...100 MW of Space Solar Power ...per single launch!

Sylvia Else wrote:
Jonathan wrote:
"Sylvia Else" wrote in message
...
Dr J R Stockton wrote:
In sci.space.history message



Perhaps you do not have a background in the physical sciences?



Perhaps you're not as clever as you think you are.



....replies Sylvia, as she attempts to toss her cognac in the face of
the rude dinner quest. But he stops her just in time, their hands
now locked in anger, their eyes engage, and as suddenly
the crescendo is transformed into two coequal legacies.
An anger with no boundaries, and a lust as capacious as the sea.
With Elysium now only as far as to the very nearest room.

The opening of a door, felicity or doom?




I know. I shouldn't let people drag me down to their level. But
sometimes it's hard to resist the temptation.

However, it is very pleasant to read a post that has reality
and knowledge in it. :-)

/BAH

wrote:
In sci.physics Peter Fairbrother wrote:
Alain Fournier wrote:

However there would be other benefits to starting a space-based economy,
for instance things can be made in space which are impossible or
expensive to make on Earth


Name something that is impossible to make on Earth or would be cheaper
to make in space for which there is an actual market.

Vacuum?


I hear this arm-waving claim from the space cadet crowd a lot, but no one
seems to be able to identify a product.



It sure would be nice to find one.

/BAH

wrote:

In sci.physics Peter Fairbrother wrote:

Alain Fournier wrote:

However there would be other benefits to starting a space-based economy,
for instance things can be made in space which are impossible or
expensive to make on Earth

Name something that is impossible to make on Earth or would be cheaper
to make in space for which there is an actual market.

Well there is no market for something that doesn't exist, so there
is currently no market for things that are impossible to make on Earth.
But here are a few things that a space based industry could possibly do.

- Alloys made of metals of very different densities.
- Metal mousse (kind of a metal air alloy, or a metal vacuum alloy(??) ).
- It is suspected that some crystals next to impossible to grow on
Earth could be made in zero g.

But I think that a space based industry would probably not be exporting
hardware to Earth, at least not at first. Exports to Earth would probably
at first be data and/or energy. So a space based industry could build

- SPS
- Giant space telescopes.
- Fuel for interplanetary probes and interplanetary manned missions.
- Interplanetary probes or parts of them.

Would you like more?


Alain Fournier

Fred J. McCall wrote:

wrote:

:If the energy density is low enough to be safe, it isn't high enough to
:be particularly usefull.
:

Wrong.

Thank you Fred. Such a profound answer really helps.

Jim:

The advantage provided by a SPS over solar energy is not in the
energy density. It is because you get your energy 24 hours a day
and you get it in a much more convenient form. You can convert
the energy you receive from a SPS much more easily because it
is all at the same wave-length. That wave-length is one you
chose for being convenient. The Sun insists on sending us
its energy across a broad range of wave-lengths and only about
half the time every day, not to mention that cloud cover can
cut down on the solar energy you receive.


Alain Fournier

In sci.physics "Greg D. Moore \(Strider\)" wrote:
wrote in message
...
In sci.physics "Greg D. Moore \(Strider\)"
wrote:

If the energy density is low enough to be safe, it isn't high enough to
be particularly usefull.



In other words you've just proven terresterial solar power doesn't work
either. I'll go tell the folks I know using it that you've proven their
systems don't work.

Terresterial solar power as a general source of electrical power (as opposed
to niche situations) only works today on an economic level because of
government subsidies in many forms.

Someday in the future the costs may come down to where it can compete on
it's own, but that day isn't here yet.


--
Jim Pennino

Remove .spam.sux to reply.

In sci.physics Fred J. McCall wrote:
wrote:

:In sci.physics "Greg D. Moore \(Strider\)" wrote:
: wrote in message
: ...
: In sci.physics "Greg D. Moore \(Strider\)"
: wrote:
: wrote in message
: ...
:
: For existing things there is the concept of minimum enroute altitude
: which ensures you are above all the obstacles for a significant
: distance.
:
: There is no getting above an energy beam from space.
:
:
: And yet people still fly into the ground or buildings. Again, it's the
: pilot's fault. Not the build, ground or beam.
:
: Apples and oranges.
:
: How do you avoid something that is invisible to all existing aviation
: sensors?
:
: Same way pilots avoid no-fly zones now. They consult their maps and NOTAMs
: and fly around them.
:
:
: While flying VFR, obstacles are avoided by eyesight and altitude, neither
: of which will work with an energy beam from space.
:
:
: Pilots flying VFR avoid no-fly zones now. I'm not sure why in the future
: you think they're suddenly going to become stupid.
:
: In any case, at the energies discussed, the power levels just aren't that
: dangerous.
:
:If the energy density is low enough to be safe, it isn't high enough to
:be particularly usefull.
:

Wrong.

Right.

Lookup the the microwave energy density levels concidered safe for
continuous exposure.



--
Jim Pennino

Remove .spam.sux to reply.

Greg D. Moore (Strider) wrote:
In other words you've just proven terresterial solar power doesn't work
either. I'll go tell the folks I know using it that you've proven their
systems don't work.

Now, this is weird:
http://www.inhabitat.com/2008/03/24/...a-solar-panel/
Then there's the spray-on plastic quantum dots one:
http://news.nationalgeographic.com/n...arplastic.html
If you can get that technologies like that to work then space solar
power only has the advantage of being 24/7...if the power satellites
are up in GEO.

Pat

jmfbahciv wrote:
Name something that is impossible to make on Earth or would be cheaper
to make in space for which there is an actual market.

Vacuum?

Oh, Vacuum...that's nothing. ;-)

Pat

Pat Flannery wrote:
Peter Fairbrother wrote:

Also a HTVL has to be carrier from the airstrip to the expensive
launch pad, then winched from horizontal to vertical between flights.
The lighter VTVL option just uses an existing airfield.

I've heard of HTHL and VTHL like the Shuttle but never HTVL, as that
means your wings are going to be useless on the way back down, unless
you are going to carry something like a ROMBUS aloft and launch it in
flight.

Sorry, meant VTHL, typo! In fact a few here, I was tired, should read:

"Also a VTHL has to be carrier from the airstrip to the expensive launch
pad, then winched from horizontal to vertical between flights. The
lighter HTHL option just uses an existing airfield."

[...]


Ever see what Mach 6.7 did to the X-15?:
http://www.youtube.com/watch?v=wHuBsBOF4R8
And that was with a Inconel X structure covered with a ablator layer.

That was at a much lower altitude and higher air density than those at
which a re-entering first stage would experience those speeds.


While it would some sort of TPS, we are not talking about the kind
used by Shuttle, something much simpler and much more robust would be
enough. We are talking about less than the silica blanket end of the
range, not CRC or foamed silica.

You get a rip in that silica blanket during ascent, and it could peel
off of the vehicle's exterior.

We aren't using a silica blanket, more like inconel or even just
titanium with maybe some transpiration cooling.

The TPS really isn't a deal-breaker. The energy to be dissipated is less
then a tenth of that for orbital re-entry, it's very much easier.

Also, since the winged stage is going to be at suborbital velocity
during descent, lower heating might be combined with higher g loads as
it gets down into the denser atmosphere quicker than something
descending out of orbit. During Shepard's suborbital Mercury-Redstone
flights, the capsule hit 11.6 g's during its descent into the atmosphere
after reaching Mach 6.94.
Even with wings to turn some of that descent velocity into horizontal
flight distance, the HTHL first stage is going to have to have a very
strong (i.e. heavy) structure to take the g loads during descent.

IIRC the maximum is about 3.2g - it's pretty fluffy, and it's not at
orbital speed.

Also, during descent, unless you figure out a way to turn the winged
booster around 180 degrees to fly back to the launch site while keeping
inside of its structural limits, you are probably going to end up
landing on the far side of the Atlantic if you take off from KSC, or on
the east coast if you take off from Edwards AFB. So now you have to get
the booster back to the starting point.

Fly 190 km west (using jet engines), turn 180 degrees, then light off
the rocket at about 10,000 m altitude and 260 m/s. The rocket flight and
re-entry takes you about 320 km horizontally east, to about 130 km east
of the airport, then you do another 180 and land back at the starting
airport.

Flight time for the booster is about 45-50 minutes.


Also there isn't such a need for ultra-light weight in the TPS[*] so
a much heavier TPS could be used. There are several possibilities, and
in general it is quite do-able. It's a bit of a challenge but not in
any way a deal-breaker.

[*] it's a first stage, a bit of extra mass here has much less effect
on overall performance than a bit of extra mass on a second or
orbiting stage.

The fewer flights you need to get all of the materials for the SPS
into LEO (it can be moved slowly out to GEO via ion engines once
assembled, and building it in LEO really cuts back on assembly crew
launch costs, as well as removing the radiation threat to the
assembly crew from solar storms) the better from a economic viewpoint,

NO NO NO! The number of flights is not relevant, the cost for the
total mass launched is the important metric (okay there are other
considerations like minimum component size and assembly costs, but
that's the most important one).

A whole pile of launches equals a whole pile of infrastructure to
support between launches, like on the Shuttle.

All you need at the airport is refuelling and second-stage loading
facilities, and some hanger space. Maintenance could be done offsite.

Yes that would take some infrastructure, but nothing like Shuttle.

The second stages weigh about 15 tons loaded but unfuelled, are about
twice the size of a 40' shipping container[*], and are lifted into the
booster in much the same way as a bomber is loaded with bombs. It just
takes a wheeled cart, at maybe a million each, and maybe 15-30 minutes.

(the second stages are carried internally in the booster, avoiding any
need to make them capable of taking any aerodynamic forces. Instead of a
payload shroud there are a couple of clamshell doors)
[*] if you use two smaller LH2 tanks rather than one big one, a cargo
second stage all fits into three standard 40' shipping containers. I'm
undecided on that, it could save a lot in terrestrial transport of LH2
tanks, but the tanks would be a little heavier, lowering payload a bit,
and they wouldn't be as useful in orbit once emptied, being a bit
claustrophobic for use as living space.

And that eats up money
fast. Even if you can get turnaround time between launches of individual
vehicles down to a really short period of time, say 3-4 days, and
despite the lower stage being able to use a robust and heavy TPS, there
is still the reusable top stage to consider - that is going to reenter
from orbit and will need a lightweight TPS like the Shuttle and need
looking at between flights.

There are two different types of second stage. Most of the second stages
do not re-enter. The main idea is to get stuff up, not down.

A few second stages would be re-entry capable, for returning passengers,
and a few more for returning the expensive bits of the semi-disposable
second stages (engines, electronics, RCS etc) - but most of the second
stages aren't re-entry capable.


Large is not necessary if you can fly several times per day - I
envisage a 10 ton payload HTHL TSTO flying once every 90 minutes from
a ground site to a location in orbit with three launchers, giving a
turnaround time of 4.5 hours.

You couldn't even get the cargo aboard it, restack the two stages, and
refuel it that fast, much less check it out and make sure it's ready to
fly again.
747's have a turnaround time between flights of around 3 hours, and
that's without loading and hoisting a C-141 onto the top of one.
Even the von Braun ferry rocket designs of the 1950's had a turnaround
time of five days, not five hours.
The shortest Shuttle turnaround time was eight weeks, although the
design originally specified fourteen days, so you are counting on your
launch system having 1/128 the turnaround time of the Shuttle's original
specs.
I can see reducing turnaround times, but two orders of magnitude seems a
bit much.

The booster turnaround time would be a bit under 4 hours. Loading a
loaded-but-unfuelled second stage would take maybe 15-30 minutes, then
you have to refuel and do your takeoff checklist - and that's all.

It's not much harder than turning a 747 around. Plenty of time for the
pilot to stretch his legs and have a fag.


Yes, that sort of thing could be done - my preferred system returns
the second stage engines, electronics, RCS and (maybe) LOX tank, but
the LH2 tank is left in orbit for either living space or
constructional material. There are other possibilities.

Now, let me get this straight...parts of a second stage are going to
come back...get recovered...and installed on a new second stage...which
then gets loaded with cargo...restacked on the flyback first
stage...fueled...and launched...in 4.5 hours?
And that doesn't even include the time of ascending to orbit, unloading
the cargo in orbit, and the upper stage's parts descending back to Earth.
Without the help of Dr. Who and the TARDIS this ain't going to work. :-D


There are multiple second stages per booster, perhaps three
winged/lifting body re-entry capable ones for passengers, and 100-150
engine sets for the non-reentering semi-disposable cargo stages.

Three reentry stages per booster might not seem enough, but there's an
advantage in using equatorial LEO - you can do first-orbit rendezvous
every 90 minutes, so the flight times are short, it doesn't take days to
get to where you want to go, just an hour or so. Assuming three flights
per week for the three boosters, that's about six days turnaround for
the passenger stages.

The cargo second stages fly more often, of course. In a week a booster
might fly one passenger reentry stage and 30 cargo stages. Engine sets
from the cargo stages would be returned maybe once per week (probably
using an ablative TPS and parachutes, which would take about half a load
to send up) giving a three to six-week turnaround time for each engine set.

It's only the boosters which fly every 270 minutes.

With three boosters a station in orbit would see an arriving cargo stage
every 90 minutes, and three passenger flights per week.


(I haven't included maintenance time in these figures, so they wouldn't
keep that rate up all the time without spare boosters)


-- Peter Fairbrother

jmfbahciv wrote:
wrote:
In sci.physics Peter Fairbrother wrote:
Alain Fournier wrote:

However there would be other benefits to starting a space-based
economy, for instance things can be made in space which are
impossible or expensive to make on Earth


Name something that is impossible to make on Earth or would be cheaper
to make in space for which there is an actual market.

Vacuum?


I hear this arm-waving claim from the space cadet crowd a lot, but no one
seems to be able to identify a product.



It sure would be nice to find one.

Foamed metals, some biologicals, and quite a lot of chemistry can be
done better and easier in micro-gee - there are a number of others.

Vacuum is available on Earth at not too high a cost - but micro-gee just
plain isn't.

-- Peter Fairbrother