interesting papers on microwave thermal launcher

Over lunched I read a couple of interesting papers by Kevin Parkin which
were presented at ISBEP II. Both are available for download he

http://monolith.caltech.edu/html/Publications.html

One describes a microwave thermal thruster and calculates its
performance characterstics; the other proposes making a 1-ton launcher
(with a 10% payload fraction) by building such a thruster into a X-33
aeroshell.

It also points out that we already have microwave sources of sufficient
power to launch one of these things to orbit -- unlike laser-launch
schemes, where the lasers are still underpowered by a couple of orders
of magnitude.

All in all, very interesting reading!

Enjoy,
- Joe

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| Joseph J. Strout Check out the Mac Web Directory: |
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Joe Strout wrote in message ...
Over lunched I read a couple of interesting papers by Kevin Parkin which
were presented at ISBEP II. Both are available for download he

http://monolith.caltech.edu/html/Publications.html

One describes a microwave thermal thruster and calculates its
performance characterstics; the other proposes making a 1-ton launcher
(with a 10% payload fraction) by building such a thruster into a X-33
aeroshell.

It also points out that we already have microwave sources of sufficient
power to launch one of these things to orbit -- unlike laser-launch
schemes, where the lasers are still underpowered by a couple of orders
of magnitude.

Extremely interesting, I agree!. I have some issues:
1. launch scheme assumes single fixed set of transmitters at a sight
favorable to microwave non-absorption (extra dry climate). Fixed
nature ensures very narrow range of trajectories, and none equitorial.
The two example sights have serious issues. (Mauna Kea & Atacama,
Chile)
A. both would mandate launch inclinations under 18 deg (both are
located nearly right on N/S 20th parallel), which prevents getting
into equatorial orbit. (accelation ends within 220 nm of launch sight,
which means unless you launch within 2 deg of the equator, you're not
getting there.)
B. Hawaii: It's politically impossible to build a huge transmitter
array to add to the numerous telescopes on Mauna Kea. Hawaii has a
serious environmental lobby, and Caltech had problems even getting
another big telescope approved. In addition, while Mauna Kea has great
conditions above it, the launcher would have to be located 80-100 mi
to the west (thus on an ocean based platform), and then "fly over"
Mauna Kea--which means also flying over (or nearly) the large
populations of Kailua-Kona and Hilo early in the launch phase. I doubt
the FAA would allow this. It also presents the launcher with the most
microwave-absorbent (wet) conditions and worst absorbance angle, right
at the most demanding portion of launch--liftoff. Astronomers would
also take major issue with polluting the exceptionally clear skies
above Mauna Kea with large amounts of exhaust water vapor and air
turbulence caused by microwave absorption. Conclusion: it's a nice
idea, but not feasible on Hawaii.
C. Atacama desert: southern location prevents launch into a 'normal'
northern inclination trajectory. In addition, a 20 deg s. inclination
from the Atacama desert sends you roughly over Ascuncion(capital city
of Paraguay) and the heavily populated SW coast of Brazil. This will
not be a problem with the very short acceleration time, but any
follow-on human launch (requiring multiple transmitters at fixed
sights to allow slow acceleration) would run into this problem big
time. It might be tough to get range clearance for essentially all of
southwest Brazil. Retrograde orbits, of course, would not have this
problem.
D. Conclusion on use of 'extra dry' launch sights: of marginal use
unless they are located w/in 2 deg of the equator. For this system to
be useful, it needs to be sea-based, with equitorial launch and
multiple inclinations available. Also, a slower acceleration profile
would be allowed that way with multiple transmitter sights available
for 'hand-off'(see 2. below). It does get you into more probelematic
power requirements, however.
2. The single transmitter site means rapid acceleration of 9-19Gs
during horizontal portion of flight (to allow all acceleration to take
place w/in line of sight of xmitter.) That prevents any human system
based on it unless you want the astronauts unconscious during takeoff.
3. The launcher paper didn't mention added weight of the required LH2
turbopump, or the LOX tank & preburner that accompany them. Of course,
this isn't ALL bad, as it would allow separate LH2/LOX chemical rocket
use in orbit, maybe even enough to get you into an equitorial
inclination. For all I know it might be possible to even use the same
aerospike as a skirt for the LH2/LOX engines(?), which would give you
the ability to just use the thermal thrusters on the boost phase of
the flight. Ratios would be timed to exhaust 'excess' LH2 at the point
the transmitter goes over the horizon. Limiting this acceleration to a
gentle 3-5 g's still allows good use of both sytems.

Tom Merkle.

In article ,
(Tom Merkle) wrote:

http://monolith.caltech.edu/html/Publications.html

Extremely interesting, I agree!. I have some issues:
....
D. Conclusion on use of 'extra dry' launch sights: of marginal use
unless they are located w/in 2 deg of the equator. For this system to
be useful, it needs to be sea-based, with equitorial launch and
multiple inclinations available. Also, a slower acceleration profile
would be allowed that way with multiple transmitter sights available
for 'hand-off'(see 2. below). It does get you into more probelematic
power requirements, however.

I'll buy that. Power probably wouldn't be a big issue if the
transmitter ships were nuclear. Are there any civilian nuclear-powered
ships, or are they all military?

2. The single transmitter site means rapid acceleration of 9-19Gs
during horizontal portion of flight (to allow all acceleration to take
place w/in line of sight of xmitter.) That prevents any human system
based on it unless you want the astronauts unconscious during takeoff.

Agreed. I thought that assuming a single transmitter site was
unnecessarily restrictive. It might well be cheaper to build a line of
sites across a continent than to harden every payload you want to launch
microsatellites to withstand 19 Gs.

3. The launcher paper didn't mention added weight of the required LH2
turbopump, or the LOX tank & preburner that accompany them. Of course,
this isn't ALL bad, as it would allow separate LH2/LOX chemical rocket
use in orbit, maybe even enough to get you into an equitorial
inclination.

Right. In fact, if your launcher just goes into the high-inclination
orbit, releases its payload, and comes back down, there might be other
ways to get the payload into the desired orbit, whether it's a different
inclination or different altitude (e.g. GEO) or both. For example, a
space tug. Or, let your satellite change its own orbit via an
electrodynamic tether (assuming you're not in a hurry of course).

Cheers,
- Joe

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'

Joe Strout wrote in message ...
In article ,
(Tom Merkle) wrote:

http://monolith.caltech.edu/html/Publications.html

Extremely interesting, I agree!. I have some issues:
...
D. Conclusion on use of 'extra dry' launch sights: of marginal use
unless they are located w/in 2 deg of the equator. For this system to
be useful, it needs to be sea-based, with equitorial launch and
multiple inclinations available. Also, a slower acceleration profile
would be allowed that way with multiple transmitter sights available
for 'hand-off'(see 2. below). It does get you into more probelematic
power requirements, however.

I'll buy that. Power probably wouldn't be a big issue if the
transmitter ships were nuclear. Are there any civilian nuclear-powered
ships, or are they all military?

Russia had several nuclear powered icebreakers. The US had exactly one
nuclear powered civilian ship, the NS Savannah, comm. 1958, deact
1971. It would have to be a military system. Decision to use nuclear
would depend on one thing--frequency of launch. The reactors required
for this power level are currently off the shelf for the US navy, but
the plants still cost around $500-700 mil apiece. The competing fossil
fuel type would probably cost less than a quarter of that. The only
advantages of nuclear are that there's no refueling required, and
naval nuclear plants are optimized for large power surges like this
scheme.


2. The single transmitter site means rapid acceleration of 9-19Gs
during horizontal portion of flight (to allow all acceleration to take
place w/in line of sight of xmitter.) That prevents any human system
based on it unless you want the astronauts unconscious during takeoff.

Agreed. I thought that assuming a single transmitter site was
unnecessarily restrictive. It might well be cheaper to build a line of
sites across a continent than to harden every payload you want to launch
microsatellites to withstand 19 Gs.

Yeah, but they did this for very good reason, basically to keep it
land based, and to still give at least *some* inclination flexibility.
You build a line of sites and you're stuck not only in that exact
inclination but also that exact orbit. Maybe big mobile transmitters
on trains? But this makes seabasing a more realistic idea. What
doesn't help is waves. Dealing with sea motion is annoying even for a
small satellite dish that has a beamwidth many miles wide. Requiring
the same performance with an enormous antenna and a target point of
centimeters is asking ALOT, although I guess if you make the platforms
big enough they could be very stable.


3. The launcher paper didn't mention added weight of the required LH2
turbopump, or the LOX tank & preburner that accompany them. Of course,
this isn't ALL bad, as it would allow separate LH2/LOX chemical rocket
use in orbit, maybe even enough to get you into an equitorial
inclination.

Right. In fact, if your launcher just goes into the high-inclination
orbit, releases its payload, and comes back down, there might be other
ways to get the payload into the desired orbit, whether it's a different
inclination or different altitude (e.g. GEO) or both. For example, a
space tug. Or, let your satellite change its own orbit via an
electrodynamic tether (assuming you're not in a hurry of course).

Cheers,
- Joe

I wonder if the Navy's ever considered a system like this for
launching boost-phase interceptors? They don't care about 19 G's.
Maybe I'll suggest it. come to think of it, Nah, requires too much
long-distance coordination to be useful on a "response" timeline like
THADD.

Tom Merkle

Joe Strout wrote in message ...

Ahh, maybe useless as a launcher for THADD, but extremely useful as a
Boost-phase energy weapon. Any system capable of launching should also
be capable of launch phase missile destruction as well, and could be
used as an anti-satellite weapon as well.

Tom Merkle

In article ,
Tom Merkle wrote:
Ahh, maybe useless as a launcher for THADD, but extremely useful as a
Boost-phase energy weapon. Any system capable of launching should also
be capable of launch phase missile destruction as well, and could be
used as an anti-satellite weapon as well.

Even with lasers, launch systems and weapons optimize very differently.
Note that the beam is quite wide and requires a surface specifically
designed to absorb it.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

In article ,
Joe Strout wrote:
It also points out that we already have microwave sources of sufficient
power to launch one of these things to orbit -- unlike laser-launch
schemes, where the lasers are still underpowered by a couple of orders
of magnitude.

He's assuming it has to be a single laser, which isn't so. (Note that he
isn't using a single microwave source!)
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

In article ,
Tom Merkle wrote:
A. both would mandate launch inclinations under 18 deg (both are
located nearly right on N/S 20th parallel), which prevents getting
into equatorial orbit. (accelation ends within 220 nm of launch sight,
which means unless you launch within 2 deg of the equator, you're not
getting there.)

More precisely, both would *preclude* orbit inclinations below their
latitudes. (The really dry part of the Atacama is at about 24degS, while
Mauna Kea is at about 19degN.) However, this matters only if there's
some great urgency about reaching equatorial orbits.

B. Hawaii: It's politically impossible to build a huge transmitter
array to add to the numerous telescopes on Mauna Kea. Hawaii has a
serious environmental lobby...

And the Native Hawaiian lobby is an even bigger problem (the volcanos
being sacred sites to them). Agreed that Mauna Kea just isn't going to
work, politically.

...Astronomers would
also take major issue with polluting the exceptionally clear skies
above Mauna Kea with large amounts of exhaust water vapor and air
turbulence caused by microwave absorption.

Not likely to be a major issue, because those disturbances won't stick
around for very long. Launches would preferably be during the day, while
*most* of the astronomy goes on at night.

C. Atacama desert: southern location prevents launch into a 'normal'
northern inclination trajectory.

Uh, what's a "northern inclination trajectory"? For maximum payload,
you'd launch due east, giving an orbital inclination of about 24deg.
(There is no "north" or "south" to an orbit's inclination.) That takes
you out over the northern tip of Argentina, northern Paraguay (well clear
of Ascuncion), and central Brazil (not great, but at least you pass north
of Rio and Sao Paulo and south of Brasilia).

For a sun-synchronous orbit, you'd be launching pretty much straight down
Chile, angling slightly offshore. Careful calculation would be needed to
decide whether that's a problem.

D. Conclusion on use of 'extra dry' launch sights: of marginal use
unless they are located w/in 2 deg of the equator.

You need to explain why you're so obsessed with equatorial orbits. You
can't get into them from the Cape either, but it's still a useful launch
base.

And the "extra dry" launch sites are very important to this system. If
I'm reading the paper right, it can't easily handle the extra atmospheric
absorption of operation from sea level.

2. The single transmitter site means rapid acceleration of 9-19Gs
during horizontal portion of flight (to allow all acceleration to take
place w/in line of sight of xmitter.) That prevents any human system
based on it unless you want the astronauts unconscious during takeoff.

Or in water immersion (for which that is quite tolerable acceleration).
Agreed, this isn't great.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

(Henry Spencer) wrote in message ...
In article ,
Tom Merkle wrote:
Ahh, maybe useless as a launcher for THADD, but extremely useful as a
Boost-phase energy weapon. Any system capable of launching should also
be capable of launch phase missile destruction as well, and could be
used as an anti-satellite weapon as well.

Even with lasers, launch systems and weapons optimize very differently.
Note that the beam is quite wide and requires a surface specifically
designed to absorb it.

True. I guess it wouldn't be that hard to develop a coating that
reflects microwaves very well. :-0

Tom Merkle

Joe Strout writes:

In article ,
(Tom Merkle) wrote:

http://monolith.caltech.edu/html/Publications.html

Extremely interesting, I agree!. I have some issues:
...
D. Conclusion on use of 'extra dry' launch sights: of marginal use
unless they are located w/in 2 deg of the equator. For this system to
be useful, it needs to be sea-based, with equitorial launch and
multiple inclinations available. Also, a slower acceleration profile
would be allowed that way with multiple transmitter sights available
for 'hand-off'(see 2. below). It does get you into more probelematic
power requirements, however.

I'll buy that. Power probably wouldn't be a big issue if the
transmitter ships were nuclear. Are there any civilian nuclear-powered
ships, or are they all military?

There have been and, depending on how the Russian icebreaker fleet is
organized, may still be nuclear-powered ships which are not military,
but their "civilian" ownership all involved a great deal of government
money and oversight.

If the few Western experiments in nuclear-powered merchantmen had
proven profitable, we would soon have had precedent one way or another
on whether governments would really allow private citizens/corporations
to sail off over the horizon with nuclear reactors, but the economics
weren't there so the politics were never tested.


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