Author Topic: The case for rocket sled assisted launch on a mountain slope  (Read 41640 times)

Offline fatjohn1408

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So I am starting a thesis about assisted launch in which i will trade off different concepts such as launch from a plane, balloon or from a rail.

Basically I still have to do the trade off but by reading and thinking I have become so convinced that rail launch by means of rocket sled on a mountain slope is the way to go.

Why?

Rocket sled technology has been around for longer than spaceflight itself. Very straight forward, no breakthroughs required. Which is a huge benefit compared to maglev.

Rocket sleds can easily propel heavy loads to Mach 3. At holloman test have occured at mach 8. This is a huge benefit compared to airlaunch and balloon launch. Which either launch subsonic or from a newly derived super vehicle of a current fighter jet which cannot carry heavy payloads.

It does not have to take off horizontally. Pitch can easily be 30-45 degrees at take-off. This means having a vertical velocity of somewhere about 500-600 m/s assuming propulsion to mach 3 by the rocket sled. The result is that it will leave the dense atmosphere in no time.

Sure the rocket sled itself will have to power at mach 3 in the dense atmosphere and will therefore be rather large. But it is fully reusable so you only need to manufacture it once every 50 launches or so. And can things move at mach 3 at fairly low (5000-6000 meters) without burning up? Sure http://www.voughtaircraft.com/heritage/special/html/sslam5.html

Are their plenty of locations to launch it? Well the best ones are located in the Andes and Himalayas but certainly a couple of mountains (check google earth if you need to) can be used.

Other plusses: Nozzle can be manufactured for near vacuum since it will leave the dense atmosphere about 20 seconds after launch.
Since you already start at 1000 m/s it will take less long to reach orbit and you only start at 30-45 degrees, thus gravity losses (which are normally accumulated at the start where the rocket moves vertically) will be very low.
Due to the short time in the atmosphere drag losses won't rise dramatically.
And even the altitude will add the equivalent of 15 m/s in potential energy.
In addition the prospect of adding lifting surfaces to your rocket may enhance the concept even further.

Surely all these benefits make it possible to design a rocket sled assisted SSTO.

Okay, that is it. Attack.

Offline Jim

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Use the search function.  This has been debated ad naseum and debunked on this forum.  Sled is too restrictive.
« Last Edit: 04/10/2011 08:41 PM by Jim »

Online Danny Dot

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There is a good video "somewhere" on this forum on using a hydrogen gun to launch propellent to orbit.  The idea is to put the gun in the ocean.
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Offline fatjohn1408

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There is a good video "somewhere" on this forum on using a hydrogen gun to launch propellent to orbit.  The idea is to put the gun in the ocean.

Yes I know, the company is called quicklaunch inc or so, totally different to what I propose though. The gun has like a 1000 g, the projectile will enter the atmosphere (sea level) at 10 km/s, etc. 

I know there have been some topics on this subject (mostly maglev related though). But I did not think the case was made yet and i did not want to pull them from under the dust. If you feel any nausea, you do not need to read nor contribute, always nice if you do however.

Offline Downix

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Studying the various mountains, the ideal location for such a setup I've found, for safety, angle, length, height, latitude, etc is Mount Kinabalu in Malaysia. 
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Offline alexterrell

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Lets say it leaves at Mach 3. the energy imparted is 405KJ/kg.

I suppose that's the same a 40km altitude balloon launch. Could be worth it.

You need an 8km dead straight track at 5g. Can you get that? You could tunnel in but then you have pressure waves in the tunnel, or you have to evacuate it.

Why rocket sledge compared to electro-magnetic?

Offline RobLynn

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Studying the various mountains, the ideal location for such a setup I've found, for safety, angle, length, height, latitude, etc is Mount Kinabalu in Malaysia. 

I quite like the #3 tallest mountain on Nepal India border:
http://en.wikipedia.org/wiki/Kangchenjunga
8.6 km tall, has a valley 10km east that is just 2.8km altitude.

Dig a tunnel from that valley to directly under the mountain - big diamter, say 10m.  Indian labour is very cheap so this will not cost nearly as much as most countries, and can work quite happily at 2.8km altitude.

Did shaft straight up from this tunnel to the peak of the mountain.  Can fill with oxygen enriched air while working on it in order to allow workers to do their job at higher altitudes.  Again thinking of about 10m

You now have a shaft 6km tall.

Catapult can be steam powered (use a disposible sabot) or use a big falling weight through geared winch at top attached to nose of craft again with some guidance sabot.  9g for 12 seconds gives 1km/s - with max q equivalent to about mach 2 at sea level.  Dial it back to lower speeds if necessary.  8.6km allows much higher expansion ratios - perhaps not quite vac engine levels, but not too far off.

Second big use could be for microgravity - 5g boost to about 300m/s in bottom 900m followed by 1 minute of free fall and then 5 g deceleration at end.  Pretty cool tourist experience.

It is possible shaft could be extended downwards as well - for greater speed or lower acceleration.  My concern with this is that perhaps drainage might be a probem.
« Last Edit: 04/10/2011 10:13 PM by RobLynn »
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Offline mlorrey

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Studying the various mountains, the ideal location for such a setup I've found, for safety, angle, length, height, latitude, etc is Mount Kinabalu in Malaysia. 

Ecuador has some good conic peaks on the equator. As Jim has said, sleds, like guns, launch rails, etc are all sorta restrictive in that they limit the possible orbital inclinations.

However, there are some possibilities, if you have a mountain that is more or less conical, you lay a rail around the circumference of the mountain, with several launch rails radiating inward from the circumference for several high demand orbital inclinations (polar, sun synchronous, equatorial, 22.3 deg, ISS, etc). You can then move your launch rocket sled around the mountain with the circumferential rail as demand requires.

This would require that the mountain you use be relatively isolated on a plain, not stuck in among other mountains, unless you are willing to dig a lot of tunnels and be scale limited by tunnel size.

Offline fatjohn1408

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Studying the various mountains, the ideal location for such a setup I've found, for safety, angle, length, height, latitude, etc is Mount Kinabalu in Malaysia. 

Nice tip, I also like Illimani (close to la paz) and the chimborazzo non active vulcano. Ten miles south of the huascaran there is also a ridge where a long approach can be made to 5500 meters. Many locations in the himalayas can be used for a rail with a nice climb to 6000 meters and even higher. But I think construction above 6000 meters is not feasible. The latitude of the himalayas (at least 27 degrees) is a big minus though. So is accessability. But you can look on and on to good mountain slopes. There are many that are good, none are perfect though.

Online hop

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You need an 8km dead straight track at 5g. Can you get that? You could tunnel in but then you have pressure waves in the tunnel, or you have to evacuate it.
Up the side of mountain, and capable of carrying hundreds of tons if it's going to get a decent payload in orbit. This alone sounds like a multi-billion dollar construction project to me.

Not only that, the OP plans to re-use the sled, so an equivalent braking zone will be needed somewhere...

I don't see what the sled buys you really. A re-usable rocket stage that reaches the same velocity is well within reach, and done properly should only cost a modest multiple of fuel costs to operate. See DC-X, Kistler, and the general approach Armadillo and Masten are taking.

Offline fatjohn1408

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Lets say it leaves at Mach 3. the energy imparted is 405KJ/kg.

I suppose that's the same a 40km altitude balloon launch. Could be worth it.

You need an 8km dead straight track at 5g. Can you get that? You could tunnel in but then you have pressure waves in the tunnel, or you have to evacuate it.

Why rocket sledge compared to electro-magnetic?

Well electro magnetic is not a proven technology yet for high thrust to weight ratios over a long track. Never seen anything electro magnetic go faster then the speed of sound. So the question is why would one use electro magnetic instead of rocket sled? Fuel costs are a negligible part of launch costs anyway. The cost to lay maglev rails will be way higher than simple rocket sled rails I presume too.

Secondly, I think that it got to be worth more then a 40 km balloon launch. How do you figure exactly?

I just made a small simulation in scilab and assuming an Isp of 325 (very low even for kerolox) an constant g load of 3 (kind off wishfull thinking), a slender (cd=0.5) single stage to orbit launcher can get 10% of its initial mass into polar orbit, don't know the figure for regular orbit which is certainly larger though. Seems to me SSTO should certainly be feasible that way as long as the structural mass can be made significantly lower than 10% which is mostly the case for kerolox stages.

Offline fatjohn1408

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You need an 8km dead straight track at 5g. Can you get that? You could tunnel in but then you have pressure waves in the tunnel, or you have to evacuate it.
Up the side of mountain, and capable of carrying hundreds of tons if it's going to get a decent payload in orbit. This alone sounds like a multi-billion dollar construction project to me.

Not only that, the OP plans to re-use the sled, so an equivalent braking zone will be needed somewhere...

I don't see what the sled buys you really. A re-usable rocket stage that reaches the same velocity is well within reach, and done properly should only cost a modest multiple of fuel costs to operate. See DC-X, Kistler, and the general approach Armadillo and Masten are taking.

Yes breaking zone is needed. But there is no reason the sled may not be a little bit robust so that it can withstand 100 g's. This leads to an additional breaking zone of 500 meters of mountain side. How to break it is also old technology with new materials i suppose.
http://books.google.com/books?id=KS0DAAAAMBAJ&pg=RA1-PA152&dq=popular+science+titanium+1950&hl=en&ei=4kO5TKvHAqWxnAefke3XDQ&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDYQ6AEwAg#v=onepage&q&f=true

I think the space shuttle launchpads are also multi billion construction projects. The cost does not need to be outrageously high. It's already built once. Just not on the right location.
http://www.holloman.af.mil/library/factsheets/factsheet.asp?id=5924
I do not know how much it costed though. If you find it please post.

It is easier to let a rocket sled slide back from the mountain than to recoup a stage from the ocean.

Edit: it is also easier when you do not need to make guidance software and electronics for a stage. Let the rail guide it.
« Last Edit: 04/10/2011 11:11 PM by fatjohn1408 »

Online hop

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It's already built once. Just not on the right location.
http://www.holloman.af.mil/library/factsheets/factsheet.asp?id=5924
I do not know how much it costed though. If you find it please post.
That doesn't meet the requirements of your launch track, you need to carry much higher payload. Also construction up the side of a high mountain is a much, much bigger challenge than doing it on a flat, dry lake bed.
Quote
It is easier to let a rocket sled slide back from the mountain than to recoup a stage from the ocean.
For the modest velocity and altitude you are adding, there's no reason to drop the rocket in the ocean. Fly it back to the launch site and land it like this: [noembed][/noembed]
Quote
Edit: it is also easier when you do not need to make guidance software and electronics for a stage. Let the rail guide it.
This cost is utterly trivial compared to the rest of the launch costs, and even more so if you re-use the first stage.

Offline fatjohn1408

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Quote
For the modest velocity and altitude you are adding, there's no reason to drop the rocket in the ocean. Fly it back to the launch site and land it like this: [noembed][/noembed]

It's still far easier to let a sled slide back than to let a booster fly back. How many haven't tried that yet? All have failed. The design of such a booster will also cost billions. It will also need to carry the dead weight of it's wings and landing gear. Much much more complex, true aerospace engineering: hard. Most of rocket sled is civil engineering: easy.

Offline sdsds

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I have become so convinced that rail launch by means of rocket sled on a mountain slope is the way to go.

It's definitely an intriguing concept!

You're right that the technology is straight forward.  I suggest you design a system with a ramp angle of 30-45 degrees at take-off.  Size the first stage and the remainder of the vehicle as you wish, and see where you would be (velocity vector and altitude) when your first stage burns out.  Then back-calculate the characteristics of a conventional first stage that could take your vehicle to an equivalent point.

Then compare the costs to operate the two systems, i.e. per vehicle launched.  Then compare the costs to establish the two systems, the sled track built from scratch versus a conventional pad at an existing rocket launch center.  (Don't forget to compare the costs of preparing the Environmental Impact Statements. ;))

It's possible that if you were going to launch every few days, your sled system would end up less expensive after only a few years of use.  But then, where are you going to get all those payloads?
« Last Edit: 04/11/2011 12:37 AM by sdsds »
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