And just for the conspiracy theorists out there: if a spacecraft like the one they depict were in Earth orbit, it would make a phenomenal anti-satellite cannon. If aimed carefully I imagine a full Li load could take out most of the valuable satellites in a couple of hours. (That is, until it jammed
Quote from: adrianwyard on 10/11/2013 05:44 pmAnd just for the conspiracy theorists out there: if a spacecraft like the one they depict were in Earth orbit, it would make a phenomenal anti-satellite cannon. If aimed carefully I imagine a full Li load could take out most of the valuable satellites in a couple of hours. (That is, until it jammed That seems like a highly inefficient way to take out satellites.
Don't forget that the loading mechanism is not going to perform at insane repetition rates. We are talking one re -loading every 10 seconds here. So this is not a high performance part in any way. It seems that they have updated the layout of the driver coils to be more cylindrical. This makes the loading even simpler. If we cant make a mechanism like to work reliably, then it might be better to just quit that space business all together.
If you told me my life depended on an automatic rifle firing once every ten seconds hundreds of times over a one year period, and never jamming, I'd be worried. And I'm worried about using FDR for human spaceflight for the same reasons.
I agree and disagree. It's a question of life-or-death extreme reliability. The loading mechanism on automatic weapons is not that complex, and has been refined over decades. I doubt you could improve it much even if you had a billion dollars to spend. Jamming is understood to be a life-or-death failure. But they do jam.If you told me my life depended on an automatic rifle firing once every ten seconds hundreds of times over a one year period, and never jamming, I'd be worried. And I'm worried about using FDR for human spaceflight for the same reasons.
Just been through this thread, and the latest update paper at http://www.iepc2013.org/get?id=372A couple of highlights:- Total space craft mass is 134 tons- The entire trip needs 120g of tritium and 80g of deuterium*I think, the text is: will require a rep rate of 1/14 sec-1. This matches the average power of 36MW.This seems very promising. It might be a little bit uncomfortable with a jolt every 14 seconds. Each impulse gives delta V of only 0.125m/s, which results in daily delta V of 780m/s. Over 14 seconds, this could be absorbed by spring movement of less than 1m. There was discussion about Tritium supply. (http://en.wikipedia.org/wiki/Tritium). 120g of tritium currently costs $3.6 million. It's made from bombarding Li-6. This process is exothermic given the neutrons. I guess you could modify fission reactors to produce more tritium.If this engine could be built to the above parameters, it would make Mars colonisation possible. I think this is the most promising propulsion technology for solar system exploration.
The loading mechanism on automatic weapons is not that complex, and has been refined over decades. I doubt you could improve it much even if you had a billion dollars to spend. Jamming is understood to be a life-or-death failure. But they do jam.
To put 134 metric tonnes in perspective that's 2 SLS flights, 6 Delta IV Heavy flights or 9 Skylon flights, or 5 Atlas V heavy flights (if it ever gets funded).If the vehicle can be fully reused (which it seems it can) this is not ridiculously expensive (but it's not cheap).
For me the most interesting thing is that it includes fuel for an orbit insertion back on Earth, meaning the spacecraft would be fully reusable right from LEO. Meaning a sustainable space exploration program.
A lot of these problems can be worked out in sounding rocket or zero g plane flights long before a full vehicle is designed.
One question: if we wanted to double the average thrust, what would be the path? Scale up the engine? Shorten time between pulses? Putting two engines in tandem does not seem to be viable.