Answer 2:
I was unable to find any information about
magnetic or electrical slingshots for spacecraft,
but that does not mean such methods are
impossible. Also, one can certainly imagine a
mechanism like that used to launch and catch
fighter jets on aircraft carriers, but on a larger
scale. I cannot comment on the viability of such a
setup, but I can imagine one.
Of the information I did find, a
gravity assist ("gravitational slingshot")
sounds most similar to the provided description. A
gravity assist cannot be used to start a
spacecraft, but can be a fuel-conserving way to
change direction, speed up (relative to
another object), or slow down (see
this site for some math ).
Science fiction provides plenty of examples of
non-rocket launching systems, such as
launch/orbital loops, linear accelerators
(essentially a rail gun), space elevators, and so
on.
I'll go into a little more detail on a few of
the more well-developed possibilities.
Solar sails are one option which could
work for both leaving one point and stopping at
another. They essentially work by reflecting
light , each photon imparting a small change
in momentum. Depending on the direction in
which the craft is moving and the direction of
that change in momentum, the craft will either
speed up or slow down. (Two related concepts are the
magnetic sail, mostly for slowing down, and
coupling a solar sail with a fixed laser. In the
latter case, the photons would come not from a
star, but from a fixed laser installation.
It is certainly conceivable that such a setup
could be used to send off and slow down a
spacecraft. I don't think the energy of one craft
could easily be captured and used to drive
subsequent launches though.)
Other options to slow down are aerobraking
and aerocapture , which essentially use
friction with an atmosphere at the
destination (obviously limiting application to
destinations that have atmospheres).
Many concepts are actually under development
today. However, technological possibility does
not indicate economic feasibility. Even those
which prove economical may have limitations on the
potential applications as well. A linear
accelerator might prove viable for launching
payloads, but only from bodies without atmospheres
(because the same atmospheric friction which
enables aerobraking could also burn up the craft
on launch) and for non-living cargo
(because too much acceleration would kill anything
on board). Regardless, there are myriad intriguing
possibilities that can be explored and which may
ultimately come into existence.
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