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GDB wrote:Congrats to Rocketlab for their first deep space mission launch.
Avatar2go wrote:The NASA CAPSTONE mission went into safe mode at the end of the TCM 3 manuever, one of several which insert it into the desired lunar NRHO orbit. Teams are in communication with the satellite and are investigating the source of the issue.
https://advancedspace.com/news/
https://youtu.be/FFkKaBxQ214
GDB wrote:
Scott Manley mentioned in his latest update how enhanced recent solar activity has affected a satellite in geostationary orbit, could it have done to same to Capstone?
Francoflier wrote:That's puzzling.
What do these cubesats use for station keeping?
Do they have electric thusters or chemical ones?
Hopefully they are able to recover it and proceed with the mission normally.
Avatar2go wrote:They mentioned that thrust was an option if they invade their margins, but they have to warm up the propellant to do that, which eats into their power budget. So my guess is they try to dampen out the tumble with the wheels first, than maybe fall back on the thrusters as a last resort.
mxaxai wrote:Avatar2go wrote:They mentioned that thrust was an option if they invade their margins, but they have to warm up the propellant to do that, which eats into their power budget. So my guess is they try to dampen out the tumble with the wheels first, than maybe fall back on the thrusters as a last resort.
Detumbling with wheels doesn't work. Reaction wheels transfer momentum within the spacecraft but the overall angular momentum remains constant. You can, of course, try to reduce or stop the spacecraft rotation with wheels but then you'll bring the wheels closer to saturation. Desaturating the wheels requires momentum dumping via external torques, in this case thrusters. So the anomaly is going to eat into their fuel reserves either way.
The good thing is, external disturbing torques on the chosen orbit are tiny compared to typical LEO satellites. The wheels should take a long time to saturate (in regular operations), so that the fuel amount required for attitude maintenance is small.
I suspect that one of the thrusters malfunctioned, providing either more or less thrust than expected. They need to properly identify and fix that issue first before returning to normal operations, or else there's considerable risk it might happen again.
Francoflier wrote:Thanks for the update.
I wonder if there's a risk that a possible thruster failure could have caused the tumble in the first and could therefore cause more trouble during the de-tumbling burn.
Or are those different thrusters?
Avatar2go wrote:Here is a direct link to the NASA information:
https://www.nasa.gov/feature/ames/capst ... o-the-moon
Avatar2go wrote:CAPSTONE is now in NRHO, having successfully completed the final burn sequence.
http://www.nasa.gov/press-release/capst ... n-missions
Avatar2go wrote:An update from NASA/JPL on the Lunar Flashlight cubesat mission, launched in December.
The propulsion package utilized a "green" monopropellant, instead of hydrazine which is highly toxic. It appears that debris from 3D printing, may have partially obstructed the propellent lines.
The team was able to increase thrust by pressurizing the propellant above safe levels, and focusing on just one thruster, but it wasn't enough improvement to salvage the mission.
Thus the team cannot get enough propellant flow to the thruster, to sufficiently alter the vehicle orbit or trajectory, before the window closes for a useful orbit. So it will return from it's flyby of the Moon, do a close flyby of the Earth, and then head out to space in a heliocentric orbit.
The cubesat is otherwise fully functional, including the instrument package, so the team will look for other opportunities to test & utilize the systems.
https://www.jpl.nasa.gov/news/nasa-call ... -successes
ReverseFlow wrote:You would have thought that they would perform a free flow test through the pipes before installing them.
And cleaning/flushing them beforehand.
Especially if it is a 'new' 3D printed part.
Avatar2go wrote:Yeah, I think it's best guess speculation, as to the most likely cause. Something has clogged the fuel passageways or the valves. I'm sure they did flush and clean. But maybe particles were dislodged during the launch vibration. Who knows.