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What We Know The X-37B Was Up To During Its 780 Days In Space

50 points by tomohawk 7y ago

walrus01 7y ago
> We also know that the previous OTV-4 mission involved the test of Aerojet Rocketdyne's XR-5A Hall-effect thruster, a type of electric propulsion system that offers greater efficiency for satellites and spacecraft maneuvering in orbit. This was officially in support of the Advanced Extremely High Frequency (AEHF) satellite program, but the technology could be valuable for other space-based systems, as you can read about more here. In August 2018, during OTV-5, the X-37B modified its orbit using an unspecified onboard propulsion system. If I had to guess, they're experimenting with novel, relatively untested ion and hall effect type thruster systems that have very low thrust in newtons or kilonewtons, but very high specific impulse. Before putting things like that on billion dollar geostationary military communications satellites (or LEO/MEO radar imaging satellites, or billion dollar NRO satellites), they'd want to qualify them in space. Maybe the spaceplane design that can return a used thruster was a happy coincidence between two different programs, allowing them to do a destructive teardown on a thruster that's been used for two years, to better determine its possible failure modes. Things in the same general category as this, but with new and radical designs. https://en.wikipedia.org/wiki/Ion_thruster https://en.wikipedia.org/wiki/Ion_thruster Extremely high specific impulse thrusters can result in satellites with much longer operating lives, for the same weight (in kilograms) of pressurized fuel tank storage, and same volume. Either from LEO things that can accelerate themselves periodically to maintain orbit, counteracting the effects of drag, or for geostationary satellites, keeping position longer than a nominal 12-15 year life span.
- jcims 7y ago
  I bet somewhere on this planet there is now emprical evidence to the efficacy or lack thereof of emdrive and/or other reactionless thruster designs.
- xref 7y ago
  Since you mentioned specific impulse a couple times this may help casual browsers: https://en.m.wikipedia.org/wiki/Specific_impulse https://en.m.wikipedia.org/wiki/Specific_impulse > A propulsion system with a higher specific impulse uses the mass of the propellant more efficiently. In the case of a rocket or other vehicle governed by the Tsiolkovsky rocket equation, less propellant needed for a given delta-v.[1][3] In rockets, this means the vehicle the engine is attached to can more efficiently gain altitude and velocity. This effectiveness is less important in jet aircraft that are lifted by aerodynamic forces, use outside air for combustion, and carry payloads that are much heavier than the propellant.
rdtwo 7y ago
It has to be an extremely high value mission because it means they were unable to use the craft for any additional launches during the 780 days.
- jcims 7y ago
  Good point. I wonder if this partially challenges the theory that the X-37B has satellite recovery in its repertoire.
  - manicdee 7y ago
    All this mission shows is that there was something the US Air Force wanted to do that warranted two years of flight time ahead of any other project, even recovering or stealing a satellite.
    - Swenrekcah 7y ago
      Have people stolen satellites from orbit?
- Rebelgecko 7y ago
  There are two of them (although so far only one has been up at a time)
doe88 7y ago
It would be funny if its sole purpose was just trolling competing defense agencies around the world into endlessly speculating about its capabilities when in fact it would just turn around and around and around.

50 points by tomohawk 7y ago

> We also know that the previous OTV-4 mission involved the test of Aerojet Rocketdyne's XR-5A Hall-effect thruster, a type of electric propulsion system that offers greater efficiency for satellites and spacecraft maneuvering in orbit. This was officially in support of the Advanced Extremely High Frequency (AEHF) satellite program, but the technology could be valuable for other space-based systems, as you can read about more here. In August 2018, during OTV-5, the X-37B modified its orbit using an unspecified onboard propulsion system. If I had to guess, they're experimenting with novel, relatively untested ion and hall effect type thruster systems that have very low thrust in newtons or kilonewtons, but very high specific impulse. Before putting things like that on billion dollar geostationary military communications satellites (or LEO/MEO radar imaging satellites, or billion dollar NRO satellites), they'd want to qualify them in space. Maybe the spaceplane design that can return a used thruster was a happy coincidence between two different programs, allowing them to do a destructive teardown on a thruster that's been used for two years, to better determine its possible failure modes. Things in the same general category as this, but with new and radical designs. https://en.wikipedia.org/wiki/Ion_thruster https://en.wikipedia.org/wiki/Ion_thruster Extremely high specific impulse thrusters can result in satellites with much longer operating lives, for the same weight (in kilograms) of pressurized fuel tank storage, and same volume. Either from LEO things that can accelerate themselves periodically to maintain orbit, counteracting the effects of drag, or for geostationary satellites, keeping position longer than a nominal 12-15 year life span.

jcims 7y ago
I bet somewhere on this planet there is now emprical evidence to the efficacy or lack thereof of emdrive and/or other reactionless thruster designs.
xref 7y ago
Since you mentioned specific impulse a couple times this may help casual browsers: https://en.m.wikipedia.org/wiki/Specific_impulse https://en.m.wikipedia.org/wiki/Specific_impulse > A propulsion system with a higher specific impulse uses the mass of the propellant more efficiently. In the case of a rocket or other vehicle governed by the Tsiolkovsky rocket equation, less propellant needed for a given delta-v.[1][3] In rockets, this means the vehicle the engine is attached to can more efficiently gain altitude and velocity. This effectiveness is less important in jet aircraft that are lifted by aerodynamic forces, use outside air for combustion, and carry payloads that are much heavier than the propellant.

rdtwo 7y ago

It has to be an extremely high value mission because it means they were unable to use the craft for any additional launches during the 780 days.

jcims 7y ago
Good point. I wonder if this partially challenges the theory that the X-37B has satellite recovery in its repertoire.
- manicdee 7y ago
  All this mission shows is that there was something the US Air Force wanted to do that warranted two years of flight time ahead of any other project, even recovering or stealing a satellite.
  - Swenrekcah 7y ago
    Have people stolen satellites from orbit?
Rebelgecko 7y ago
There are two of them (although so far only one has been up at a time)

doe88 7y ago

It would be funny if its sole purpose was just trolling competing defense agencies around the world into endlessly speculating about its capabilities when in fact it would just turn around and around and around.