Re: sci space policy targeted by disinformation experts?

On Mar 26, 10:52 pm, Willie.Moo...@xxxxxxxxx wrote:
A lot of speculation - I recall reading really interesting stuff, that
just falls off the radar screen so to speak for no damned good
reason.  Usually when something doesn't work for a sound technical
reason, you can find some arcane journal article explaining why.  When
you cannot find that, there is a possibility - if the ideas are sound
otherwise, they've been taken black.

One way to check that out is to track the researchers.  Are they
teaching and not doing a damned thing, or are they busy and have moved
from where they were to points West and stopped publishing?

Thats another inferential point to anyone who cares.

Energy is a problem with high speed flight.  Aurora nominally burning
hydrogen in air in an external combustion scramjet - and a 10%
structural fraction - producing thrust by intercepting the shock
waves.  You eject the fuel into the stream at the stream velocity -
right at the shock wave at the nose - so its stationary in the flow.
By the time it reaches the thrust structure at the rear of the
aircraft, its mixed with an oxidizer - you stablize that with an
expansion shock, and detonate it with a laser or spark or particle
beam - and the shockwave and thrust surface are shaped to interact to
produce thrust.

Mach 6 and drag coefficient gives you an estimate of power. The X-15
had a drag coefficient at hypersonic speeds of Cd = 0.095

Drag force is equal to

  F = 1/2 rho V^2 * Cd * A

http://en.wikipedia.org/wiki/Aurora_aircraft

area looks to be in the 30 sq m range

http://en.wikipedia.org/wiki/Scramjet_Programs

http://en.wikipedia.org/wiki/Mach_number

Mach 6 is around 1,800 m/sec, and rho=0.01 kg/m3

So,

   F = 1/2 * 0.01 * (3.24e+6) * 0.095 * 30
      = 46,170 newtons
      = 4,701 kgf
      = 10,343 lbf

at around 50 km altitude

Force times distance is energy.
Force times speed is power

So, 46,170 newtons x 1,800 m/sec = 88.106 megawatts

Hydrogen when burned in air releases 143 megajoules per kg.  Assuming
1/4 of this energy is usefully applied to the propulsion system,and
3/4 of the energy is wasted in various ways - means 35.75 megajoules
of propulsive energy is available per kg of hydrogen.  This gives us a
burn rate of 2.46 kg/sec to maintain that thrust.  With a 50% cycle
efficiency - fuel use is cut in half 1.23 kg/sec

This is the likely fuel consumption of hydrogen for the aircraft at
this speed - from first principles.

Going back to our models of Aurora - it likely has a 600 cubic meter
fuel volume.  and hydrogen has a density of 70 kg per cubic meter
which obtains 42,000 kg fuel mass.    Enough to power the aircraft for
4 hours and 45 minutes at Mach 6 cruise - at thelower efficiency, and
9 hours 30 minutes at the higher efficiency.  Enough to fly 3/4 of the
circumference of the Earth at cruise at the lower efficiency, and 1.5x
around the world at the higher efficiency.

One can imagine a number of interesting missions for such an aircraft
if it exists.

.

A hydrogen powered turbofan could be used for subsonic flight - or a
jet fuel spare tank with turbofan - or a turbofan stage. All are
possibilities. If I were building the thing, I'd use a liquid fuel
rocket booster - JATO - that would be big enough to get me to my
operating altitude and speed to turn on the hydrogen scram jet.
Recover the liquid booster - glide back. The aircraft wouldn't stop
anywhere - it just flies out and back - and lands at the take off
point. One can imagine big circles being flown with increasing
diameters - until they encompass great circles - gentle sweeping turns
- at Mach 6 you'd want to keep them that way to keep gee forces under
control. A 1 gee turn at mach 6 has a radius of 330 km - a diameter
of 660 km!!! And taks 10 minutes to do a 180 degree turn around at
speed!! pulling one gee!!

For comfort, limiting maneuvers to say 1/4 gee - would increase turn
radius to 1,320 km - and a 180 degree turn would cover 2,640 km - so,
this starts to give you how you might use the aircraft
operationally.

Other energy sources that might be tapped in an unpiloted aircraft
are;

1) nuclear isomers
2) antiproton boosted microfission
3) antiproton initiated microfusion
4) direct antiproton heating of air/propellant

and of course

5) laser driven jet/rocket

all built into a MEMs based propulsive skin.

This would give very high performance >30 gees, without a pilot, and
unlimited range

.

Relevant Pages

  • Re: Ju-252
    ... supply enough food, fuel and amunition. ... Getting an aircraft into the air is a matter of priorities. ... So given the easier handling of cargo and deducting the allowance ... The Ju 252 had far greater cruise speeds; ...
    (rec.aviation.military)
  • Re: sci space policy targeted by disinformation experts?
    ... By the time it reaches the thrust structure at the rear of the ... had a drag coefficient at hypersonic speeds of Cd = 0.095 ... efficiency - fuel use is cut in half 1.23 kg/sec ... This is the likely fuel consumption of hydrogen for the aircraft at ...
    (sci.space.policy)
  • Re: The magic of a Prius automobile
    ... is better' arguement does fail at slower speeds -- air resistance goes ... as more or less the square of velocity, the 'hotel load' on the engine ... divided by energy in times 100 and speed has nothing to do wiith it. ... Energy is a function of fuel. ...
    (sci.physics)
  • Re: Low Cost Hydrogen is here to stay
    ... This library page holds a collection of hydrogen energy resources. ... But please do NOT call Hydrogen a fuel. ... one MIGHT foolishly object and say that oil coal and natural gas ... water down into its component parts and retain the hydrogen, ...
    (sci.energy.hydrogen)
  • Re: ETHANOL OR METHANOL?
    ... An Energy Revolution ... The world economy is currently running on a resource that is ... percent fuel saving over existing models, and none of them drove more, ... THE ECONOMICS AND TECHNOLOGY HAVE ARRIVED?NOW FOR THE POLITICS ...
    (sci.energy)
Loading