Revisiting Project Orion - Article.

RobertDyck · 2005-04-03 15:45:51

Plutonium 238? I thought fission bombs used plutonium 239. A breeder reactor exposes uranium 238 to neutron radiation, some is absorbed to briefly form U239 which beta decays in a fraction of a second to neptunium 239, then it beta decays with a half life of 2.355 days to plutonium 239. Pu238 has a half life of 87.74 years instead of 24110 years for Pu239, so Pu238 would make much better bomb material, but how to make it? You could expose thorium 232 to alpha radiation to make uranium 236, then expose that to neutron radiation to make uranium 237. U237 will beta decay with a half life of 6.75 days into neptunium 237. That's the naturally occurring isotope of neptunium but Np is rare, Th is more common. Np237 is stable with a half life of 2.14*10^6 years, but then expose it to neutron radiation to convert it to Np238. Np238 will beta decay with a half life of 2.117 days into Pu238. Cool.

Now can we focus on engines to take us to Mars that are not fuelled by weapons of mass destruction?

John Creighton · 2005-04-03 16:39:05

Out there idea time. If Orion rides on a plasma wave how about a magnetic field instead of a pusher plate? Perhaps the field could even be shaped so it slightly cups the blast thus increasing efficiency. Moreover, it would be easier to dispense bombs though a magnetic field the holes cut in a pusher plate.

In terms of really big probably never affordable ideas. I think that such a vehicle could do a ground landing if it had a blast cavity with as much area as a big city and equal depth. After landing the vehicle would probably have be able to travel on land to a radiation free zone before it could unload crew and cargo. A vehicle that big could probably take off with large nukes but might need small ones for a soft landing. Basically it would be a fling city and would cost billions if not trillions of dollars. Well beyond our current industrial capacity but really cool.

yales · 2005-04-03 16:58:11

GCNRenger wrote:
"Second, that Orion doesn't make sense as a reuseable vehicle. Orion is unable to land for intents and purposes, so if it were to be reused as an orbit-to-orbit ship after launch (or assembly), a different means of launching and landing cargo efficently would be required to make use of its huge payload... But if you have a means of efficent launch/landing already, then Orion's biggest strength - massive ground launch, is redundant. Also, if you can't reuse an Orion for ground launch, then building a new Orion every time isn't economicly practical in the slightest."

During a radio interview on Project Orion, Dr. Freeman Dyson, the physics leader of the project, discussed that very point:
================================

{CALLER}: Well, my question is why would you not build this ship in space, thereby overcoming the problem of the dirty bombs in the atmosphere?

{Dr. DYSON}: It's just too expensive to do that.
Of course, we thought of it, of course, right at the beginning. But the cost of getting the ship up using conventional rockets turned out to be much, much larger than the cost of building it on the ground, so you'd lose all the advantage of doing it cheaply.

{CALLER}: Would the advantage of a long-distance trip--would the overall efficiency--wouldn't that overcome the disadvantage of initially getting the material in space?

{Dr. DYSON}: No. It turns out not to.

===========================================

GCNRevenger · 2005-04-03 17:37:12

Out there idea time. If Orion rides on a plasma wave how about a magnetic field instead of a pusher plate? Perhaps the field could even be shaped so it slightly cups the blast thus increasing efficiency. Moreover, it would be easier to dispense bombs though a magnetic field the holes cut in a pusher plate.
In terms of really big probably never affordable ideas. I think that such a vehicle could do a ground landing if it had a blast cavity with as much area as a big city and equal depth. After landing the vehicle would probably have be able to travel on land to a radiation free zone before it could unload crew and cargo. A vehicle that big could probably take off with large nukes but might need small ones for a soft landing. Basically it would be a fling city and would cost billions if not trillions of dollars. Well beyond our current industrial capacity but really cool.

Thats actually one of the upgrades assumed to be available for a pulse-nuclear ship to make a medium sized one (like, ~1,000MT) more efficent then GCNR or VCR-VASIMR. Trouble is, you still need a shielding plate of some sort, since the magnetic field wouldn't stop the EM pulse (microwave, thermal, visible, UV, X-Ray, and hard Gamma like nukes make).

Move the whole ship over ground away from the landing site? Ummmm no.

I'm not even real sure how the thing would land at all without having to free-fall the last hundreds of meters or something.

"Now can we focus on engines to take us to Mars that are not fuelled by weapons of mass destruction?"

Bingo. The most exotic form of propulsion, at the moment, that I am willing to consider for the first Mars missions would be a GCNR engine. Even the VCR-powerd VASIMR is probobly too much trouble... Your right BTW, it is Pu-239 that is used for bombs.

John Creighton · 2005-04-03 19:08:25

I'm not even real sure how the thing would land at all without having to free-fall the last hundreds of meters or something.

It would land just like a VTOL rocket. It would have a huge half spherical cavity to contain the blast but it would have places for the plasma to exhaust out after landing. I am not sure the minimum size of such a half spherical cavity that would be needed. I guessed the diameter of a city to be safe. Clearly it depends on how small nukes can be made. I suppose there is definite heat exchange issues to work out as well. Another option for a plate design would be to have landing legs that extended out way past the plate. So on lunch and landing the plate could be suspended a hundred meters off the ground or so. I understand it is not freezable but that doesn’t mean I still can’t discuss how it could be done.

Chazbro38 · 2005-04-03 22:25:30

What about the VASIMIR? A prototype has been tested in a vacuum chamber and it seems to work just fine. It seems that this is the way to go for near term propulsion if we are to travel to Mars and other planets in a reasonable time. As for Orion, I don't see how anyone is going to get their hands on the hundreds of nuclear weapons that would be required for its operation. If I'm missing something about any of this I would welcome enlightenment!

Charles

GCNRevenger · 2005-04-04 06:01:22

The biggest problem with VASIMR is what to power it with. It needs an energy source that produces a great deal of power for a minimum of weight. Right now, conventional solid-core nuclear reactors can make enough energy to operate VASIMR, but because of their mass it will partially counteract VASIMR's efficency.

For VASIMR to be a practical "super" drive and be superior to simple solid-core nuclear rockets, it would need a new kind of energy source. The only two practical options are both nuclear reactors that haven't been invented yet unfortunatly, a fusion reactor or a vapor-core fission reactor. The latter of which, however, is not far out of reach technologically.

RobertDyck · 2005-04-04 08:46:05

"Don't find fault. Find a remedy." - Henry Ford.

I've said before we could use Timberwind now. That's a solid core NTR with much lower reactor mass than Nerva. The radial flow pebble bed has the problem that hot spots form between pebbles causing pebbles to melt together; fine, that makes it a single use engine. I'm not sure how long the nuclear fuel would last anyway; the reduced mass is due to rapid reaction. A combination might be possible: use the principle of highly enriched uranium with no moderator in a controlled flow design similar to Nerva. Eliminating all that graphite from Nerva might reduce reactor mass close to Timberwind levels, but it would be a completely new engine.

VASIMR does require a lot of power. Another idea I proposed on this board before was modifying a nuclear reactor to directly produce electromagnetic radiation in the band required for hydrogen absorption. Use wave guides to direct that EM from reactor to VASIMR fuel heating chamber. This increases efficiency by eliminating the conversion from heat to electricity, then from electricity to EM, and finally from EM to heat. The goal is to heat exhaust gas in VASIMR to plasma, no reactor could directly produce that heat. Conversion from electricity to EM is very efficient, and from EM to heat only depends on absorption. However, conversion from heat to electricity is very poor efficiency. It would take a nuclear engineer who really knows what he's doing, but it is theoretically possible. Hey, someone could get their PhD out of this.

GCNRevenger · 2005-04-04 11:29:30

And now for you, PO, even though you are trying to ignore the cold reality...

Virtually everything that we debate and discuss here on this board is based on some assumptions. In fact, much of physics and chemistry and whatnot was built on assumptions. There is nothing wrong with assuming something, so long as the assumption is reasonable.

The fact is that building atomic explosives for any reason whatsoever is a wildly controvertial issue. The RNEP garnerd signifigant domestic and foreign as well as governmental and NGO opposition. To build an atomic explosive with limited "consequences" that could be deliverd from orbit in number would radically change change in the balence of power and the lethality of warfare... Simply issuing little assurances that "but they're nukes for PEACE!!!" will ring hollow with those both in and out of power because of their obvious and irresistable military application. Hence, it is a reasonable assumption to make that Orion will meet resistance.

Fault: Orion uses WMDs and places them into orbit
Solution: Don't use Orion

"Nukes are small potatoes. Anyone with access to deep space can easily maneuver an asteroid into the Earth's path... So, following your line of reasoning, ALL space travel should be made illegal in the interests of peace. I disagree."

Please PO, accept my appolgies for the delay while I wipe the tears of laughter from my eyes... And I'm not laughing with you. Oh, would you be so kind as to inform me when you return from la-la land? Terrorists or rouge nations maneuvering asteroids to destroy states on Earth? Ummm, it would be lots lots easier just to steal some Plutonium and commertial heavy water to make a megaton class nuke... Which there would be plenty of if Orion warheads were in serial production.

"Over a million people died last year in automobile accidents. Nobody would die from an Orion launch sensibly orchestrated. Nuclear fire is scary but so is anti-matter and Gas Core Nuclear Reactors. Even plain old industrial age fire has claimed millions of lives and consumed whole cities. Perhaps we should go back to living in caves?"

Again, I will say it only one more time... there is an inherint MORAL difference to atomic bombs and gasoline because of the formers' potential to be used in malice. Your statement is so irresponsably obtuse to border on a farce... are you really seriously implying that gasoline and hydrogen bombs are equivilent?

All the rest of your inane rambling that I won't specifically touch on... I'm sorry but I can't take you the least bit seriously anymore, you are just as silly and far out as Errorist... Building a huge mining factory in only one launch that can build copies of Orion? The metal cutters, the rock crushers, the ovens, the zero-G metal smelters, the volitiles plants, the chemical refineries, zero-G casting foundries, the factories to build extremely large structures... the Uranium, which you may not be able to get from the asteroids, the Uranium enrichment, the Plutonium seperators, the warhead core casting... All this on a single vehicle no bigger then a oil tanker?

Try a million tonnes... you are out of your mind if you think we could build something like this any time soon for any reasonable sum.

Now I'll just skip down to the end, where cover your ears and chant loudly about my imagined ignorance, so that you don't have to answer my charge: You cannot develop space without an efficent line of communication from Earth. You CANNOT. For the forseeable future, men and materials must be brought from Earth on a regular basis. Orion simply cannot do this very well because of its fantastic per-launch cost and because of its size, it is too big. This is an inherint consequence of the large requisit size for Orion to be efficent. This alone dooms it.

And you cannot wave your magic wand and make Orion efficent as an orbit-to-orbit transport by dumping the launch responsabilities on "utility vehicles." In order to USE Orion's massive payload, you would need these vehicles to be able to launch the huge multi-thousand-tonne payloads and fresh bombs, right? ...But if you can do that, why do you need Orion?

I will not entertain any more of your inane attempt at commentary unless you address these two inherint problems that I have cited, PO.

GCNRevenger · 2005-04-04 11:35:19

"Don't find fault. Find a remedy." - Henry Ford.
I've said before we could use Timberwind now. That's a solid core NTR with much lower reactor mass than Nerva. The radial flow pebble bed has the problem that hot spots form between pebbles causing pebbles to melt together; fine, that makes it a single use engine. I'm not sure how long the nuclear fuel would last anyway; the reduced mass is due to rapid reaction. A combination might be possible: use the principle of highly enriched uranium with no moderator in a controlled flow design similar to Nerva. Eliminating all that graphite from Nerva might reduce reactor mass close to Timberwind levels, but it would be a completely new engine.
VASIMR does require a lot of power. Another idea I proposed on this board before was modifying a nuclear reactor to directly produce electromagnetic radiation in the band required for hydrogen absorption. Use wave guides to direct that EM from reactor to VASIMR fuel heating chamber. This increases efficiency by eliminating the conversion from heat to electricity, then from electricity to EM, and finally from EM to heat. The goal is to heat exhaust gas in VASIMR to plasma, no reactor could directly produce that heat. Conversion from electricity to EM is very efficient, and from EM to heat only depends on absorption. However, conversion from heat to electricity is very poor efficiency. It would take a nuclear engineer who really knows what he's doing, but it is theoretically possible. Hey, someone could get their PhD out of this.

The problem is you can't build a reactor that produces ONLY the exact EM energy that corresponds to the absorption for Hydrogen. Conversion from heat to electricity to EM is unavoidable for a nuclear powerd VASIMR engine, the problem is increasing the conversion efficency and reducing reactor dead weight.

A Vapor Core reactor could do this. The core itself is in a gas state, and the Uranium vapor is circulated around the reactor cooling loop, but is only permitted to reach criticality in the reactor. This way heat is transferred directly from the Uranium

It also has a very, very neat trick... it would use an MHD generator. The Uranium would actually get so hot it would become a plasma, and a plasma moving through a coil can be coaxed into producing electricity directly with no thermal-turbine-electricity conversion. The high operating temperature also radically reduces the radiator size needed... You thusly produce much more electricity per pound of reactor then a conventional solid-core one.

Austin Stanley · 2005-04-04 14:46:47

It also has a very, very neat trick... it would use an MHD generator. The Uranium would actually get so hot it would become a plasma, and a plasma moving through a coil can be coaxed into producing electricity directly with no thermal-turbine-electricity conversion. The high operating temperature also radically reduces the radiator size needed... You thusly produce much more electricity per pound of reactor then a conventional solid-core one.

The only problem I see is that the MHD generators I have read about have relativly poor efficency (10-20%) when compared to conventional turrbines. Although I suppose their reduced mass and size would help to compinsate for this in space applications. I'm also worried by the potential for criticality in a location other than the reactor.

GCNRevenger · 2005-04-04 15:30:39

What? I thought that it was the other way around, that it was more efficent because of the direct conversion... At least for a more advanced one.

Criticality cannot occur outside the core because the core is surrounded by a neutron reflector (BeO probobly). Anywhere else in out outside the plumbing, the neutrons released in reaction would be lost and it would not be self-sustaining. You should worry much more about the potential for thermal damage to the vehicle if the reactor should fail.

Austin Stanley · 2005-04-12 22:43:54

Well it is realy hard to beat the efficency of traditional turbine. Most of the work I have seen involves using a MHD to augment a traditional turbine system. In this fashion they can get some fraction of that 10-20% efficency on top of the turbines already excelent efficency. I'm not sure of what efficencies a MHD could eventualy reach. But I do know that it has quite a long ways to go before it challanges the allmight turbine.

GCNRevenger · 2005-04-13 08:34:14

Hmmm perhaps that is what the INSPI people were implying when they gave their efficency figures, but they did seem pretty enthusiastic about advanced MHD converters, though skeptical if they would be easy to develop.

Anyway, the may they scale up better than a turbine system, and can certainly operate at higher temperatures (like those in a VCR or Fusion reactor) since they never actually have to touch the plasma, or at least have no moving parts. The problem with current reactors is that they can't really run hot enough to be super efficient.

SpaceNut · 2020-06-28 18:32:23

I see from the names that we had a nuclear specialist in the past...

kbd512 · 2020-06-30 23:26:10

SpaceNut,

Robert is correct insofar as we don't need fundamentally new technology to start exploring the solar system, but we can't seem to get a decent mass spacecraft off of this rock in anything remotely resembling a cost-effective manner because we keep trying to develop gigantic all-in-one solutions to fundamentally different problems. Lighter nuclear reactors would certainly help with powering larger spacecraft, but the issue of mass-efficient propulsion remains intractable with current technology. Without resorting to absurd temperatures or power requirements, you just don't get much of a total efficiency boost. Solar panels are good enough to get to Mars, though not to colonize Mars, and nuclear anything makes people loose their marbles. I just want to get a few of us off this rock to once again prove to everyone that it can be done.

We really should build a miniature ISS with acres of thin film solar panels to power ion engines for cruise propulsion and orbital maneuvering. We can use existing commodity rockets like Falcon Heavy and create habitable modules or storage space from empty propellant tanks. We can strap Falcon or Centaur upper stages to it for the impulsive maneuvers. If SpaceX's orbital refueling idea is all it's cracked up to be, then we ought to fly a vehicle / space station to Mars first and debate "the best way" of getting there and back at a later date.

Water is storable indefinitely, necessary for human life, and also makes one hell of a rocket propellant combination if you use solar power to split it into its chemical constituents. We can also use LOX/LCH4, provided we have enough power on Mars to do that. However, we already have commercially available unattended LOX/LH2 plants here on Earth that only require input power to operate. We get full Sun in space for at least 12 hours per day in orbit and 24/7/365 during transit, so I think we've adequately covered power and propulsion to travel to and from Mars. Earth / Mars / Venus happen to have an unlimited supply of CO2 in one form or another, so we may as well use that for the booster stages to increase thrust.

I think a custom Mars-to-Orbit solution may be required, possibly something that only requires CO2 to produce a LOX/LCO bi-propellant using Martian atmosphere only. In terms of energy requirements, that seems to give us the best bang for our buck over both LOX/LCH4 and LOX/LH2. LOX/LH2 in the form of storable H2O for in-space propulsion, whether chemical or ion engines, and whatever is cheapest for orbital transport (LOX/LCH4 for Earth and LOX/LCO for Mars or Venus). Ultimately, we may need to resort to the use of atmospheric scoops to provide some significant portion of the propellant mass.

Oldfart1939 · 2020-07-01 22:12:49

I've been disappointed over the years because NASA seems to have put Nuclear Thermal propulsion on the permanent "back burner," and have focused too much on traditional chemical propulsion. I'm actually not complaining about SpaceX and BO optimizing the Methylox system, but NASA seems to still have a love affair with hydrolox. The powers that be seem stuck in the 1970's, and only the commercial operators are truly innovating. The monopoly the Government has on Nuclear is stifling innovation.

tahanson43206 · 2020-07-02 07:37:10

For Oldfart1939 ... While I agree that US (political) leadership seems unwilling to take the risk of expanding nuclear fission applications, there are other countries who have a nuclear capability and different motivations and constraints.

If Russia were less obsessed with defense projects, it could have led the way in nuclear fission powered space flight.

India and China are both potential developers of nuclear fission propulsion systems.

Other potential candidates have been omitted from this tentative list.

Google came up with naval propulsion when I asked about the status of nuclear propulsion. That makes perfect sense.

Here is a citation that came up when I added the term "space":

Nuclear Thermal Propulsion: Game Changing ... - NASA www.nasa.gov › game_changing_development › Nucle...
May 25, 2018 - The first U.S. space-based space fission system to be launched in decades will be a tremendous first step toward the development and ...

I can't see the content due to the limitations of the older system I am using, but I'll investigate it further later today.

(th)

GW Johnson · 2020-07-02 08:33:55

Well, one does have to be careful with nuclear propulsion schemes, because of the unique potential dangers.

The original Orion scheme done by General Atomics for USAF in the 1950's through 1965, was based on 1955-ish fission device technology with the neutron reflector geometry revised to make the energy release directional (a sort of shaped-charge effect). They understood the fallout risk for launching these things from the surface of the Earth, and even quantified it as equivalent to a single atmospheric test of a megaton-range bomb.

What they didn't understand was the EMP risk, because that did not become in-your-face apparent until the Starfish Prime in-space nuclear explosion test over Johnston Island in 1962. That one crashed the phone system and part of the electric grid 900 miles away in Hawaii. Had there been significant solid state electronics in those days (and there were not), such would have all been destroyed.

NERVA didn't run an EMP risk because it did not explode (nor could it). But there was a severe radiation risk in the exhaust plume. They spent over 20 years getting that under control at the test facility, in Jackass Flats, Nevada. By the end of the program, it was about the same as Orion, actually. You don't want to be in the vicinity of a firing, but it is no world-ender, either.

There was a nuclear ramjet program called Rover, too. It was intended for cruise missile of effectively-infinite range and endurance. This was early 1960's stuff, also located nearby to NERVA at Jackass Flats. The cruise missile was Mach 3 at low altitude, and spewed hard radiation in its exhaust plume. It was to carry a megaton-range warhead. The two side effects were just intolerable: lots of people killed by the radioactive plume, and lots of people killed by the trailing shock wave at low altitude (only a thousand feet or thereabouts). The estimates were that these would kill more people than the warhead.

There are ways and locations where any of these technologies could be used. Just not the ones originally envisioned. Nuclear is a double-edged sword, but it is also a great enabler for deep space missions. In particular, I think the open-cycle gas core nuclear thermal concept should be developed. It has a radioactive exhaust, but out in space that is no objection. The advantage beyond just high Isp at high thrust is an empty steel can, not a core, when you shut it down. BIG safety advantage!

GW

Last edited by GW Johnson (2020-07-02 08:35:34)

RobertDyck · 2020-07-02 09:13:46

GW Johnson wrote:

There was a nuclear ramjet program called Rover, too. It was intended for cruise missile

That was Project Pluto. An unshielded plutonium reactor. Was intended to carry multiple nuclear bombs, each megaton range. It would be air dropped by a B-52 bomber over the ocean, so radioactive exhaust and shock wave would not damage the US, would only affect open ocean. Obviously it would affect Russian soil once it starts flying over land, but that's the enemy. And weapons designers said they would turn a peace time liability into a war time asset: after it dropped it's last bomb it would head to another Russian city and fly figure 8s.

GW Johnson wrote:

I think the open-cycle gas core nuclear thermal concept should be developed. It has a radioactive exhaust, but out in space that is no objection. The advantage beyond just high Isp at high thrust is an empty steel can, not a core, when you shut it down. BIG safety advantage!

We came to the same conclusion.

RobertDyck · 2020-07-02 09:15:36

GW Johnson, did you see my thread for "Large scale colonization ship"? What do you think?

tahanson43206 · 2020-07-02 09:39:18

For RobertDyck re #46

GW Johnson reported a few days ago that his primary computer is "on the fritz" (or words to that effect). He connected to NewMars using his wife's computer for text only.

Hopefully he will be back in full mode soon.

(th)

GW Johnson · 2020-07-03 08:27:07

Oops, got the wrong project name. Pluto it was for the nuclear ramjet. The original concept was intended to fly a holding pattern waiting for the "go" code, which would have been in the Alaskan/Canadian Arctic, very much like the strategic bombers. The difference is that it would not be endurance-limited. The collateral damage forced them revise the concept to orbit over the ocean.

I have seen RobertDyck's thread for a giant ship, but have yet to understand and absorb.

Computer seems OK, mostly, except that Microsoft keeps loading shit I never asked for onto it over the internet, screwing it up again. I wish there was some way to turn them and that function off. My slide rule NEVER EVER gave me this much trouble.

I corrected what turned out to be small errors in my spreadsheet-based 2020 estimates for Starship to Mars. Had clicked on the wrong cell assigning delta vee to the mass ratio calculation. I corrected the "exrocketman" article in a very transparent way.

I have been looking at lunar mission orbits. Should have something posted "soon".

GW

tahanson43206 · 2020-07-03 12:13:34

For GW Johnson re #48

Re RobertDyck's vision of an expedition ship ... I am hoping the two of you can try to arrive at points of agreement ....

The work you have done to show advantages of the two year mission plan (with guaranteed safe return in case of wave-off) seems to me worth supporting. My ability to provide support is so limited it is laughable, but then I see someone like RobertDyck come along with similar concepts but focus in areas that MUST be included in a master mission plan that would pass muster with potential funders.

In another thread (quite recently) kbd512 gave conditional support to the idea of looking into a joint venture with India, which is working hard on its own space program and which appears to be in (relative) good graces with the United States.

At this time of maximum confusion, in the US and around the world, it seems to me it is also a good time for bold vision that is designed to entice folks to think longer term than is pretty typical for most of us.

***
Regarding Microsoft and its updates .... I am NOT kidding when I offer you this suggestion .... Unplug the system from the Internet!

Get another lightweight system for online activity. I ** highly ** recommend Linux!

I have multiple systems at this location, due to my interest in trying everything that comes along. One of them is an XP that runs four screens and does ** exactly ** what I built it to do. It is backed up six ways to Sunday, and just keeps running and running.

In your case, if you can make the investment in another system and a small network capability for your home, you can isolate the Windows system from the Internet, and just use it for the work you want to do, without ever again being bothered by updates intended to solve problems you do not have.

(th)

Last edited by tahanson43206 (2020-07-03 12:14:50)

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Re: Revisiting Project Orion - Article.

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#30 2005-04-03 19:08:25

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#32 2005-04-04 06:01:22

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#33 2005-04-04 08:46:05

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#34 2005-04-04 11:29:30

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#35 2005-04-04 11:35:19

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#36 2005-04-04 14:46:47

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#37 2005-04-04 15:30:39

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#38 2005-04-12 22:43:54

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#40 2020-06-28 18:32:23

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