Comment by binarycoffee
8 years ago
True, interesting idea.
[Long edit]
Thinking further about this idea, I realize this may even mitigate the catch 22 problem of very low orbits (<180km): the lower the orbit, the larger the drag and the required thrust power, meaning the solar arrays must be bigger, which in turn further increases the drag... Calculations suggests that with current solar array and thruster technology, flying lower than 150km with this concept is impossible.
But with an elliptic orbit, energy from the solar arrays can be stored on the low-drag portion of the orbit too and used during the perigee dip, thus decreasing the requirements in terms of solar arrays area.
I'm now imagining a craft that folds up its solar panels before dipping into the atmosphere to gather fuel / accelerate. I'm sure I've built that in KSP, :p.
That is not particulary far-fetched either: the ISS already reorients its solar panels when not illuminated by the sun. They call it the "night glider mode" [1].
[1] https://en.wikipedia.org/wiki/Night_Glider_mode
Night Glider sounds vaguely like some 80s TV show. I do hope everyone on board is required to wear non-functional sunglasses during night glide.
> The implementation of drag-reducing flight modes of the space station resulted in saving about 1,000 kg of orbital-maintenance propellant per year.
Here's an example where the authors propose doing this for planetary gravity assists, e.g., instead of using Venus for a normal gravity assist, dig into its atmosphere. Everything would need to be folded up first.
"Hypersonic Interplanetary Flight: Aero Gravity Assist"
Al Bowers & Dan Banks, 2006
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/200900...
Discussed in a podcast here: https://theorbitalmechanics.com/show-notes/al-bowers