This may be difficult in terms of agreements with NASA, even on Mars... But a Kilopower without its Stirling engines, or power generation could use extended heat pipes as a direct water mining tool. Maybe the unit will need too much shielding to make it useable, but conversely secondary heat pipes may possibly be made 10's of metres long to provide heat for mining water at a distance from the reactor itself. This is using the power directly without all that electric mumbo-jumbo.... Mirrors could also be set up to heat a cathode using concentrated sunlight, and a high capacity heat pipe used to transfer this heat energy to mine large quantities of water. Others have suggested habitats in ice caverns so made.
Quote from: Joseph Peterson on 04/29/2018 06:35 pmQuote from: speedevil on 04/28/2018 10:16 amSNIPYou get three per synod if you can turn off the methane generation during the night.SNIPElectrolysis, not methane generation. Methane generation can continue as long as there is enough hydrogen left in the buffer. The hydrogen buffer is there to allow steady state operations, reducing catalyst degradation.The whole process from whatever it takes to gather resources on. If you can modulate down to match insolation, without peak/averages costing you more than 1/3 in terms of mass, means you can mostly skip batteries.I was being less careful in my wording as I was correcting a three orders of magnitude implication (500MW vs around 500kW) for near-term power use.
Quote from: speedevil on 04/28/2018 10:16 amSNIPYou get three per synod if you can turn off the methane generation during the night.SNIPElectrolysis, not methane generation. Methane generation can continue as long as there is enough hydrogen left in the buffer. The hydrogen buffer is there to allow steady state operations, reducing catalyst degradation.
SNIPYou get three per synod if you can turn off the methane generation during the night.SNIP
Quote from: speedevil on 04/29/2018 07:21 pmThe whole process from whatever it takes to gather resources on. If you can modulate down to match insolation, without peak/averages costing you more than 1/3 in terms of mass, means you can mostly skip batteries.I was being less careful in my wording as I was correcting a three orders of magnitude implication (500MW vs around 500kW) for near-term power use.It's easy to make a minor mistake on a secondary point. I do it far more often than I'd like.1/3 of what in terms of mass?
The whole process from whatever it takes to gather resources on. If you can modulate down to match insolation, without peak/averages costing you more than 1/3 in terms of mass, means you can mostly skip batteries.I was being less careful in my wording as I was correcting a three orders of magnitude implication (500MW vs around 500kW) for near-term power use.
Quote from: Joseph Peterson on 04/30/2018 08:08 amSNIP1/3 of what in terms of mass? Total landed mass.If your extraction hardware (whatever is the hardest part to scale) weighs more as it has to deal with instantaneous solar power, not average daily power from the solar panels, then batteries plus continual extraction hardware may be lighter.From the ebay thread, you can fit around 750kW into 150 tons, or 500kW with batteries to smooth it over the whole day.
SNIP1/3 of what in terms of mass?
I'm not understanding the logic of using total landing mass. <snip>We might not be looking at actual saving though. How much landed mass is one person-hour of Martian labor worth? We are only going to have so many workers on Mars. It could easily be worthwhile to send an extra tonne so human labor can do other things.
Quote from: Joseph Peterson on 04/30/2018 07:19 pmI'm not understanding the logic of using total landing mass. <snip>We might not be looking at actual saving though. How much landed mass is one person-hour of Martian labor worth? We are only going to have so many workers on Mars. It could easily be worthwhile to send an extra tonne so human labor can do other things.I have not carefully read the above post, and need to, but as a more general point, what else would you be optimising for?Surely the goal is to get capabilities on Mars, and the lighter you can do this (if it does not make it too much more expensive), the more capabilities you can fit in 150 tons. (modulo density limits).To start with, at least, those initial capabilities would be improvements in landing safety, life support capacity and the capacity to manufacture propellant, and maintenance,but what you want after the next synod is an interesting question.'What you should optimise for' is a fun question for subsequent synods, at least initially it's fairly simple.
Quote from: speedevil on 04/30/2018 08:47 pmQuote from: Joseph Peterson on 04/30/2018 07:19 pmI'm not understanding the logic of using total landing mass. <snip>We might not be looking at actual saving though. How much landed mass is one person-hour of Martian labor worth? We are only going to have so many workers on Mars. It could easily be worthwhile to send an extra tonne so human labor can do other things.I have not carefully read the above post, and need to, but as a more general point, what else would you be optimising for?Surely the goal is to get capabilities on Mars, and the lighter you can do this (if it does not make it too much more expensive), the more capabilities you can fit in 150 tons. (modulo density limits).To start with, at least, those initial capabilities would be improvements in landing safety, life support capacity and the capacity to manufacture propellant, and maintenance,but what you want after the next synod is an interesting question.'What you should optimise for' is a fun question for subsequent synods, at least initially it's fairly simple.I think one thing to optimise for especially early on is: "likely-to-work-out-of-the-box-first-time and continue-reliably-with-no-input-or-servicing and overall-minimal-manpower-input" So a battery that just works, period... despite its mass, is better than something else that requires development and tending! Especially as all activity is compromised by power problems. (However even lots of batteries eventually run out so they are only part of a solution)This as we all frequently repeat is very much one of EM's principals. (The BFS is not optimal mass for every mission... it is optimal amortization of design and manufacturing costs, to reduce individual mission cost, and so increase overall transport capability, (and hasten HSF to Mars) )
I am optimizing for the terrestrial market. That means low costs, specifically maintenance costs, are critical. I have to make the money to get to Ceres* somehow and there is free renewable electricity being curtailed. In some cases, people are even paying others to take electricity away. This could result in a carbon neutral fracking replacement at a lower price.My system will eventually be mass optimized.
Quote from: Joseph Peterson on 05/01/2018 03:12 amI am optimizing for the terrestrial market. That means low costs, specifically maintenance costs, are critical. I have to make the money to get to Ceres* somehow and there is free renewable electricity being curtailed. In some cases, people are even paying others to take electricity away. This could result in a carbon neutral fracking replacement at a lower price.My system will eventually be mass optimized. Ah!That makes sense.My above posts were in the context of near-term mass trades on how much you can pack onto BFS, trying to base on current commercially available hardware as a realistic floor.This makes costs to a first degree irrelevant. (for initial missions if they're under $1000/kg or so)
The ISRU pathfinder is not terribly efficient.
Some recent Mars ISRU power and production numbers, in Mars ISRU: State-of-the-Art and System Level ConsiderationsSee esp.: "Mars ISRU Pathfinder Demo Payload Options"Production: .48 kg/hr O2 & .12 kg/hr CH4 using 5.75 kW (ISRU power only, excluding other systems)Application example: Operating continuously without losses, that ISRU plant would fill one pair of SpaceX ITS tanks, using 41 TJ, over 228 Earth years.
Quote from: Robotbeat on 05/07/2018 04:41 amThe ISRU pathfinder is not terribly efficient.Which design changes might best improve efficiency, quantitatively?
Application example: Operating continuously without losses, that ISRU plant would fill one pair of SpaceX ITS tanks, using 41 TJ, over 228 Earth years.
Quote from: LMT on 05/07/2018 03:31 amSome recent Mars ISRU power and production numbers, in Mars ISRU: State-of-the-Art and System Level ConsiderationsSee esp.: "Mars ISRU Pathfinder Demo Payload Options"Production: .48 kg/hr O2 & .12 kg/hr CH4 using 5.75 kW (ISRU power only, excluding other systems)Application example: Operating continuously without losses, that ISRU plant would fill one pair of SpaceX ITS tanks, using 41 TJ, over 228 Earth years.What supports this as 'state-of-the-art' except for NASA's PowerPoint title?
No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.