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4

Here is a spherical-cow physicist's estimate. Beware: spherical-cow physicist's estimates are extremely dangerous when dealing with climate: for instance the obvious model of how the greenhouse works that physicists (including me) have is simply wrong: it's not approximately right, it's wrong, and it totally mispredicts the effect. So be very wary about ...


5

No, that's impossible. You can't compress an ionized gas and put it into a cylinder like that. All familiar ordinary matter, including gases, is not ionized, or else only slightly ionized. If you try to squish a large amount of ionized oxygen atoms together to reach a dense gas, let alone a super-compressed one, the following will happen: The oxygen will be ...


2

Cereals are largely composed of complex sugars: starch and cellulose. Simpler sugars combined with an oxidizer are sometimes used in rockets, and there seems no fundamental reason that more complex sugars wouldn't work. A solid fuel rocket is, however, a serious pressure vessel, unlike a silo.


22

Since the term "grain" already in use in the solid rocket context, I'm favoring the term "cereal". Cereals contain about 66–76% carbohydrates -- mostly starch (55–70%) plus some sugars and cellulose. Cellulose combusted with gaseous oxygen yields surprisingly good specific impulse, up in the 240 sec range; sugars with potassium nitrate ...


3

The main technical challenges I see are accuracy, survivability, and range. All of these drive cost, since better performance usually requires higher technology, which can get very expensive. On the other hand, as has been mentioned, for tight enough speed requirements, it's not just competitive, it's the only way to succeed. Accuracy requirements are set ...


2

As I said in a comment, I think this question might belong in worldbuilding. Here however is a proposal for how you might solve the problem. I think valves (vacuum tubes) would be very manufacturable using relatively simple technology, certainly compared to semiconductor manufacture. For a probe which spends its time in hard vacuum or which is willing to ...


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