The discussion about safety has me wondering. Will commercial crew have some kind of flip maneuver or other visual inspection to see if the heatshield of the capsule is fit for reentry (i.e. that there hasn't been any micrometeorite damage to its heatshield during its stay at the ISS)?
Quote from: yg1968 on 09/10/2015 02:10 pmThe discussion about safety has me wondering. Will commercial crew have some kind of flip maneuver or other visual inspection to see if the heatshield of the capsule is fit for reentry (i.e. that there hasn't been any micrometeorite damage to its heatshield during its stay at the ISS)?The heat shields won't be visible, they're protected by the trunk/ SM so MMOD damage/ damage on ascent isn't a concern like it was for the orbiters who had an exposed TPS
Quote from: Robotbeat on 05/31/2015 01:33 pmThe MMOD thing for CC is very odd. Surely this must be an overly conservative estimate or ISS, Mir, Skylab, or the various Salyuts would've no doubt been punctured in their pressurized sections by now (considering they've been nearly permanently in orbit since the early 1970s). Even Shuttle didn't receive a fatal strike to its enormous heat shield from MMOD.models have been updated based on more data and a lot, LOT more debris. Recall ISS is now flying lower to mitigate risk of MMOD. Yes, the capsule heat shields are protected but they are going to be up there for 6 months with their butts into the debris wind so to speak for Node 2 forward. A lot can happen.
The MMOD thing for CC is very odd. Surely this must be an overly conservative estimate or ISS, Mir, Skylab, or the various Salyuts would've no doubt been punctured in their pressurized sections by now (considering they've been nearly permanently in orbit since the early 1970s). Even Shuttle didn't receive a fatal strike to its enormous heat shield from MMOD.
At the risk of going off topic, the ISS originally orbited around 390 km, dropped back as low as ~330 km, and then went up to ~440 km when the Shuttle retired. It has now sunk to just over 400 km. Is it trying to keep a constant drag/density to balance the MMOD risk with reboost fuel usage?
CST-100 looks OK with the SM protecting until reentry. Dragon could have cameras in the trunk to perform checks. Or a shield if no unpressurized cargo.
I will also note that the Russians, and before as the Soviets, have been keeping Soyuz on-station in LEO for up to six months at a time for, well, more than 30 years, going back to Salyut 6. They haven't lost any of them, not one of the dozens upon dozens, to TPS damage. And they have nothing more or less than Starliner or Dragon will have, a module covering the main TPS.None have ever been holed by MMOD to the extent they lost pressure or critical systems, either.
Shuttle was different because its TPS was always fully exposed to MMOD, and it had a far more fragile TPS than Dragon or Starliner will. The Shuttle-style TPS inspections will not be needful for the new commercial crew vehicles.
Quote from: the_other_Doug on 09/20/2015 03:31 amI will also note that the Russians, and before as the Soviets, have been keeping Soyuz on-station in LEO for up to six months at a time for, well, more than 30 years, going back to Salyut 6. They haven't lost any of them, not one of the dozens upon dozens, to TPS damage. And they have nothing more or less than Starliner or Dragon will have, a module covering the main TPS.None have ever been holed by MMOD to the extent they lost pressure or critical systems, either.My thougts as well. It is a concern of NASA but I don't understand where that concern comes from.
If I remember correctly the TPS inspections were introduced because of possible damage on start, not because of possible MMOD. It would cover MMOD as well though. While the SpaceShuttle heat shield would be exposed for a much shorter time it is much shorter and probably more sensitive.