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As an hard fiction writer, I was looking for a good but realistic propulsion system for the spaceships of my next space opera.
I was skeptical about Orion, but I was captured by this very cool short movie:
https://www.youtube.com/watch?v=uQCrPNEsQaY
after I read this old document,
http://www.projectrho.com/public_html/r … 09vIII.pdf
where every potential problem of Orion Drive is very well addressed, from thrust vectoring control to pusher plate protection and shock-adsorbers cooling...
It seems it can really works, so I decided to open a topic about it.
We can minimize fall-out, using a very large metal plate at the base of the launch pad or taking of from Antarctic with conventional solid boosters and fire the Orion just outside the atmosphere, or assembling it in LEO or (in a future) building it on the Moon.
But I'm interested in exploring a future hypothetical scenario, were humanity is spread-out in the solar system where has built thousands of space habitat from Venus to main belt asteroids, gas giant's moons and KBO and ground habitats in Mars and in Mercury poles. Peoples travels from Mercury to the Kuiper belt using Orion propelled spaceship. So even private space ship owners can buy pulse units, that are very poor nuclear warheads, but still contain weapon grade uranium.
One can think that this kind of society is a bit unrealistic, because every religious fanatic or psychopath can arrange a nuke, but the real problem is that even without uranium, a spaceship with a high performance propulsion system is a weapon of mass destruction per se.
Imagine a 300 ton spaceship impacting with a space habitat at 10-12 km/s: it does a lot more damage than a poor 1 kiloton Orion's pulse unit, theft from the habitat service station.
So, how can we have a stable society and use 4000-7000 Isp spaceships?
We can image a lot of countermeasures like autonomous killing vehicles that intercept spaceships in collision course before they hit the habitat, sealed magazines for the pulse units, that can be opened only by uranium guild guys or something like that...
An alternative is a space transport system controlled by military, with Orion propelled space-liners with civil passengers and cargo, but navy crews, but this is more boring...
Have you some ideas?
Last edited by Quaoar (2015-01-30 15:55:30)
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Nukes in civilian hands is not going to happen. The proliferation of nuclear weapons is of great concern, it is bad enough when only nations have them, but what about individuals? My guess is commercial fusion reactors will be available, probably magnetic confinement fusion. Deuterium and tritium will be fused to make helium-4 and to get different thrust levels, the exhaust will be mixed with plain hydrogen, the more hydrogen, the greater the thrust, the less hydrogen the greater the ISP. My feeling is there will be one kind of rocket used to take off from a planet's surface, a fusion powered Nerva rocket, the exhaust of this rocket will be hotter than a Saturn V, but will be almost pure hydrogen, this will produce the multi-g thrust required to get off a planet's surface, and once in orbit a lower thrust but more efficient fusion drive will be used to travel around the Solar System, I believe it would take 1 to 2 weeks to get to Mars from Earth. Otherwise a space elevator may be used.
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Nukes in civilian hands is not going to happen. The proliferation of nuclear weapons is of great concern, it is bad enough when only nations have them, but what about individuals? My guess is commercial fusion reactors will be available, probably magnetic confinement fusion. Deuterium and tritium will be fused to make helium-4 and to get different thrust levels, the exhaust will be mixed with plain hydrogen, the more hydrogen, the greater the thrust, the less hydrogen the greater the ISP. My feeling is there will be one kind of rocket used to take off from a planet's surface, a fusion powered Nerva rocket, the exhaust of this rocket will be hotter than a Saturn V, but will be almost pure hydrogen, this will produce the multi-g thrust required to get off a planet's surface, and once in orbit a lower thrust but more efficient fusion drive will be used to travel around the Solar System, I believe it would take 1 to 2 weeks to get to Mars from Earth. Otherwise a space elevator may be used.
I doubt that magnetic confinement fusion reactors will be lightweight enough to be placed inside spaceships. They are very massive and needs huge waste heat radiators to cope with neutron heating, so a fusion propelled spaceship will have at the best a thrust just a little better than electric propulsion, unless we will be able to make pure fusion mini-bombs, like Project Dedalus pellets. But at the moment we don't have fusion, so hard fiction writers are forced to use fission, chemicals of solar electric propulsion.
Military nuclear warheads make a lot of damage if detonated in a planet atmosphere, but, if detonated in space, are not so dangerous like a 500-1000 tons spaceship impacting at 10-20 km/s. So in an Earth centered scenario you are perfectly right in not giving Orion Pulse Units to civilians.
But in my scenario, Earth is declined, poor and polluted and most part of mankind live in rich and beautiful space habitats, in Earth Moon Lagrange points, on Moon, Mars and Mercury (poles) surface, in Venus and Mars orbit, around the Main Belt's asteroids, and the moons of gas giants. So these guys, born and grown-up in an artificial space habitat and never been on Earth, will probably fear a kinetic kill more than a nuke strike.
The real problem is that a spaceship is a WMD, even without nuke, by only its kinetic energy, so if private civilians can buy spaceship, the risk for the habitats remains.
So the question in my opinion is not "private Orion or not private Orion", but "private spaceship or not private spaceship".
Last edited by Quaoar (2015-01-31 04:21:38)
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Tom Kalbfus wrote:Nukes in civilian hands is not going to happen. The proliferation of nuclear weapons is of great concern, it is bad enough when only nations have them, but what about individuals? My guess is commercial fusion reactors will be available, probably magnetic confinement fusion. Deuterium and tritium will be fused to make helium-4 and to get different thrust levels, the exhaust will be mixed with plain hydrogen, the more hydrogen, the greater the thrust, the less hydrogen the greater the ISP. My feeling is there will be one kind of rocket used to take off from a planet's surface, a fusion powered Nerva rocket, the exhaust of this rocket will be hotter than a Saturn V, but will be almost pure hydrogen, this will produce the multi-g thrust required to get off a planet's surface, and once in orbit a lower thrust but more efficient fusion drive will be used to travel around the Solar System, I believe it would take 1 to 2 weeks to get to Mars from Earth. Otherwise a space elevator may be used.
I doubt that magnetic confinement fusion reactors will be lightweight enough to be placed inside spaceships.
I guess you never heard of the Dynamak Reactor.
http://www.americansecurityproject.org/ … n-reactor/
It is about the size of a small truck.
They are very massive and needs huge waste heat radiators to cope with neutron heating, so a fusion propelled spaceship will have at the best a thrust just a little better than electric propulsion, unless we will be able to make pure fusion mini-bombs, like Project Dedalus pellets. But at the moment we don't have fusion, so hard fiction writers are forced to use fission, chemicals of solar electric propulsion.
Military nuclear warheads make a lot of damage if detonated in a planet atmosphere, but, if detonated in space, are not so dangerous like a 500-1000 tons spaceship impacting at 10-20 km/s. So in an Earth centered scenario you are perfectly right in not giving Orion Pulse Units to civilians.
But in my scenario, Earth is declined, poor and polluted and most part of mankind live in rich and beautiful space habitats,
Why would it be, if fusion was available, why burn coal. Coal is a lot bulkier than fusion fuel I would expect fusion to be everywhere if it was available for spaceships, coal fired plants are simply less efficient.
in Earth Moon Lagrange points, on Moon, Mars and Mercury (poles) surface, in Venus and Mars orbit, around the Main Belt's asteroids, and the moons of gas giants. So these guys, born and grown-up in an artificial space habitat and never been on Earth, will probably fear a kinetic kill more than a nuke strike.
Think is you can detect kinetic kill devices approaching, its velocity gives it away, a nuke by contrast is not what it seems, it can be smuggled into a city and detonated, the only way a kinetic kill device works is if it is fired at high velocity, you can't do this from inside a city.
The real problem is that a spaceship is a WMD, even without nuke, by only its kinetic energy, so if private civilians can buy spaceship, the risk for the habitats remains.
By virtue of its kinetic energy, the thing is, a kinetic kill device makes a lousy surprise weapon, you can always see the kinetic kill missile approaching with the right detection system.
So the question in my opinion is not "private Orion or not private Orion", but "private spaceship or not private spaceship".
You can always stop a kinetic vehicle with another kinetic vehicle, you just have to detect the first's approach. Presumably there will be rules against spaceships approaching too fast, or they will be destroyed. A ship simply moves into the path of the oncoming object. I think Government would do a terrible job of operating spaceships economically, the government wastes resources as it can always get more from the taxpayer.
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I guess you never heard of the Dynamak Reactor.
http://www.americansecurityproject.org/ … n-reactor/
It is about the size of a small truck.
Bussard's Polywell has the size of a washing machine and Lerner's DPF is even smaller, but first we have to see if they works.
Why would it be, if fusion was available, why burn coal. Coal is a lot bulkier than fusion fuel I would expect fusion to be everywhere if it was available for spaceships, coal fired plants are simply less efficient.
We still don't know if fusion will be available and the hypothetical reactor will be economic and lightweight enough. Another possibility are the hybrid fission-fusion reactors: in this case sub break-even huge magnetic confinement reactor are coupled with thorium-uranium power plant. Hybrid plant are fixed and lightweight fission rocket use U233 produced by plants.
I surely hope Bussard's Polywell eventually will work and we will have fantastic water propelled QED rocket with high thrust and 2000-3000 s of specific impulse, but how can we know?
Think is you can detect kinetic kill devices approaching, its velocity gives it away, a nuke by contrast is not what it seems, it can be smuggled into a city and detonated, the only way a kinetic kill device works is if it is fired at high velocity, you can't do this from inside a city.
By virtue of its kinetic energy, the thing is, a kinetic kill device makes a lousy surprise weapon, you can always see the kinetic kill missile approaching with the right detection system.
It's not so simple: everything traveling at a relative velocity more than 3 km/s has a kinetic energy greater than its weight in TNT. So a spaceship can launch multiple rubbish object, that may be difficult to localize and intercept.
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Small objects are more difficult to track, but they also deliver less kinetic energy, and they aren't any different from meteors hitting a space settlement The larger the object the further out it can be detected. 3 km/s isn't that much, there are a lot of objects moving through the Solar System at 3 km/s, anything designed to stay in space has to deal with those. One way is simply to have a double hull, the object hits the first hull and vaporizes thus protecting the second hull. Anyway whoever fires a kinetic kill device is revealing himself as the projectile can be tracked right back to its point of origin. This is the equivalent of someone showing up with a gun and firing into a crowd, most people don't do this because they care about getting caught. With a nuke bomb, the bomb destroys the evidence of who planted it when it detonates.
Anyway as for Fusion, I think Lockheed as an interest in not making wild claims that it can't back up, I think if Lockheed announced that it can build a fusion device, there must be something to it. I think they probably ran a computer simulation that show it would work. Besides, its been long enough, a fusion reactor is going to be built sooner or later, or else these fusion scientists look incompetent!
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Well, that depends on what you have to intercept them with. A Battlestar, armed with a laser and containing a billion tonnes of water ice to act as a massive heat sink, could perhaps be used by the Space Patrol to vaporise any vessel which enters a velocity restricted area...
I think we're going to need velocity restricted areas, based on the time it takes to identify and destroy a vessel, and of course the path that the debris takes. Say, having standing orders to destroy any vehicle travelling faster than 300km/s that comes within 1 million km of a planet? That would give us just under and hour to destroy it. Perhaps it would be best to scatter a smart pebble screen around each world, to destroy any oncoming vessel that doesn't slow down.
Use what is abundant and build to last
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Well, that depends on what you have to intercept them with. A Battlestar, armed with a laser and containing a billion tonnes of water ice to act as a massive heat sink, could perhaps be used by the Space Patrol to vaporise any vessel which enters a velocity restricted area...
I think we're going to need velocity restricted areas, based on the time it takes to identify and destroy a vessel, and of course the path that the debris takes. Say, having standing orders to destroy any vehicle travelling faster than 300km/s that comes within 1 million km of a planet? That would give us just under and hour to destroy it. Perhaps it would be best to scatter a smart pebble screen around each world, to destroy any oncoming vessel that doesn't slow down.
How long would it take to reach 300 km/sec? Seems to be easier just to move a space station aside and let the 300 km/sec object pass. 300 km/sec is about 10 times as fast as the fastest manmade object ever launched to date. Be easier to hit planet than a space station. Space Stations you can move. Anyway anything you put in front of the object would vaporize it, it doesn't have to be a Battlestar, could just be an asteroid and a space tug to move it into position. I think a space station would be surrounded by a network of "suicide" drones that block the path of any object moving towards the space station too fast.
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No, it really, really isn't that easy to move a space colony. You either intercept the object, or people die. It's even harder if the target is on a planet.
I think interception is the only viable method, and that needs to be done with velocity restricted zones. I believe that they already have a 500m safety zone around vessels at sea? It's really an extension of that principle, except that the exclusion zones are measured in hundreds of thousands of kilometres...
I think a screen of smart pebbles might be the cheapest way to shield a colony. But then you have to deal with the fact that such vessels are going to be designed to move around or destroy such debris... I think big lasers might be necessary. You can't really dodge a laser beam.
Use what is abundant and build to last
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Orion seems to me the best propulsion system we have at the moment: in a future we can avoid giving uranium to civilians having transport spaceships with military crews and civilian passengers and merchants who rent the cargo bay space for their goodies.
The estimate specific impulse of the conceptual vehicles was: 1850 s for a 10 m pusher plate diameter spaceship, with 3.5 MN of thrust and up to 390,000 kg of dry mass and 3150 s for a 20 m pusher plate diameter spaceship, with 16 MN of thrust and up to 390 MT of dry mass and up to 2,000,000 kg of dry mass.
This using conventional nukes modified for propulsion. According to the authors, using new nukes especially projected for propulsion, with full optimized collimation of plasma jet on the pusher plate, an Orion drive can reach an Isp up to 20,000 seconds.
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The Orion explosion drive is a really oddball piece of physics. It works more efficiently the bigger your ship. For the small vehicle NASA looked at that would take a small crew to Mars, it didn't look that much different from the nuke thermal rocket. That's where your numbers like 1850 sec come from.
In much larger sizes is where numbers like 10,000 sec or 20,000 sec come from. The baseline design of 1959 was 280 feet long, 185 ft diameter, and about 10,000 tons at launch. That goes with 10,000 sec Isp, and T/W around 2 to 4. Bigger still is where the 20,000 sec Isp comes from: above 20,000 tons.
The nukes they use for this are fractional-kiloton in the atmosphere, a few kilotons in space. They are "shaped charges" in the sense that you can design for a spindle-shaped radiation "blast", meaning two intense spikes of it 180 degrees apart. Things like that make very lousy blast weapons down here. Atom bombs of the type we have for warfare down here make lousy Orion-drive devices, precisely because the radiation "blast" (and the real shock wave blast) is omnidirectional.
The original 10,000 ton design of 1959 was intended for a 3 year mission to Saturn and back, stopping off at the moon and Mars "on the way". I think they intended to land the thing, but that function would be better served with a landing craft, parking the Orion in orbit. Remember, this is 1954-1959 we are talking about.
They weren't supposed to test the principle back then, but they did it anyway. 1-meter flying model propelled by pulsed high-explosive blasts. It worked. The survival data for the pusher plates came from the surface tests of nuclear weapons in Nevada in the 1950's, plus some of the damage assessment data from Hiroshima and Nagasaki, and from the early tests against naval vessels in the Pacific.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Hmmm. Have an Imperial Corporation with a monopoly on fast interplanetary travel? It doesn't have to be run by the military, but it does have to be a monopoly. For cargo, however, being shipped by slow unmanned SEP vessels, it would be a free market.
Though, if you give an SEP vessel enough time, it will be able to build up quite a bit of speed. Honestly, I don't think you'll be able to resolve the WMD issue by attempting to gain a monopoly. Especially if people have free access to gigawatts of power - and if you're going to colonise throughout the solar system, they will, either from solar collectors at Mercury, or fusion power in the outer system. What's to stop them from building a beamed-power system to accelerate a payload to 100km/s, which will allow it to do a kilorick of damage (i.e. each tonne is worth 1 kilotonne explosive power)?
I think we need to develop tracking and interception capability, rather than attempt to stop anyone from trying. We'd need to succeed every time. They'd only need to succeed once.
Use what is abundant and build to last
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The Orion explosion drive is a really oddball piece of physics. It works more efficiently the bigger your ship. For the small vehicle NASA looked at that would take a small crew to Mars, it didn't look that much different from the nuke thermal rocket. That's where your numbers like 1850 sec come from.
In much larger sizes is where numbers like 10,000 sec or 20,000 sec come from. The baseline design of 1959 was 280 feet long, 185 ft diameter, and about 10,000 tons at launch. That goes with 10,000 sec Isp, and T/W around 2 to 4. Bigger still is where the 20,000 sec Isp comes from: above 20,000 tons.
GW
With better understanding of pusher plate ablation and jet collimation, and miniaturizing the pulse units using the status of the art of three stage nukes, it will be possible to build a quite efficient lightweight space corvette in the range of 1000 tons of dry mass, with 5000-6000 s of specific impulse?
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I honestly don't know, Quaoar. An explosion-drive vehicle that size could certainly be built. What Isp it might have, I don't personally know how to calculate.
GW
GW Johnson
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"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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I honestly don't know, Quaoar. An explosion-drive vehicle that size could certainly be built. What Isp it might have, I don't personally know how to calculate.
GW
I found in this site ( http://www.projectrho.com/public_html/r … ject_Orion ) a the plans of USAF version of Orion: a 10 meters pusher plate spaceship with a predicted specific impulse of 3357 seconds. The project is very detailed: there is also the loading mechanism of pulse units.
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Hmmm. Have an Imperial Corporation with a monopoly on fast interplanetary travel? It doesn't have to be run by the military, but it does have to be a monopoly. For cargo, however, being shipped by slow unmanned SEP vessels, it would be a free market.
Though, if you give an SEP vessel enough time, it will be able to build up quite a bit of speed. Honestly, I don't think you'll be able to resolve the WMD issue by attempting to gain a monopoly. Especially if people have free access to gigawatts of power - and if you're going to colonise throughout the solar system, they will, either from solar collectors at Mercury, or fusion power in the outer system. What's to stop them from building a beamed-power system to accelerate a payload to 100km/s, which will allow it to do a kilorick of damage (i.e. each tonne is worth 1 kilotonne explosive power)?
I think we need to develop tracking and interception capability, rather than attempt to stop anyone from trying. We'd need to succeed every time. They'd only need to succeed once.
Having a monopoly defeats the purpose of having it private.
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When did the military become the only part of the government, Tom?
Use what is abundant and build to last
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