X 37B

[ORAC]

Russian propagandists are agitated: frozen Russian assets will go to Ukraine to be used for the war with Russia.

The USSF-52 [Falcon Heavy] mission was contracted 5 years ago, we didn't know the payload back then - now today we find this is the X-37B spaceplane. Which previously launched on a Falcon 9 with RTLS booster recovery. So this is getting a much bigger yet…

The solicitation required 6,350kg to GTO, which is heavier than previous X-37B launches, so maybe it's got a bigger service module for high orbit injection?

This will be the first time a spaceplane returns from such a high orbit, it'll be a real test of the heat shield….

I expect it won't be LEO, it's possible that they have a Mid altitude orbit that is going to intentionally cross van allen belts for the payload…

https://t.co/eRJEEOWGaW

ARLINGTON, Va. (AFNS) -- The Department of the Air Force Rapid Capabilities Office, in partnership with the United States Space Force, is scheduled to launch the seventh mission of the X-37B Orbital Test Vehicle Dec. 7, 2023 from Kennedy Space Center, Florida.
​​​​​​​
The X-37B Mission 7 will launch on a SpaceX Falcon Heavy rocket for the first time, designated USSF-52, with a wide range of test and experimentation objectives. These tests include operating the reusable spaceplane in new orbital regimes, experimenting with future space domain awareness technologies, and investigating the radiation effects on materials provided by NASA…..

[Marly Lite]

Originally Posted by ORAC

This will be the first time a spaceplane returns from such a high orbit, it'll be a real test of the heat shield….

Hmm. Why would a return from a higher orbit be a greater test of the heatshield?

[HOVIS]

Originally Posted by Marly Lite

Hmm. Why would a return from a higher orbit be a greater test of the heatshield?

I think, though I could be wrong, higher orbits require higher velocities. Ergo, returning from said orbit will entail a higher speed of re entry.
I think.
Edit, nope I'm completely wrong... It's opposite.

https://seedscientific.com/how-fast-...%20per%20hour.

[tartare]

Very interesting piece here:
https://www.thedrive.com/the-war-zon...y-rockets-help

Note the reference to xGEO orbits, Cislunar and beyond.
Have seen the odd reference prior to this hinting that the US is already operating beyond GEO - fascinating area...

[pasta]

Originally Posted by HOVIS

I think, though I could be wrong, higher orbits require higher velocities. Ergo, returning from said orbit will entail a higher speed of re entry.
I think.
Edit, nope I'm completely wrong... It's opposite.

https://seedscientific.com/how-fast-...%20per%20hour.

Orbital mechanics is all about exchanging kinetic and gravitational potential energy - it's the total energy that counts. So you may be going slowly in a high orbit, but you have lots of potential energy. When you deorbit, that potential energy is converted to kinetic energy, so you're going much faster by the time you hit the atmosphere. It's a bit like aerobatics; imagine drifting over the top of a loop, but only pulling out 22,000 miles lower.

[Marly Lite]

All I know is it makes me brain hurt. Higher orbit is slower. You reduce speed to fall to earth but pick up potential energy on the way and end up faster (!).

My bet is that re-entry speed is roughly the same for all re-entries otherwise you’d not be able to re enter vice remaining in orbit. Err if that makes sense.

Happy to be corrected.

[pasta]

Definitely not the same. I appreciate Wikipedia should be used with caution, but from their page on Free Return Trajectory:
"The atmospheric entry interface velocity upon return from the Moon is approximately 36,500 ft/s (11.1 km/s; 40,100 km/h; 24,900 mph)[4] whereas the more common spacecraft return velocity from low Earth orbit (LEO) is approximately 7.8 km/s (28,000 km/h; 17,000 mph)."

[ORAC]

https://science.howstuffworks.com/satellite6.htm

https://physics.stackexchange.com/qu...-transfer-work

[B Fraser]

The Apollo capsules were able to "fly" i.e. generate lift upon initial contact with the atmosphere and climb to reduce speed before making a second re-entry. The fastest Shuttle re-entry was at Mach 26, much faster than the normal Mach 25. IIRC, it was the Hubble servicing mission which descended from a higher than normal orbit. That crew got a special Mach 26 patch of course, some things never change. ;-)

[B Fraser]

Originally Posted by Marly Lite

Hmm. Why would a return from a higher orbit be a greater test of the heatshield?

Heating is proportional to the square of the Mach number. Concorde was Mach 2 and the materials could cope. The US SST was designed for Mach 3 but was cancelled on "environmental" grounds. I think they really meant that the materials could not cope with the operating environment.