Speculations on Future Micro/Nanosatellites?

We've seen spacecraft for many uses shrink considerably, to the point
where 1-kg CubeSats can do useful science. The military, through the
TacSat and ORS programs, is flying relatively small (400 kg) craft
with multispectral imaging and other high-tech capabilities that
normally need spacecraft weighing tons. Computers on chips, carbon
nanotubes, etc. have already brought dramatic breakthroughs. What's
in the future, 10-30 years down the road? Cooperating swarms, ever-
tinier spacecraft, deep-space micro-constellations, or things we
haven't even put on drawing boards yet?

Matt Bille
(working on a paper for the next Conference on Small Satellites)

On Mar 17, 2:13 am, Matt wrote:
What's
in the future, 10-30 years down the road? Cooperating swarms, ever-
tinier spacecraft, deep-space micro-constellations, or things we
haven't even put on drawing boards yet?

While I am sure there will some very interesting things, other things
have very real physical limitations to size. For example telescopes
are diffraction limited and light limited, you can only go so small
before you can't see anything even with interferometry. There are
similar limitations on gamma ray and x ray detectors, you need a
certain mass of detector to have a good chance of detecting things.
Same goes for antennas and communications.

Also there are propulsion limits to useful lifetimes as well. Smaller
makes it harder to have a decent mass budget for station keeping--
however smaller does make some photon based station keeping easier up
to a limit. Also evaporation cooling (ie He for thermal cameras) has a
minimum size before mission life time becomes an issue. Solar cells
must be big enough and hence mass etc...

Areas where cube sats could really be interesting? Well its not a sat,
but if you could fit say 3 or 4 rovers in the mass budget of one of
the current mars rovers, you could get a lot more ground covered for
your buck.

The thing is once you pay for a launch, 100kg is not really more
expensive than 1kg (so many costs don't scale with mass, but launch
count--or even "interface count"). So you might as well use the space
and mass you have.

Greg

Matt wrote:
We've seen spacecraft for many uses shrink considerably, to the point
where 1-kg CubeSats can do useful science. The military, through the
TacSat and ORS programs, is flying relatively small (400 kg) craft
with multispectral imaging and other high-tech capabilities that
normally need spacecraft weighing tons. Computers on chips, carbon
nanotubes, etc. have already brought dramatic breakthroughs. What's
in the future, 10-30 years down the road? Cooperating swarms, ever-
tinier spacecraft, deep-space micro-constellations, or things we
haven't even put on drawing boards yet?


I think sats below some size - say 30 cm for detectability reasons - may
actually be banned, in time. Too much risk of collision, if not
destructive cascade.

For better coverage etc, maybe sats should be put into layers, and only
use circular, not elliptical orbits.

Perhaps military sats could have 100 miles to 130 miles and 550 miles to
600 miles - earth observation sats 130 miles to 160 miles -
human-carrying sats, space stations etc have 200 miles to 350 miles -
and small sats 95-100 miles, 160-170 miles and 540 to 550 miles - and
so on. A bit like frequency allocations.



Perhaps orbital inclination could also be a criterion, with eg polar
orbits only allowed to cross the equator within some narrow height band,
though they could perhaps be elliptical with the long end in the polar
direction


Transiting these layers at a reasonable rate would obviously be allowed,
both on the way up and down. Transiting at unreasonably slow rates would
be cause for action of some kind - censure, legal, military or whatever
else was suitable.



Matt Bille
(working on a paper for the next Conference on Small Satellites)


This is only a half-baked idea; maybe you cold bake it some more?




-- Peter Fairbrother

Great comments so far.

Peter, you have to start the baking process somewhere I've worked
on microsat programs, expecially for military applications, before,
but the time horizon is always a few years (or a few budget cycles).
So I'm starting by casting a broad net for thoughts, suggestions, and
references on what may come.

Greg, absolutely right, you do not always want to go smaller just for
the sake of being smaller: depends on mission, launch, and all kinds
of other things. There is interesting work being done (unfortunately
the Air Force TechSat 21 was canceled) on using large numbers of small
satellites in virtual apertures for interferometry and other things
that currently need a single large antenna or mirror. Some science
missions could take the THEMIS constellation idea generations further
and provide readings from many points (There was a 100-nanosat science
contellation proposed by someone, I'm still trying to find the
reference.)

Mini-rovers, crawlers, or hoppers are interesting too.



Matt

Perhaps military sats could have 100 miles to 130 miles and 550 miles to
600 miles - earth observation sats 130 miles to 160 miles -
human-carrying sats, space stations etc have 200 miles to 350 miles -
and small sats 95-100 miles, 160-170 miles and 540 to 550 miles - and
so on. A bit like frequency allocations.


I love the idea of functional orbital allocation!! I wonder what is
the best place for a "human orbital zone"? in terms of human health
(cosmic rays/magnetosphere or space junk impact), stability of
satellite orbit and cost of transport to and from satellite. Perhaps
raising the international space station will give us some data? Also
these zones would give clear priority to any effort to clear space
junk and or tracking.

Richard Jay