You bet! Orion Rocks!

*wouldn't*

oops. lol

Yes! I knew it! Thanks guys for the quick reply, much better than I had expected

And I would as well of course.

It seems like there are people like us who are fascinated with the perspectivve of humans in space and who see in Orion an unique opportunity. However, it seems like these persons, apparently the only ones who are thinking actively about the concept, are doing this during their free time, computing things fur fun and discussiong stuff in forums.

Now I have a new question. Forget about the copious salary. Suppose the fundings were scarce, just enough to carry out the project given sufficient perseverance and ingenuisity to optimize the costs, efficiency and safety of the design. And set aside political considerations; suppose that testing bombs and Orion prototypes would be possible. Would you still join?

I would.

Even if it was just a hopeless gesture, I would still be willing to do it. I mean we would still get lots of valuable data out of it and if it was played right, we could even get some good press and advertising for the concept.

GoogleNaut, remember, the price of the pulse units go up very fast the smaller you try to make them. I don't no if the overall price would still go down, but it would probably be more worthwhile to try making the full scale one first. (after all, we might only get one shot at it as the governments would know what we were doing then and might try to stop later ones while they still have a chance instead of waiting for them to be ready to launch)

One thing I'm doing is research into various space technologies, to try making an overall set of plans instead of relying on just one type, even a significantly superior one, to hold the entire mission. Thus, while the Orion would be the major, and first, launcher, I am also working on what it would carry, and what follow up missions what need to have and do. Would a thread for that also be something to have in here?

quote:

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Originally posted by: GoogleNaut
Still, this requires access to nuclear explosives which would of course require government cooperation (unless of course you just happen to have your own private nuclear infrastructure ) Still, its doable....!"

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Let's face it: Realistically, resuscitating Orion is NOT doable, no matter how much we may wish it were.

Something like a Mini-Mag Orion might however be doable towards the middle of the century, as it doesn't involve the use of bomb-type portable nukes....

Its certainly true that "Politics move" (I never thought I would live to see the end of the Soviet Empire, after leaving Czechoslovakia....). 
But I'm skeptical nonetheless.
Claiming that Orion bombs have nothing to do with nuclear weapons may be true, but I doubt that it would fly :  Consider for example nuclear fusion power. The international ITER project wants to spend something like 15 billion dollars on a reactor that, at best, will demonstrate that practical (economic) fusion power plants are at least 50 years away. By contrast, we could build practical fusion plants today, based on the PACER concept, using contained explosions initiated by small fission bombs. But do you hear anyone seriously talking about building PACER plants ? No, because everyone "knows" that you can't use bombs -- not even for peaceful applications that would save you billions of dollars, hasten the arrival of fusion power by decades, and help reduce dependece on foreign energy sources.
Also, in response to your question, "Do I miss an important aspect of the problem?" I would say yes, the problem of radioactive fallout from the bomb blasts. While we know that the problem is not serious (except locally at the launch site, which may be situated in a remote area), I do not believe that it would be easy to convince people (politicians) of the facts -- starting with the issue of abrogating the treaty prohibiting atmospheric bomb testing. Note that EPA regulations do not even allow open air testing of nuclear thermal rockets, never mind bombs.
As for "Which country would be the best candidate?" for Orion development, I would say they're all extremely unlikely candidates, but if one must name some, I would say the least democratic ones - China and Russia - would probably be the best bet (a few years back, there were some news reports that China might actually be interested in building PACER-type plants..... until they decided to fall into line with the rest of the world community and scrap the idea).

Yeah, I know what you mean....

I think Jaro is probably right in the sense that the perception of the danger of fallout is the major obstacle of Orion. However, some have proposed using a chemical rocket booster to loft an Orion to perhaps 50 to 100 km before it initiates its pulse engine.

Some fission products would still intersect the top of the Earth's atmosphere, and presumably almost all of the plasma debri trapped in the Earth's magetic field would eventually intersect the upper atmosphere to become fallout later. I have no idea what time scale this happens over, so some (perhaps most) of the radioactivity associtated with nuclear fission explosions could decay before reaching the ground. It all depends on how much fission products are produced, how much is trapped and intersects Earth's atmosphere, and then how long it takes to migrate to the troposphere before reaching the ground. A lot of unknowns which--ironically--have probably already been studied in detail during the atmospheric testing programs conducted by the US in the late 1950's and early 1960's. Of course, ALL of that data is still classified secret.

These are the kinds of questions that would need to be answered in order for Orion to fly (atleast off Earth.)

Well, the fission products for each burst is pretty small. Most of the radioactive debri will come from the pulse unit casing, tamper, channel filler, and of course, the reaction mass (which for the 'small' version of Orion is usually a manhole cover sized plate of tungsten about an inch or two thick.) By carefully analyzing the isotopic compositions of likely structural materials given a certain arrangement, it could be possible to to get an estimate of fallout loading for each pulse unit. I'm not sure how well air can be radioactivated, but I think their is a little radioactiviation issue their as well. Nitrogen and oxygen will most likely form short half life radionucleides which of course will remain gasseous anyway, so this may not be a serious issue.

In any case, whatever the true radioactive nucleide production is, this is substantially amplified by the fact that with hundreds or perhaps nearly a thousand fission explosions in a pretty short period of time (over a period of about five to ten minutes) the total amount of radioactive materials will likely be many tons. What their activity level will be will depend on the kinds of materials used to make the pulse units. A detailed analysis of natural isotopic abundances of materials would be needed in order to come up with a reasonable answer. Once this is done, then different materials could be substituted to reduce the fallout signature. Further reductions could be made by isotope enrinchment--shifting the natural abundances of isotopes in a material to one that favors a less neutron activateable form. This can be done at great cost by using processes similar to the ones used to enrich uranium. This would likely result in very low activation materials, but their cost will be perhaps 1000 times more than standard materials.

As for using chemical launchers--I think it was Rhys Taylor who did some really nice work on some Orion renderings on this board at:

http://nuclearspace.com/gallery_project_orion_2.htm

I don't know if he did any engineering calculations on the idea, but the concept was to slap 12 space shuttle SRB's around the perimeter of the pusher plate of a 4000 ton version of Orion. I was skeptical until I did some of the math--I am now convinced that such an idea has merit. It might not be just as simple as slapping SRB's on (thrust vectoring might be a problem for boost phase) but the SRB's have the raw power to loft such a monster to the proposed height of 50-100km before Orion turns on its pulse engine. This mitigates some of the issues with multiple nuclear bursts in the troposphere. Also, this prevents the damage or destruction of launch facilities, which because of their size, will likely also be the vehicle assembly point with all of its attendent infrastructure--the destruction of which would clearly mitigate any cost gains one hoped to get from Orion!

Well, the 4000 ton Orion breaks down about like this:

1000 tons for pusher plate.
1000 tons for propulsion super structure.

1000 tons flight structure, pulse units, coolant and RCS propellant.

1000 tons payload.

Let's just say the equivalent of 12 SRB's worth of conventional booster--6 space shuttle flights at 50,000 lb each: 300,000 pounds for space shuttle. 12 SRB's 4 at a time in a Space Shuttle Derived Vehicle able to loft 250,000 - 300,000 lb each gives: 750,000 to 900,000 lb of payload delivered. Orion is much closer to the 2 million pound delivered, so I guess this meets the criterion.

I would accept a superiority factor of atleast 2 to be in the ballpark. However, this is all very rough. Without completing an actual engineering design, it would be difficult to nail it down more than that. Of course, it's all moot if a test article fails to perform....

Despite this, I'm confident that once a design is nailed down, the numbers would favor an Orion with a payload performance 2-3 times better than any chemical booster could achieve.

True, but as far as the run time of the SRB's are concerned, that's just about right for a quick trip above the stratosphere....

I have to admit, that I never thought of using SRB's until I saw that rendering that Rhys Taylor did. It just never occured to me...then again, that's one reason why I like this board. New ideas springeth forth...

The only other chemically boosted Orion I know of was a much smaller ship which dates back to the time of the original NASA studies in 1962 or so. A Saturn 5, or an evolved Saturn 5, or possibly a Nova 1 booster would be the first stage pushing a 1000 ton Orion well above most of the Earth's atmosphere. I think they even looked at using two flights to assemble and outfit this Orion with enough pulse units and provisions for a quick trip to Mars.

The concept of an 'air start' Orion has been thoroughly explored--atleast about as far as paper designs can go.

A ground start Orion, one that uses nuclear pulses all the way up, could be built much larger. The first couple of pulses would probably be tricky.

I would think that an Orion could be raised to the top of a quartet of expendible concrete towers (or perhaps they should be steel as some of the the calcium in the concrete could be easily radioactivated to become strontium-90) and initially lofted with a sub kiloton charge vaporizing and atomizing a million gallons of fresh water in a tank. This ought to 'gently' shove Orion upward atleast until its own first pulse unit could take over. Still, it would probably take five to ten pulse units before Orion had climbed high enough to use full power pulse units (or full momentum charges.) Again, this would of course depend on a more fleshed out design that would allow estimations of vehicle mass, dimensions, and mass distributions.

The main problem in dealing with start-transients is rebound of shockwaves reflected from the ground, as well as convection of launch debris up to the Orion. Rebound of shockwaves (depending on their intensity) could actually set up a resonance with the pusher plate causing it to vibrate at its natural frequency. This could be bad as it could result in almost immediate structural failure. Actively seeking and then damping those resonance modes will be a must. Another problem will be the convection of launch debris from the ground. Physical contamination of Orion's structural mechanisms by rocks, chunks of concrete, and droplets of molten steel must be looked at and shielded against or eliminated altogether, especially if the debri is radioactively 'hot'. Also, a dense debris cloud surrounding the base of the Orion will likely give ample opportunities for x-ray 'back scatter' from subsequent shots requiring the crew compartment to be extensively shielded. Possibly using a double 'hulled' arrangement in which the crew compartment could be immersed in a water tank with several feet of water between the inner and outer hull. Such shielding should also give good protection from solar storms later on. If allowed to freeze, it could proved excellent micrometeroid protection as well.

I have an idea. Would it be possible to initiate the Orion launch with a really, really big balloon?

Supposing a 4000 t. Orion that would be lifted with a balloon filled with hydrogen, we would need about 3.5E6 cubic meters of hydrogen, which, supposing no backpressure effect, corresponds to a balloon about 188 m in diameter. But the balloon itself is expected to be very heavy - we would need incredible cables to distribute the great load stress if such a thing is possible - so supposing an additionnal 1000 t. for the balloon structures, we are up to 204 m diameter.

With such a balloon, I admit a really, really ambitious one, our problem would be solved. Orion could be lifted and gently carried over the sea by the breeze, before initiating its powerful propulsion system.

Hmmm, strange that you mention hydrogen in a big balloon. About fifteen years ago I explored the idea using a Hydrogen filled dirigible to float up a "rectenna" to very high altitude to intercept a microwave power beam from a solar power sattelite. I decided that if the structure were high enough, the density of the power beam could be made high, and so a roguhly equilateral triangular structure about 1.5 km on a side (just shy of 1 miles) would float at about 20 km altitude. The antenna would actually ride inside of the balloon.

A system of two anchor cables at each corner of the triangle would provide stability against stratospheric winds and wind loadings applied to the cables. The cables would directly transmit power to the ground, as well as provide a means of piping up makeup hydrogen from an electrolysis plant on the ground. Aircraft navigation hazards lights would be strung at regular intervals along the lengths of each cable.

Overall, such an idea is fairly sound, however, the problem with such a huge floating structure is what I call 'launch transients.' Because of the dynamics of boyancy and such it may be easier to fix the cables at the ground, and have the ballon structure haul all the cable up with winches on the balloon. The winches 'payout' cable as the balloon rises. This helps to mitigate somewhat the dynamics of boyancy with ballast--in a sense, the cable is the ballast.

Anyways, large balloons are fine. But God Help You if a breeze comes up. A balloon two hundred meters in diameter will have enormous windage. Also, the weight of cables will be substantial to support Orion: atleast a couple of hundred tons, perhaps more. There is also the problem of the 'launch' mode. Will Orion cut free of the cables, fall for a short moment and then fire its pulse engine? What happens to the balloon? You don't want your Orion to chance intersecting a wildly lifting balloon trailing a couple of hundred tons of 400 m long steel cables.

Dusty,

I suppose the giant 'doughnut' balloon is a possibility, but the hole would have to be humongous.

Orion would still have to clear an aweful lot of cables for a safe launch. And I wonder about the x-ray backscatter off of balloon stucture (well, the steel parts anyway) that would occur as the pulse units went off in succession. True, as Orion passed through the hole, the next pulse unit would probably vaporize and disperse most of the balloon, but that's still several thousand tons of stuff just hanging there.

Also, a doughnut balloon has a much higher surface area to volume ratio than a sphereical configuration, so the balloon will end up being even bigger (and weighing even more.)

Rocket launches have been done with balloons in the past, although usually the balloon is such thin and frail stuff that as long as the rocket cleared the suspension lines, it could just fly right through the balloon! A booster balloon for Orion is likely to have practically a net of suspension cables so this does not seem like a good possibility.

Alternatively, an Orion could possibly be launched slightly 'off axis' from the balloon so that it could clear that way. But I have no idea what effect this would have on vehicle stability--it might want to tumble and this would probably be very bad for passengers and crew alike.

O.K., you got me interested. I did a google search on "Spectra Rope" and found a website for Pelican Rope at:

http://www.pelicanrope.com/peli05a.htm

1" Spectra rope has a tensile strength of 78,000 lb-f with a linear density of
21.50 lb/100 ft.

1" Vectran rope has a tensile strength of 110,000 lb-f with a linear density of
34.00 lb/100 ft


Now supposing that we have a 4000 metric ton Orion suspended by lines beneath a balloon of arbitray design--let's further suppose that the lines come straight down (no angles as this will significantly effect the tension on each!) from the supporting structure to the Orion.

Let's suppose that the cables attach somewhere near the vehicle perimeter around the CG (center of gravity) of Orion, and extend upward 100 m to the supporting balloon. Let's further assume a 50% safety load factor (each rope is only stressed to 1/2 of its ultimate tensile strength.)

Orion's mass is 4000t, so it's weight in Newtons is 4*10^6*kg*9.800665*m/s^2=
39.230 million Newtons of force.

Utilizing the 1" Spectra rope with tensile strength of 78,000 lb-f (347,000 N) with a 50% safety factor, then the number of suspensor ropes needed is:

n=39.230*10^6/(0.5*347000)=227 ropes.

Similarly for 1" Vectran with tensile strength 110,000 lb-f (489000 N) and the same 50% safety factor yields:

n=39.230*10^6/(0.5*489000)=161 ropes.

What mass of rope will be needed?

For Spectra with linear density of 21.50 lb/100 ft (32.00 kg/100m)
the mass of rope needed will be:

m=227ropes*100m/rope*32.0kg/100m=7264 kg

For Vectran, similarly:

m=161ropes*100m/rope*50.6kg/100m=8147 kg

So here, the 'stronger rope' will actually weigh more!

In all honesty, 7 or 8 tons of rope seems pretty reasonable, considering the huge load they support. I had expected quite a bit more than that. Still the difference of 227 Spectra lines or 161 Vectran lines seems substantial. I would take the weight penalty, use the stronger rope because 161 lines is less complex that 227, and that's just less connection hardware that could fail!

Interesting exploration. Thanks!