Low budget space vehicle tracking

Len wrote:

[...] I do
think that $200 million could be enough for a space
transport system capable of carrying about one tonne
at a time. One just needs to be somewhat clever about
the design and the development plan.

It may be possible, but quite a few people have tried and failed. Leaving
that experience aside though, what's the mission? What is the market?

One tonne LEO uplift isn't enough for tourism, except for the most reckless
kind. Space manufacturing? One tonne is okay for some cargo flights, eg drug
manufacturing, or getting something small there in a hurry, but you have to
get the people and the factories there first.

Lots of small LEO comsats? That's one possible application, but it's only
one application, and afaict it's the only application. If it fails you are
SOL, and it looks a bit dicey to me. Some years ago Bill Gates was
reportedly interested in a 250-sat system but didn't pursue it, at least
partly because of lack of air- and orbital- space.

I don't think $200 million is anywhere near enough capital to build a system
that would launch 3-4 sats a day for $500,000 each, $250 per lb, either
(which you would need to put and keep 4,000 sats in orbit). As capital costs
are already eating up a fair chunk of your operating income, increasing the
capital investment isn't going to be pleasant. You need more market.




There are so many markets you can service with a 10 ton system that you
can't do with a 1 ton system. Might I suggest - perhaps a 10 ton payload
system for $500 million might be a better bet?

It's probably about as doable. The cost of a system does not scale linearly
with payload - much of the costs are the same whether you are building a 1
ton or a 10 ton system, and for others it's only about about twice as
expensive.

You might even get your capital back from that, but once someone does it
successfully and mokes some money there is going to be a lot of competition,
and the big money is going to be made on the systems developed in that part
of the curve. You could jump to there by a large initial investment, say
$4-10 billion, probably the higher end of that range because of the almost
inevitable entry into the market of various governments.




But I still reckon technically for a minimum capital system you need $450
million for a one ton system and $1 billion for a ten ton system
(immediately-reuseables or mass-produced part-expendables, for high launch
rates and low per lb cost, which is after all the point). At $250 per lb the
one ton system just about breaks even, while the ten ton system makes a
reasonable profit.

Up those figures to $700 million and $1.5 billion, thereby increasing the
launch rate, and at capacity and $250 per lb the one ton system is in profit
(if you can find the market), while the ten ton system is making serious hay
- you could half the price and still make loads-a-money!


--
Peter

Rocket science is easy - even rocket engineering isn't that hard - rocket
finance is the nightmare

David Summers wrote:

So, assuming that we can build an orbital vehicle, get a launch permit,
etc - what is the best (or cheapest) method of tracking the vehicle
after launch?

Well i have looked at this myself. A passive self tracking vehicle is a
option i like. Now gyros etc all have too much drift unless you buy
military spec. A simple alternative is startrackers, sun/moon trackers and
horizon detectors. (some of these can be combined). at initial launch you
can track the sun on fine days. But the drift on COTS-MEMS
gyros/accelerometers is OK for the short period to "clear" sky viewing.
There are many details I'm leaving out. But if you know the UTC time, the
relative postion on the moon, earth and sun and say even some planets/stars
you can accurately determin your location.

But you still need to transmit that back to earth..... I haven't figured out
that one yet.

Greg

bob wrote in
:

Well i have looked at this myself. A passive self tracking vehicle is
a option i like. Now gyros etc all have too much drift unless you buy
military spec. A simple alternative is startrackers, sun/moon trackers
and horizon detectors. (some of these can be combined). at initial
launch you can track the sun on fine days. But the drift on COTS-MEMS
gyros/accelerometers is OK for the short period to "clear" sky
viewing. There are many details I'm leaving out. But if you know the
UTC time, the relative postion on the moon, earth and sun and say even
some planets/stars you can accurately determin your location.

But you still need to transmit that back to earth..... I haven't
figured out that one yet.

Greg


How accurate is this tracking? I know its not down to a couple feet like
GPS, but is it down to a couple miles?

Tom

Tom Kent wrote:
bob wrote in
:

Well i have looked at this myself. A passive self tracking vehicle is
a option i like. Now gyros etc all have too much drift unless you buy
military spec. A simple alternative is startrackers, sun/moon trackers
and horizon detectors. (some of these can be combined). at initial
launch you can track the sun on fine days. But the drift on COTS-MEMS
gyros/accelerometers is OK for the short period to "clear" sky
viewing. There are many details I'm leaving out. But if you know the
UTC time, the relative postion on the moon, earth and sun and say even
some planets/stars you can accurately determin your location.

But you still need to transmit that back to earth..... I haven't
figured out that one yet.

Greg


How accurate is this tracking? I know its not down to a couple feet like
GPS, but is it down to a couple miles?

Accurate starmaps are trivial.
Sun/moon sensors are trivial to get to .1 degree (256*256 pinhole cameras).
This gives you a plane of reference. (that admittedly only works on the
dayside, but good enough for initial orientation.)

So, you know the plane of the earth-moon-sun system.
Now, you stare at the horizon, and watch as stars rise over it,
timing them accurately.

This gives you a very good idea of the orbit - but not the position
of the earth. This is where the time comes in.
Time to within a week gives you a very good idea of the axial tilt of the
earth.
Time to the minute tells you where under the orbital track the earth
is, to within 30Km.

In principle, it could be very accurate, but you end up either wanting to
include a hyper-accurate clock, or put a GPS on it to get the time.
And once you've got a GPS on it, this would probably be your
secondary means of position determining.

Ian Stirling wrote:
In principle, it could be very accurate, but you end up either wanting to
include a hyper-accurate clock, or put a GPS on it to get the time.
And once you've got a GPS on it, this would probably be your
secondary means of position determining.

Backup or redundancy is good. Give a easy way for sanity checks.

But seriously, how accurate does it need to be? We got to the moon without
GPS.

Greg