How Long to Make an Orion Rocket?

[Sea Skimmer]

You'd end up with some kind of sealing band with a lot of possible launchers, I question if a a rifled gun would really be used though simply because it would mean the rifling at the barrel tip is exposed to erosion via atomic blast. This would also allow the use of much longer projectiles

Five years is probably optimistic for any confidence at all in a project like this. Industry could build a lot of stuff in 5 years, but we'd have damn few people qualified anymore to say anything about what to build up front.

[cosmicalstorm]

What is the likelihood anyone will try to build a true Orion anytime soon?

Sometimes I like to daydream that China decided to build and launch it from some desert. Is the radiation-problem too bad if you do it in some remote region. Will they fry a lot of electronics with EMP, maybe ruin all the nearby satellites?
Seems whoever built one first, they could dominate orbital space for a while or maybe forever if they launch a huge load of weapons into space.

Does that make any sense?

[Sea Skimmer]

Orion stopped making any sense once ion engines were a thing. Nuclear bombs aren't even all that cheap. It really never made much sense for anything, compared to say building extremely large rocket boosters in serial.

And yes, it would fry satellites like mad. Though in concept a means exists to deploy a system of ground antennas and booster satellites that could reverse the van allen belt pumping, that would only help long term durability of spacecraft that survived to initial blasts, which would probably be nothing but a few a military EHF satellites in extremely high orbits.

If we wanted nuke power in space at this point it would make far more sense to explore far more advanced drive systems like fission fragment engines.

[MrDakka]

I don't think its in question we could build the blast shield without testing though if it was just allowed to be very heavy, we aren't really talking about structural requirements higher then face hardened battleship armor crossed with a forged nuclear pressure vessel lid. If you can forge it all into one piece it's going to hold up. But it's like trying to forge a whole battleship turret at the same time.

Wouldn't it be easier/more practical to use scale up a laser sintering machine instead of trying to forge a plate this large? Either way just setting up the manufacturing process will take a while

[Dass.Kapital]

What is the likelihood anyone will try to build a true Orion anytime soon?

Sometimes I like to daydream that China decided to build and launch it from some desert. Is the radiation-problem too bad if you do it in some remote region. Will they fry a lot of electronics with EMP, maybe ruin all the nearby satellites?
Seems whoever built one first, they could dominate orbital space for a while or maybe forever if they launch a huge load of weapons into space.

Does that make any sense?

I don't think Orion's blasts outside of the atmosphere will generate EMP. I think that's an atmosphere propagation thing (Quite probably wrong, am sure experts will add in corrections)

Well... if the folks who really want to colonize Mars any time soon manage to set up shop over there...

Then I can see them trying to build such a vessel to make the journey times between the 'Ranch' and home just that much quicker and cheaper, heck if not just for the moving things 'quickly' between the two and not wanting to rely on the 'lower energy' costs of orbital mechanics.

Just an idea. It's not like a sun-blasted dust ball with no atmosphere etc is going to worry too much about some of the effects. Every one's already living inside domes, etc...

[Simon_Jester]

One problem is that even if they don't create EMP in the thin extremity of the upper atmosphere, they still create particle radiation and fallout (from the vaporized bomb casing and ablated fragments of the plate). The Earth's magnetic fields are an efficient trap for charged radioactive particles. Thus, an Orion drive launch would have the effect of 'pumping' the Van Allen belts (the aforementioned traps) full of an unusually high density of radioactive nuclei and stray particles. The radiation would then bounce around in the Van Allen belts and cause disproportionate harm to anything which happened to be in Earth orbit at the time.

Or that's how I think it goes.

[Sea Skimmer]

Wouldn't it be easier/more practical to use scale up a laser sintering machine instead of trying to forge a plate this large? Either way just setting up the manufacturing process will take a while

To laser sinter you have to super powderize all your feedstock first, no trivial thing to do when were talking about a 300-3000 ton kind of plate. The operation would then take literally forever, the layers are in the tens of microns thick. I really don't see how that's going to work out to be practical. If you failed at it, you'd then take forever again to try again. Its basically a massive weld, which isn't ideal from a toughness standpoint as things go. Additive manufacturing has its places but just making a giant blast shield isn't going to be one of them. It might do the job, I can't see why try unless you are building in space, where other forms of metalworking could be a lot more difficult. No gravity means simple ideas like pour metal into a mold no longer work.

For a forging operation we aren't talking about needing exceptionally high pressure at that point at all, its only about the physical size of the forge. Which yeah expensive to set up, but still I bet not over 1-2 billion range, basically your just making bigger jacks and bigger beams, we could do that in a very straightforward manner as long as we aren't talking wider then say, 50 feet. For final machine work I know CNC mill machines that are 100+ feet in span already exist. They scale up all you want since its just about the running rails rigidity at that point.

If you wanted bigger I think you might need to go to a multi segment piece keyed together, which I bet could be made to work fine too. Laser sintering might have a place for joining that sort of structure but a lot of things might work.

Take this for example of huge forging without needing that elaborate of a operation in relative terms. You could totally go x10 bigger. It's just in real life we don't have much demand for such things anymore, nobody needs stuff like 500 x 60in caliber battleship barrels forged like our modern wonder technology can totally make happen.

[Elheru Aran]

In other words: It's much easier to physically clout a massive plate of red-hot steel into shape than it is to painstakingly laser-weld it into place molecule by molecule.

[Sea Skimmer]

Yeah. And key thing is that powderization thing. You MUST do that for the laser sintering, if you've done it then you can forge the material much more easily then you could forge solid ingots.

https://youtu.be/vg6KedXnTR0?t=40
This is China forging a 428 tonne shaft for a rolling mill, apparently a world record, and the kind of mass we are talking about for the smallest Orion Drive plates. The press doing the job only exerts 18,500 tons of pressure, about a third of the most powerful presses. Obviously squishing this billet into a big plate shape would take a lot of time and reheats, but it's still nothing very demanding. Just expensive.

[Elheru Aran]

A bit of necromancy-- apologies for that-- but I thought this picture was relevant as an example of the size of things that it's possible to forge with modern industrial technology...



(Image is from FB, so if it goes down or you can't view it, let me know and I'll upload elsewhere)

Apparently it's part of a nuclear reactor being forged at a facility in France. If they can forge something like this (looks like about eight, ten feet interior diameter... easily... and quite possibly a foot *thick*), it should be possible to forge slightly larger engine bells at least for an Orion rocket.

[Sea Skimmer]

Final thickness would probably be 250mm since its French, and it looks looks its the center portion of a nuclear pressure vessel pretty close to finished.

It would have started as a large round ~300 ton ingot cast somewhere nearby, been punctures through the middle with a mandrel, and then forged into a steamless tube seen here with progressively larger and larger mandrels and various jigworkas show in the image.

Like this


This is more or less exactly how we make large caliber artillery barrels, and engine bearings for that manner, just with a lot different proportions and scale. The end caps will be forged as single pieces themselves in pressing operations and then full penetration welded together, except for whatever the access hatch is for refueling, that's bolted.

For a nuke plant they forge just about everything possible, and all in a seamless manner by poking through ingots. You could roll and weld many of the mere pipes involved for much less money, but welds are troublesome by nature, let alone in a nuke plant and all the certification involved.

[Sky Captain]

I suspect big problem with Orion rocket would that there is no redundance since all designs I have seen have only one engine. Pusher plate and shock absorbers would have to stand up to immense forces thousands of times. If there is irrepairable breakdown of major drive component then loss of vehicle and crew is likely. With pretty much any other form of propulsion it is easy to have several main engines to achieve redundance.

[Simon_Jester]

Yeah, good luck using a cluster of Orion drives in any way, shape, or form; the blast from one engine's bombs going off would almost inevitably interfere with the others while in operation, and the forces involved are too large for them to be anything other than perfectly aligned with the center of mass.

About the best you could do is put an Orion drive pusher plate on both ends of your ship, and that would be a tremendous amount of extra mass.

[Starglider]

About the best you could do is put an Orion drive pusher plate on both ends of your ship, and that would be a tremendous amount of extra mass.

But not a total waste because at several percent of c you're going to need a pretty serious shield against interstellar dust anyway.

[Sea Skimmer]

You'd only be going that fast if you started in space for an orbit-orbit mission, not surface to orbit. This will require different ship designs by nature. Also if you use the pusher plate as a debris shield it will quickly be rendered unfit for use as a pusher plate, no unitary steel plate will do a good job of it and the direct and shock damage will be immense. Your shock absorbers that work for riding nuke blast will do nothing useful against a 2% C hit.

You need lasers to vaporize any large particles and then a deep spaced armor package. Probably one replicated several times over so that at a certain point of damage you can eject the upper layers and throw them aside, before they breakup and create a debris hazard.

Worrying about pusher plate and shock absorber redundancy is the same as worrying the space shuttle wings will fall off anyway. What you would worry about given even the best design, and have realistic margin for redundancy for, is multiple guns to fire the nukes with in the first place. Thermal considerations might require that you use several as it is since you need a pretty high ROF for ~1000 rounds of nuke. Also fast neutrons might destroy the muzzle. Trick would then become designing a magazine that can feed multiple guns with redundant feed paths, and switch over quickly enough for everyone to not die. I'm imagining we might end up with many robotic arms simply placed along the linkless feed rollers so they can physically try to clear jams, certainly not going to use a human mechanic for this.

All that aside, turns out people designed Orion drives with outright nozzles that might be mass competitive and provide much higher economy, but only for use in orbit-orbit scenarios.

[Sky Captain]

Worrying about pusher plate and shock absorber redundancy is the same as worrying the space shuttle wings will fall off anyway.

I gues to achieve that kind of confidence in shock absorber and pusher plate assembly would require extensive preflight testing. How it would be possible? Chemical rocket engines can easily be tested on test stand to make sure they can last required burn time. How would you test an Orion propulsion module? Conventional explosives on the ground? Would it be accurate enough to reliably confirm that propulsion module will survive flight under nuclear power?

[Elheru Aran]

Worrying about pusher plate and shock absorber redundancy is the same as worrying the space shuttle wings will fall off anyway.

I gues to achieve that kind of confidence in shock absorber and pusher plate assembly would require extensive preflight testing. How it would be possible? Chemical rocket engines can easily be tested on test stand to make sure they can last required burn time. How would you test an Orion propulsion module? Conventional explosives on the ground? Would it be accurate enough to reliably confirm that propulsion module will survive flight under nuclear power?

Extrapolating the power of nukes by using conventional explosives is well practiced and understood, from what I understand. Skimmer will know better than us, of course.

The Orion concept has already been tested, there are YouTube videos out there... rather cute.

I honestly don't see how it would work as a ground-to-space concept though, without setting off some serious environmentalist alarm bells. But I can't see how you would be able to get the hardware up to space otherwise without some hideously massive boosters...

[Sea Skimmer]

Its pretty hard to simulate nuke effects at high pressure ranges with HE, but in practical terms such testing could work for the structures needed. But for example they would not probably use a big stack of HE in a pile, but a large dedicated shock tube assembly that burns a fuel air bomb. This tube would be like a subway tunnel level of win, and cost bonus money.

If we can't explode nuclear weapons for tests the whole idea is bunk though, at least with present technology, at some point computers might actually be able to simulate it. Even if you (might) get away with using HE for testing the place and shocks, you're going to need to nuke blast the damn ship itself to test it against the electromagentic effects.

Any thing else is crazy, when the whole idea is we fire off 1000+ nukes right beside this thing, and it's no shit 'flyaway' cost is probably 30 billion dollars for the first one. Also while most nuclear effects can be simulated by the right machinery, that machinery has to be big enough to handle the ship...it gets very expensive in it's own right. The 20 ton or 1 kt nuke would be cheaper.

Also remember if your serious about actually doing this then crap would have to be done like building the launch pad, and then blowing that up with a large conventional explosion just to be sure it's not going to damage the ship on the mother of all blast offs. The amount of money this would consume out of hand is such that we could go to some fairly elaborate efforts to contain the effects of free air nuclear testing. For example we already proved back in the original project win zone testing period that asphalting the ground would massively suppress fallout. They did this to facilitate various specific other tests, and model effects of nuke burst on cities.

The point being, paving the nuclear blast zone is plausible. At that point you could then detonate the nuclear pulse propulsive device on a 300ft high tower and you'd generate almost no fallout at all except the actual bomb case material. Wetting down the asphalt would help. Concrete would be even better and used near the tower base, but just cost way more to actually go and do that, for a pretty small advantage.

But that's a huge problem with the whole Orion concept, even in orbit to an extent. They want a low yield nuke, unless it's a huge ship, in which case you start to need some pretty high yield devices. But a sane Orion would want rather small ones, which means inefficient nuclear weapons. That means a lot of bomb material remains as highly active fallout, and to increase the actual pushing effect the idea is generally to use a layer of metal, typically tungsten, to create a shaped charge effect towards the ship. That metal? That's all wonderful fallout now. Even in space it's going to hang around as this big radioactive metal cloud now circling the planet.

Oh also we'd need a new highly compact nuclear warhead design as the propellant, that's going to need it's whole own test series, though most of that could be done underground. Still it would be highly desirable to fire some live rounds out of the nuclear propellent gun before trying to launch the 30 billion dollar spaceship.

Even in space, where failure does not mean loss of ship, if the system misfires, say it jams up after 30 shots, you'll be in a pretty bad situation since the rear end of the ship is now pretty damn radioactive. Repairs would need to wait weeks for it to cool off. In 2016 we don't have the robotics to deal with that decently, it does not seem like it will be much longer before they can.

[The_Saint]

I've always thought of Orion rockets being mostly practical only in a nigh-apocalyptic period like that shown in 'Flood' and 'Ark' by Stephen Baxter.

Where it's a case of "we need off this planet ASAP!! and we need to get a lot off of it!!!" You need to launch heaps, you don't have time to assemble in space particularly as some of the parts are obscenely large and once the ship has flown you care not one wit about the launch zone.


Personally I've always thought the more realistic approach for anyone trying to get serious-mass off planet fast would be Russia cranking up Proton production. I could be wrong but that seems to be the most flight proven system that could be scaled up production and launch wise and with possibly the best redundancy against launch failures (from memory it has possibly the most launch pads of any current build 'heavy' launch systems)

[Sea Skimmer]

You'd crank up everything production at that point, Space X would almost certainly take the lead on that front since its main engine is so easy to build. Not man rated, who gives a damn at that point? But it is really a question of how much lead time you actually have. If it isn't at least several years very little is getting accomplished. If its over five years then clean sheet designs could be taken a lot more seriously.

Realistically the approach to take is just trying to shelter humans in place. I mean okay a big enough rock kills everyone on earth, but a dino killer kind of rock does not have to do so. Unless we already have a Mars colony operating a quick burst of resources into space would just mean a few hundred people get to die in space instead of the earth.

Something not often dealt with that I've heard of sci fi wise is that for a large portion of the earth if a dino killer like rock hit, you could totally survive it in a surface shelter if modified well. You don't have to be under Yucca mountain, what do you do need is a several year supply of food and a way to filter your air for the first several months. The trick is having enough warning time to stockpile that kind of food, and lay in stocks of fuel and spare parts and equipment for resuming farming. If you had 5 years....humanity could get pretty damn far. The problem would be making people take it seriously.

[Simon_Jester]

Honestly, it seems a lot more cost-effective to deflect the dinosaur-killing asteroid by slamming it over and over with nuclear weapons* launched by a bunch of boring but conventional rockets, than to try and build space stations or moon bases or whatever.

*(We could even use Orion-drive propulsion bombs that are optimized for directional momentum transfer! I kid, I kid... I think...)

[Sea Skimmer]

You'd hope we could try, but if multiple threats appear together or the damn rock is big enough even a massive nuclear attack might not prevent all hits. Side problem is actually tracking objects with great precision at long range gets hard to figure out what to do with a threat cloud. We could face a situation in which the best thing we can do is limit the hits to one side of the planet. It's not likely no, but we don't know everything orbiting the sun and won't until we spend some pretty crazy amounts of money deploying satellites in solar orbits to look for them.