Well said GoogleNaut! The Orion Gallery is meant to inspire the imagination. Hopefully we can attract more artists. Eventually we plan to add 3D rendered Orion movies to the Gallery.

I have to agree, Jaro. In order to expect humans to ride something like Orion, responsibility requires us to test the thing first. Although huge risks were incurred during Columbia's first flight in 1981 in which two astronauts rode the machine for its first flight without an unmanned test flight--the first time (and only time) in history if memory serves.

My guess is that a smaller Orion test vehicle could be built and boosted into space with a heavy lift launcher of somekind. Perhaps a smaller unit that is like Put-Put's big cousin that perhaps uses conventional HE charges, or perhaps several tiny mini-nukes with yields of sday 25-30 tons equivalent (0.025-0.03 kT.)

My first inclination is to think that Orion may be attempted as a part of a more mature space program--large scale space industrialization infrastructure in orbit and on the moon could provide almost all of the raw materials for a 'world' class full up test. The surface of the moon is practically an ideal environment for launching Orions anyway--there is no atmosphere to cause x-ray backscatter from the pulse units. Also, no atmosphere for fallout to be carried, and surface contamination shouldn't be that big a deal. If a really big problem develops and a messy explosion results, a team of robot bulldozers could safely shove regolith over the whole mess to contain any contamination. Radioactive gasses should escape quite readily to by ionized by solar-uv and carried off with the rest of the solar wind.

A lunar Orion Base places less stringent demands on acceleration and environmental concerns, leaving the project more or less free to do all the testing that is needed.

Still, transport costs would mandate that such a program still will require substantial funding, but as a part of a mature space industrialization effort, presumably the economics may be more favorable.

Well, shucks....

Orion would look really cool on liftoff.

Of course you'd better be wearing your welding goggles and have your SPF 100000 on if you want to watch a launch from the view stands!

Seriously though, Jaro you bring up good points.

Engineering wise, I think it could work. However, there are some pretty severe problems such as steering. A rocket nozzle can be gimballed to adjust the thrust vector. Two nozzles can provide roll control as well.

Orion has no gimbal capability or roll control, however I wonder if the whole upper structure could be mounted on a system of rails mounted to a bearing platform (like an X-Y Table.) Using a couple of hydraulic rams, the whole upper part of the vehicle could be shoved to one side or the other, thus providing a means of shifting the center of gravity. This is of course a brute force method (which goes along well with Orion I think!) and this does not seem to be compatible with a nice smooth ride (the passengers are liable to spill their Martini's on take off, I am afraid!) Roll control could be accomplished either by using large gyros (which would be sensitive to momentum saturation,) or large RCS thrusters or both. Only by using two Orion vehicles together, and then very gently angling the pusher plates could roll control be accomplished. This would be a very delicate thing however because of the huge forces involved. My guess would be that a dual, parallel Orion using large gyros could provide good, stable attitude control. The roll control moment gyro could periodically de-saturate with a large angular imput provide by cooridinated pulses with gimbled plates. Still, its gonna be a bumpy ride!

Of course, then there's the problem of blast coupling from one pulse unit to the other.

Perhaps a single, multi-segment blast plate could be used. Hyrdraulic rams could precisely angle the plate segments--angular movements of only a degree or so would be needed--to catch and deflect momentum to provide all attitude control during boost phase. Hmmmm. Makes me wonder if I could patent that....



The problem here, though, is if your plate segments become impact welded. Then your in deep doo. You will have a vehicle with a fixed roll, yaw or pitch or some combination which will very quickly result in a termination of flight.

Still, it would look really cool....

Yes, I have heard of this "candle" concept before -- although not quite as you describe it.

What you need is a fuel/moderator mixture which is kept slightly subcritical by the addition of a "burnable poison" (ie. neutron absorber) like gadolinium. The thruster end of the candle can be made to go supercritical some way (say, by extra reflector material or addition of U-235). Once it fires, the strong neutron flux will burn off the poison just upstream, thus propagating the reacting section up the candle.

This would all happen very quickly, consuming the whole candle in something like a few seconds, at most (depending on the length of the candle). If you tried to slow the burn rate by increasing the poison concentration, then the candle would simply fizzle, because of the ejection of the fuel in the critical region out the nozzle, and/or because the super-hot moderator in the critical region no longer contributes to neutron moderation, because of reduced density and high temperature (cold moderator is required for effective moderation). 

Its not a good design, because the burnup of the fissile fuel would be minuscule -- one cannot simply assume a high burnup (like 10%), as Zubrin did in his NSWR idea, which is actually fairly similar. The true figure would be a tiny fraction of a per cent -- comparable to the energy produced by chemical combustion.

- - - - - - -

As regards the "high-power fission reactor/energy conversion system," it may not be very efficient, but then neither is exploding bombs dozens of meters behind an Orion ship. On the other hand, a reactor operates continuously, whereas a bomb blast lasts on the order of a millisecond, and is only repeated every second-or-so. Temperatures higher than 1000 degrees C can be achieved in a gas core reactor quite easily, and the surrounding beryllium oxide moderator is a very light material too. Cooling systems are made light by rejecting heat at high temperature. This reduces thermal efficiency, but what we're looking for is high power-to-weight ratio, so that's OK.

Well, I suspect that the reason you didn't hear about it is because its simply not a valid concept -- the nuclear scientists who have given it a little bit of thought, quickly rejected it and it hasn't been heard of since. Trouble is that to non-specialists, it sounds convincing enough that they buy it -- very much like the Urban Legends that frequently circulate on the internet.

I was told about the candle idea by a retired nuclear scientist at Chalk River Nuclear Laboratories a few years ago, following a seminar on nuclear space propulsion. He just described it briefly, with a big grin on his face, as an idea that came to him many years ago. Trust me -- if there was any value to the idea, it would have been advanced by numerous scientists decades ago.

Regarding your comment that "there is so much we don't know about the behaviour of ultra-hot stuff in space!", please note that "hot" is exactly the issue with thermal neutron reactors which use a moderator like water or graphite : the safety of these reactors depends to a great extent on the fact that the moderator has a strongly negative reactivity with increasing temperature -- an overheated moderator will not support a chain reaction. Specifically, the fission x-section of uranium decreases rapidly with increasing neutron energy. You overheat the moderator, and the thing shuts itself down.

Its possible to get a big power spike, if the reactor arrangement is such that the uranium fuel is segregated (as in fuel rods) from the moderator, because there is a delay in moderator heating, due to a limited rate of heat transfer. This is how you get an explosion like that of Chernobyl, or in experimental reactors like Borax-1, SPERT, etc. But the energy yield is very small compared to a nuclear bomb -- typically equivalent to just a couple of sticks of dynamite. In terms of the fraction of uranium fissioned in such a power burst, it is very much less than one per cent. In a homogeneous fuel-moderator mixture the heat transfer to the moderator is practically instantaneous, so that any power spike (achieved, say, by pulling all the control rods out) is much smaller still. The reason that a bomb gets much higher fuel burnup, is simply that the chain reaction, which in this case operates on neutrons which are NOT moderated (ie. "fast" neutrons, with about 80-million times higher energy) proceeds very much faster than the rate of material dispersion due to heating.

The advantage of a high-temperature Vapour Core Reactor (VCR) is that by operating continuously, it can achieve a fuel burnup that is many times higher than what you get from a single high-power burst. The surrounding BeO moderator/reflector is cooled by the recirculated, condensed fuel stream, before re-injection into the vapour core. The vapour core operates at close to 4000K, while the BeO is maintained below 2000K. The radiator is expected to mass around 0.005 to 0.007kg/kW, and overall conversion efficiency of 22%, using an MHD generator. Overall plant specific weight is about 0.32 kg/kWe, for a large system >200 MWe (ie. total weight ~65 metric tonnes for a 200 MWe plant, not including the VASIMR thruster).

Some additional info about the Vapour Core Reactor - MHD conversion system :

Output from a PC-based VCR-MHD simulator by INSPI, including thermodynamic parameters, superimposed on a schematic of the system. Note particularly the Net Cycle Efficiency of 22% :

http://www.cns-snc.ca/branches/quebec/INSPI_VCR_MHD_simulator.jpg

VCR-MHD mass and performance estimates for a range of reactor sizes (note especially the decreasing specific mass, with increasing reactor size) :

http://www.cns-snc.ca/branches/quebec/INSPI_VCR_MHD_specific_mass_estimates.jpg

Illustration of one particular MHD arrangement of INSPI's VCR-MHD concept :

http://www.cns-snc.ca/branches/quebec/INSPI_radial_line_VCR_MHD.jpg

Close-up view of a single MHD radial line :

http://www.cns-snc.ca/branches/quebec/INSPI_radial_line_detail_VCR_MHD.jpg

Ty, it sounds like you know a lot more about MHD generators than I do. But to answer your question, it appears that the reason for six smaller MHD's instead of one large one is a matter of efficiency :  Their original design used a disc MHD at one end of the vapor core reactor cylinder. The idea was to maximise the number of highly-charged fission product atoms in the MHD nozzle, by having the nozzle irradiated by the strong neutron flux right next to the core (the schematic diagram in the simulator picture, BTW, is *not* intended to represent the true physical arrangement !! ). As I understand it, this disc arrangement had the undesirable effect of causing a lot of "swirl" in the MHD nozzle. So to kill the swirl, they simply chopped up the disc into a series of radial MHD nozzles, thus guaranteeing pure radial flow.

You really need to see the whole presentation -- I will send it to you. Maybe you could then explain it to the rest of us ?

Hi Terry,
Thanks for the "pre-preview" of the Orion Gallery. Don't forget to mention the short video "Mission to Enceladus" that I will be producing with the model of a Mark 2 Orion I am constructing. They will be intercut with historical imaging to give a flavor of alternative history as "Man Conquers Space" bu Surfaces Rendered is exploring Von Braun and the Moon and Mars missions we could have had in the 60s and 70s.

By no means complete, the Orion Gallery will have many aspects of space travel, including bases, landings, like Bonnestell renditions for Colliers. All artists, model builders and whatever talents anyone has to develop the project should be welcomed.

I have spoken to George Dyson and will advise on the progress and while this idea is budding, it can be used as a tool to promote public interest in Orion in space.

Thanks again,

Rolando (Orion contributing artist)

Nice renderings there! Good job on the engineering details (the steel thrust coupling structures that couple the Space Shuttle SRB's to the Orion Pusher Plate are a nice touch!

Also, nice idea about using a ship or barge as a mobile launch platform to menuver the Orion into launch position--how else are you gonna move something that masses 4000+12*750 (the SRB's)=12000 tons+ on take off?

Nice rendering of Orion igniting its pulse engine at 100 km (is that the Red Sea in the background, I see?) This would put the launch site somehwere near Kenya?

[OK, my curiousity was aroused. Nice maps availble courtesy Google Images at www.indiana.edu/~librcsd/ mapafr/africa-s.jpg

I would put the launch site somewhere just south of the Ethiopean capital of Addis Ababa. Looks like some fairly large rivers nearby, which could make for easy transportation (assuming of course there aren't any waterfalls along the way!) or perhaps in the Eastern part of Sudan--more difficult to reach.]

Bravo!

One little detail bothers me about the classic 'bullet shaped' Orion, the conventional ogive aeroshell (what we would call the payload fairing) would experience a phenomenal loading do to atmospheric friciton. Orion ought to punch right through max-Q (maximum dynamic pressure) at Mach One pretty quick. I'm guessing that this unit had 12 SRB's (it could have more) At take off, a standard SRB has a thrust to weight of about 2.1 to one, so that means each SRB will be delivering approximately 700 tons of (net) thrust to Orion (2.7 million lbs total thrust minus 1.3 million pounds takeoff weight for each SRB.) 12*700=8400 tons of net thrust. Orion should sit up and MOVE! Two g's vertical acceleration right at the word go. For such a large vehicle this would be a real hot rod! Saturn 5 Apollo only achieved about 1.3 g's at take off, so it took several seconds to clear the launch umbilical tower.

Max-Q then might be a little 'hairy.' To reduce dynamic loading, a longer more tapered nose might be needed, or perhaps adding a launch escape tower coupled to a crew 'capsule' could also serve a dual purpose as an aerodynamic 'stinger' to 'part the air' as it were.

Nice job!

Well, yes, i had briefly looked at menuvering with Orion. It is very difficult to 'gimbal' (tilting the whole plate assembly, ever so slightly) a thousand ton dish, but not impossible. The main problem isn't thrust vectoring, per se, it's impulse modulation. The problem with tossing a bomb 'off axis' is that the impulse assymetry can literally tear your ship apart! The seconday shock absorbers were designed to absorbe huge impulses, but only those carefully aligned along the main axis of the ship. Small off axis variations are possible, but too far off, and the off axis impulse could literally cause the shock absorbers to buckle.

I toyed with some ideas around this problem by using a radially segmented thrust plate just aft of the primary gas momentum conditioners. If the plate segments were tilted only a fraction of a degree, then a serious amount of momentum could be imparted as spin. Tilting another way would impart yaw, and pitch impulses. Now I assumed that since these impulses are likely to be large and thus hard to control, it follows that many trajectory correction commands would be sent out by the navigation computer. This would make for one hell of a bumpy ride.

Now if somewhere near the center of gravity of the Orion vehicle there were a system of three large gyroscopes--momentum wheels--say maybe, oh, 100 metric tons each, driven by a 1000 hp electric motor (I don't know--the application may require thousands of horsepower, in which case some kind of high speed hydraulic motor may be needed. It's going to need a lot of torque!) Anyways, the momentum wheels could provide the means for primary yaw, pitch and roll control for Orion. A secondary system, such as the adjustable thrust plates could then be used to gradually 'desaturate' the gyros--dump momentum--when they were spun up to almost their maximum speed. A teritiary reaction control system could then be used. such as steam jets (as in the case of "Footfall's" Michael Archangel) or liquid by propellant motors, or even smaller NERVA engines. The problem with using a chemical RCS system with an Orion, is that Orion is HEAVY. You could literally expend a thousand tons of mass on chemical RCS propellants. This is why I like the idea of using reaction wheels. For fine translation control, I would recommend a lower Isp VASIMR engine RCS system. Provided Orion's bulk can shield an on board nuclear reactor for Auxilary power, then VASIMR engines could be used for a very slow approach and dock.

Anyhow, RCS hasn't really been too well addressed with Orion. It's a big ship, and to make even small attitude and translation adjustments requires a lot of thrust, and the expenditure of a lot of propellant.

For instance, if Orion were, say, 4000 metric tons on orbit (4 million kilograms,) and it used the same propellant combination for RCS as does the space shuttle, notably N2O4 and Monomethyl Hydrazine, then to create an Orion as nimble as a space shuttle would require something like this:

For an RCS translation burn along the long axis of the orbiter requiers four 800lb thrust engines fireing, burning about 12 lbs (5 kilograms) of propellant per second. Let's just the say the orbiter's mass is about 200,000 lbs for this exercise. So for our 4000 ton Orion, we would need about 40 times this thrust: 40*3200=128,000 lb of thrust. Using the same propellants, we can expect to consume 40 times the propellant per unit time: 480 lb/s (200 kg/s.) Thus a five second translation burn consumes a metric ton of propellant!

Roll control is provided similarly by two forward and two rear 800 lb RCS thrusters on the shuttle. The exact roll performance will of course depend upon the distribution of mass onboard Orion, the exact moment of inertia of the ship will determine how much thrust must be applied to cause what angular acceleration. This also helps determine placement of thrusters: thrusters placed farther away from the axis of rotation have more 'moment arm' to torque the mass of the ship. For simplicity's sake, let's assume the same scaling apply to the roll control thrusters: four 800 lb primary thrusters are needed for roll control of the shuttle. Orion will use 40 times this: 128,000lb of thrust. N202 and monomethyl hydrazine generate about 258 seconds of Isp in vacuum, so a one second 'roll burn,' followed a short time later by a one second 'breaking burn' will consume something like: (128,000/258)*2=1000lb of propellant! For Orion to perform a controlled approach and docking with something like the ISS would likely consume many times the budget of propellant for the entire ISS!

In a sense Orion can 'afford' this, it is after all a 4000 ton nuclear powered space ship. While the Space Shuttle can carry with it nearly 30,000 lb of RCS propellants, representing almost 15% of its total on orbit mass, an equivalent RCS propellant loading for a 4000 ton Orion would be nearly 500 tons! If a choice was made to go with more efficient, non-toxic propellants, such as high performance liquid hydrogen and liquid oxygen, this could be shaved a bit. Assuming our LO2/LH2 RCS thrusters operated at 350 seconds Isp (pressure fed to 1000 psi, six to one mixture ratio) we could get by with only: 500 tons*(258/350)=370 tons. This is better, until we realize that this amount of liquid oxygen and hydrogen is about 1/2 of the capacity of a space shuttle External Tank!

A chemical RCS system for Orion is quite a weight penalty--and anything less than chemical becomes weight prohibitive from the standpoint of diminishing payload capacity. Thus the "Archangel's" super heated steam RCS system would work just fine for a few minutes, then after a thousand tons or more water boiled off, it would be kaput!

It stands to reason that using the main propulsive drive for as much of the trajectory shaping and thrust vector control is essential to an operating Orion. While a chemical RCS system may be essential for tiny velocity/orientation corrections such as in reundezvous and docking, Orion must rely on a more efficient system. Reaction wheels for attitude control and VASIMR thrusters for translation control seem like a good bet for this.

I am familiar with Larry Niven and Jerry Pournelle's work "Footfall" and I'll have to read it again when time permits! I know they used the idea of tossing bombs slightly off-axis for their main attitude control and trajectory shaping while under boost. I think the physicists and engineers who worked on Project Orion did come to the conclusion that random placement errors more or less cancelled each other out--which stands to reason with a fairly large number of pulse units (100 to 1000 or more.)

For the "real deal," Orion will need some way to control its trajectory. As it would seem to be impractical to gimbal the momentum 'dish' as in a conventional rocket engine, and still have the secondary shock absorbers function, then some other method must be used to shape Orion's trajectory. Using more or less conventional chemical RCS systems would seem to be impractical for primary attitude control as the propellant mass penalty would probably be too high--even for Orion.

So perhaps some combination of large momentum wheels, and a chemical RCS system, or one of my favorites: mass shifting. [Well, that's what I call it anyway!]

If the upper part of Orion, the payload and crew compartments were mounted on something resembling a large x-y axis table, then a pair of large hydraulic rams could shift the heavier upper section relative to the lower section. Displacemenst of several feet ought to do--by physically shifting the center of mass of Orion, we could accomplish indirectly what a rocket engine gimbal does--we cause the whole vehicle to 'lean' to one side or the other. I haven't done the math yet, but in principle such a system ought to work. The weight penalty of some extra structural steel, a flat thrust bearing, and some big hydraulic rams should more than make up for the requirement of carrying a couple of thousand tons of chemical RCS propellants!

Orion is not a conventional rocket, it is a ship and that's the beauty of it. Weight is not nearly the Stingy God of Newtonian Mechanics it is with chemical rockets. If it ends up weighing more, then the pulse units can be tweaked to generate more energy and momentum. No big deal. A few hundred extra tons is not a problem for Orion. In the overall bulk of the ship, it just won't matter. A few thousand extra tons--then that starts to become a problem. This is why I think that Orion must not rely on a conventional chemical reaction control system. Attitude could be handled with reaction wheels and mass shifting (during boost) and perhaps small translations could be performed by chemical RCS or arcjet or VASIMR thrusters.

Shape the Orion into a sphere, presumably with the pusher plate on the outside...?

Never heard of that one, however I thnk I can comment on it.

In all honesty, I am neither an engineer or a physicist, however, I know a little something about both.

The problem with shaping Orion as a sphere is one of weight. A spherical Orion would require a spherical external pusher plate (I assume that this is what you meant.) Assuming a reasonably sized unit, say 50m across (25 m radius) with a pusher 30cm thick composed of steel (density 7.2 g/cm^3) the gross mass of the spherical pusher would be about: 4*pi*25^2*7200kg/m^3=56.5 million kg (or about half the mass of a Nimitz Class aircraft carrier!)

The flat pusher plate design of Orion, while inefficient from the standpoint of capturing only a fraction of the energy/momentum available from a particular pulse unit, is still just about the MOST efficient way to capture momentum from a pulse unit! Going to a half spherical plate will capture something less than half the momentum available but would suffer from 'hoop stress,' necessitating a thicker plate. [Hoop Stess is a function of the force acting on a unit area of the plate (pressure) and the tensile forces to resist it, which are a function of the curvature of the plate segment and the tesile strength of the material (thickness.)] Thus any gain in momentum efficiency would likely be more than lost by thhousands of tons of added weight. A flat plate design suffers from much less hoop stess (only the stesses involved in momentary deformation of the plate as momentum is transferred to primary shock absrober system,) and can thus be made thinner. Still, a 50m diameter plate of steel, almost a foot thick (30cm) is going to have some serious mass to it! George Dyson's book mentioned that the project scientists expected a 100 foot diameter plate, one foot thick at the middle, tapering to 3-4 inches at the edge, would still 'bow' upwards by 3-4 feet at the edges from the impact of the plasma from a 1 kiloton pulse unit, 150 ft away! This gives some idea of the forces involved--steel would behave 'elastically' (I suspect that the plate may have to manufactured from either tool steel (a little too brittle) or cast from armor alloy (like battleship armor.) Just the right 'springy ness' would be needed.

As for shock absorbing the cabins: anyone involved in a vehicle collision severe enough to deploy the airbags knows how serious deceleration forces can be. Airbags, while an important piece of life saving equipment, because of their power can be injurious all in themselves. I have personally seen people with black eyes, strained necks, scratched and bruised chins from airbag deployment. Primary shock absorption for an Orion would involve shocks perhaps a hundred times greater than shocks imposed during a moderate vehicle collision. Despite one's best efforts with airbags, or something similar, the occupents of a similarly 'cushioned' Orion would quickly turn into jelly!

Ironically the solution is brute force in nature. Make a flat pusher plate thick and heavy. Use perhaps 25-30% of the entire vehicle mass in this single piece of steel. Behind that, put a network of gas springs or even a few thousand automobile tires (this will be the primary shock absorber.) Behind that, put another plate with heavy structural steel to transfer mechanical loads to the secondary shock absrobing system. The secondary shock absorbing system is composed of say, 6-12 long stroke gas and liquid charged shock absorbers (not unlike gigantic versions of a car's shock absorbers) with a stroke of say 30-50 feet. Now when a pusle unit goes off, the pusher plate recieves a momentum impulse accelerating it at say 100 g's. This is rapidly decelerated by the primary shock absorbing system and transfered to the secondary system. Now because of the long strong, the pusher plate is decelerated at say 8-10 g's. Now because the plate is about 1/3 to 1/4 of the vehicle mass, the momentum pulse should be smoothly transfered to the rest of the vehicle causing it to accelerate at anywhere from 2-3 g's. Now timing the next pulse so that the pusher plate has recoiled back to its nominal 'start' position, another pusle is fired. The plate is almost instantly decelerated and accelerated back toward the Orion, starting the whole process over again.

The problem (well, I don't see it necessarily as a problem, really) is that the first pulse that goes off must be a 'half momentum charge' because a 'full momentum charge' will impart twice the momentum to a pusher plate at standstill than one that is recoiling away from the vehicle. We don't want the pusher plate to 'bottom out,' the resulting collision may cause the passengers to become very upset!

Perhaps another way would be to increase the stroke length, and then go ahead and use a full momentum charge: subsequent charges will be fired at a nominal half-stroke length. This could be something worth exploring...

Then there are the mechanical details, such as cooling the primary and secondary shock absorbing systems (the oil will get very hot after a while, and the tires in the primary shock aborber would probably melt just from the mechanical loadings!). Pulse unit delivery (an entire chapter in Dyson's book is entitled "Coca-Cola" for good reason!) Etc.

Still, I think Orion could work. It would be a strange affair: truly a 'delicate' balance of efficiency and inefficiency; of brute force and finnesse. I love it!

I like the gyro system for turning the ship, tho they would be massive.  Heinlein used them as key points in a few of his stories, if I remember right, since there are some problems with them.  Mass can be reduced if they can be made to go fast enough, but the law of diminishing returns strikes as it gets harder to manufacture them.  Tho one way to lower mass is to combine them with the coolant system for the shock absorbing systems.  If the water/steam cycle is used to cool the shocks, the steam could be used to spin up the gyros, tho that is limited in the speeds that can be reached.

The CG shifter system would actually be one way of gymballing the blast plate, since the less massive part of the ship would move farther.  An interesting way of managing things, make the overal setup simpler and the details harder.  (probably)  Tho I guess that also fits in with Orion as this discussion shows.  Maybe we should have this moved to a different section, 'possible techincal dificulties and potential solutions to them'?

The spherical ship runs into some of the gyro and CG shifter problems at the same time while adding its own, tho the concept would be valid on the ground where it has something to push against.  If the entire outer hull is a blast plate, (that doesn't apear to be your sugestion but I'm trying to cover all the possibilities in order) then the only way to have a shock system would be to mount a spherical ship inside a spherical shell, probably not being able to turn either because of the springs holding them together.  An alternate version could have a hinged shell, but that would be much harder to build, and much weaker.  And the third type uses a more conventional pusher, with the shock system mounted on tracks so it can move.  Besides making the whole assembly more prone to go taking a jaunt appart form the ship in case of a misfire, you the ship would be spinning one way while the pusher spins the other so you would need something like gyros anyways.  Tho the first type might make an interesting small unmanned high-g Orion, like an asteroid interceptor.

One of the easiest ways to take care of the cooling is to use water as they did in Footfall.  And when it has turned to steam, it can also be used to spin up the gyros, or, when desperate, be aloud to vent for manuevering.  It would also be added radiation shielding, fuel (after electrolysis) for small vehicles, and of course for life support.

And since it is being discussed, I am in my second semester at an engineering college.  Tho I was homeschooled all my life till then.  And both my parents and two of my grandparents were science teachers before I was born.  The other two grandparents had a family machine shop after leaving the Air Force. (or Army Air Corp, can't remember which it was when they left)  So I know a lot of arcana but still not enough of the basics to be completely sure, tho I'm more likely to know some of the more obscure facts since I found them more interesting. lol

GoogleNaut wrote :

Nice rendering of Orion igniting its pulse engine at 100 km (is that the Red Sea in the background, I see?) This would put the launch site somehwere near Kenya?

[OK, my curiousity was aroused. Nice maps availble courtesy Google Images at www.indiana.edu/~librcsd/ mapafr/africa-s.jpg

I would put the launch site somewhere just south of the Ethiopean capital of Addis Ababa. Looks like some fairly large rivers nearby, which could make for easy transportation (assuming of course there aren't any waterfalls along the way!) or perhaps in the Eastern part of Sudan--more difficult to reach.]

Actually I'm limited in my choice of launch site by the software. Doesn't like me at all if I rotate the planet, results look hideous. This is due to my utter ineptness when it comes to rendering planets. I actually wanted to have ocean in the background to show up the particle effects better. An ocean-based launch would probably be sensible anyway since it could be in the most remote possible area. Couldn't show an ocean as the launch site since that takes a very long time to render, so I had to go for a ground launch version.

Most of the discussion here is way over my head, but there's a good reason I made a bullet-shaped Orion : the alternative was ugly as sin.

Also, the flat pusher plate captures more momentum than you'd expect, as most of the mass of the bomb actually goes towards the ship and not in all directions. It is apparently very easy to do this, says Dyson.

Philipum : A spherical Orion could twist on its own axis, but that wouldn't affect the direction it was travelling in until it fired some more bombs. I'd expect ships of any shape could pivot around their own axis though. This would only change which way the ship was pointing, not the direction of its motion.

To Rhysy:

Maybe I must give more explanations to make me fully understood. Of course, it was always implicitely meant that the direction change is made by blasting more bombs. The whole idea is to change the direction of the pushing module before firing the additional bombs. Of course this can be done with ships of any shapes, but at the expense that you must eject large amounts of propellant in order to change the total angular momentum, or have heavy gyroscopes inside. My idea was to turn the propulsion module in one direction and the ship in the other, thus not requiring any change of the total angular momentum. But for allowing all directions, this can be possible only with a spherical ship.