In this video overview of NASA's proposed EM-1 mission, the solar panels on the Orion spacecraft are initially shown extending perpendicular to the spacecraft (at around 3:46).
Shortly after that, as the perigee raise maneuver begins, the panels are shown dramatically swept back (at 3:52):
At 5:24 in the video, while flying by the moon, the panels once again extend perpendicularly, but are rotated to face the sun.
At 6:18, during a propulsive maneuver using the service module engines, the panels are now swept far forward.
What's going on here? Why do the panels sweep both forward and back?
Obviously the sweep isn't for aerodynamic purposes.
The only explanation that makes any sense to me is:
- The forward sweep helps get the panels out of the way of the expanding exhaust plume from the service module's engine (an AJ-10-190 repurposed from space shuttle OMS);
- Having paid the weight and complexity cost of a forward sweep mechanism, sweeping backward using the same mechanism reduces mechanical stress on the mountings during ICPS burns.
However, the RL10 engine on the ICPS develops about 110kN; against the 40 tons of stage and spacecraft at the end of the burn, this is only about 1/3g acceleration. It seems wrong that the extended solar panels wouldn't be able to support their own weight in Earth's gravity, if only for convenience in assembly of the spacecraft.