David,
The existing standards (there are many at this point) for CubeSats allow up
to 6 kg of mass in a 3U. I am not aware of any that dense which have
launched but wouldn't discount it. In the small sat world density has
become free and we are taking advantage of it. I wouldn't put the upper
limit at 4 kg without detailed data. Don't forget the mass of the dispenser
as well. Speaking of which, there are many different types, all of which
add some extra features to the CubeSat standard. My impression is that the
standard is currently broken because of how much extra volume satellite
makes can get depending on which dispenser is used. However, if you are
doing dedicated CubeSat launch there is no longer any reason to 'think
inside the box' and you may be able to come up with a better interface
which is backward compatible with CubeSat rails. No one is terribly happy
with how much they rattle around in the dispensers. And, since volume is
the most precious resource for the smallsat designer, they may be happy if
you can accommodate more volume as well.
3U satellites have been a workhorse of the past decade, but as satellite
constellations have become better capitalized and the lower hanging fruit
of capabilities are getting picked off. I foresee small satellites moving
up to larger sizes, 6U or larger. Like rockets, satellites also greatly
increase capability with scale. I believe an examination of in-development
CubeSat projects will show more investment in 6U and larger sats than 3U
and smaller.
I think the orbit is useful and no one is going to be launching small-sats
lower than 20 degrees and higher orbits take too long to decay. At those
inclinations, magnetorquers are ineffective because the B field is in
basically the same direction during the entire orbit. A program I worked on
almost took advantage of a launch opportunity to a near-equatorial orbit
but the magnetic fields would not have allowed us to have attitude control.
If your cost is $95,000 per launch you will have a healthy profit margin. I
don't see much of a point in selling that low when rideshare prices are
much higher.
Thanks,
Lars Osborne
On Fri, Mar 8, 2019 at 8:56 AM David Summers <dvidsum@xxxxxxxxx> wrote:
A question for all you guys out there building satellites:
Our rocket vehicle design has finally closed, and we are trying to make
the corner from mostly amateur to mostly professional. We're talking with
the FAA about our launch license, and plan to start orbital flights roughly
a year from now if all goes well.
I want to make sure that we are making a vehicle that is useful, though.
There are significant reasons to make a smaller vehicle with our specific
technology (minimum gauge issues are virtually non-existent), but I don't
want to completely eliminate the market!
Would a launch of a 4 kg, 3U satellite to 600 km between 20 degrees and
sun synchronous be a useful capability? Price is expected to be $95,000.
What would make or break this vehicle? (Obviously, until we fly we have
nothing, etc.)
Fun facts from my market research: There were 1058 3U micro-satellites
launched as of the beginning of the year - almost half of all satellites!
Thanks!
-David Summers