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"Pulsed Nuclear Space Propulsion and International Law: Some Preliminary Observations"

Any fan of SF and law has got to be interested in this one.

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Besides being InstaPundit, Prof. Glenn Reynolds has also written and taught about, among other things, space law; he and Leigh Outten (a former student of his who has a master's in nuclear engineering from MIT) have cowritten an article on space law and Orion drives, which I found very interesting. The abstract:

Pulsed Nuclear Space Propulsion, researched in the 1950s and 1960s by such eminent physicists as Freeman Dyson, Ted Taylor, Theodore von Karman, and Hans Bethe, involves propelling large spacecraft using compact nuclear explosions from specialized atomic devices. This technology is often known by the name of the Air Force project in which it was developed, Orion.

It has long been believed that the 1962 Limited Test Ban Treaty prohibits the use of nuclear pulse space propulsion. After a survey of the Orion project and its results, and a review of the applicable law, this paper concludes that language in the 1967 Outer Space Treaty may override the Test Ban agreement to permit non-weapons use of nuclear explosives for propulsion.

With a new space race taking place, and with important actors like China not subject to the Test Ban Treaty at all, the subject of pulsed nuclear space propulsion deserves another look. We hope that this paper serves as a springboard to discussion.

Much worth reading, and only 23 pages.

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  1. While I am skeptical of the Orion concepts, I'd note that nuclear explosives may be the only way to deflect a 500-m or larger asteroid from hitting the earth

    1. I should have noted that there is a significant body of relevant research research on the topic (defence against cosmic objects)

    2. An engineer would agree with you on the grounds that we don't have full-scale test data. On the other hand, bombs are incomparably more mature technology than the "nuclear light bulb" or "nuclear salt water" reactor concepts.

      If we get months of warning, small continuous thrust might be all that would be needed to spoil the impactor's aim. Imagine how little wind it would take to make a thousand-yard rifle shot miss a small target. On the scale of the Solar System, we are a small target indeed.

      1. While true that small continuous thrust may be all that is needful, it will take considerably more than "months" of warning for that to be true. Consider the acceleration and coast time out to the asteroid, deceleration time to make a landing soft enough to not destroy your engines, installation and set-up time, all of which must occur before the engines fire for the first time. Add in more time to deliver (or mine) the necessary reaction mass. And all that ignores the decision time and bureaucratic delay to go from discovery of the danger to launch. I would be very surprised if the mission could be undertaken in less than a year and more likely three to five years.

        Bomb-based deflection has some significant drawbacks but it does not require soft-landing or additional fuel. A bomb-based deflection could be reasonably attempted on a time-scale of months.

        1. Have any of you calculated the impulse (= integrated force over time) of a nuclear detonation? That’s why many pulses are needed to drive Orion or the impactor. One will not cut it.

          Nuclear detonations are much less impactful in a vacuum.

          1. If you were going to use a nuclear detonation on an asteroid, it would either be to break it up, or to apply a major impulse, and both would require a sub-surface detonation.

          2. I've not personally calculated the impulse but I've read (and spot-checked) studies that did for various assumptions of asteroid mass, composition, trajectory, etc. You are correct that untamped explosions are far less efficient in the transmission of mechanical energy but it's worth noting that some of the deflection acceleration in an asteroid deflection scenario is from the a single explosion can still be sufficient - for some scenarios. Other scenarios, as you suggest, will require multiple. However, they will not require the many, many small pulses posited for the Orion drive. Orion is constrained by the acceleration and jerk (rate of increase in acceleration) that can be tolerated by humans and/or sensitive electronics.

            1. I've not personally calculated the impulse but I've read (and spot-checked) studies that did for various assumptions of asteroid mass, composition, trajectory, etc. You are correct that untamped explosions are far less efficient in the transmission of mechanical energy but it's worth noting that some of the deflection acceleration in an asteroid deflection scenario is from the ejection of the vaporized mass of the asteroid itself driven by the transmission of thermal energy from the nuclear bomb. (That impulse-from-vaporization is why I think Brett is not necessarily right about the advisability of a sub-surface detonation.) The result is that a single explosion can still be sufficient for some combinations of mass, trajectory, etc. Other scenarios, as you suggest, could require multiple.

              However, even the scenarios requiring multiple nuclear blasts will not require the many small pulses posited for the Orion drive. Orion is constrained by the acceleration and jerk (rate of increase in acceleration) that can be tolerated by humans and/or sensitive electronics. In most asteroid deflection scenarios, we are assuming that we do not want to break up the asteroid but even so, rocky asteroids can take higher forces than squishy humans.

              1. " The result is that a single explosion can still be sufficient for some combinations of mass, trajectory, etc."

                Well, sure. As I remarked below, given enough warning, you can deflect an asteroid with a coat of paint; Just alter it's reflectivity, and sunlight will do the rest.

                That's why I specified that a subsurface detonation would be required for a "major impulse".

                My assumption here is that, given the entrenched anti-nuclear views of those in authority, a nuclear detonation would only be resorted to if all else had failed, and so a significant impulse would be required, not just a gentle nudge.

            2. Please ignore the comment above at 5:51 pm. Darned squirrels grabbed a version of the comment before I was done editing. The reply at 5:59 is what I was trying to say.

  2. It was an interesting concept. 2001 the movie's original script called for this type of propulsion for the Discovery Spacecraft, but Kubrick thought it would be confusing to show this (and it looked a little like Dr Strangelove his previous movie). And you have this issue with having to launch nuclear weapons on a chemical rocket from Earth (what if it has to be blown up by the range officer if it has a major malfunction).
    All that said it is perhaps the most viable technically nonchemical reaction engine for long distance space flights. You can have massive payloads for trips to Mars, Jupiter and beyond.

    Until fusion is perfected (and that might be never), this is the best thing we have other than good old chemical rockets

    1. And you have this issue with having to launch nuclear weapons on a chemical rocket from Earth (what if it has to be blown up by the range officer if it has a major malfunction).

      We've launched multiple rockets with nuclear payloads. Some failed. We're all still here.

  3. Oy... So, there's a couple things to deconvolute here.

    1. Project Orion, in terms of a ground to orbit system is a non-starter. The number of bombs you'd need to detonate would just lead to pollution and fallout levels that are too high.

    2. Project Orion, in terms of an space propulsion system may be more feasible. What's honestly a better bet there (and probably legal) is a laser-assisted deuterium fusion pellet device (which also may be legal under the terms of the treaty). More controllable, smaller discrete elements, and so on.

    3. In terms of explosives, that depends on timing. For an immediate risk, nothing beats nukes. But if you have a little time....mass impactors can be reasonable and deliver significant impulse to divert asteroids.

    1. 1) Politically, I agree with you. In terms of fallout, it would be possible to throw the Orion craft high enough with an initial non-nuclear blast that the subsequent nuclear explosions would be air-bursts that didn't produce fallout. (Fallout is a result of sucking up and irradiating solid matter.)

      Also, it's apparently possible to design the bombs to have a very low neutron radiation profile.

      But, while the total radiation release would be relatively minor on any objective scale, as a society we're incapable of being rational about nuclear energy, sadly.

      Space based societies that have to routinely deal with radiation, and can't really afford to be irrational, would likely adopt Orion in a heartbeat. And probably will, if something better doesn't come along first.

      2) Laser assisted inertial confinement fusion hasn't had the kind of success that would be needed to make a propulsion system out of it. In practice, it's mostly been used to fine tune nuclear bomb modeling, and do materials testing. And keep a lot of physicists employed, of course.

      There are a host of fission and fusion propulsion concepts out there, besides Orion. Some of them even look feasible.

      3) Yes, the more time you have, the easier it is to divert an asteroid. With enough time, a bucket of paint will do it.

      The real priority for asteroid deflection is better detection. We need to put some good telescopes in orbit around the Sun, closer than Earth, to be able to see all asteroids with Earth crossing orbits well lit. The ones that spend most of their time closer to the Sun are practically invisible from Earth orbit.

      1. 1) Even if you could avoid the initial blasts to get off the ground, you still have quite a number of air bursts. And while airbursts have less local fallout, that just means it's dispersed globally. And...that's substantial. There were roughly 500 above-ground nuclear weapons tests in history, and they had the effect of raising global 14C levels dramatically (roughly 70% of global 14C is from nuclear weapons testing). Not insubstantial. Estimates shift, but some argue that "project Orion" would require 800 or so small bombs. For a single launch.

        https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

        You also have to take into account the risks in high altitude nukes, (IE Project Starfish) and the dramatic EMP-like damage that can cause. It's....just a non-starter.

        2) What makes laser-assisted confinement appealing is that it uses a light substance (Deuterium) as a fuel, in combination with lasers (which are powered by electricity, from presumably an on-board nuclear reactor and/or solar energy) to provide a high specific impulse. In addition, it can be better controlled, where as the concept of a bomb "pushing" you...every single time...has a certain amount of risk to it.

        3) Yes, detection is key. The 2022 DART test will also be informative.

  4. Treaties are hypothetical. They are only binding on nations that are technologically obtuse. Once China (or someone else) figures out a practical nuclear propulsion, lawyers will find a way to claim treaties don't apply. And if they do "invade us an try to stop us." Which no one will. Instead people will beg, borrow, mimic, or steal the new technology.

    1. Treaties are not hypothetical. Unless China is entirely independent of other countries, political costs matter.

      Space exploration and exploitation is a fine example of treaties laying out a framework everyone can agree on.

      1. "Unless China is entirely independent of other countries, political costs matter."

        But are clearly not decisive, because China routinely violates international law and treaties, if they see a net gain in doing so.

  5. The Ewoks should have used space law to stop the building of the Death Star…delay it with so many lawsuits the Galactic Empire would eventually give up on building it.

  6. If we needed an Orion drive to deflect an asteroid, I think the objection of launching nuclear weapons into space could be overcome.
    The near 100% risk of a large asteroid hitting the planet contrasted with the not insubstantial, but much smaller risk of nuclear fallout producing accident should be enough to clearly access the relative risks.

    1. I would also propose that any asteroid lage enough to create a serious threat should if possible be captured rather than destroyed if it seems feasible to re-engineer it into a viable spacecraft or space laboratory.

  7. Remember the Precautionary Principle, y’all, and who will accept liability for failure.

    This seems like a rationale for a tyrannical One World Government that can’t even cure Glow-Ball Warning!

  8. Another interesting article on Project Orion (which includes Freeman Dyson's 2012 comments on why it does not have a future): https://inference-review.com/article/reflections-on-project-orion.

  9. It worked in Niven & Pournelle's Footfall.

    1. That novel had some great lines. "Eat hot gamma rays, alien scum!"

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