Atomic ramjet for exploring Titan

On Mar 21, 7:52*am, Van Chocstraw
wrote:
Jeff Findley wrote:
"Van Chocstraw" wrote in message
...
Rick Jones wrote:
Frogwatch wrote:
In the late 50s and early 60s, the USA had "Project Pluto" a nuclear
reactor powered ramjet whereby a reactor directly heated incoming
air to provide thrust. *It could be capable of flying for months but
emitted a lot of radiation, maybe even a lethal dose to anything
nearby.
So, say we want to explore Titan completely from the air, we drop a
Pluto style ramjet into the atmosphere of Titan where it flies
around for months sending back data. At the end of its life, we
could simply allow it to crash OR we could use onboard solid rockets
to accelerate it to escape velocity from Titan and allow it to
either go in orbit about Saturn or to drop into Saturns atmosphere.
Such a flying machine might be just what we need to explore Venus
too. *The dense atmosphere would allow for fairly low speed flight
there.
Apart from a present lack of humans, why would it be any better for a
nuclear reactor to be spewing radiation into the atmosphere of Titan
or Venus than it would be for Earth?
The sun is spewing much more radiation than a jump engine would.

Apples and oranges. *Not all radiation is the same. *There is a world of
difference between visible light radiation and, say, gamma radiation.

The whole argument is awfully silly though. *If engineers can't build and
fly nuclear ramjets on earth, how can engineers design, build, and test one
to fly on Titan? *Not to mention the hazard of launching the thing.
Launching RTG's encased in protective cases designed to withstand a launch
accident and subsequent reentry is not the same thing as nuclear reactors.

Jeff

You don't think the sun puts out gamma radiation? Think again. Just
because the earth's magnetic field and atmosphere filter it out don't
mean it's not there.

--
//--------------------\\
* * * * Van Chocstraw
*\\--------------------//

Our moon puts out a thousand fold more gamma than does our sun. The
sun is certainly worthy of X-rays and UV a/b/c, plus a random shot of
gamma only now and then whenever there's a substantial halo CME.
Otherwise our sun is kind of passive.

With our magnetosphere failing us at -.05%/year, it's a good thing
that most CMEs are not directed at us. Unfortunately, our Selene/moon
isn't gamma or X-ray passive.

~ BG

Alain Fournier wrote:


Even a wind of a few kilometeres per second may make it impossible
for the vehicle to land and stay in one place for long enough to
either analyze the soil or take a sample, as the envelope of the
balloon will act like a sail and drag the probe around, particularly
in the very low gravity and with the dense atmosphere.

Yes. In fact that would even be true about a wind of a few meteres per
second.
Oh! is that what you meant to say instead of a few kilometeres per
second :-)

Yeah, you got me on that one; it was indeed to be "a few meters per
second" :-)
If it had been otherwise, the landing view from Huygens would have been
interesting indeed.


It might be smarter to have the balloon drop small surface probes as
it flies along without landing itself, and have the probes relay
signals up to some sort of satellite in Titan orbit for transmission
to Earth.
The same landing problem would apply to any sort of winged
aircraft...you probably get it to land in one piece, but taking off
again could be a real problem.
Maybe a atomic-powered helicopter is the answer?
In that low of gravity with that thick of a atmosphere maybe that
could be made to work, and it probably would be heavy enough to stay
in one place once landed without the wind blowing it around till it
finished its surface examinations and lifted off again.
The combo of a thick atmosphere and very low gravity is so odd that
it makes it hard to figure out what is possible and impossible in
those conditions. You don't know if you want to go with aircraft or
submarine type analogies in regards to designs of things.

The way I would see it happen would be that you only make rather high
altitude measurements when you cover an area the first time. Before
you cross a path already covered, you decide which attainable spot
deserves special attention and go down to that place. You could have a
"probe on a rope", you throw it to the ground let it do what it can
for a minute and pull it back in.

But let me be clear. I don't think that ballooning is the best method
to study Titan. Just because it could be done doesn't mean it is the
best way to do it.

An aircraft of some sort would be preferable in regards to flying where
you wanted to over its surface.

Pat

Pat Flannery wrote:

Getting a reactor of the size needed on the way to Titan is a real
problem though.
The Russians have put small true nuclear reactors into space on their
RORSATs, but the scale of this thing is in a whole other ballpark:
http://www.bisbos.com/rocketscience/...o-reactor.html

So you are going to need a huge booster or assemble it in orbit from
component parts
When you take the probable cost of this concept into account, it's a
slick idea that probably would never be funded.

The anti-nuke nuts go crazy over the RTGs, think what they will say
about an unshielded reactor. They might even have a kernel of a point in
this case.

Brett

Brett Buck wrote:

:Pat Flannery wrote:
:
: Getting a reactor of the size needed on the way to Titan is a real
: problem though.
: The Russians have put small true nuclear reactors into space on their
: RORSATs, but the scale of this thing is in a whole other ballpark:
: http://www.bisbos.com/rocketscience/...o-reactor.html
:
: So you are going to need a huge booster or assemble it in orbit from
: component parts
: When you take the probable cost of this concept into account, it's a
: slick idea that probably would never be funded.
:
: The anti-nuke nuts go crazy over the RTGs, think what they will say
:about an unshielded reactor. They might even have a kernel of a point in
:this case.
:

Not really. Until it's actually been powered up, a nuclear reactor is
a pretty benign thing. It's all the trash it produces once you start
making power with it that is dangerous.

Van Chocstraw wrote:

The whole argument is awfully silly though. If engineers can't build
and fly nuclear ramjets on earth, how can engineers design, build,
and test one to fly on Titan? Not to mention the hazard of launching
the thing. Launching RTG's encased in protective cases designed to
withstand a launch accident and subsequent reentry is not the same
thing as nuclear reactors.

Jeff
You don't think the sun puts out gamma radiation? Think again. Just
because the earth's magnetic field and atmosphere filter it out don't
mean it's not there.

There was nothing to indicate that SLAM/Pluto wouldn't have worked as
advertised if it had been built.
They had the nuclear ramjet up and running, and that was certainly the
major hurdle that needed to be cleared.
In fact, a pretty much stock SLAM could have worked on Titan, as its
engine just relies on heating a atmosphere, not combusting it, so the
composition of that atmosphere need not include oxygen.
SLAM's Mach 4 (1.361 k/sec) speed at 10,000 meters (Mach 3 on the deck)
would mean it was traveling at around 1/2 of Titan's escape velocity
(2.639 k/sec).
BTW, SLAM was estimated to have a total range of around 182,000 km, or
over 4.5 times the distance around the Earth at the equator, so given
Titan's circumference of 16,170 km, a SLAM could circle it over ten times.
Getting a reactor of the size needed on the way to Titan is a real
problem though.
The Russians have put small true nuclear reactors into space on their
RORSATs, but the scale of this thing is in a whole other ballpark:
http://www.bisbos.com/rocketscience/...o-reactor.html
So you are going to need a huge booster or assemble it in orbit from
component parts
When you take the probable cost of this concept into account, it's a
slick idea that probably would never be funded.

Pat

The orbital elements of Saturn and Earth are;

Planet a (AU) e i (deg) Omega (deg) w
(deg) L (deg)
Earth 1.00000011 0.01671022 0.00005 -11.26064 114.20783
100.46435
Saturn 9.53707032 0.05415060 2.48446 113.71504 338.71690
49.94432

Launching a spacecraft with a hyperbolic excess velocity of of 11.2 km/
sec at Earth in the right direction takes it to the Saturnian system
in 6 years 14 days and 16 hours 48 minutes. It arrives slightly in
front of Saturn, which catches up to the spacecraft with a speed of
5.44 km/sec.

By performing minor course adjustments, the precise time of arrival at
Saturn can be varied over the 14 day period of time it takes for Titan
to orbit Saturn. So, the spacecraft arrive at precisely the right
time and position to aerobrake in Saturn's atmosphere, and then make
their way 1.4 million km to Titan, where they undergo a second
aerobrake maneuver to enter orbit and land on the planet.

Using data from;

http://ssd.jpl.nasa.gov/horizons.cgi#top

Ephemeris Type [change] : ELEMENTS
Target Body [change] : Titan (SVI) [606]
Center [change] : Saturn (body center) [500@699]
Time Span [change] : Start=2009-03-23, Stop=2009-04-02, Step=1 d
Table Settings [change] : defaults
Display/Output [change] : default (formatted HTML)

Allows us to calculate the precise speeds and arrival times.
Basically, we've got to enter a transfer trajectory from the radius of
Saturn to Titan, from a hyperbolic entry speed of 5.44 km/sec.

An aerobraking maneuver through the atmosphere of Saturn knocks a few
km/sec off the speed and brings the spacecraft into the Titan system -
where it aerobrakes again.

There the spacecraft breaks into the orbiter segments and the lander
segments. Three orbiters and three landers separate from a bus as
they approach titan, and you end up with three orbiters and three
landers.

With a mass 0.0225 that of Earth, orbital speeds are 1/296.3 x
slower. Since the planet is synchronous with Saturn, and has zero
inclination to its orbital plane, satellites at L1, L4 and L5 provide
complete coverage of the surface communication wise and from orbit.
In addition to these six units, a seventh unit is added as a close in
radar mapper in polar orbit above the planet.

Each subsatellite has a mass budget of 500 kg - a total of 3,500 kg -
3.5 metric tons, and a bus has a mass of 500 kg - a total payload of 4
metric tons.

Each satellite has a 10 kW TPV nuclear thermal reactor with 50%
efficient TPV unit on board - with a nuclear light bulb.

Keeping with the advance nuclear theme, as a demonstrator; a
microfission nuclear pulse stage produces 4 tonnes of thrust and
masses 800 kg empty. With a 2,200 sec Isp - a Ve=20 km/sec - we
require;

u = 1 - 1/exp(Vf/Ve) = 1 - 1/exp(11.2/20) = 0.48279

That's the propellant fraction needed so, 3.6 metric tons of pulse
units are needed - most of which is inert material to shape the blast
- to propel the 4.8 metric tons of payload - to an excess of 11.2 km/
sec.

The nuclear pulse stage is not operated until the entire package is
safely on an escape trajectory 1 million km from Earth (with zero
hyperbolic excess velocity)

So, a 8.4 metric ton payload is propelled to an escape trajectory, and
the nuclear pulse stage is used to kick it to a minimum energy
transfer orbit to Saturn.

Electrically driven resistojet MEMs based thrusters over the skin of
each of the subsatellites and bus, provide 1,100 sec Isp (Ve=10 km/
sec) delta vee for the package as it flies toward Saturn - an aerogel
aerobrake sheild - very light weight - with MEMs based resistojet
rockets - powered by the nuclear lightbulb in each subsatellite -
provides attitude control as well as maneuvering delta vee.

The Atlas 551 lofts this package reliably to escape trajectory where
it operates.

So, to recap, there are 7 subsatellites, each 500 kg mass budget. 3
orbiters - taking up stationary positions around the surface of Titan
- to communicate with the landers. 3 landers - which are similar to
the Sikorski Cypher - powered by a nuclear lightbulb - TPV - and
adapted to fly in the Titanian atmosphere. A seventh subsatellite
enters polar orbit close in to Titan, to do radar mapping of the
moon. In addition to 3.5 metric tons of satellites, there is a 500
kg bus, and an 800 kg nuclear pulse rocket stage, that carries 3.6
metric tons of microfission bomblets - that propel the entire assembly
to Saturn. Each bomblet is 3.6 kg each - with only a few milligrams
of fissile material each. The inert material shapes the blast and
makes the propulsive elements more efficient - with 1,000 bomblets
detonated. Fusion compression techniques are adapted to make fission
triggers of very small size.

CONSTANT BOOST FUSION ROCKET

Using anti-matter triggers, to detonate small fusion devices made of
Lithium-6/Deuteride

D + 6Li $B"*(B 2 4He + 22.4 MeV

Which produces a fusion reaction with an exhaust stream velocity of

Ve= 23,258.6 km/sec.

Which are easily collimated with electrostatic and electromagnetic
fields, since the alpha particles are highly charged and lightweight,
and the reaction is totally aneutronic!

A booster that operates with this exhaust velocity, and boosts at a
constant 1/20th gee from Earth escape would travel the 790 million km
to Saturn in 29 days 9 hours and 28 minutes. Boosting away from
Earth for half that time, and away from Saturn half that time. The
spacecraft attains a velocity of 616 km/sec - nearly 1/500th the speed
of light. The Delta Vee needed to achieve this level of performance
is 1,232 km/sec. The propellant fraction is given by

u = 1 - 1/exp(Vf/Ve) = 1 - 1/exp(1,232/23,258.6) = 0.0516

so, only 5.16% of the total vehicle mass is lithium deuteride
propellant. The vehicle here could be 11% propellant, and it would
be capable of depositing a payload and returning to Earth to be
reused.

With this kind of performance we don't need aerobraking - and in fact,
aerobraking at these speeds is problematical.

Using the same 4 tonne reference mass as before, and a 1 to 1 thrust
to weight ratio - with a 1/20th gee - so we're talking a 600 kg system
with a 600 kg top thrust - that pushes around 4 tonnes of payload, 0.5
tonne booster, and 628 kg of lithium deuteride microfusion pellets - a
total mass of 5,228 kg - to recap -

3 orbiters at 500 kg each - nuclear light bulb powered
3 landers at 500 kg each - nuclear light bulb powered
1 polar orbiter radar mapper 500 kg - nuclear light bulb powered
1 bus 500 kg
1 aneutronic fusion rocket - 600 kg - 600 kg top thrust - carrying
628 kg of li6-d pellets

The vehicle boosts to Saturn in less than 30 days - slowing down
enough to drop the payloads off on trajectories that bring them to
their desired locations around Titan, and then returns (with the bus)
30 days later - and descends - to a powered landing on Earth - the
bomblets heat air to increase their thrust dramatically while reducing
power levels - allowing for brief bursts at high gees.

In fact, the nuclear fusion powered ram/rocket is used to launch the
system.

Consider that with an exhaust velocity of 22,258.6 km/sec and a thrust
of 600 kg (5.88 kN) is a rocket engine with 83 GW continuous power.
Increase the mass flow 33.16 times and reduce the exhaust speed to 20
km/sec - and thrust increases to 600 tons!!! With a maximum need of
say 9 tons - power levels can be reduced to 1.2 GW at maximum air
augmented thrust at lift off - and then power increased as mass flow
rates are reduced.

I guess what I'm saying is that we can build a 5.3 metric ton vehicle
- that is mostly payload - that lofts off of Earth, deposits a
sophisticated payload set around Titan in 30 days - and returns to
Earth 60 days after launch - ready to do it again.

This would be a great proof of concept vehicle - and with an assembly
line of low cost common core deep space satellites - and an
interplanetary internet protocol - a small fleet of these boosters
would put up a network of interplanetary explorers - while
demonstrating all the features of larger piloted systems that would
come next.

A 4 tonne piloted capsule - carrying 3.6 tonnes of payload. At 3 kilo
per day per person - 100 days - 300 kilos - a crew of four - 1.2
metric tons - each crew member has 600 kilos allocated to them - for
equipment and their own weight.

40 days out and 40 days back - with 15 days at target and 5 days spare
- we have a distance at 1/20th gees. This little booster can travel
anywhere inside the orbit of Saturn, land and take off on any planet
or moon with an atmosphere.

The smaller moons of Saturn, and Jupiter, the Earth's moon, and
Mercury, have a surface gravity low enough to allow take off and
landing and maneuvering with 1 gee thrust - in a 1/4 or less gee
environment.

Venus, Mars, Titan, Earth - adequate atmosphere for landing and take
off at multiple gees.

Diemos, Phobos, Ceres, Jovian Moons, Saturnian moons, Earth moon,
Mercury - landing and take off without atmospheric assist.

On Mar 18, 7:45*pm, wrote:
The only problem with nuclear powered aircraft is that they provided a
clear proof of concept for engines that didn't need oil products to
fuel them.

http://www.strange-mecha.com/aircraft/APA/APA.html

In that case, simply figure out how Big Energy and the Rothschilds can
make an even bigger killing off the nuclear alternative, and we're
good to go.

~ BG

On Mar 24, 1:35*pm, wrote:
A 4 tonne piloted capsule - carrying 3.6 tonnes of payload. *At 3 kilo
per day per person - 100 days - 300 kilos - a crew of four - 1.2
metric tons - each crew member has 600 kilos allocated to them - for
equipment and their own weight.

40 days out and 40 days back - with 15 days at target and 5 days spare
- we have a distance at 1/20th gees. * This little booster can travel
anywhere inside the orbit of Saturn, land and take off on any planet
or moon with an atmosphere.

The smaller moons of Saturn, and Jupiter, the Earth's moon, and
Mercury, have a surface gravity low enough to allow take off and
landing and maneuvering with 1 gee thrust - in a 1/4 or less gee
environment.

Venus, Mars, Titan, Earth - adequate atmosphere for landing and take
off at multiple gees.

Diemos, Phobos, Ceres, Jovian Moons, Saturnian moons, Earth moon,
Mercury - landing and take off without atmospheric assist.

In that case, yourself and Steven Chu that would follow your lead
should get cracking. Are we otherwise supposed to wait another decade
for no good reason?

~ BG