25%c Interstellar Probe in Our Lifetime

The principle of particle beam propulsion to accelerate a
magsail starship to high speeds is well known, but it
seemingly requires powerful long range particle beam
emitter technology.

Instead, I propose using powerful short range fission
powered beam emitters, acheivable with near term technology.
These disposable emitters are laid out in a long line along
the acceleration path of the starship.

Particle Pulse Emitter:
________________
/ |
/ /|SSSSSSSSS|
/ PPP / |TTTTTTTTT|
( PPPPP( | : - hydrogen propellant
\ PPP \ |TTTTTTTTT| - fission fuel
\ \|SSSSSSSSS| - fusion fuel
\________________|

The particle beam emitter looks like a nuclear thermal rocket.
The "reactor" in the rear heats up hydrogen gas, which escapes
out the nozzle. Unlike a normal rocket, we only care about
the exhaust gas; the rest of the rocket vaporizes upon use.
It's a nuclear bomb.

The bomb is a basic Tellar-Ulam fission-fusion-fission
design, with some hydrogen "propellant" inside the last stage.
Upon detonation, the final fission stage efficiently fuses,
creating a dense imploding plasma with 84MeV per fission
fragment. This heats the hydrogen gas, which escapes out
the nozzle at speeds up to 40%c. The secondary
fusion-fission stage is not actually cylindrical, but is
instead tapered in order to help direct the hydrogen
rearward out the nozzle. In particular, a bell shaped
section in the rear can help direct the hydrogen rearward.

Assuming a 2:1 ratio of fission fragments to hydrogen and
perfect thermal transfer, the hydrogen is given 56MeV of
energy for an exhaust velocity of around 33%c. This
corresponds to a mass ratio of 236:1. This mass ratio
only considers the mass of the final stage plus hydrogen.
With the overhead of the rest of the bomb and stationkeeping
rockets, let's say the mass ratio is 500:1.

Uranium:H Mass | Exhaust Velocity
---------------+-----------------
236:1 | 33%c
120:1 | 29%c
30:1 | 20%c
14:1 | 13%c

By adjusting the amount of hydrogen in the "reactor", it's
possible to trade-off between mass ratio and muzzle velocity.
Since the mass ratio for lower muzzle velocities is much
greater than for higher muzzle velocities, it's worth
optimizing the muzzle velocity along the bombtrack, starting
with lower muzzle velocities where the starship is slow and
gradually increasing the muzzle velocity along the bombtrack.

With practical particle pulse muzzle velocities of up to
maybe 33%c, accelerating a magsail starship up to 25%c
should be doable. This starship could be a lightweight
flyby probe, unburdened by massive fuel tanks.

This mission can be done with near term technology! The
particle pulse unit is VERY similar to existing nuclear
bomb designs, which have been extensively studied and modeled.
It would not take a heavy extra investment to perform the
basic initial design. Underground or space testing of a
modest number of bomb units could provide information about
the amount, velocity, and directionality of the hydrogen
particle pulse.

The starship itself can be lightweight and compact, especially
if it uses an M2P2 sail. Either a traditional magsail or
an M2P2 sail needs further R&D and testing in space, but such
sails are potentially very useful for interplanetary missions
so it's worthwhile regardless.

Testing of sail performance can be conducted using plasma
thrusters and a modest number of pulse unit tests conducted
at low speed. This is because the stresses on the sail are
greatest during the initial acceleration. As the sail moves
faster and faster, the "push" from each pulse unit gets
smaller and smaller.

Assuming the magsail technology has already been developed
for other purposes, there is relatively little extra R&D
required to make this flyby probe a reality. With a
mission time of around 2 decades (including time for
return data), the project duration is reasonable and it's
not plausible that a later mission with improved
technology could arrive faster/sooner.

Isaac Kuo

IsaacKuo,
Now this sort of topic is making some sense, thus unfortunately you'll
not be getting a gram of expertise support or any other viable feedback
from this usenet of need-to-know and otherwise disinformation that
sucks and blows.

Unlike a normal rocket, we only care about the exhaust gas;
the rest of the rocket vaporizes upon use. It's a nuclear bomb.

The bomb is a basic Tellar-Ulam fission-fusion-fission design,
with some hydrogen "propellant" inside the last stage.

I may have some furth questions that are specific to your design,
although a few suggestions as to a similar notion may get involved.

Although your "Uranium:H Mass | Exhaust Velocity" methods seems
perfectly doable, I was wondering a wee bit if you could polish
(meaning not to distroy) the notions of what I'm suggesting as per
utilizing that of Ra--Rn breeder reactor, and of thereby using the
rather nifty Rn byproduct as fuel and/or of creating those extremely
fast moving ions.

Ra226--LRn222--Rn222--ion

Doesn't energy-in = energy-out?

If the energy-out were to be that of essentially fast moving spent
Rn222 as per becoming lead, as such wouldn't that substance be even
better off than using hydrogen that's somewhat mass deficient?

This might not even be rocket-science. You tell me.

Possibly the LRn could seemingly become a part of your fusion or
fission fuel, along with a touch of LXe should put the combined density
way over the nuclear reaction line of accomplishing something short of
being an atomic bomb, that which might otherwise have somewhat similar
drawbacks to utilizing such amounts of energy in space, especially
where there's no alternative pitstop along the way.

Brad Guth

Brad Guth wrote:

Unlike a normal rocket, we only care about the exhaust gas;
the rest of the rocket vaporizes upon use. It's a nuclear bomb.

The bomb is a basic Tellar-Ulam fission-fusion-fission design,
with some hydrogen "propellant" inside the last stage.

I may have some furth questions that are specific to your design,
although a few suggestions as to a similar notion may get involved.

Although your "Uranium:H Mass | Exhaust Velocity" methods seems
perfectly doable, I was wondering a wee bit if you could polish
(meaning not to distroy) the notions of what I'm suggesting as per
utilizing that of Ra--Rn breeder reactor, and of thereby using the
rather nifty Rn byproduct as fuel and/or of creating those extremely
fast moving ions.

I'm not a nuclear physicist, so I don't know how good a Ra--Rn
reaction would be in comparison to current Uranium and
Plutonium reactions.

Ra226--LRn222--Rn222--ion

Doesn't energy-in = energy-out?

If the energy-out were to be that of essentially fast moving spent
Rn222 as per becoming lead, as such wouldn't that substance be even
better off than using hydrogen that's somewhat mass deficient?

For the purposes of my "Nuclear Pulsed Puff Propulsion" concept,
hydrogen is the ideal propellant. In a gas, temperature is
essentially kinetic energy per atom. The kinetic energy is the
same for a heavier or a lighter atom--but since kinetic energy
is 1/2mv^2 that means a lighter atom moves faster.

For this reason, thermal rockets ideally use hydrogen propellant.
My thermal rocket is simply a heck of a lot hotter than any
existing thermal rocket.

However, I do turn traditional nuclear thermal rocket concepts
inside-out. Traditional solid-core, liquid-core, and gas-core
nuclear thermal rockets lack the exhaust velocity for interstellar
travel, but they can be very efficient for interplanetary travel.
They take a large amount of hydrogen and funnel it through a
small amount of fissionables in order to get a lot of "low grade"
thrust out of every ounce of fissionable. I'm doing the opposite;
taking a large amount of fissionables and using it to heat up
a small amount of hydrogen in order to get a small amount of
"high grade" thrust.

Note that the fission products only travel at around 3+%c.
However, the fission products are two orders of magnitude
heavier than hydrogen atoms. Even with a square root
involved, this still means fission heated hydrogen can get
an order of magnitude better speed than directly using
the fission products.

Isaac Kuo

IsaacKuo,
This well founded argument of your's makes no tit-for-tat sense;
The kinetic energy is the same for a heavier or a lighter
atom--but since kinetic energy is 1/2mv^2 that means a lighter
atom moves faster.
So what's the difference if energy-in still equals energy-out, and if
1/2mv^2 is being fair and square by the regular laws of physics, then
perhaps shooting out relatively cold but fast moving Rn222/lead should
surpass the heck over shooting out wossy superheated H/U238 ions any
day of the week. If need be, the Rn222/lead matrix could even become a
laser ion cannon of worthy thrust that's capable of exiting a
considerable density of matter at nearly 'c'.

My thermal rocket is simply a heck of a lot hotter than any
existing thermal rocket.
Up to a viably containable point of total thermal nuclear melt-down,
heat is certainly a good thing to take advantage of, especially if any
of that energy as being released as heat represents that such IR
photons are actually going to transfer this horrific energy into
pushing something along without having to burn away at your spacecraft
in the process.

Wouldn't a relatively cold thruster that's tossing out extremely heavy
ions as leaving town at a horrific velocity be at least somewhat
interesting. Especially if the vast bulk of the necessary Rn element
can be breeder reactor made as a reactor byproduct while on the fly?

In other words, if we applied a TJ of input energy to the likes of a
LRn--Rn and whatever else reaction chamber as opposed to a reaction
chamber of H and whatever U238, whereas that fact of your wossy H
having the greater exit velocity potential of supposedly going so much
faster is sort of wasted on the KE formula that usually implies that it
takes a given mass in order to push upon other mass. However, if we're
to be going by your plan of lighter is offering a better net thrust
reaction, then its photons that are going to achieve the absolute best
amount of thrust. Of course those photons of nearly 'c' exit velocity
are obviously fast moving little 2D (quantum string like) items, but lo
and behold, it seems the hard-science has proven that you're hardly
moving a kg worth of spacecraft per TJ of energy input, especially if
all that's exiting such photon thrusters are of those naked and/or
nearly empty photons.

What I'd like to know is; If H ions can become laced with U238, then
how much extra mass can a photon haul?

Can a sufficiently IR photon even be tricked into hauling a U238 ion,
or perhaps the Rn222 ion?

Interstellar travel via gravity-well to gravity-well exchanges is
what's most likely going to make for the most all around energy
efficient and viably fast though somewhat lethal alternatives, whereas
kicking out ions of H as having been loaded to the gills with a touch
of U238 might actually become the next best do-everything ticket to
ride. However, we currently know how to safely extract and thereby
create LRn, thereby having established a viable 1600 year half-life of
providing LRn--Rn222 (which is already better off than packing lead)
on the fly as safely derived from good old Ra226 which was obviously
once upon a time U238.

Short of creating and having to sustain a nearly continuous nuclear
bomb; how do you go about safely extracting and thus utilize the raw
and somewhat nasty element of U238 for accomplishing any reasonable
form of H/U238 as energy conversion into ion thrust?

It seems merging U238 with H isn't exactly something you'd want to be
anywhere nearby, especially if the matrix process got a touch out of
control.

In one way or another, an extremely large inventory of LH2 has to be
taken along for the ride, surviving along with the cash of U238 which
has to get consumed along the way without getting every soul onboard
summarily dead in the process, which might remain as a secondary
qualifier unless you're speaking of purely robotics going where no
robot has gone before. Actually, I tend to favor on behalf of robotics
accomplishing a good million to one capability over much of anything
which humanly involves going further than the LL1/ME-L1 zone that's
associated with our moon.

There's no doubt that a nuclear blast formulated method of thrust is
something that's doable, and that reasonably good thrust results can be
obtained. However, perhaps our DNA would like a second opinion before
being attached to a series of thermal nuclear thrusters that tend to
burn off everything in sight to a fairlywell. I believe there are
certain limits even for robotics.

Brad Guth

IsaacKuo,
BTW; turning "concepts inside-out" is exactly what I think needs to
happen before it's too late. One of the best arguments for establishing
the LSE-CM/ISS is for obtaining He3 from our moon before we all have to
die in WW-III over the lack of affordable fossil fuels.

I'm doing the opposite;
taking a large amount of fissionables and using it to heat up
a small amount of hydrogen in order to get a small amount of
"high grade" thrust.
This is exactly my argument on behalf of utilizing Rn before it's turns
into lead, as it's a good deal of energy that's rather quickly going to
waste before our dumbfounded eyes.

Brad Guth

Brad Guth wrote:
IsaacKuo,
This well founded argument of your's makes no tit-for-tat sense;
The kinetic energy is the same for a heavier or a lighter
atom--but since kinetic energy is 1/2mv^2 that means a lighter
atom moves faster.

So what's the difference if energy-in still equals energy-out,
and if 1/2mv^2 is being fair and square by the regular laws
of physics, then perhaps shooting out relatively cold but fast
moving Rn222/lead should surpass the heck over shooting out
wossy superheated H/U238 ions any day of the week.

The difference is that the Rn222/lead and/or whatever other
heavy atoms you consider would NOT be moving fast. All the
kinetic energy in the world isn't worth squat to the magsail
if it can't even catch up with the magsail in the first place.

Note that the uranium atoms and its resulting fission products
never move faster than about 3.8%c. Nevertheless, they can
heat up the hydrogen atoms up to 40%c because they are so
much heavier than hydrogen atoms. It's these fast hydrogen
atoms which can catch up with and push forward the magsail.
The heavier atoms are simply "waste mass" as far as the
magsail is concerned.

If need be, the Rn222/lead matrix could even become a
laser ion cannon of worthy thrust that's capable of exiting a
considerable density of matter at nearly 'c'.

No, it couldn't. The particles produced couldn't reach
anywhere near the speed of light. The reaction simply
isn't energetic enough.

My thermal rocket is simply a heck of a lot hotter than any
existing thermal rocket.

Up to a viably containable point of total thermal nuclear
melt-down, heat is certainly a good thing to take advantage

"Melt-down"? This reactor does not merely suffer a
"melt-down". This "reactor" suffers an absolutely
catastrophic high yield detonation! However, the imploding
"reactor walls" only push inward at around 3%c--this gives
the much faster hydrogen atoms the chance to squeeze out
the rear nozzle opening.

then its photons that are going to achieve the absolute best
amount of thrust.

No, the light pressure from a nuclear bomb blast would be
weak. Light pressure is only efficient for very high
relativistic velocities.

Interstellar travel via gravity-well to gravity-well
exchanges is what's most likely going to make for the
most all around energy efficient and viably fast though
somewhat lethal alternatives,

No. Except for black holes, gravity wells are terribly
weak compared to the velocities involved in fast
interstellar travel.

Short of creating and having to sustain a nearly
continuous nuclear bomb; how do you go about safely
extracting and thus utilize the raw and somewhat nasty
element of U238 for accomplishing any reasonable
form of H/U238 as energy conversion into ion thrust?

I have been assuming the use of U235, not U238.
Either way, the method is very simple and I've already
described it--nuclear bombs of a slightly modified
Teller-Ulam design. There is no "nearly continuous
nuclear bomb". There are a bunch of little nuclear
bombs along the acceleration path of the starship.
Each one detonates in turn as the starship passes by,
spitting out a fast puff of hydrogen plasma to
accelerate the starship.

It seems merging U238 with H isn't exactly something
you'd want to be anywhere nearby, especially if the
matrix process got a touch out of control.

There is no "matrix". There's an imploding tapered
cylinder of uranium. Within this cylinder is some
hydrogen--perhaps in gaseous form.

The uranium cylinder acts like a "gun barrel".
The hydrogen acts like exploding "gunpowder".
There is no "bullet", because a "bullet" would merely
slow down the expanding gases down. The result is a
puff of hydrogen plasma blasting out of the "muzzle"
of this "barrel".

It's the hydrogen puff of plasma which catches up with
the magsail and gives it a shove forward. In order
for the puff of plasma to do its job, it simply has to
be moving fast enough to catch up with the magsail.
Placing any sort of "bullet" in its way directly
interferes with this goal.

Isaac Kuo

Isaac Kuo;
Note that the uranium atoms and its resulting fission products
never move faster than about 3.8%c. Nevertheless, they can
heat up the hydrogen atoms up to 40%c because they are so
much heavier than hydrogen atoms. It's these fast hydrogen
atoms which can catch up with and push forward the magsail.
The heavier atoms are simply "waste mass" as far as the
magsail is concerned.
Atomic boosted rockets are not exactly new, or even unproven. Your
methods are simply offering us a supposed improvement upon an otherwise
extremely all-or-nothing lethal alternative that perhaps only robotics
should venture to use.

NOTE; I didn't realize Earth had an affordably obtainable surplus of
U235 and/or Plutonium, as I'd thought most was in the process of
becoming artificially created/enriched at a rather enormous energy
influx and otherwise having been allocated for our end-user friendly
WW-III WMD. However, we do seems to have a fairly easily obtained
volume and thus tonnage of Ra226 at our disposal, and there's plenty of
folks that would like nothing better than to figure out how to best get
that much less nasty than U235/plutonium stuff, as in getting the
remainders of Ra226 as far away from Earth as possible.

No, it couldn't. The particles produced couldn't reach
anywhere near the speed of light. The reaction simply
isn't energetic enough.
Going by all of your overwhelming slue of interested and involved topic
contributors, I'm thinking there's a good chance that perhaps you're
looking at this from the wrong perspective. Either that or you are
simply into pretending at being another extremely narrow mindset bigot
of an idiot that actually can't think outside the box nearly as much as
you thought. Sorry that I interrupted your train of thought by
suggesting anything. Yourself and "tomcat" are equals but opposed on
absolutely everything, and why is that?

No. Except for black holes, gravity wells are terribly
weak compared to the velocities involved in fast
interstellar travel.
Obviously you're into interpreting everything for achieving the utmost
negative perspective conceivable. In which case I think you're the
DNA/RNA cloned son of Hitler because, that's exactly what that SOB
would be doing again and again, that is if he hadn't exterminated
himself, which is somewhat of the ultimate proof-positive that I'm
right about folks acting that. While you're at it, why don't you assume
that Earth is flat and that there's absolutely no possibility of other
life outside of Earth.

BTW; unless you're God or perhaps the son thereof, there's still no
hard-science whatsoever that stipulates black holes represent gravity
pits. Just photon pits is what seems a sure bet because, there's just
as much chance those supposed holes are nothing more than a cloud of
nearly resting photons surrounding a batch of antimatter.

BTW No.2; I was talking about a starship as leaving one nullification
point behind and going towards a significant other point-source of
gravity, such as Sirius. Of course, you'd be one of those
all-or-nothing SETI types that would never consider anything that close
as worth squat, thus going hundreds if not thousands of lightyears is
the very least you'd consider as being worth while.

Your "spitting out a fast puff of hydrogen plasma in order to
accelerate the starship" might actually work just fine and dandy if
there's never a glitch along the way. Of course the deployment and
timing of each of those hydrogen puffs might get a wee bit testy if
there any gravitational influence upon much of anything, whereas
alignment and timing would be your priority No.1, as for being off by a
millionth of a degree or a microsecond at those speeds and you could
kiss something resembling your sorry butt goodbye for good.

It's the hydrogen puff of plasma which catches up with
the magsail and gives it a shove forward.
Understood, although summarily quite dead since you can't so easily
manage to avoid whatever it is that you're about to encounter by way of
altering course without exterminating yourself. Or is your starship
also outfitted with an good array of those 100 TJ class of laser
cannons for vaporising whatever's in your path?

For every action there's an equal reaction, which obviously doesn't
apply to any of your little deployed hydrogen puff generating bombs.
Perhaps energy-in = energy-out doesn't apply either. I guess what I'm
saying is that these little H-plasma bombs may need to be attached to
and/or at least up against the sail butt of your nifty starship, like
laying so many exploding eggs that just keep arriving at the rate of
one per second from the internal inventory/cash of perhaps a million of
these nasty little suckers would give 278 hours worth of atomic get up
and go (69.5 hours worth available thrust going each way, that is if
we're including any notions of having to bring things to a stop at
either end of the trek).

If each exploding egg weighed 10 kg, that's merely 10 million kg to
deal with. Gee whiz folks, where's the problem in that picture?

Brad Guth