$5M Moon Rock Stolen From Malta Museum

In article ,
Vincent Cate wrote:
However, the tether deployment, spin-up, and control are basically research
projects, whereas rocket stages are fairly well understood.

On the other hand there is not so much room for improvement in rockets.

Actually a debatable point, but one wouldn't undertake rocket R&D in a
context like this. (The whole point of the rocket approach would be to
reduce risk and shorten the time before revenue starts flowing, by using
at least an *approach*, if not actual hardware, that is reasonably proven.)

You're right, the results probably would be better, but it's a
longer-term project with higher risk.

From a venture capital standpoint, a system that had a bit more risk
in the R&D but then lower operating costs and produced 100 times as
much product seems better...

Maybe, and maybe not. Venture capital tends to have limited planning
horizons, and to weight risks heavily. This is already a somewhat iffy
venture, with technical risk (a lot of new hardware to develop), political
risk (nobody knows how the government would react), and market risk (will
the stuff *sell*, and how quickly?). That's a bad combination; VCs would
prefer to see one or two of those categories, not all three. Anything
that reduces any of those risks will be attractive; anything that
increases any of them will be very much Not Wanted.

The tether would be very interesting as a *second generation* system,
after a minimum-innovation rocket system paves the way politically and
proves that there is a lucrative market there. In fact, for the initial
system, you might want to forget the new design and pay the Russians to
revive the Luna sample-return system, despite the need for a Proton launch
and the very small return payload.

If a company like spacex or spacedev
were developing a tether system, I don't think it would really take
too long...

The control needed for precise operations in low orbit around an irregular
Moon strikes me as a non-trivial issue. This isn't just a simple rotating
tether, it's a highly dynamic variable-length rotating tether... and the
dynamics are the biggest question mark in such systems already.

Rad-hard electronics and solar arrays are very hard on the budget (and on
the schedule, because of availability problems).

Ouch. I can't buy an off-the-shelf rad-hard module that does
my computation, guidance, and communications?

Not as such, no. You can buy some, perhaps all, of the necessary pieces
to put one together yourself. But on closer inspection, those pieces
typically are not really "off the shelf": the first thing you get to do
is to negotiate a price (high) and a delivery time (not soon), because
they don't keep an inventory of the things.

Also, there's rad-hard and there's rad-hard. Electronic gear that can
take modest amounts of radiation is not hard to find. But a slow passage
through the inner Van Allen belt is a whole new order of magnitude. That
gets you into territory populated -- rather thinly -- by cost-is-no-object
hardware designed for fighting nuclear wars.

(Which brings in the ugly topic of arms control... Rad-hard electronics
is somewhat sensitive. Ultra-rad-hard stuff is very much so, I believe,
given its traditional primary application.)

Do ion drives tolerate radiation ok?

The thrusters themselves generally aren't bothered, but there are
typically plenty of semiconductors in the power-processing electronics box
right behind the thrusters. (Ion thrusters need multiple well-controlled
voltages, with current limiting and some other precautions, so the power
supply is not a simple piece of hardware.)

The difference in initial launch mass between an all-chemical-rocket mission
and a tether/ion/regolith-thruster mission, for a given payload returned,
seems to be something like a factor of 100 to 1000. As long as launch
costs are high, this seems like an overwhelming advantage.

Only when operations costs become the dominant problem. The problems of
first-generation systems, at least, will be dominated by development costs
and risk mitigation.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

In sci.space.policy Pat Flannery wrote:


Henry Spencer wrote:

Yep. Too much of a single-point design for my taste, especially given
modern electronics. Full guidance and a capability for small midcourse
corrections just isn't that big a deal any more.


I always thought it was a great example of the Soviet Union's KISS*
philosophy in regards to spacecraft; no midcourse correction needed
means no failure of midcourse correction equipment; gravity (one can
hope) won't break down.
Of course you end up having your choice of landing sites severely
curtailed; but if it's a propaganda victory as opposed to useful lunar
science you are after, then it's a pretty clever way of keeping down
both the weight and complexity of your return spacecraft. It would be
interesting to know how they handled the possibility of the lander
coming down on uneven or sloped ground, so as to keep the ascent stage
aimed straight upwards.

My guess would be they didn't and just corrected after blast-off. yes you
get an additional failure mode (larger slope angle than anticipated)
but i doubt an electro-mechanical gadget letting you do this with
resonable precision would have been that large.


*- "Keep It Simple, Stupid!"

Pat


--
Sander

+++ Out of cheese error +++

"Terry Goodrich" writes:
[About a robotic moon sample return]
Questions:

2. Could the orbital GPS system possibly help with guidance? Would it have
the range?

This is an interesting question; I suspect it could be made to work.
You would be using the satellites on the far side of the earth, using
the radiation that is aimed at the earth but missed. The beams of the
GPS transmitters are wide enough that you will (probably) be in the
primary beams of some satellites (the Earth covers +- 13 degrees from
the GPS, but the primary beam is about 18 degrees wide) and in the
sidelobes of many (these go out to about 40 degrees). Experiments
such as 'Falcon gold' have detected these with simple patch antennas
out to GEO altitudes.

http://www.navsys.com/papers/Falcon_Gold_Project.pdf
http://www.navsys.com/Papers/9901001.pdf

The moon is about 10x further away, but all the
GPS satellites are in the same direction, so a higher gain antenna
can be used, if you keep can keep it pointed at earth.

The accuracy is probably more than good enough. There is no ionosphere
to compensate for. The range (distance from Earth) has no geometry
problems, and will probably be good to a meter or so. Position on
the sky (or moon) will have geometric dilution of accuracy, since
the satellites are all in one direction. The moon is about 20x
further away than the GPS orbits. From geometry, this should lead
to estimates about 200 times worse in the cross directions, I think,
though I'm no GPS expert. But that's still only 200 meters or so.

So I guess GPS could be used. It could certainly be experimentally
tested, and if it works once it should be OK after that (at least
until they upgrade the satellites. More sophisticated GPS
satellites might have narrower beams or reduced sidelobes.)

Lou Scheffer

Vincent Cate wrote:

(Henry Spencer) wrote in message ...
In article ,
Vincent Cate wrote:
If you use an ion-drive to get to lunar orbit and back and a tether to
collect samples, you don't need to be so mass-limited in your design
and you could bring back much more lunar mass. The difficulty of having
the end of the tether pickup some samples seems much less than having
a couple more rocket stages...

However, the tether deployment, spin-up, and control are basically research
projects, whereas rocket stages are fairly well understood.

On the other hand there is not so much room for improvement in rockets.

There's not a lot of room for improvements in efficiency (Isp), but
we've barely scratched the surface as far as cost reduction is
concerned.

[deleted]

Pat Flannery wrote:
Of course you end up having your choice of landing sites severely
curtailed; but if it's a propaganda victory as opposed to useful lunar
science you are after,

That's one thing a lot of people miss when analyzing the fUSSR and its
actions/designs/plans, especially in the military arena. They were
not a clone nor a mirror of the US, their problems, goals, and
resultant strategies were often quite different as a result.

D.
--
Touch-twice life. Eat. Drink. Laugh.

People,

Please don't loose track that we are trying to just get 20 kilo or so
of moon rocks to sell to collectors, not mine the moon. While I can
see the value of developing tethers and ion drives for a long term
project (I have a lot of interest in ion and vasmir drives), I don't
believe we have a budjet for any heavy duty R&D ($400~500 million).
Remember the more moon rocks on the market the lower the price will
be. I'm not an accountant or speculator and really have no idea what
the optimum amount of rocks would be for the highest payoff.

I believe in the future will will be mining titanium and helium 3 and
such from the moon, but not until the value of these items grows
enought to offset production and shipping cost, which at the rate
we're going will be a very long time. I don't want to be a cynic, but
space flight,manned and unmanned, in general will never become
affordable until resources in space, moon, etc. can be exploited by
private concerns.

Just my 2 bits.

Terry

In sci.space.policy Henry Spencer wrote:
In article ,
Sander Vesik wrote:
Rad-hard electronics and solar arrays are very hard on the budget (and on
the schedule, because of availability problems).

compared to what? The availability of tethers is rather worse so far and
unlike almost anything else, ramping up rad hard electronics production
is not that hard...

Yeah, but they're not going to *do* that for you unless you're spending
millions, maybe tens of millions, on parts alone. I'm talking about
practice, not theory.

As a launch will cost an order of magnitude more than that, given multiple
launches.


The practical reality is that it's hard to do anything low-cost with parts
that cost several orders of magnitude more than commercial ones (and no,
I'm not kidding about the "several" part), and have acquisition lead times
of many months rather than one UPS package travel time.


Yes, so you basicly have a catastrophicly high NRE for the design (this is not
unique - ASICs have the same problem) followed by specialty manufacturing. Similar
practices as were brought to bear on asic problems should work here too -
design for testability, patch manufaturing etc


--
Sander

+++ Out of cheese error +++

Sander Vesik wrote:

My guess would be they didn't and just corrected after blast-off. yes you
get an additional failure mode (larger slope angle than anticipated)
but i doubt an electro-mechanical gadget letting you do this with
resonable precision would have been that large.



I'll bet it was done this way: The stabilization gyros in the ascent
stage were mounted in some sort of bottom-weighted gimbal assembly that
allowed them to pivot back and forth till they were vertical in relation
to the Moon's gravity field; then locked-
at liftoff they commanded the vehicle to bring them on axis with the
vehicle's ascent trajectory, so that the vehicle ended up ascending
vertically.

Pat

In article ,
says...
In article ,
Doug... wrote:

Where are you getting your cost estimates? Off the top of your head?
You have no real idea what the costs would be on either side. Good luck
getting capital based on your gut feelings as to what the costs ought to
be...

To be fair, Vincent Cate has more to go on that gut feelings. He has
fairly detailed simulations, and cost-estimate spreadsheets, all of
which are open and available to critics. He also seems to have a small
group of helpers who presumably might point out any blatant mistakes in
the simulation or estimates.

Of course he could still be blatantly wrong for some reason, but it's
not fair to say that he's just making stuff up. He's put a fair amount
of time into getting reasonable numbers.

OK -- I'll accept that he's put some time into getting his numbers.
That is certainly not obvious in his posts, where he simply tosses out
numbers like "this will cost from 100 to 1000 times less than chemical
rocket systems." Without any clue as to his assumptions and premises,
it's hard to accept those kinds of figures.

I still have a hard time believing in his faith in tether systems -- I
truly believe that the engineering aspects are going to be far more
difficult to manage than he seems to think. One of the things I can't
understand about his proposal for getting lunar materials via tether is
that he seems to be proposing that you can deploy a tether from lunar
orbit and affix a scoop to the end of that tether that will scoop up
lunar materials. I know quite well how uneven the lunar surface is at
the scale of a scoop attached to what amounts to a constant-length
tether, and I have a fair idea of how much energy the impact of that
scoop along such an uneven surface will take out of the system. And how
many oscillations it will set into the tether. I just don't see those
issues being addressed.

I'd love to see them addressed, since *any* system of moving mass from a
planetary surface into an orbital state is worth exploring. While I
accept your statement that Vincent has done a lot of research into this
issue, I haven't seen the real ball-buster issues addressed in his
posts...

Doug

"Dick Morris" wrote in message
...


Vincent Cate wrote:
On the other hand there is not so much room for improvement in rockets.

There's not a lot of room for improvements in efficiency (Isp), but
we've barely scratched the surface as far as cost reduction is
concerned.

Come on now, rockets have been under continous development
for most of a century. There can't be very many ways to improve
engines with that much history. What could you possibly do to
improve them. Are you willing to say that they are not near
perfection now? :-)