From: Eugene Leitl (Eugene.Leitl@lrz.uni-muenchen.de)
Date: Fri Mar 23 2001 - 07:24:32 MST
On Thu, 22 Mar 2001, Michael Lorrey wrote:
> Okay, here is what we really need bad to make micro-sats and microprobes
> feasible: an SSPS: Solar System Positioning System so that space probes
SPS, rather.
Yeah, it's overdue. Actually, since matter tends to aggregate in
recursive/hierarchical arrangements, you need to retain several
positioning system (me-relative (ultrasonics and solid state camera),
Earth-relative (GPS), Sun-relative (SPS), Galaxy-relative (er, UPS, I
guess)), and use coordinate transforms from one another.
Actually, with IPv6 you can combine the logical and physical addresses,
e.g. by shifting WGS 84 latitude/longitude/altitude to 32 bit each,
reserving the leading 32 bit of an IPv6 address for future purposes.
If I get my math right, that's about 1 cm resolution at Earth surface (so
it's not enough for nano, blame the IPv6 designers. If one thinks of it,
there are lots more of addressable objects in the local galaxy that
can be described by 32 bit either. Clearly we shouldn't have settled
with mere 128 bit but would have gone straight to 256 bits).
> can easily figure out their position at all times and run their
> navigation routines off that data rather than having to deal with star
> sighting, wasting fuel and/or power on spinning the spacecraft around
> trying to get a reading. I mean, what are we, in the 17th century or
I don't know, wouldn't a few low-res solid state cameras would give you
plenty on orientation relatively to stars, and more than a bit of
navigation when used with planets, if equipped with a good clock? Given
that we now have 3-axis accelerometers with better than 1e-6 g resoltion,
there is probably not all that much requirements for a solar positioning
system (SPS). Plus, with isotropic radiators you'll need a lot of wattage
to cover the terrain, unless you stud the space evenly with nodes each
covering a space of a lightsecond, or so.
What probes really need are built-in survival reflexes. A little orrery in
their digital brain, which plots their future course, and some dumb AI
which knows "it is probably not a good idea to fly into solid objects at
Mach 19", "account for estimated future burns in respect to fuel use",
etc. This will make them refuse obviously suicidal instructions, unless
explicitly overriden.
> what? Why are we still using ancient navigation techniques? There should
Because we're not a spacefaring species, and only poke our noses a little
outside of the atmosphere.
> be an SSPS satellite in each of the three Earth-Sol Lagrange points.
> This would be a good investment of public money, and its even
> constitutional for libertarians: space is a 'channel of commerce', or a
> 'navigable waterway', so the gummint is responsible for maintaining
> their navigability.
>
> I am currently designing a 180x200x200 millimeter probe bus that will
> use GaAs/GaAnt solar cells fed focused sunlight from 2 inflated 2 meter
> dia. mirrors (theoretical output: 2.99 kW) to power the electric
> thruster of choice. Fuel tank is 150mm dia spherical. Pick your own wall
Neat.
Maybe you can help me:
When thinking about a cloud of coke-can sized satellites for digital pulse
radio and wireless networking (no stabilization, realtime beamforming
using active antennas), one has the following problems: the systems need
to be gossamer, yet able to survival rough (shrapnel-size) deployments.
Initially I thought about using vanilla rectangular monocrystalline Si
cells on springed hinges (jack-in-the-box type panel unfolding). However,
these things are rather brittle. So I thought freezing the sat into a
sublimating solid cube (water, or dry ice), which will vanish within
few hours under orbital conditions. However, this will eliminate the
advantages due to higher weight. I then thought of a photolythic foam
envelope, then of a pyrotechnical envelope (shrapnel deployment scenari),
which doubles as protection and propulsion.
Any ideas in that area?
> thickness, pressure, contents. Maneuvering thrusters will be solid state
> pulse ignition chemical micro-thrusters off-the-shelf. Navigation will
> depend on SSPS to be in place.
>
> You decide what payload you want and how quickly you want it wherever
> you are going. I figure with this size bus you could deliver a laptop
> sized replicator facility to any NEA within a few months of launch.
Officer, arrest that man. He's obviously dangerous.
This archive was generated by hypermail 2.1.5 : Sat Nov 02 2002 - 08:06:37 MST