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Minimum usable acceleration for a spacecraft
Looking at the statement on the Project Rho site, I'm really not impressed by it. It is vague and problematic on multiple fronts. Specifically:

a) 'Practicality' is a rather subjective concept and often context dependent. What is impractical in one situation is fully practical (or at least the best option available) in another. In this context, questions of mission parameters, mission goals, and what other options are or are not available would all play a role in determining whether or not a given propulsion system is 'practical'.

b) On a related note - given that most of what Project Rho covers are futuristic space propulsion systems based on technology we haven't achieved yet, making 'practicality' the hill to die on in this specific instance seems...odd and even out of character. At a guess, this was either written a long time ago or more recently by 'new management' (I have heard the original founder of the site had passed away) with a different take on things or vision or the like.

c) Light sail spacecraft have existed as a concept for decades and been studied and written about by multiple people. If their acceleration was an issue making them unworkable, I suspect we would have heard about it by now.

d) It's not clear what the statement is referring to. The mention of 'orbits' is odd. Yes, orbits play a role in interplanetary travel, but I've not seen acceleration mentioned in the same breath. Normally it's a matter of achieving a certain velocity and getting to a certain place by a certain time to match velocity with the destination and the like. All of that routinely takes years, so I'm not sure why that's an issue here. Unless we're talking orbiting satellites and changing their orbits - but I can't recall ever hearing or reading about solar sails being used that way.

e) Using one of the many available acceleration calculators online, it comes up that a constant acceleration 3 milligee boost gets you across an AU of distance in about 52 days. The reality is much more complicated as I indicate above, what will needing to match velocity with your destination and solar sails needing to spiral out from Earth orbit for a good bit before really getting going - but even if all that takes 'years' - it's not really all that different from various other methods.

f) While the Dawn spacecraft used ion propulsion rather than light sails, an experimental light sail has been deployed - LINK - even if it only operated in orbit.

Putting all this together, I think the statement is imprecise, unclear, may have logic problems, and doesn't offer any supporting evidence for itself nor does it offer counterarguments against past research, math and even some limited RL activities.

Hope this helps,

Introverts of the World - Unite! Separately....In our own homes.

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RE: Minimum usable acceleration for a spacecraft - by Drashner1 - 01-31-2023, 04:17 AM

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