NASA again delays Boeing Starliner's return home
phys.org
phys.org
Weird they just didn't plan for this incredible opportunity from the start but sounds like they are just taking extra time as an opportunity not because they need to evaluate any safety issues (at least per Boeing).
This is not a new new delay. This is the same delay they announced on the 14th.
On the other hand, if the leaks are at the manifold then starliner might become an ISS module indeed, but taking up an airlock is bad news nonetheless so they would still have to find a way to jettison it.
Every single person at Boeing should be full of shame at this entire process. The thing is an utter joke to everyone.
If Crew Dragon needs to be launched to bring back the Starliner's passengers, that should be the final nail in Starliner's coffin.
I'm seriously shocked that NASA allowed themselves to be bullied by Boeing to allow this thing to have been launched at all.
I'm gonna go with Hanlon's razor here. The Starliner team seems to have enough trouble just getting a single Starliner to the ISS without issues, I can't imagine they're capable of devising a malicious plan to interfere with a competitor.
I know that's probably a joke, but that would be incredible bad for NASA. There is already strong competition for access to docking ports on the ISS. Losing one would badly complicated logistics on the station.
Consider Apollo - https://en.wikipedia.org/wiki/Apollo_command_and_service_mod...
> The command module attitude control system consisted of twelve 93-pound-force (410 N) attitude control thrusters, ten of which were located in the aft compartment, plus two in the forward compartment. These were supplied by four tanks storing 270 pounds (120 kg) of monomethylhydrazine fuel and nitrogen tetroxide oxidizer, and pressurized by 1.1 pounds (0.50 kg) of helium stored at 4,150 pounds per square inch (28.6 MPa) in two tanks.
https://www.uky.edu/~garose/helium#:~:text=Helium%20is%20use....
If the pressure in the tank drops, the propellant would turn into gas which would effectively be lost and potentially dangerous (by allowing flames to go the wrong way).
As your link points out, helium is nice because it is inert and remains a gas even at liquid hydrogen temperatures.
IANA rocket scientist, but this doesn't ring true to me. Vaporization of LH2 is related to the partial pressure of Hydrogen, not the absolute pressure of the gaseous phase. You're going to lose ≈PV/RT of hydrogen molecules to the gas phase regardless (P being the vapor pressure of Hydrogen at the tank's temperature and V the volume of the tank).
You still need the absolute pressure for structural stability. He has ≈twice the molar mass of H2, so H2 is better for the dry mass in the rocket equation anyway: what is left in the tank isn't wasted, but used for rigidity.
You just need Helium because it won't have phase transitions: it's always a gas so it is easier to regulate pressure.