One of the few good uses for solid rocket motors

[GW Johnson]

The accepter plate they looked at long ago was an enormous chunk of steel. They were looking at steel hulls, etc., too. Cheap, easily-fabricated materials. Built in something resembling a heavy shipyard. Once launched, it stays up there, as an orbit-to-orbit transport. Why land such a thing? Leave that to a craft designed for it, and just carry several with you.

Plus, in a ship that size, you can spin at a reasonable 3-4 rpm and get a fair fraction of one gee artificial gravity in a hull 200-400 feet diameter. The steel plate hull and interior bulkheads and decks provides pretty good protection from solar flare radiation bursts, and also against the slow drizzle of cosmic radiation. Furthermore, it's pretty good protection against micrometeroids and small space junk. And, it's easily repaired.

Building something really heavy and strong like that is a well-known way to obtain something that will last for a very long time. Something you can update and improve for decades, even centuries. Imagine where we might be today, if we had launched a half dozen of these 40-50 years ago. We might well have manned outposts as far out as the Kuiper Belt.

There's a lot of available iron and carbon in this solar system, much of it accessible in asteroids already out in space. I think steel will be a prized material for a long time to come, once we quit dinking around with puny chemical rockets too weak to push it. One of the better methods of steel-making is a vacuum-melt process. At least that "vacuum" part ought to be a lot easier to set up, out in the vacuum of space.

The nuclear devices themselves are indeed more efficient today, plus, we can build the fractional-KT devices for surface launch that did not exist the 50's. The 10,000 ton design used fractional-KT charges for surface launch, increasing to single-digit KT devices out in space. Launch fallout was said roughly equivalent to one 9-MT atmospheric test.

Scaled up larger, so that thermonuclear devices become an option, there is a further efficiency increase, in that fusion is about 10 times as efficient turning matter into energy as is fission.

Looks to me like we need to locate a whole lot more uranium. That's the critical material.

One odd thing most folks don't think about, with regard to pulse propulsion, is that there is no blast (shock) wave in the vacuum of space. It's entirely an intense thermal and nuclear radiation event, plus some small amount of very fast-moving plasma from the vaporized materials. This is also something to consider when you think of deflecting asteroids with nukes. Near-miss bursts don't act the way one would assume, based on Earthly experiences.

[rjaypeters]

...is that there is no blast (shock) wave in the vacuum of space. It's entirely an intense thermal and nuclear radiation event, plus some small amount of very fast-moving plasma from the vaporized materials. This is also something to consider when you think of deflecting asteroids with nukes. Near-miss bursts don't act the way one would assume, based on Earthly experiences.

The material in the event cone will be energetically vaporized and provide the impulse to the target. Something we badly need to sub-scale and full size test before the Big One shows.

[GIThruster]

GW, I'm not an expert but I've seen some of the data before. If you build a spacecraft out of steel, it absorbs and re-radiates enough energy, and the types of energy, that it would kill everyone inside. I think it's cosmic turns into X-Ray or some such. Besides, using a high mass/strength material like steel instead of composite or liquid metal is a waste of space inside the craft. Why have half the internal space for the same mass, when you can create a much larger ship with better radiation protection out of liquid metals or composites?

[GW Johnson]

I'm no expert, but from what I've heard, the re-radiation or secondary-shower effect depends upon the thickness as well as the type of material. I thought the critical number with iron was 5 inches, but I could easily be wrong.

I'd make pressure hull shells and pressure bulkheads/decks/partitions out of whatever steel it takes structurally, up to around maybe 1 inch plate. Don't see the need for thicker armor. Maybe it's 1/4 or half-inch plate we use; I dunno. I did missiles for a living, not this stuff.

The rest of the structure can be whatever we want. And, yes, tanks of water or wastewater or bio-reactor life support fluids make wonderful radiation protection. Absolutely.

I have a little concern about where we might get mass quantities of organic composites in space. Steels, yes. Even metal-matrix composites made of rock fiber from a melt of in-situ materials out in space somewhere. But shipping stuff up out of Earth's gravity well would be expensive.

You would definitely have to build these ships on Earth if you used a lot of organic composites in them. Sooner or later, some idiot will object to the fallout from surface launch of atom bomb-propulsion ships. Not logical, but there it is. It exists.

I'm just saying don't be afraid of steel plate because of a possible interaction of high-energy radiation with iron. They use a lot of it, as well as steel-reinforced concrete, in nuclear power plants. Not the same radiation environment, to be sure. But if there were a really serious problem with secondary-shower radiation, we'd know about it by now.

BTW, the space treaty bans weapons. Whether pulse propulsion is a "weapon" or not is interpretation. A kitchen knife is a weapon, for crying out loud. Anybody tries to ban my kitchen knives will see me in person, up front and very personal, with much deadlier weapons.

[TallDave]

Imagine where we might be today, if we had launched a half dozen of these 40-50 years ago.

I know, it kills me. Even if space is mostly worthless, at least we would be mastering the Solar System. I'd feel better as a species.

[GW Johnson]

Lessee, there was a comment above about asteroid deflection with nukes. No blast wave in vacuum for the near-miss detonation, but there is a thin plasma spherical front, or a plasma jet if the device was a directional shaped charge. Thus there is an impulse mechanically delivered to the asteroid, yes.

What I saw at the asteroid deflection meeting in Granada, Spain last year said it was a different effect that creates a by-far larger deflection force. The intense burst of "thermal" radiation (most of it gamma and X-ray) induces vaporization and considerable surface spallation on the asteroid. It is the momentum reaction of the rapidly-departing spall fragments and vapors that provides the most significant force.

This spallation effect is absent in the pulse-propulsion scheme. Based on damage and debris observations from the old nuclear weapons tests in Nevada, it appears that the acceptor plate does not erode, which is due in part to its being steel, and in part to its immense size as a thermal sink. Even the debris in the two cities nuked in Japan reflected this effect with massive steel structures.

The problem with using nukes to deflect asteroids isn't the nuke, it's the asteroids. We don't yet have a lot of field data, but from what we do have, most of them do not appear to be solid, monolithic bodies. Most seem to be loose, fairly-dry rubble piles, not even "glued-together" by any significant ice content. Push on them, and they would fly apart into zillions of pieces, because your applied force is so very much stronger than the self-gravity binding the rubble pile together.

Do that close in, and the whole swarm of pieces hits the Earth. Same total mass, same total energy, just a wider area damaged. Shotgun blast vs a single bullet. That's a really bad unintended consequence.

If you do that far enough out so that the swarm has time to spread by astronomical distances, then only part of the swarm hits the Earth (this pass). Less total mass, less total energy, damage still spread out over a wide area (shotgun blast effect, but birdshot, not buckshot). Still not a good outcome, but not as bad as the close-in disruption, or no deflection attempt at all. That's the real concept behind any last-ditch defense with nukes.

The real trouble with disrupting these things is that, sooner or later, the orbits cross again, and the debris swarm you created earlier comes back to haunt you. Once disrupted, there's not much we can do to mitigate things, nothing but just but endure the future meteor storms. They could be pretty bad.

It makes sense to start very early (meaning years-long early-warning times are needed), and it makes sense to use deflection techniques (like the gravity "tractor" and some others) that do not disrupt the asteroid. To do this job requires a lot of in-the-field science that we currently don't have (probes and missions to these objects are therefore necessary).

It requires propulsion and ships that we don't currently have to take men and / or instruments out that far, and it requires a telescopic survey and search for threatening objects. That last is underway, but suffers from both underfunding and from fundamental observation limits of telescopes we know how to build. The propulsion and ship designs are just plain lacking, period.

The job also requires some engineering development of the deflection techniques, on these bodies "in the field". Men absolutely do have to go out there to do this. Currently we cannot, and I see nothing on current drawing boards that could take us there.

The old "Orion" explosion drive could, easily. The old nuclear thermal rockets could, barely. Going there is about like going to Mars, by the way. Far more challenging than going to the moon ever was. Even with the slide rules in the 60's.

[rjaypeters]

... The intense burst of "thermal" radiation (most of it gamma and X-ray) induces vaporization and considerable surface spallation on the asteroid. It is the momentum reaction of the rapidly-departing spall fragments and vapors that provides the most significant force.

Isn't that what I said?

Push on them, and they would fly apart into zillions of pieces, because your applied force is so very much stronger than the self-gravity binding the rubble pile together.

My first thought is to put a big baggy behind the pile before the nuke goes off. I imagine the reacted pile moves into the baggy and gets surrounded. We could also used a "drawstring" to close off the bag. Repeat as necessary.

Since it's a close-approach orbit, think about bring the baggy into earth orbit for resource exploitation.

Lots of fun engineering and things that need to be tested.

The job also requires some engineering development of the deflection techniques, on these bodies "in the field". Men absolutely do have to go out there to do this.

Please see the early parts of thread: "The next generation of spaceflight." Most of your correspondents agree with you. I bet there is more than one fan of the REAL Project Orion on the forum.

[kunkmiester]

have a little concern about where we might get mass quantities of organic composites in space. Steels, yes. Even metal-matrix composites made of rock fiber from a melt of in-situ materials out in space somewhere. But shipping stuff up out of Earth's gravity well would be expensive.

Most asteroids are mostly carbon, as I recall. Thus, you'll have plenty of carbon available--in fact, I was thinking you'd be using carbon composite for a LOT of auxiliary stuff, and maybe even a lot of primary stuff.

The big thing with Project Orion is that it's so cheap per mass that weight almost becomes irrelevant to the project. If you built a non-fission based thermonuclear device, say using an explosively pumped generator to generate a small fusion pulse to set off a larger secondary, you'd completely get rid of the fallout hazard, and eliminate any practical protest to launching the things.

I was looking at launching an 800 foot Bernal Sphere, monolithic. The big problem at this point is chicken-and-egg. You'd really want to build a space colony in space, but there's no infrastructure, and there's not much point in the infrastructure if you don't have anything to do, etc. etc. You build a medium sized thing like a sphere, and you launch everything with it and BOOM(literally!)--you have a place to work, you have ships to send out to asteroids and NEOs to mine, a place to send those materials to be worked, Everything at once. Maybe two or three and then you have enough to sustain space development.

Fun thing about refining metal in space is free energy--really big mirrors are easy, and you can get more than enough to slag almost anything, even tungsten. There's all sorts of things you can do up there that puts shame to what we have to deal with down here.

[JLawson]

I bet there is more than one fan of the REAL Project Orion on the forum.

I think it's a great idea myself - but the side effects would be a bit... extreme. Especially on launch - that thing's going to dig divots that'll scatter fallout for hundreds of miles downwind getting airborne. Once they get a couple miles up and then to orbit it won't be so bad, but that first step's a killer.

Would the whole thing work? Judging by the video of a test-bed using conventional explosives, I think it would. I'd want to be a LONG way off when the thing's launched, though!

[rjaypeters]

... but the side effects would be a bit... extreme. Especially on launch - that thing's going to dig divots that'll scatter fallout for hundreds of miles downwind getting airborne. Once they get a couple miles up and then to orbit it won't be so bad, but that first step's a killer.

So who says one must launch from the ground? Ocean launch is acceptable. You said something about wanting to be far away, right?

The REAL project Orion would work and since the idea was first proposed some technology advances have made the idea even better. Certain people know a lot more about how to make cleaner nuclear explosions. For the right reasons, e.g. international emergency, these people can be persuaded to share that knowledge so the earthly fallout is greatly reduced.

The idea humanity could have been cruising the solar system for decades is immensely frustrating for Orion enthusiasts. At the expense of much, much less fallout compared to the entire nuclear bomb development programs of the twentieth century, you and I could have been writing these posts on the MOON.

[GIThruster]

This is why we have no space program, because there's something in engineers, that at times they utterly lack common sense. There is no way an open cycle fission rocket could ever be built. If it could, the infrastructure for the bombs you throw out the back would cost many billions, and the security for handling it could cost trillions.

We can't even get a closed cycle fission motor built and flown. We're not even flying fission reactors for space power.

This kind of "brainstorming without the brain" is exactly why we have no human spaceflight program. People just don't pay attention to practicalities. Someone tell me please, why did we ever embark upon the Ares 1 program, when for a tiny fraction of the cost to design a new rocket, we could have had a better performing rocket, just by man rating Atlas? Why?! Because there are times when people demonstrate they have no common sense.

Throwing bombs out the back of a rocket is NEVER going to be sold to the public. They simply will not allow it. Likewise, it's a violation of current treaty and we're not going to see the treaty changed for the sake of human spaceflight. So why giggle at the notion of a completely unworkable idea? It wasn't ever a good idea!

IMHO.

[rjaypeters]

Throwing bombs out the back of a rocket is NEVER going to be sold to the public. They simply will not allow it.

For the right reasons, e.g. international emergency...

Like a large object heading our way?

Likewise, it's a violation of current treaty and we're not going to see the treaty changed for the sake of human spaceflight.

Just like the United States would NEVER leave the ABM treaty?

A short story: Back when I was working with a small portion of the Department of Energy, I met with a colleague who had been around awhile (I think since the beginning of the Atomic Era). Anyway, my colleague allowed he would be pleased to run the program if the US decided to cheat on the CTBT Treaty by setting off a nuke in _deep_ space. It would be a fun program, but it wouldn't happen except in a emergency.

The fault of not having a decent space program lies not in the wild imaginations of engineers without common sense. Seriously, does writing and talking about Project Orion really harm the work space entrepreneurs and government space agencies do?

[GIThruster]

Seriously, does writing and talking about Project Orion really harm the work space entrepreneurs and government space agencies do?

I suppose not. I'm still wrestling with the fact we're about to go without human launch ability for the first time in 4 decades, when it was obvious the most expedient thing to do was man rate Atlas. This could easily have been done by now if the proper people had really owned a sense of urgency to keep us in the game. Instead, because they were able to blame others, and because they insisted NASA has to have its own rocket rather than pay for launch service; they accepted a "gap", and then a larger gap, and a larger gap, and now we don't even have a possible project for human spaceflight on the horizon. So you can guess, the idea of throwing bombs out the back of a rocket, as absurd an idea as this is, is want to set me off a bit.

way too early for a drink, though, so excuse the rant. . .

[rjaypeters]

way too early for a drink, though, so excuse the rant. . .

No excuse needed for a rant, especially on the launch gap! I was supposed to be an asteroid miner and look at me, sitting on my couch.

[GW Johnson]

Shoot, I went to the Naval Academy back in the late 60's, because I wanted to become an astronaut, and go on the Mars mission, then planned for 1983. Baseline propulsion: solid core nuclear thermal rocketry. Preferred solution: gas core nuclear thermal rocketry. None of that ever happened.