Alternatively, your power source could by one big flywheel (or gang of smaller ones).

Say you conduct a launch once a month. The average power draw would be 1125MJ/2592000s = 434W! You could safely draw this off the grid and store it in your flywheel for when required by the launch. The flywheel would require some power to overcome losses but the average power draw should still be fairly low.

EDIT:
Some links:
Compensated pulsed alternator
Flywheel energy storage - Amusement ride

 

[Biscuit]

...
Say you conduct a launch once a month. The average power draw would be 1125MJ/2592000s = 434W! You could safely draw this off the grid and store it in your flywheel for when required by the launch. The flywheel would require some power to overcome losses but the average power draw should still be fairly low.

But that works out to about 1500 kwh per hour. The average U.S. household only uses around 1000 kwh per month.

Plus, with future tech like the DGs available, I would think the launches would be more frequent, more on the order of 1/week, although that could be very wishful thinking.

The monthly usage would be (if I got the decimal in the right place) around 1100 Megawatt hours per month. A launch/week would be around 4400 Megawatt hours per month ... the smallest nuclear plant I could find in the U.S. is routinely generating over 300,000 Mwh per month ... so, yeah, a dedicated nuclear plant MIGHT be a little bit of overkill. :blink:

I really like the flywheel power storage idea, though. I hadn't thought of that.

 

[gwilc]

NASA considers rail/sled launch system.

If you go to the web site space.com, look under the tech tab and scroll down onto the story about new proposals for launch systems, here is your answer: http://www.space.com/businesstechnology/rail-launched-scramjets-new-nasa-technology-100914.html

NASA is currently studying using the new tech of scram jets to launch using a rail system for future launch's.

I wonder what the folks at Gerry Anderson / Fireball XL5 think about that?

 

[Polaris]

The Soviets designed a system like the one seen in "XL5", but I doubt it was built. By the way, the same system was used to launch the rocket in "When World Collide".