Something completely different (ref Blue Parrot)

This is something that has not been covered by news nor (as near as I
can tell) has it been the subject of a press release. But it is
fairly well known to those in the business.

NASA Ames brought a 1.2 MW, 110 GHz gyrotron for testing beamed energy
propulsion. They still need the power supply, which is 70 kV at 30 A
but it's a relatively small cost. Up close it will provide well over
10 MW/m^2.to test hydrogen heaters.

They intend to offer it the same way as the wind tunnels, as a
national engineering test asset.

I think it is an accepted truth that you need single stage to orbit
and that it must be a reusable launch vehicle to get the cost to GEO
down to where power satellites make sense economically.

Given the current state of material science and the best exhaust
velocity you can get from chemical propulsion, neither of these are
feasible.

To put numbers on the problem, it takes 9000 m/s to get into LEO. For
4500 m/s rocket engines, that's a delta V of twice the exhaust
velocity. The rocket equation gives a mass ration of 7.4 which means
the vehicle and payload can't be more than 13.5% of the takeoff mass.
For a vehicle to be reusable, the accepted minimum structure is 15%,
leaving less than zero for payload. (Skylon cheats by burning air
partway up, but it's not enough to get a lot of payload to LEO.)

But if you have 9000 m/s exhaust velocity, which can be done with
hydrogen heated with microwaves or lasers, then the mass ratio is a
little less than 3. So vehicle and payload can be 36% of takeoff
mass. If half vehicle and half payload, that's 18% each. So a 300
ton vehicle with a dry mass of 54 tons could put 54 tons in LEO.

The falling cost of microwave power and laser power makes these
options possible.

Beamed power doesn't make economic sense unless you are talking cargo
volumes in the hundreds of thousands of tons per year.

I should also add that I never thought NASA would do something so
sensible. Those of you who know Pete Warden might send him a thank
you note..

Keith Henson

Keith Henson wrote:

I think it is an accepted truth that you need single stage to orbit
and that it must be a reusable launch vehicle to get the cost to GEO
down to where power satellites make sense economically.

No. SSTO is a ridiculous idea. What you need is two stages. TSTO is
cheaper and gives a much bigger payload,

More importantly, the first stage should be highly reuseable with a
quick turnaround.

As for the second stage, well here's the obvious-but-clever bit. You
have maybe 100 (or 10,000) second stages per first stage.

The parts of a launch system which go into orbit have to stay there for
a while for operational reasons, for maybe a few weeks to a few months.
If it's a SSTO then all the expensive ground launch parts are sitting
around doing - nothing.

For a TSTO, the expensive main engines and launch and recovery systems -
wings wheels, VTOL gear, or whatever - can be sending up another second
stage while the SSTO is sitting around in orbit looking pretty. And
another second stage. And another.


Whether the second stages are reusable or not is not fixed. I'd like to
see both versions, reusable ones for passengers and disposable ones for
cargo.

The passenger versions need to have a lot of equipment in them for
humans survival and safety. This is expensive, so it should be reusable.

For the disposable cargo versions of the second stage, if you have
on-orbit assembly you can return the expensive bits - the engines,
control systems and electronics - for reuse. You can also leave the
cheap bits - the tanks - in orbit for use as on-orbit scrap building
material, living space, tankage, storage, whatever.


-- Peter Fairbrother

On Jul 9, 1:48 pm, Peter Fairbrother wrote:
Keith Henson wrote:
I think it is an accepted truth that you need single stage to orbit
and that it must be a reusable launch vehicle to get the cost to GEO
down to where power satellites make sense economically.

No. SSTO is a ridiculous idea. What you need is two stages. TSTO is
cheaper and gives a much bigger payload,

As I noted SSTO is flat out impossible--given chemical exhaust
velocities.

More importantly, the first stage should be highly reuseable with a
quick turnaround.

As for the second stage, well here's the obvious-but-clever bit. You
have maybe 100 (or 10,000) second stages per first stage.

I proposed this he http://www.theoildrum.com/node/7898 a two stage
to GEO using the Skylon as a first stage. The problem I don't know
how to solve cleanly is getting the first stage back to the launch
site. Using Skylon as a first stage it comes down 10,000 km down
range. The best I can do is fuel it back up and fly it back. (This
has to be done on the equator, and good locations with a non ocean
10,000 km down range are few.)

The parts of a launch system which go into orbit have to stay there for
a while for operational reasons, for maybe a few weeks to a few months.
If it's a SSTO then all the expensive ground launch parts are sitting
around doing - nothing.

I agree. The approach I have been thinking about has the first stage
do one orbit and land.

For a TSTO, the expensive main engines and launch and recovery systems -
wings wheels, VTOL gear, or whatever - can be sending up another second
stage while the SSTO is sitting around in orbit looking pretty. And
another second stage. And another.

The market I have been thinking about is GEO, at half a million tons
per year.

Whether the second stages are reusable or not is not fixed. I'd like to
see both versions, reusable ones for passengers and disposable ones for
cargo.

Agree. I have 3 an hour arriving at GEO. They are entirely consumed
making power satellites.

The passenger versions need to have a lot of equipment in them for
humans survival and safety. This is expensive, so it should be reusable.

For the disposable cargo versions of the second stage, if you have
on-orbit assembly you can return the expensive bits - the engines,
control systems and electronics - for reuse. You can also leave the
cheap bits - the tanks - in orbit for use as on-orbit scrap building
material, living space, tankage, storage, whatever.

If you can't do anything else with it, you can hang mass on long
tether (600 km) and use it to stabilize a platform by gravity
gradient.

Keith

-- Peter Fairbrother

Keith Henson wrote:
On Jul 9, 1:48 pm, Peter Fairbrother wrote:
Keith Henson wrote:
I think it is an accepted truth that you need single stage to orbit
and that it must be a reusable launch vehicle to get the cost to GEO
down to where power satellites make sense economically.
No. SSTO is a ridiculous idea. What you need is two stages. TSTO is
cheaper and gives a much bigger payload,

As I noted SSTO is flat out impossible--given chemical exhaust
velocities.

More importantly, the first stage should be highly reuseable with a
quick turnaround.

As for the second stage, well here's the obvious-but-clever bit. You
have maybe 100 (or 10,000) second stages per first stage.

I proposed this he http://www.theoildrum.com/node/7898 a two stage
to GEO using the Skylon as a first stage. The problem I don't know
how to solve cleanly is getting the first stage back to the launch
site.


It's not too hard if the balance is skewed a bit towards maximum
performance in the second stage - say the second stage is LOX/LH2
powered for example, and the first stage only does a bit more than going
up and down.

For a winged first stage, the use of jet engines can also be useful. No
kidding. How many heavy winged objects with jet engines take off and
land successfully every day?

Taking a 747 or as an example, but it's not an aircraft, it's a
spacecraft. TOW is 460tons. It takes off and climbs and flies west on
air-breathing jet engines to 30,000 ft, then turns east, when it weighs
400 tons.

It then burns 160 tons of LOX/kero in rocket engines, which takes it to
110 km altitude and 2,000 m's eastward horizontal. These are
altitude-optimised rocket engines, of course.

On the way up, after the burn, it deploys a 65 ton second stage with a
LEO payload of 8-10 tons.

It then falls out of space into the sky at about 500 km west of it's
turnaround point, or about 350 km from it's takeoff point, and flies
back to takeoff point.

Mostly this is done using it's own kinetic energy, but if it needs a
boost, needs to divert, or needs to go-around because the runway is
closed, it has jet engines and fuel to do that sort of stuff.


Assuming all goes well, it gets back to the runway 39 minutes after it
took off. That gives 50 minutes for refuelling and loading another
second stage in order to catch the next first-orbit rendezvous -
assuming a near-equatorial launch and an 89 minute orbit for the
on-orbit assembly station.

Though the every-two-orbit 3-hour turnaround is probably better.


Now let's talk kT-L/y, or kilotons to LEO per year.

If we build 5 first stages, and two of them are working at any one time
with three in maintenance, and they launch six times per day 300 days
per year, and the payload is nine tons, then that's 30 kT-L/y - or
thirty thousand tons per year to LEO.


Could be done for about $7-9 billion total up to the end of the first
30,000 tons lifting. It would take maybe 4-5 years. No new technology
involved, at least nothing radically new, just fitting rocket engines on
an aircraft. Re-entry is slow, and a known-cheap problem. Mass-producing
suitable second stage engines might be a little new.


-- Peter Fairbrother

On Jul 12, 4:17 am, Peter Fairbrother wrote:
Keith Henson wrote:
On Jul 9, 1:48 pm, Peter Fairbrother wrote:
Keith Henson wrote:
I think it is an accepted truth that you need single stage to orbit
and that it must be a reusable launch vehicle to get the cost to GEO
down to where power satellites make sense economically.
No. SSTO is a ridiculous idea. What you need is two stages. TSTO is
cheaper and gives a much bigger payload,

As I noted SSTO is flat out impossible--given chemical exhaust
velocities.

More importantly, the first stage should be highly reuseable with a
quick turnaround.

As for the second stage, well here's the obvious-but-clever bit. You
have maybe 100 (or 10,000) second stages per first stage.

I proposed this hehttp://www.theoildrum.com/node/7898a two stage
to GEO using the Skylon as a first stage. The problem I don't know
how to solve cleanly is getting the first stage back to the launch
site.

It's not too hard if the balance is skewed a bit towards maximum
performance in the second stage - say the second stage is LOX/LH2
powered for example, and the first stage only does a bit more than going
up and down.

For a winged first stage, the use of jet engines can also be useful. No
kidding. How many heavy winged objects with jet engines take off and
land successfully every day?

Taking a 747 or as an example, but it's not an aircraft, it's a
spacecraft. TOW is 460tons. It takes off and climbs and flies west on
air-breathing jet engines to 30,000 ft, then turns east, when it weighs
400 tons.

It then burns 160 tons of LOX/kero in rocket engines, which takes it to
110 km altitude and 2,000 m's eastward horizontal. These are
altitude-optimised rocket engines, of course.

On the way up, after the burn, it deploys a 65 ton second stage with a
LEO payload of 8-10 tons.

It then falls out of space into the sky at about 500 km west of it's
turnaround point, or about 350 km from it's takeoff point, and flies
back to takeoff point.

Mostly this is done using it's own kinetic energy, but if it needs a
boost, needs to divert, or needs to go-around because the runway is
closed, it has jet engines and fuel to do that sort of stuff.

Assuming all goes well, it gets back to the runway 39 minutes after it
took off. That gives 50 minutes for refuelling and loading another
second stage in order to catch the next first-orbit rendezvous -
assuming a near-equatorial launch and an 89 minute orbit for the
on-orbit assembly station.

Though the every-two-orbit 3-hour turnaround is probably better.

Now let's talk kT-L/y, or kilotons to LEO per year.

If we build 5 first stages, and two of them are working at any one time
with three in maintenance, and they launch six times per day 300 days
per year, and the payload is nine tons, then that's 30 kT-L/y - or
thirty thousand tons per year to LEO.

Could be done for about $7-9 billion total up to the end of the first
30,000 tons lifting. It would take maybe 4-5 years. No new technology
involved, at least nothing radically new, just fitting rocket engines on
an aircraft. Re-entry is slow, and a known-cheap problem. Mass-producing
suitable second stage engines might be a little new.

-- Peter Fairbrother

Have you done a second by second spreadsheet including drag and
gravity effects? I have a model one if you want it.

Keith