Revisiting Project Orion - Article.

GCNRevenger · 2005-03-25 23:20:02

Ah yes, good ol' Orion...

Technical problems asside, the number one issue is quite simple... cost

Developing a new nuclear weapon of the appropriate size with superior reliability and a minimum of fission fragment residues would be quite expensive, politically and fiscally... You can almost hear the parinoid delusionals cry out from here, "Bush is building new nukes and his orbital Death Star atomic howitzer to vaporize the Middle East!"

The mechanism to eject these out the rear of the vehicle with precision, but resist the explosion itself, would also be very expensive.

I don't know if I trust the "active" shock-absorber system either, and the consequences if it were to fail.

And how do we get Orion back down from space? The "fuel" for the vehicle would also be extremely expensive, easily running into the billions of dollars. It will never be cheap to operate on a regular basis, so large bases or colonization would be unaffordable if Orion were used to shuttle between Earth and the destination.

The huge size of the ship itself will be a tremendous cost burden... You can't make a mini-Orion either, as the diameter of the pusher plate is critical, that it must be very wide in order to access the high performance offerd. The small Orion ship for proposed to launch off of a Saturn-V would have only had a few thousand seconds specific impulse.

And this... "This is an inherent limit in all non-pulsed designs."

Is not true concerning "regular" nuclear-thermal engines. The secret is just to not use a solid nuclear core. One of the more beautiful and clever ideas for the use of nuclear energy for space travel, whos acronym is my namesake, is not bound by this limitation. The Gas Core Nuclear Rocket instead uses a vortex of liquid hydrogen propellant, assisted by external magnets perhaps, to confine the dense nuclear material to the heart of the engine without any support structure or contacting the walls of the engine. In this way, the core can reach temperatures of up to 50,000K in theory, and specific impulses ranging from 3,000 to 5,000 seconds.

Not quite as high as a giant Orion megaship, but high enough for a trip to Jupiter, and high enough to colonize Mars, but capable of being scaled down to a quite compact size for reasonably sized near-term ships and applications. Without the political cost of building a nuclear space howitzer nor the expense of 1,000 nuclear bombs, instead just liquid hydrogen and some Uranium Hexafluoride, too.

Trebuchet · 2005-03-26 02:07:46

NASA came up with something better than both Orion and gas-core propulsion concepts - ACMF (antimatter catalyzed microfission/fusion), which is sort of "Orion without bombs" and has a much smaller minimum size.

Instead of using chemically-imploded nuclear bombs, you wrap a thin layer of uranium over a deuterium core, fire them out the back, and hit it with a fraction of a nanogram of antimatter, as antimatter will spark a nuclear reaction in even the smallest pieces of uranium. The majority of the actual power comes from the fusion of deuterium, however, not the fissioning uranium.

The antimatter needed is within the puny antimatter generation capabilities of today, and the total weight of the system is about the same as a nuclear rocket, but with Orion-or-better ISPs and plenty of thrust.

Plus, you don't need to build the Battlestar Galactica to go cruising around the solar system.

GCNRevenger · 2005-03-26 09:46:35

If the beauty of Orion is its ability to launch ultraheavy payloads from Earth's surface, then its pretty worthless if you can't bring it back down.

I think you may also underestimate the power of large numbers of whiney nuclearophobes and conspiracy nuts... but anyway, the fiscal cost of developing and building a thousand warheads for every flight pretty much precludes common use of Orion.
------------------------------------------------------------------------
I am skeptical about the ACMF concept. It sounds like a pretty complex mechanism, and frankly too good to be true. The claim that it would have Orion or GCNR-like thrust is also kinda dubious if each pulse unit is so small.

GCNRevenger · 2005-03-26 17:28:39

ACMF doesn't use antimatter, it uses antiprotons. Antiprotons are relativly easy to make and creating the desired quantity is not beyond our technology. The big problems are currently storage, where a compact Penning trap can only hold them for a few days, and the mass of the device needed to fire the antiprotons to the nuclear fuel pellets without being damaged by the blast. The pellet dispenser itself will not be trivial either, considering it must also resist the blast.

Launching Plutonium into space is one thing, but Orion is quite another. Developing and testing a new low-yeild low-fallout nuke will arouse the ire of groups, perhaps even nations, that have more clout then giant-puppet-loving Green-"peace." The potential for military spinoff, if a very low fallout is achieveable, would not be overlooked... especially if the warhead could survive reentry, in which case Orion would be a ready-made orbital nuclear bombardment platform to boot... just set the timers for 30sec instead of 0.5sec and aim.

Thats the thing though, a very small number of extremely expensive ultraheavy launchers is NOT what we need to conquer the solar system. Most of what we send up will still be rocket fuel or other bulk substance, which can and should be sent up in smaller batches with inexpensive chemical propellants in reuseable vehicles. Sustainable, scaleable, and accessing economies of scale unlike the giant Battlestar Orion being launched every few years at the cost of billions in bombs.

"There would ofcourse be tests but only one launch would be needed. A ship large enough to carry the industrial infrastructure necessary could use fusion bombs a thousand times more powerful and cleaner than the old fission devices originally proposed back in the 60's."

I don't think that even one Orion worth of stuff would be enough to build industrially signifigant infrastructure anywhere, especially given the assembly times of all the stuff in it.

Orion also can't use the mega state-burning super nukes, infact because of its small size, you want the smallest bombs that are efficent to build... down in the single-digit or even fractions of a kiloton. It is actually very hard to make a really small bomb, given that you need a minimum mass of Plutonium to make any practical atomic explosive.

PurduesUSAFguy · 2005-03-27 12:16:02

I know that the military has recently invested alot of money into developing 'clean' fusion weapons that don't use fission primaries, so advent of fall-out free nuclear weapons that you fear will likley happen in any event (I have a sneaking suspision(sp?) that such weapons wouldn't fall under any current treaty thus getting around no new nukes)

Although I think Orion could have worked, if we were going to build it at all we should have done it in the 60s. Now if we are going to invest some serious money in revolutionizing acess to space ACMF or GCNRs are the way to go, you get alot of benefits from not having to deal with pulsing thrust.

Actually, I'd settle for just plain jane nuclear thermal rockets for ground launch. Hydrogen doesn't ionize so the only thing you'd have to worry about for launch saftey is internal reactor ablation which I am could be solved with through engineering.

....you'd just have to have green peace offed to do it, which I am suprisingly comfortable with

GCNRevenger · 2005-03-27 17:20:43

Yes I've heard about the possibility of a pure-fusion warhead, which would be kinda cool, but I don't think it would apease the "No nukes!!!" people with power much more then one with fission primaries... The military would love such a thing though.

I still doubt that the warheads would be inexpensive enough to make an Orion-type vehicle practical though, and the warheads themselves would have to be signifigantly bigger and heavier probobly.

The ACMF would be a pulse-type engine too, but since the pulses are smaller it could get away with a faster pulse rate, and make the ride somewhat smoother.

Firing a regular NTR engine before you reach orbit is a non-starter I think, I'm as pro-nuke as they come, but even I think that wouldn't be safe enough... The amount of radiation that the reactor would put off would be a major pad hazard, and the low thrust/weight ratio combined with large fuel tanks make NTR unsuitable for first stages.

As an upper stage, it would also have the thrust/weight problem, and if there were any kind of a failure and the reactor failed to reach orbit, the hot core would come back down far from the launch site... southern Europe or northern Africa or further east, and there is no sufficent crash hardening that is worth the increased performance (and engine cost).

But putting an NTR or GCNR engine on a chemical rocket and only fire it in orbit? No problem... if Green"peace" activists want to chain themselves to the pad? Great, let um', thin out the shallow end of the gene pool a bit.

GCNRevenger · 2005-03-27 23:07:04

"Matter" in laymens' terms is usually referring to atoms, the smallest particles that behave have different identities and behaviors like macroscale materials, subatomic particles don't... Symmantics really.

Politics and finance are the two biggest problems with the Orion idea, you can't sweep them under the rug with a "opponets won't hold water" or "we don't know they will resist" bla bla bla. Developing ANY new atomic bomb for ANY reason, particularly tactical scale ones that readily lead to being used, is sure to meet lots of domestic and foreign political resistance. This is NOT like building other machines, this is a weapon of mass destruction, which has with it societal taboos that other technologies do not... We know very well that there will be political resistance, and the fight for Orion won't be pretty.

"You are wrong. Its exactly whats required."

Certainly not. Orion will be so expensive and controvertial that only flying it now and then will doom it. Whatever system is used to begin the exploitation of space has to be scaleable, and it has to be able to fly pretty often. Orion can do neither of things without becomming prohibitively large or expensive or dangerous. A space elevator would be a much better investment.

Overall, I think you are way off in your beliefe that a few thousand tonnes launched by a practical sized Orion worth of stuff would be enough to start an asteroid factory-city that would lead to critical-mass sustainable industrial growth, that is enough infrastructure to contribute industrially to the home planet or to expand without much help from Earth.

Building a giant super mega Orion, large enough to make use of multikiloton bombs, would be way too expensive. The scale of that kind of project is a non-starter.

GCNRevenger · 2005-03-30 09:47:22

"They've been after that since Trinity. I wouldn't hold my breath. Would be nice though. A fallout free nuke removes the last obstacle to building Orions."

Nope. The pure-fusion device, most likly an explosively-pumped induction coil to magneticly compress a fuel pellet (see Z-Machine, EMP bombs), will be much heavier then a comperable yeild fission device.

"The main problem with NTR is preventing the engine from melting down."

Nope. That problem has been basically solved already in the 60's and 70's. The only real problem with them for ground launch is low efficency payoff for the increased risk if the reactor doesn't reach orbit, and the extra trouble of building a nuclear launchpad.

"I'm telling you its a waste of time to get hypothetical about such matters here... No data to draw your conclusions from. You don't even know how the public would respond."

Nope. Thats being terribly irrational of you. See RNEP (Robust Nuclear Earth Penitrator)... We actually can make a pretty good guess that the public will reactor poorly to a rocket launched by lighting new "reduced" fallout bombs (which could make an otherwise conventional war go nuclear) considering the public apathy to spaceflight.

"Surveys indicate an increasing acceptance of nuclear energy"

Nope. *Bzzzzz.* You are being intellectually dishonest or at least deluding yourself by lumping reactor and bomb technology into the same breath. The public is wary but accepting of reactor technology, but building nuclear bombs to kill people is different. The public isn't stupid enough to fall for the "pulse units" misnomer.

"Unsubstantiated opinion. You don't even know how much it costs."

Please, more evasiveness. "You have no concrete data so you can't form any guess at all" is a pretty poor argument... Spending 1,000 brand new, ultra-reliable, super miniaturized nuclear bombs for every flight is not what I would consider "cheap." Plus the simple fact that BUILDING A NEW ORION for every flight isn't too good of a financial proposition either.

"Who said anything about a few thousand tons?"

Nonsense. You are out of your mind if you think we could build a huge mega 100,000MT "Star Destroyer" in this current economic era.

"You and I both know it will take an atomic rocket to open up the final frontier. Pulse is superior to steady burn. It avoids many of the inherent engineering challenges."

No it isn't. The lack of reuseability alone for its stated strength, ultraheavy ground launch, dooms it. Especially combined with its ultraexpensive "fuel." Nuclear ground launch otherwise just doesn't have a huge enough performance edge to be worth the risk, made worse by addition of radiation/crash shielding... This pretty much leaves only the space elevator and Shuttle-II/III for ground launch, perhaps with chemical HLLV supplimenting.

Pulse isn't inherintly better for smaller, more reasonably sized vessles either. The lack of a huge pusher-plate will severely limit the specific impulse.

http://www.astronautix.com/lvs/oriturnv … iturnv.htm

If this is correct (which I am suspect), even with a big 10m plate, you only get 1,800-2,500sec. GCNR or VCR/VASIMR could slap that silly. Even the 41m giant 150-seat Orion Planetary would only have a 3,000sec Isp, which GCNR could easily match and VCR/VASIMR would crush.

http://www.astronautix.com/lvs/orietary … ietary.htm

EDIT/addendum:

The military consequences of a low-radiation nuke really are very signifigant if its possible. Just swap out the "pulse unit" detonator with an altimeter fuse and slap a JDAM tailkit on and off you go.

Even a pure-fusion bomb wouldn't be "pure" either, since the neutron radiation could cause the soil under and kicked up by Orion to become highly radioactive too. You also aren't ever going to have an Orion spaceport...

The only reason that Orion has any edge versus GCNR or VCR-VASIMR is that it can use its engine to get off the ground. If you can't to that, then Orion makes zero sense instead of little sense.

John Creighton · 2005-03-30 19:47:58

I with GCNRevenger. Until people can be moved cheaply back and forth from orbit there is little nead to lift a 100 000 MT payload. And once the time comes that we can move people cheaply to orbit perhaps cheaper options will be available like building the infrastructure from the moon and asteroids instead of the earth. Anyway, if you can get a politician to support Orion good for you it is a step forward, not the best step forward but a step forward. China may be a good candidate for project Orion because they have large deserts in the north and cheaper labor. I don’t know if launching 100 000 MT payloads every 5-10 years is the best way to settle space. Committing that many resources early on before we gain adequate experience living off the land may not be the best approach. There is a lot of room for mistakes and inefficiencies.

John_Frazer · 2005-03-30 22:01:48

This has been gone over a few times on another thread here

Interplanetary transportation
» Nuclear Propulsion - The best way for space

And I'm sorry, but Orion still has a lot of promise.

How many technical breakthroughs are required for GCNR or VASIMR?
and the main objection to Orion's feasibility is the cost of the pulse bombs and the difficulty of landing it?
please.

And Orion is not only best for lifting from the ground.
3 weeks transfers to Mars, with 45%+ of the IMLEO being payload.
I haven't seen any qualified technical publications countering General Atomics' finding that the cost of the Saturn-V booster was the greatest part of the cost of their 10 meter, ~500 ton, 8 person ship design.
More recent NASA looks at it (dubbing it EPPP) improve the isp by nearly triple the original ~1800. and still the hardest technical challenge is some way to toss kegs aft at ~10 meters/sec and recoating the pusher plate with grease mist.

I haven't heard any way that GCNR or NSWR beat that.

At least, I insist that it not be laughed out of consideration! At this early stage, by amateurs on a 'net discussion board!

Personally, I don't think very much of the 16,000 ton+ ground launch monsters (until somebody can show me that it could be clean enough, and then it's instant interplanetary civilization time!). Not that I think little or poorly of it, but I don't include it in my thoughts very much, because of the space-assembled HLV-boosted option.
Even if you don't like to allow the consideration of the old 10 meter design, which starting pulsing it at ~80 km, it still has a lot of promise.
Six or so HLV shots to LEO with modular sections corresponding to the old 10 meter ship, and we've got a hell of an interplanetary capability. Any large scale interplanetary mission architecture I've seen starts with a similar IMLEO, and nothing I've seen that's as near term offers similar performance.

Long term even, if technical improvements come about allowing the feasibility of things that are more exotic than "Old Bang-Bang", Orion still stays in consideration because any of these breakthroughs would only make some form of nuclear pulse even that much more attractive -even a fission bomb initiated design of some sort.
100,000 ton interplanetary liners with thousands of people setting out for a 3 month voyage to the colonies around the Jovian moons with stopovers at Mars before getting back to Earth orbit -without refueling en-route?
Not at all far-out or even unsuitable to me.

And shorter term, I refuse to plan around appeasing people like the hysterical nuclear-phobic nuts who claimed that a booster malfunction during the launch of Cassini would have given 10,000 cases of cancer to everyone alive. I read one such nutcase (in this guy's case, I don't hesitate to use this kind of flanguage) who said that there's no moral difference between enjoying never-before-seen images of another planet from a space probe using nuclear power, and getting your rocks off watching a PGM hit an Iraqi bunker.
I will not tolerate planning our future in space as if they have a reasonable voice in policy and public education about space and the hope and promise of space. If they want to chain themselves to the launch pad to protest a probe that has RTGs or thermal warmers, let 'em have at it.

GCNRevenger · 2005-03-30 22:01:50

"There is no real limit to how clean we can make nukes."

Wrong, this is a clear example of your incomplete knowledge about the subject you are arguing. A nuclear weapon will always produce excess neutrons, since it must have as many as possible to detonate efficently. This pulse of neutron radiation will make the dirt itself radioactive... which you will be spreading all over.

"...NERVA have a peak operating rate well short of making them launch capable."

Not entirely true. Reactors of aproximatly flight-weight were test fired. The NERVA program, at the time of its cancelation, mainly was devoted to technology development and not nessesarrily building production engines. The huge multigigawatt reactors for the NOVA rockets are an example. This is a relativly mature technology.

"No. You are being a fearmonger and assuming the public as a whole is irrational."

Nonsense. You are exibiting all the classic traits of someone desperatly trying to save their failed pet project with the monotinous and tired old "but you don't KNOW!" refrain. No "data" is required to know that deploying nuclear technology in the atmosphere will be a controvertial issue, it would obviously be, and intentionally building nuclear bombs (with ~6kg of Pu each) - which I might add you intend to detonate several hundred of which in the atmosphere - with obvious implications in lowering the barrier to the use of WMDs in warfare, will be a very controvertial issue.

To say that one cannot make a prediction without "evidence" by your unreasonable standard is irrational, especially with something like this that is obviously so. The only "nonsense" is your view that the above prediction is without "hard evidence" or whatever that is.

Oh, and I just love this contradiction: "Most of the public doesn't know the difference... Stop imagining that the public are mindless sheep..."

Well, which is it? Is the public too stupid to understand that a reactor is not a bomb, or are they all wise in the ways of all things nuclear?

Again, you are just covering your ears to what is so clearly true... it does not matter, not one little bit, that these bombs aren't specifically intended to kill people. It really doesn't. The fact that they COULD be used to kill, and do so with great efficacy, is in itself enough of a taboo that Orion will never fly... Oh, and who has experience with mini-nukes? Yep, thats right, the military. So, how do you think it will look when the military helps out with bomb development? ...Which just so happens would give the military the ultimate weapon, a nuke with "reduced" consequences, which opens a whole pandoras' box of WMD evil.

"Just as your car petrol tank is also a bomb."

Yes, but it isn't capable of killing a million people in the blink of an eye, nor is it a weapon that the military would just itch to use. I must say that this is an especially dumb analogy... Let me say it again, there really IS a difference, a moral taboo, that makes nuclear bombs different from other sources of energy purely because of their potential as a killing tool.

"Uranium is cheap"

Weapons grade (>90%) Uranium or Plutonium-238 is not. In fact, there really aren't any facilities in the world for producing large quantities of Plutonium at the moment.

"Look at how much it cost to build that pathetic International Space Station."

Please, the most lame straw-man of all...

...Time for a word not of specifics, but of overall strategy:

The idea of building JUST ONE or only a few super-mega-ultra-giga-lifters, and setting up shop at some asteroids or putting the thing into orbit over one of the rocky worlds as a beach-head is a competly irrational idea that is fully and wholey unmarried from reality. Get a grip...

If you build a beach-head some place, you absolutely MUST have the capability, you have to, of traveling back and forth from Earth and this destination regularly and efficently. Not every few years and not at the cost of billions per flight.

Now, logically speaking, if Orion's biggest strength was its ability to launch stuff efficently from Earth... but we would already need a different and also efficent means of launch, then what is the point? Even with an Orion bigger then 135ft across like the original concept, the Isp of Orion is still going to be hardly any better then other, more compact nuclear systems - and with a space elevator fuel efficency is arguably unimportant at all - then justifying Orion's hyperexpensive fuel for everyday transit makes no sense either.

Regular, scaleable, small/medium-scale travel it absolutely required. We cannot have commerce nor open-ended colonization or anything else without it. Hence due to the small size, and the pre-exsisting efficent launch infrastructure, Orion has no advantage beyond mega-ultra-giant-jumbo vehicles. Speaking of which, just as there is a minimum practical limit to build spaceships, I believe there is a maximum limit too, when the construction and operation of the vehicle simply becomes so complex, that it is beyond our ability to engineer. An Orion of the scale you are talking about would be such a craft.

And as far as my use of "we," I don't think that the disposable income of all the space agencies in the entire world for years and years is enough to seriously contemplate building a colony-in-a-box mega giant Orion, the only configuration that justifies its creation.

Orion is just not a good idea. Period.

Edit: Cool, #3000

GCNRevenger · 2005-03-30 22:26:16

How about this for "data?"

http://story.news.yahoo.com/news?tmpl=s … ...r_fears

Austin Stanley · 2005-03-31 05:43:06

I recently finished reading Footfall a decent work of "Hard" science fiction by Larry Niven. **Minor Spoiler** which involves the use of a Orion type space battle ship being launched in a counter offensive against the aliens. Not terribly unrealistic IMO, though I did wonder where they got the thousands of nukes to power the silly thing. Its a good (if some what off the wall) example of a potential use of Orion. If your intrested in the Orion concept you should read it just for that, I can almost guarantee that you will like it.

Now I agree with some of what the article says. Modern advances do make Orion look better than when it was orginaly concived. Especialy with regard to new and smaller nuclear weapons. But many of our nuclear advances won't help at all. For example, MT and tenths of MT devices are MUCH smaller and cheaper then they used to be, but these sorts of weapons are really to big for nearly all Orions.

But in the end I agree with what GCNR has to say. The development and mass production of new nuclear devices, even realtivly small ones, will be objected to seriously by both Americans and the world at large and may be violations of critical arms control treaties such as SALT, PTBT, and Outer Space Treaty.

Realise that for any Orion system you are talking about a signifigant increase in the current US stockpile of about 10,000 weapons. At 900 or so weapons a pop other countries can not help but be nervous about a 10%+ increase in the US stockpile, even if they are of "relativly" small yeild (although there is nothing small about the yeild of a 2kt device). We would certianly be nervous if China or Russia start such an increase, and rightly so. And this is just for one launch.

But the concurns don't just stop there they get worse. Not only are you talking about constructing nearly 1,000 new weapons, you are also placing them in orbit where the could be delivered at any time without warning on opposing nations, just like the old soviet FOBs. Such a first strike weapon is incredibly scarry, so much so that the US was considering striking first should the USSR chose to deploy it.

Now I am not overly concurned with the threat of multiple nuclear detonations, even hundreads of them within out atmosphere. If detonated in a sufficently remote area, it probably could be safe. However, the general public is NEVER going to allow the it. That I can also pretty much guarantee. I myself am slightly worried about the dangers of high-altitude EM pulses on our electronics.

And the cost is likely to be enormous. Nuclear weapons aren't cheap. And developing and constructing a entirely new line of weapons system is even more expensive. I haven't seen any cost analysis, but I would be supprised if it came up much cheaper then current systems. And if doesn't cost less, then what realy is the point. It is going to take some time. We just aren't geared up for that kind of production anymore.

I like project Orion and Nuclear weapons in general. Nukes, along with landing on the moon are the two greatest scientific/engineerign achivments of man to date. But even so we must be realistic in our application. Divert an incoming asteriod, sure. Use to rise from earth? No way.

GCNRevenger · 2005-03-31 09:15:19

How many technical breakthroughs are required for GCNR or VASIMR?
and the main objection to Orion's feasibility is the cost of the pulse bombs and the difficulty of landing it?
please.
And Orion is not only best for lifting from the ground.
3 weeks transfers to Mars, with 45%+ of the IMLEO being payload.
I haven't seen any qualified technical publications countering General Atomics' finding that the cost of the Saturn-V booster was the greatest part of the cost of their 10 meter, ~500 ton, 8 person ship design.
More recent NASA looks at it (dubbing it EPPP) improve the isp by nearly triple the original ~1800. and still the hardest technical challenge is some way to toss kegs aft at ~10 meters/sec and recoating the pusher plate with grease mist.
I haven't heard any way that GCNR or NSWR beat that.
At least, I insist that it not be laughed out of consideration! At this early stage, by amateurs on a 'net discussion board!
Personally, I don't think very much of the 16,000 ton+ ground launch monsters (until somebody can show me that it could be clean enough, and then it's instant interplanetary civilization time!). Not that I think little or poorly of it, but I don't include it in my thoughts very much, because of the space-assembled HLV-boosted option.
Even if you don't like to allow the consideration of the old 10 meter design, which starting pulsing it at ~80 km, it still has a lot of promise.
Six or so HLV shots to LEO with modular sections corresponding to the old 10 meter ship, and we've got a hell of an interplanetary capability. Any large scale interplanetary mission architecture I've seen starts with a similar IMLEO, and nothing I've seen that's as near term offers similar performance.
Long term even, if technical improvements come about allowing the feasibility of things that are more exotic than "Old Bang-Bang", Orion still stays in consideration because any of these breakthroughs would only make some form of nuclear pulse even that much more attractive -even a fission bomb initiated design of some sort.
100,000 ton interplanetary liners with thousands of people setting out for a 3 month voyage to the colonies around the Jovian moons with stopovers at Mars before getting back to Earth orbit -without refueling en-route?
Not at all far-out or even unsuitable to me.

Not many. Entry-level solid core reactor powerd VASIMR capable of <100day trips to Mars are possible today (less with orbital departure boost), and the Russians ponderd building a GCNR engine years ago. Generally speaking, I think that materials science is aproximatly ready for GCNR or VCR reactors and could be accomplished if we put signifigant effort into it.

What you don't realize John, is that the technical reasons of the inability for Orion to land is and the large requisit pusher-plate are fatal to the concept. Only a very large Orion, much more then 10m across (say, >40m), would offer radically superior performance to a mature GCNR or VCR/VASIMR for orbital transit. It is my view that no ship of massive size can be built in today's economic and engineering environment. Therefore, Orion has little space-only advantage; GCNR or VCR/VASIMR or NSWR would offer competitive performance without the political trouble of manufacturing new weapons.

Plus, you can refuel these vehicles with Hydrogen or even just water at their destinations, ISRU after a fasion. Orion cannot.

And if you are intending to reuse Orion, which you would have to to make it useful for space commerce or colonization, you have to bring it back to LEO. We have to have the ability to launch large amounts of cargo efficently to reload its extremely large payloads, right? Well if we can do that, then why do we need Orion? If its biggest strength is efficent ground launch, then it would be redundant.

And the cost of the bombs question is not one you are seriously quesitoning, is it? Because "there aren't any price estimates" for 1,000 superhigh quality brand-new nuclear bombs does not mean you can ignore their price when apraising the cost of Orion. Again, just like ProjectOrion tried to say, "but you don't know" does not mean that a rough estimate cannot be made, and definatly the lack of "hard data" is not a valid argument that it will be cheap... I believe it is very reasonable to believe that the "fuel" for Orion will cost many billions of dollars, which would make each weapon cost only millions each.

This however is nothing in comparison to building a brand new mega Orion ship every time you want to fly. Even if the bombs were free, Orion wouldn't be going anywhere on a regular basis. Even if you want to confine Orion to orbital use and build a reasonably sized one in space, then other smaller engines would have comperable efficency without all the muss and fuss.

Orion doesn't have a long term.

Edit:
For comparison, GCNR has a theoretical upper limit of around 5,000sec, VCR/VASIMR up to 10,000sec perhaps with advanced reactos, and NSWR would also be in the high thousands or low tens of thousands of seconds. It is worth reminding you that all these options could be "refueled" by in-space water and some onboard Uranium as needed.

GCNRevenger · 2005-04-03 11:02:23

Whatever, PO... I will stop labeling you as ignorant as soon as it stops being true...

Oh yes, and you want to place a "thick steel pad" a kilometer or three in diameter under the Orion pad? Or float the thing out to sea even though its heavier then water and all its billions of dollars of investment would sink if there were a leak? And what about the cloud of radioactive steam? No no... there is no such thing as a completly clean Orion, even with pure fusion bombs.

Anyway, back to the biggies:

1: You insist that an actual sociological study be undertaken by real people with real money to gather at least some data, however unreprisentative, before any reasonable prediction of the public reaction to the implications of Orion can be made. The classic but you don't KNOW! defense, for analogy, see the pathetic "Precautionary Principle" except to the opposit extreme.

I don't know how many times I've seen before from somebody trying to save their doomed idea... Such a statement is just stupid and you are wilfully trying to get us to ignore Orion's problem that building new atomic bombs for any reason will meet serious political opposition. Nothing would be gained by trying to "educate" the public that Orion's bombs could only be for peaceful use, because the public would think you a liar. And they would be right. If a almost-clean mini-nuke is possible, its military applications would be irresistable... especially if they could be deliverd from orbit with ease. I think its somewhat safe to say that the public can be relied upon to make a decision that you won't like PO.

"Most of the public has no interest in commercial nuclear energy or military hardware. It's the Space connection to nuclear energy that will awaken some interest."

Well I hate to break it to you, but if the public doesn't care about Earthly atomic power, why do you think they would care if you put nuke+space together? If nuclear energy is so ho-hum, why would people get deleriously excitied just because its used for space travel?

2: You are ignoring the economic realities of the development and colonization of our solar system. That in order to do either of these things, a responsive, reuseable and scaleable means of sending personel and materials to and from Earth's surface and the destination must be available. You cannot build an open-ended colony by launching a 10,000MT ship every few years any more then a commertial airline or the military could operate if forced to ride in a single transport plane the size of Rhode Island every other year... Even if it were faster and efficent then regular sized planes per-pound.

The physics behind Orion precludes it from doing any of these things. In order to make Orion more efficent then other nuclear systems, it must be very very large, but if it is that large, you can't afford to build many of them. And if you don't have many of them, then Orion as a transport fails since it is not responsive.

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.

Orion is not scaleable well either. You cannot scale it down since the smaller pusher-plate and lower specific yeild of the bombs lowers its performance to GCNR/VCR-VASIMR/etc levels. You cannot build many big Orions if you need extra lifting capacity, because of their high cost as they are expendable and their high "fuel" costs.

Again, Orion is just not a good idea

Edit: Another thought... when Orion gets to its destination, what exactly are you going to do with it? It can't land, you can't put your giant-mega-huge payload down in large pieces (the lander would be way bigger then the Saturn-V first stage), and whatever lander you use will STILL require that much of your payload is taken up with conventional landing fuel.

J.J. Moesker · 2005-04-03 11:41:32

PO, can this technology be demonstrated in a responsible manner? What approach should we, the nut and bolt engineers take to build such a 'device'. Can this technology be ‘sandboxed’?

GCNRevenger · 2005-04-03 12:04:56

Other then "borrowing" a B-61 from the Air Force, how would you test it? The thing is pushed by high-energy plasma waves of intense power, which I doubt you can simulate well with chemical explosives.

John Creighton · 2005-04-03 13:16:40

On of the supposed strengths of Orion is it is more near term then other propulsion concepts. Is this really the case or a statement by naive armchair engineers. As mentioned previously how to you test the thing? I doubt the smaller models are simmilar to the big models at all, and GCNRevenger mentioned the difficulties of trying to simulate the thing on the computer. It would be impossible to know how good the simulation models were because you wouldn’t be able to easily validate the results. Each nuclear blast would introduce multiple modes of vibrations over a large range of frequency and area. This would put a large amount of stress on the structure. Just the structural engineering challenges alone would be formidable and would the thing be easy to control? You have a large vibrating vehicle with nuclear blasts in the rear and shock on the front of the vehicle. Would the vibrations be stable or would they grow out of control and snap the vehicle in half. How many degrees could the vehicle turn before the nuclear blasts could not bring it back straight. What would the time delay be between the time the controller recognizes it has to straighten the vehicle and the time the shock wave of the corrective explosion travels though the pusher plate all the way up to the nose. In short, not only do we not have small enough nukes developed but even if we had the nukes developed it still wouldn’t be cheep to design build and fly. If it costs a hundred billion to build each vehicle and you have to test 100 of them, just imagine the development cost that must be amortized.

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