SPS & Beamed Energy Propulsion

From C. C McMullen Aust 11th Feb 05
Reply to "SPS- Kosky" and Asgard
SPS & Beamed Energy Propulsion

Actual figures from LTI (Lightcraft Tech inc) claim an altitude
record at 233ft back in Dec 2000 but that is just nit-picking. I
agree entirely, this a very long way from 110mile or, more
realistically, the 23,000 miles to a GEO.
I apologise for not detailing many of the objections I have with a
space tether, it is not because I haven't given it a lot of
thought.
I was in fact initially strongly in favour of a space tether. Only on
long consideration did I change my mind. I accept that carbon
nanotubes (theoretically) could have the strength to achieve your
goal, but a ribbon with 2% carbon does not make it even remotely
viable and there are also major concerns with deterioration from age
and UV radiation. There are other issues, but by far my main problems
and concerns are based on the practical considerations that may be
purely my opinion but are still highly relevant. It seems to me that
another fusion hunt could well be avoided by just a little common
sense.
It seems to me, BEP, using masers, could be developed at and from the
ground in easy stages (as previously presented) with almost instant
potential for sounding `rockets' of all sizes, near-earth
observation
missions and then building to high-altitude gliders and commuter-
range flights and sub-orbital hops etc. without doubt, a direct lift
to GEO is the ultimate goal but there are major benefits and options
along the way.
The space tether on the other hand is a one-shot, single purpose
venture that is literally tied to one spot. And there really can be
no complete answer to the way it would affect all other orbital
flight-paths. For example, there has to be a limit to how fast this
lumbering elephant could be moved sideways, out of the path of
satellites (and space junk) in LEO, not to mention ground to air
missiles. I believe (and I accept it's only my opinion) that a
single
sitting duck like a space tether would be far too vulnerable to too
many potential disasters that could shut off supplies to everyone off-
world who might be relying on its continued operation. This is
entirely unlikely with a BEP system.
My main interest now is to raise awareness of the options that a
beamed (maser) energy system will open up and question whether we
shouldn't be starting by first dramatically reducing the cost and
efficiency of the launch technology. It might seem a `long bow to
draw' to suggest that BEP holds the answers but when everything
is
broken down to basics, I believe this really is the case. When
developed, BEP will slash launch costs so dramatically we will wonder
what all the fuss was about.
Is it possible? I have reason to believe that, given time, I can
eventually prove it.
Even if we had a SPS beaming energy toward the ground, the reality is
that, from GEO, the E/D at the ground would not be sufficient to
fully power a craft directly. If safety concerns are addressed, as
indeed they must be, SPS will not be allowed to produce energy levels
directed at the ground that exceed reasonable safe limits. Such
limits will undoubtedly be no more than ~10 kilowatts/m2 rather that
the 1000kW/m2 needed to power a craft or burn up your neighbours or
enemies
Just what those limits might be will obviously depend on many
factors. A set absolute maximum would seem reasonable but other
factors, like the proximity of sensitive fauna, will also have a
bearing.
There are a few points to be made:
1. is that SPS and BEP is not just about what is technically feasible
but also what is safe and practical.
2. though lasers might be ideal for small micro-craft, they are far
from ideal for larger craft, therefore.
3. the sooner we start to develop a maser system, the quicker we will
have a cheap and effective launch system that costs (possibly far
less than) $200/lb to orbit, instead of $2,000/lb, the cheapest
option presently available (according to earlier listing/member).

To this end, I would like to inspire the consideration of what
practical factors will affect craft design and power supplies. I am
interested in what will a craft powered by BEP look like (in profile)
and how power can most effectively be collected, directed and used,
both at the craft and at the ground. Give it some thought and send me
an email.
I confess, I do have an ulterior motive. I developed a hypothesis
many years ago when approaching this technology from an entirely
different angle. I believe that once engineers and enthusiasts start
to really consider these options, they will inevitably make the same
conclusions I reached and that will start the ball rolling

With a BEP manned craft, there are a number of options, some more
acceptable than others:
1. Lasers have great range in ideal conditions but ideal
conditions are rare, making masers by far the most attractive option
within the atmosphere.
2. For propulsion, a beam E/D of anything up to 1Mw/m2 is
required at the craft. This is basic math, based on Lightcraft tests
etc. It is also enough to ionise the surrounding air.
3. To limit unwanted or premature ionisation, the beam would be
transmitted (or reflected) from a wide area to be brought to a focus
beneath the craft. This makes focussing reflected energy received
from a SPS an attractive option to power a BEP craft, though other
options (ie from ground sources) are still available.
4. The design of the launch platforms and collector/reflector
fields that make these various options possible are significant
elements of design to be considered.
5. The beam directed at the craft would be a major safety risk
if pointed toward the ground but no more than a great defence system
if pointed upwards. Targeting the craft is also far easier and more
effective from below where the range is no more than 100's of
miles,
not 1000's.
6. Whilst reactant air can be injected between pulses, as in the
Lightcraft, a reactant must still be carried onboard for use from the
TOA. Total fuel (to LEO) is estimated at only 50% of AUW, as against
>95% for conventional rockets. However, flight within the atmosphere
requires NO onboard fuel and no engines! Something to think about.
7. If sufficient energy can be directed forward, above the
craft, an air spike could provide significant lift and virtually
eliminate sonic drag effects. How this energy is collected and
controlled might also be a significant design feature.
8. In space, it might become feasible to collect energy from the
SPS at higher E/Ds without serious consequences at the ground.
Another feature to consider?
9. BEP is ideal for a direct lift to GEO on power delivered from
orbit. With reflectors on the ground, theoretically, energy could be
supplied continuously from one point (above or below) throughout the
whole launch. The beam also supplies automatic craft guidance, like a
ball on a column of air.
I would be interested to receive any thoughts on the basics of craft
and launcher design.
CCMcM