area is from slide 8 of SpaceX’s FCC Starship Gen2 filing (says V2 in the table but the 2000kg mass is V3-scale)
wattage is Forethought’s guess (257 m² area x 1361 W/m² solar constant x 20% AM0 cell efficiency x 0.721 system derating = 50,400 W), not including 95% capacity factor and 8% annual degradation. It’s 2.5x what Musk claimed FWIW
Thanks for this guys, re Murphy’s law, it’s true we can just have system level failures (e.g. cooling unit, unseated connects, flywheel breaks and we lose pointing etc.) Then worst case we lose an entire satellite this way. It’s difficult to say quantitatively what failure rates may be so we bill this as a key uncertainty. ‘Space quals’ would mean every part would undergo extensive testing and many iterations for reliability (tests include e.g. vibe table, acoustic, pyroshock, vacuum testing and EMI/EMC) so a host of possible bugs would be worked out before the data centers get off the ground. Even so, certainly things do fail. One way of getting at this could be again via Starlink which has over 10k active satellites. It looks like failure rates for Starlink V2 have been around 1.1% (3 out of 5 years into their lifecycle) based on this catalog by McDowell. It’s my understand that SpaceX finds it more economical at their scale to actually skimp a bit on space quals and accept higher failure rates since Starlink’s satellites are relatively cheap. This would flip the other way if you have valuable chips on board. On the other hand there are more moving parts and more potential points of failure for ODCs than for Starlink sats so not clear to me which way this swings. You could say for example perhaps 1% of all ODC satellites fail or you could go higher or lower for the reasons I mention and then tac that on at a X% all-cost increase. True failure rates are a significant uncertainty overall.
re: back calculation, the wattage and scale is consistent with SpaceX/Musks V3 specs, we just move them to the dawn-dusk-SSO orbit instead of the typical orbit where they get higher power draw.
My impression (not the author):
area is from slide 8 of SpaceX’s FCC Starship Gen2 filing (says V2 in the table but the 2000kg mass is V3-scale)
wattage is Forethought’s guess (257 m² area x 1361 W/m² solar constant x 20% AM0 cell efficiency x 0.721 system derating = 50,400 W), not including 95% capacity factor and 8% annual degradation. It’s 2.5x what Musk claimed FWIW
not sure where array mass comes from
Thanks for this guys, re Murphy’s law, it’s true we can just have system level failures (e.g. cooling unit, unseated connects, flywheel breaks and we lose pointing etc.) Then worst case we lose an entire satellite this way. It’s difficult to say quantitatively what failure rates may be so we bill this as a key uncertainty. ‘Space quals’ would mean every part would undergo extensive testing and many iterations for reliability (tests include e.g. vibe table, acoustic, pyroshock, vacuum testing and EMI/EMC) so a host of possible bugs would be worked out before the data centers get off the ground. Even so, certainly things do fail. One way of getting at this could be again via Starlink which has over 10k active satellites. It looks like failure rates for Starlink V2 have been around 1.1% (3 out of 5 years into their lifecycle) based on this catalog by McDowell. It’s my understand that SpaceX finds it more economical at their scale to actually skimp a bit on space quals and accept higher failure rates since Starlink’s satellites are relatively cheap. This would flip the other way if you have valuable chips on board. On the other hand there are more moving parts and more potential points of failure for ODCs than for Starlink sats so not clear to me which way this swings. You could say for example perhaps 1% of all ODC satellites fail or you could go higher or lower for the reasons I mention and then tac that on at a X% all-cost increase. True failure rates are a significant uncertainty overall.
re: back calculation, the wattage and scale is consistent with SpaceX/Musks V3 specs, we just move them to the dawn-dusk-SSO orbit instead of the typical orbit where they get higher power draw.