Non-chemical launchers - Let's get off the ground cheap.

Kenshin · 2004-01-30 17:06:37

We all know how expensive it is to get a spaceship off the ground and into orbit.

Why, then, have we not looked at alternative launching methods seriously?

Something I thought of (probably not original, but hey, I haven't seen it talked about much):
One way to at least get a launch vehicle off the ground would seem to be a launch tube, similar to those used for ICBMs, but deeper, and instead of using fuel onboard to get moving, to instead use a rail system to propel the vehicle via hydrolics or electromagnetics. Once near the top of the tube, the launch vehicle could use its chemical (or other) propulsion to keep itself going, but would have saved a LOT of fuel if the launch tube were deep enough and had accelerated it to a good speed.

Is this a reasonable way of launching something?

Also, are there other ideas out there on how to save on launch costs?

Euler · 2004-02-01 20:31:32

I have heard about many types of non chemical launch ideas including: rail launch, space elevator, Orion, nuclear thermal, nuclear fusion, nuclear isomer, lightcraft, balloon, air-breathing, big gun, antigravity, tethers, antimatter. Some are more practical than others. The rail launch idea could be implemented without that much difficulty (compared with some of the others). However, it probably would not save as much fuel as you think. To get to orbit, a spacecraft would need a velocity of roughly 20,000 mph, and getting the rail launcher to accelerate up to a significant portion of this amount would be difficult.

dicktice · 2004-02-02 10:00:19

When you calculate the amount of fuel that was needed just to lift the Saturn V off the launch pad, not to mention getting up to (say) 20,000 feet, I imagine the entire first stage could be eliminated by maglev rail-launching the rest of that stack up an equatorial strato-volcano, like Kilimanjaro, on a platform that decelerates before reaching the summit, and coasts backward down to a spur rail, while generating braking emf to help energize the launch vehicle next in line.

Rxke · 2004-02-02 12:48:43

I like the lightcaft idea... a lot.

Only problem is to get the initial generator in orbit...

Also, it sounds too good to be true...

Kenshin · 2004-02-02 21:42:20

When you calculate the amount of fuel that was needed just to lift the Saturn V off the launch pad, not to mention getting up to (say) 20,000 feet, I imagine the entire first stage could be eliminated by maglev rail-launching the rest of that stack up an equatorial strato-volcano, like Kilimanjaro, on a platform that decelerates before reaching the summit, and coasts backward down to a spur rail, while generating braking emf to help energize the launch vehicle next in line.

Hmm... yes, launching up a mountain like that would be perfect. Much easier than digging a deep hole or building a really tall structure.

Michael Bloxham · 2004-02-02 22:10:43

I'm a little skeptical of alternative launch methods. Launch costs aren't a factor of materials or fuel, but research and development, construction, and maintenance. I don't see how any of these novel designs cut back on these. If, however, you did find a way to operate a giant launch tube effectively, the ideal location for constructing such a tube might be Antarctica (I have become a little obsessed with this great continent in recent years, as confirmed in my other posts in 'Nuclear, Pro & Con'). I imagine it would be relatively easy to tunnel a 100+ km launch tube in the ice sheet, and an ideal trajectory curve could easily be implemented in the design, due to the extreme depth of the ice. On top of that, the exit of the launch tube would automatically be above 14,000 ft. You might also be able to construct an additional 5000+ ft 'ice pyramid': built from gigantic ice blocks carved from the ice sheet. I'm not sure of the compressive strength, or the structural properties of the ice, but I'm led to beleive it's entirely possible to build such a pyramid. But one of the biggest advantages of the antarctic is also it's greatest disadvantage: It is almost completely isolated.

Shaun Barrett · 2004-02-06 05:56:21

Hi Dicktice!
I think you might possibly be underestimating the task your maglev rail launcher faces in trying to replace the first stage of the Saturn V.
At burn-out, the Saturn V's first stage had lifted the rest of the rocket to an altitude of 200,000 feet (38 miles) and given it a velocity of 6000 mph (roughly 8 times the speed of sound at sea-level).
Kilimanjaro is 'only' 19,330 ft high, or less than 10% of the altitude to which a Saturn V first stage propels itself and its cargo.

I'm not saying your idea isn't a good one, I just think in this case you may be a little over-enthusiastic in your comparisons!

Byron · 2004-02-06 06:53:51

Okay, everyone repeat after me....Space Elevators!

The way I see it, the amount of energy needed to lift a significant amount of mass up through the atmosphere (and the fact that you have to carry all your fuel with you as well) will ensure that "conventional" space launches will remain a terribly expensive proposition. The idea of "space guns" is a neat one, but are impractical inside Earth's thick atmosphere, imo, plus you'd have to deal with the high accelerations, etc.

Space elevators would essentially solve all of these problems and more (like the destruction of the ozone layer everytime a rocket passes through it) and will be THE key to opening up space as a viable frontier. If only the U.S. would initiate a "Manhatten"-style project to design and build a space elevator instead of re-doing the Moon, building a space station that's not really needed, etc...maybe one of these days, people will see the light..lol.

B

dicktice · 2004-02-06 08:58:04

Aw, gee, Shaun. I gottta go to work now, but I'd like to take you on regarding the strato-volcano, maglev launch scheme. Get ready to pull up your space-socks, mate!

And Byron, not that I'm not greatful for your help in getting me back on-board, but--space elevator(s)--plural, yet! Not a chance in my lifetime, so I won't even try to argue for (or against for that matter) since for me it'd just be a waste of time. Besides, you'd need other means of launching in order to . . . there I go, encouraging you to respond. Durn!

Byron · 2004-02-06 12:52:01

Hehe... Well, why I don't do this... While writing one of my stories a while back, I came up with an idea of a passenger space plane, which was a reusable single-stage orbital craft. To make this possible, there would be a kilometers-long super-high tensile cable laid out in a desert or some other place where there's a lot of flat, empty land. Much like how gliders are slung up into the air with cable tows, this cable system would lift the spaceplane about 10,000 meters or so and Mach 2 or so, at which point the cable would release and the plane's engines would kick in, ferrying it up to orbit.

Could something like be feasible outside the pages of a SF novel? To me, this system would be much simpler and cheaper to construct than a full-fledged mass driver, which would probably cost almost as much as a space elevator would.

B

Gennaro · 2004-02-06 14:03:12

Always when I read threads like this I start feeling sorry for the aliens who might have to start off from a home world with twice the Earth's gravity.

Byron · 2004-02-06 14:51:18

Always when I read threads like this I start feeling sorry for the aliens who might have to start off from a home world with twice the Earth's gravity.

And just think about how easy it would be for those leaving a planet with just half of Earth's gravity...lol

B

Gennaro · 2004-02-06 18:34:16

Indeed. Why can't those low-gravity folks just come over here and show us how to do it?
Then we might go and help the stranded heavy gee aliens joining the interstellar community as well.
:laugh:

Mad Grad Student · 2004-02-06 20:43:41

I don't think that the whole maglev-launch system would work very well, simply on the principle of atmospheric friction. No one is going to build an acceleration tower 80,000 feet high, it would be easier just to build a space elevator. However, the only alternative is to build the accelerating rails on the ground, where the atmosphere is very thick. In order to reach orbital velocity, you have to get to mach 24 or so, about 17,500 mph. Sure, by the end of the first Saturn V stage they were going mach 6 or seven, but they were practically in space by that point, where the airframe only felt about 100 mph-worth of atmospheric resistence. Doing the same speed at sea level would very quickly melt any vehicle materials, as well as violating noise restrictions. :laugh:

A possible solution I thought of revolves around the rocket equation. This simply states that the eventual speed of a rocket is determined by the amount of fuel and speed of the exhaust. Right now rockets have to be about 97% fuel to reach orbit because they have relatively slow-moving exhaust. However, if you could get the exhaust speed up to 17,500 mph you would only need a 63% fuel rocket.

Let's suppose you could get the propellant into the nozzle at aobut 12,000 mph. This could be concievably done with some turbopumps in overdrive and through some careful engineering. Once they reach the nozzle, the two fuel jets intersect and the sheer heat produced triggers combustion, which then accelerates the exhaust at the necessary speed. An engine like this would do amazing things for efficency, for example, the space shuttle Endeavour could be launched with only 200,000 lbs of fuel!

Of course, I'm open to other suggestions, but this seems reasonably practical and doable with today's technology. We won't be able to rely on chemical rockets forever, but we should get the most efficent ones possible in the interem.

RobS · 2004-02-07 10:04:31

Have you done any research about how fast pumps can move stuff? I doubt they can even push fuel at 1,000 mph, but I don't know.

One obvious problem is an energy source. Rocket engines are something like 60% efficient in converting chemical energy to thrust. The energy source to run the pumps would probably be less efficient than that, which means the fuel and oxidizer to run the pumps would mass more than the fuel and oxidizer you're pumping!

The main use of a rail system for launching that I've heard of is to accelerate the shuttle to a high enough speed to use air-breathing supersonic or hypersonic engines. It seems to me I heard that the launch speed needs to be about 500 mph. The launch vehicle in *2001: A Space Odyssey* (the book, not the movie) was of this sort.

dicktice · 2004-02-09 10:41:22

Well, sticking to my obsession with MagLev launching up the western slope of Mount Kilimanjaro--as a substitute for the conventional vertical pad-launched chemical first stage--ahem:
The conventional second stage becomes a single-stage-to-orbit, riding on a magnetically-levitated railcar powered from energy stored prior to each launch. The rocket stack is assembled horizontally under shelter at the altitude of about 2,000 feet at the base of the mountain, switched to a straight track, accelerates on wheels until levitation speed is achieved, then climbs at 45- to 60 -degrees while continuing to accelerate until Mach 0.9 is reached, at 19,000 feet, whereupon the railcar decelerates and coasts to a stop, while the H2/LOX engine(s) ignite to propel the stack up to LEO.
The railcar returns down the mountain, generating power stored as energy available to help launch the next stack awaiting its turn to go.
Payloads of all sorts can be accomodated: Knocked-down trusses, solar arrays; crew fly-back vehicles; water-ice, filling compartmented habitats, which can then be processed in orbit, using directed sunlight, into liquid water, then by solar powered electrolysis into O2 and H2, and finally liquified and stored in the shade, for rocket propulsion.
Nothing need re-enter the atmosphere unnecessarily, since spare containers of consumables and spare hardware are maintained in orbit by thrusters using H2/O2, produced in orbit.
Payloads are necessarily limited in size and/or mass as to what can be accelerated up the mountain, but this limitation can be made-up-for by the consecutive-launch capability of such a spur-rail-switched mountain launching means, by doing away with the present pad-launched chemical first stage.

clark · 2004-02-09 10:53:51

I had posted this in the wrong place.:)

Wouldn't your fancy h2/LOX engines melt the track?

How is energy derived from the return of the rail car? Isn't it returning on a mag-lev rail? If so, there isn't any friction to transfer energy/heat. How does that work?

Wouldn't you also need to decelerate the rail car to begin with on it's return? If so, you need more energy to slow the thing down, thus reducing any gain you might receive.

Where does the h2 and o2 in orbit come from? Wouldn't the production of this stuff be a requirement prior to the development of the launch system?

I would hate to imagine a misfire in the sequence to launch the stack to LEO- if it can't seperate from the rail car, you're going to be picking up a lot of pieces of your vehicle and launch systems off the side of a very tall mountain.

dicktice · 2004-02-10 11:03:45

Thanks for your interesting queries, Clark.

The entirely conventional, throttle-able h2/LOX engines won't go full-throttle until after the railcar clears the mountain track.

The newes NASA mag-lev track scheme is both contact-wheeled below levitation speed, and levitated at higher speeds. But, on the return down the mountain I assume the mag-lev principle will work in reverse as a generator, feeding emf back to the power plant for storage, using one or a combination of methods. I believe I've read that dynamic braking is inherent in the design. So the railcar would accelerate downslope until the back-emf builds enough to provide braking force so as not to overspeed, by the power plant as it stores energy, and allowed to run along straight, horizontal track beyond the slope on wheels until stopped by friction and/or an upwards-going run-out slope. Switching engines, and all the conventional paraphenalia of railroading would come into play--the way the Soyuz stacks are handled on their railcars, prior to launch.

The h2 and o2 come from water-ice, launched as payloads as needed, melted on demand by selective exposure to sunlight, with the resulting water broken down into h2 and o2 by electrolysis powered by solar-heated/space-cooled thermocouple generated emf--the processes all being housed in orbiting multipurpose tanks (left over from previous launches) which have been designed for the purpose.

The railcar continues on uphill, automatically released by the railcar decelerating, at just under Mach 1.0, susteined in the air by ground- and/or lifting-body effects (better left to the aerodynamicists amongst us to explain) until clear for the full-throttle burn. Failure to accelerate for any reason will result in the stack's continuing ballistically to impact the booster, and parachute the payload (if crewed and non-lifting) into the Indian Ocean. Dry runs up and down the track are feasible, offering greatly improved launch reliabilities.

clark · 2004-02-10 14:35:44

What if we don't have a mountain?

I am not being critical, btw, written words tend to translate poorly without the tone to set it into context. here is a warm smiley to prove it to you ... see.

So, let's assume it will work, but you don't have a mountain... let's think of a way to reduce it's footprint.

Now, I don't know about this, but here is an idea:

Imagine one of those water slides, usually found at water parks, where it's a long coiled tunnel. Would something like that work where we create a coil, stacked upon itself (thereby going higher and higher), finally shooting out into a vertical launch with the tube pointing out (on the outward end)?

dicktice · 2004-02-11 14:48:34

But, Clark, we DO have such a strato-volcano in northern Tanzania. What a fortunate source of potential development for them! It's within five degrees latitude of the Equator, which will provide launches with about as much rotational velocity additional "boost" as anywhere on Earth.
Only Mt. Kenya, although slightly lower, is better situated right on the Equator--but it is religiously taboo at present and the terrain about its base looks very mountainous and uneven. (We'll require a lot of relatively flat land west of the launch slope, for loading, parking and switching the railcars around, and the terrain leading to Kilaminjaro looks made to order. Access to the Indian Ocean port is also fortuitous.

Kenshin · 2004-02-11 20:08:48

Well I can't wait for the space elevator either, but you try telling the carbon nanotube people to hurry up development. :;):

I'm liking the sound of a maglev up Mt. Kilaminjaro more and more.

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#1 2004-01-30 17:06:37

Re: Non-chemical launchers - Let's get off the ground cheap.

#2 2004-02-01 20:31:32

Re: Non-chemical launchers - Let's get off the ground cheap.

#3 2004-02-02 10:00:19

Re: Non-chemical launchers - Let's get off the ground cheap.

#4 2004-02-02 12:48:43

Re: Non-chemical launchers - Let's get off the ground cheap.

#5 2004-02-02 21:42:20

Re: Non-chemical launchers - Let's get off the ground cheap.

#6 2004-02-02 22:10:43

Re: Non-chemical launchers - Let's get off the ground cheap.

#7 2004-02-06 05:56:21

Re: Non-chemical launchers - Let's get off the ground cheap.

#8 2004-02-06 06:53:51

Re: Non-chemical launchers - Let's get off the ground cheap.

#9 2004-02-06 08:58:04

Re: Non-chemical launchers - Let's get off the ground cheap.

#10 2004-02-06 12:52:01

Re: Non-chemical launchers - Let's get off the ground cheap.

#11 2004-02-06 14:03:12

Re: Non-chemical launchers - Let's get off the ground cheap.

#12 2004-02-06 14:51:18

Re: Non-chemical launchers - Let's get off the ground cheap.

#13 2004-02-06 18:34:16

Re: Non-chemical launchers - Let's get off the ground cheap.

#14 2004-02-06 20:43:41

Re: Non-chemical launchers - Let's get off the ground cheap.

#15 2004-02-07 10:04:31

Re: Non-chemical launchers - Let's get off the ground cheap.

#16 2004-02-09 10:41:22

Re: Non-chemical launchers - Let's get off the ground cheap.

#17 2004-02-09 10:53:51

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#18 2004-02-10 11:03:45

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#19 2004-02-10 14:35:44

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#20 2004-02-11 14:48:34

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#21 2004-02-11 20:08:48

Re: Non-chemical launchers - Let's get off the ground cheap.

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