Author Topic: A chemically powered orion?  (Read 3249 times)

Offline constantius

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A chemically powered orion?
« on: 02/17/2012 11:09 PM »
I'm really gonna go on a limb with this one...

I know that Orion (the nuclear one) will not happen in an age when many people are frightened of atmospheric NTR's. However, could we test the technology with a chemical bomb powered Orion. Would it be less efficient than a plain old rocket?


Offline Jim Davis

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Re: A chemically powered orion?
« Reply #1 on: 02/17/2012 11:20 PM »
Would it be less efficient than a plain old rocket?

Yes, it would. Orion, even if it worked as advertised, had a very low thermal efficiency, i.e. relatively little of the energy released did useful work. For a chemically powered vehicle where the energy source and reaction mass are the same this is a complete deal breaker.

Offline colbourne

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Re: A chemically powered orion?
« Reply #2 on: 02/18/2012 01:19 AM »
If we eventually had massive space stations we could have a pressurised indoor race using pedal powered propellers or simply swimming races.

Offline peter-b

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Re: A chemically powered orion?
« Reply #3 on: 02/18/2012 01:25 AM »
Chemical explosive bomb-propelled rockets were developed and flown during the original Orion Project as proof of the concept.

See 'Project Orion', by George Dyson, which contains pictures.
« Last Edit: 02/18/2012 01:27 AM by peter-b »
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Offline ArbitraryConstant

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Re: A chemically powered orion?
« Reply #4 on: 02/18/2012 06:46 AM »
I'm really gonna go on a limb with this one...

I know that Orion (the nuclear one) will not happen in an age when many people are frightened of atmospheric NTR's. However, could we test the technology with a chemical bomb powered Orion. Would it be less efficient than a plain old rocket?
Chemical explosives actually have way lower energy content than an equivalent mass of LOX/your favorite fuel. Rockets win on thermal efficiency, and win again on specific energy.

Offline Archibald

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Re: A chemically powered orion?
« Reply #5 on: 02/18/2012 08:36 AM »
Answered differently - let's suppose the SLS throws 130 tons of C4 into low earth orbit. Could a - probably very small - Orion be propelled to any destination with that ?  ???

Offline JohnFornaro

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Re: A chemically powered orion?
« Reply #6 on: 02/18/2012 02:11 PM »
I'm really gonna go on a limb with this one...

Not a problem.  Me too...

And by "limb", I mean the "spreading upper portion of a gamosepalous calus or gamopetalous corolla as distinguished from the lower tubular portion", as the term is commonly used.

But I gotta go now.
Sometimes I just flat out don't get it.

Offline ArbitraryConstant

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Re: A chemically powered orion?
« Reply #7 on: 02/18/2012 08:04 PM »
Answered differently - let's suppose the SLS throws 130 tons of C4 into low earth orbit. Could a - probably very small - Orion be propelled to any destination with that ?  ???
Why not launch a 130 ton EDS instead for way more delta-v instead?

It's not that it can't work, it's that any idea along these lines will always lose to existing rocket technology.

Offline go4mars

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Re: A chemically powered orion?
« Reply #8 on: 02/22/2012 11:20 AM »
Answered differently - let's suppose the SLS throws 130 tons of C4 into low earth orbit. Could a - probably very small - Orion be propelled to any destination with that ?  ???
Perhaps an even smaller mass of nuclear to high earth orbit... I don't see a proper boom boom Orion as being allowed to leave from the surface, but it might be okay to use once away from earth.  Once treaties are changed...
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Offline QuantumG

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Re: A chemically powered orion?
« Reply #9 on: 02/22/2012 11:23 AM »
once away from earth.  Once treaties are changed...

No treaties need to be changed.. use of nuclear bombs in space is only prohibited by the OST if they are being used as weapons. This topic comes up all the time in planetary defense discussions.
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Offline RanulfC

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Re: A chemically powered orion?
« Reply #10 on: 03/09/2012 05:04 PM »
I'm really gonna go on a limb with this one...

I know that Orion (the nuclear one) will not happen in an age when many people are frightened of atmospheric NTR's. However, could we test the technology with a chemical bomb powered Orion. Would it be less efficient than a plain old rocket?
As stated the simple answer is "it would be much less" but that doesn't mean it hasn't been looked at:
http://www.angelfire.com/stars2/projectorion/EPPP.html
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000097368_2000138015.pdf

http://up-ship.com/blog/?p=5864

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740015362_1974015362.pdf

This suggests the use of so-called "Super-High-Explosive" which while they exist, are not used for military or civil puposes because of some-or-another disadvantage that would not so preclude them from propulsion.
(One mentioned aspect would be "can't be stored for over six-months without self-detonation" which while is a 'downside' wouldn't be a problem if you made it and used it within a short period of time)

The thing is they MIGHT work for a short-term use, (such as the suggested ability to "ground-launch" a nuclear ORION spacecraft) but the overall cost, difficulty and lack of wide-spread application would tend to negate any real advantage.

Randy
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Online HMXHMX

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Re: A chemically powered orion?
« Reply #11 on: 03/10/2012 03:33 AM »
I'm really gonna go on a limb with this one...

I know that Orion (the nuclear one) will not happen in an age when many people are frightened of atmospheric NTR's. However, could we test the technology with a chemical bomb powered Orion. Would it be less efficient than a plain old rocket?



For a treatment of the idea in fiction, see King David's Spaceship by Jerry Pournelle.  I didn't spend much time "engineering" the idea for Jerry beyond what was needed for his story, so keep that in mind.  As I recall, the planet had less than one G of pull, too, and that made things easier.

Offline gbaikie

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Re: A chemically powered orion?
« Reply #12 on: 03/10/2012 11:32 AM »
Would it be less efficient than a plain old rocket?

Yes, it would. Orion, even if it worked as advertised, had a very low thermal efficiency, i.e. relatively little of the energy released did useful work. For a chemically powered vehicle where the energy source and reaction mass are the same this is a complete deal breaker.

Well, you wouldn't need to carry the chemical bombs. You fire missiles with chemical explosive warheads at the pusher plate.
It might way to get Orion in orbit.
So Orion has no payload, has say 10%-20% of thrust on board of Orion to get off launch pad and getting some elevation. Then fire missile that explode near pressure plate. At near orbital velocity, it might be too difficult to catch it, so use onboard bombs to achieve orbit.

So this just to get the Orion into space, then you nukes for propulsion to get to Mars quickly. Allowing one to reuse vehicle to transport crew to and from Mars with one way trip time of about a month.

Offline Jim Davis

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Re: A chemically powered orion?
« Reply #13 on: 03/10/2012 04:57 PM »
Well, you wouldn't need to carry the chemical bombs. You fire missiles with chemical explosive warheads at the pusher plate.

So instead of one launch to get something to orbit we now need thousands of launches all within about 10 minutes.




Offline Patchouli

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Re: A chemically powered orion?
« Reply #14 on: 03/10/2012 05:20 PM »
Well, you wouldn't need to carry the chemical bombs. You fire missiles with chemical explosive warheads at the pusher plate.

So instead of one launch to get something to orbit we now need thousands of launches all within about 10 minutes.





Use a gun to launch the explosives.

Though this negates Orion's biggest advantage which is high ISP with high thrust.

It also should be noted a fissile was one of the big fears with the nuclear Orion as the debris could damage the pusher plate.
« Last Edit: 03/10/2012 05:22 PM by Patchouli »

Offline indaco1

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Re: A chemically powered orion?
« Reply #15 on: 03/10/2012 05:51 PM »
If an airbreathing pulse detonation engine could have a thermodynamic efficiency higher than turbojets, turbofans and, of course, scramjets and if it will work up to mach 5 with a decent T/W.... maybe this could change a little the game for space launch.

http://en.wikipedia.org/wiki/Pulse_detonation_engine

I'm aware this is a different animal, but it's more interesting.
Non-native English speaker and non-expert, be patient.

Offline Andrew_W

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Re: A chemically powered orion?
« Reply #16 on: 03/10/2012 07:30 PM »
This discussion is like speculating that we can replace turbofans and turbojets on airliners with pulse jets, the loses in efficiency far out way gains (if any) in engine simplification.

The only advantage of the nuclear Orion concept was the massive gain in exhaust velocity, go non-nuclear and you throw that only advantage away.
« Last Edit: 03/10/2012 07:31 PM by Andrew_W »
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Offline indaco1

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Re: A chemically powered orion?
« Reply #17 on: 03/11/2012 12:13 AM »
A  pulse detonation engine is very different from an old style pulse jet.
Non-native English speaker and non-expert, be patient.

Offline RanulfC

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Re: A chemically powered orion?
« Reply #18 on: 03/12/2012 06:39 PM »
Well, you wouldn't need to carry the chemical bombs. You fire missiles with chemical explosive warheads at the pusher plate.

So instead of one launch to get something to orbit we now need thousands of launches all within about 10 minutes.





Use a gun to launch the explosives.

Though this negates Orion's biggest advantage which is high ISP with high thrust.

It also should be noted a fissile was one of the big fears with the nuclear Orion as the debris could damage the pusher plate.
Note the papers I cited here, especially "Externally Pulsed Plasma Propulsion" actually suggests this method :)
http://forum.nasaspaceflight.com/index.php?topic=28095.msg871294#msg871294

Imagine if you will several dozen "batteries" along the ground track with high-speed 5" guns throwing specially time-fuzed shells as the Orion flies over. From what I gather the shells would use shape-charge/self-forging technology to produce plasma "impactors" for propulsion. Or I could have just read that wrong :)

For a treatment of the idea in fiction, see King David's Spaceship by Jerry Pournelle.  I didn't spend much time "engineering" the idea for Jerry beyond what was needed for his story, so keep that in mind.  As I recall, the planet had less than one G of pull, too, and that made things easier.
I remember that one. Super-high-speed rotary cannon (gatling) with shells timed to explode pretty much as they left the barrel. One rough ride, but if you didn't really know any better and were working against a serious deadline as per the book...


Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

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