h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

1. Protium fusion is not an achievable goal.

2. Dueterium-dueterium fusion, and dueterium -tritium
fusion is an achievable goal.Matter-antimatter annhilation
is also an achievable goal. A feasible ramjet must carry
onboard fission, fusion, or matter-antimatter reactors, and
the fuel for them as its power source, unless a laser/maser
electric ramjet is used.

3. A feasible ramjet will probably be able to collect only
a few grams of reaction mass per second. A ten tesla
(100,000 gauss) electromagnetic field ramscoop can collect
at least 1 gram of mass per second.

4. Assume a 1,000,000 kilogram mass ramjet vehicle, that has
a 2/1 mass ratio. It has both a ramjet propulsion system,
and a rocket propulsion system. It might resemble a star trek
science fiction vessel a liitle bit.It could have a cylindrical
body with a rotating crew habitat, and two cylindrical ramjet propulsion modules attached to it. The main cylinder contains
the nuclear powered rocket engines, their propellant, and the
nuclear power sources for them. The ramjet modules will use
nuclear powered electric ion or plasma rocket engines.

Let us then discuss this design further
5.A plasma ramjet engine can be created in the following way.
You take a hollow steel cylinder. Then you wrap about about
100 superconducting steel electromagnetic solenoid coils around
it, and surround them with a liquid helium cooling jacket.
You charge these solenoid coils with about 1000 amps of electric direct current , so that they can generate an electromagnetic funnel
of at least 10 tesla power level. Such a field will have an ion collection radius of 1000-3000 kilometers.Minimium ramjet takeover velocity will be between 100, and 10,000 kilometers per second.
This will collect somewhere between 1 and 100 grams of hydrogen
gas per second from space.

The ramjet collection radius can be increased by placing a negatively charged ring at the ramjets
mouth that has an electrostatic charge on it. In space a -10 volt
electric field can draw all ions within a 300,000 kilometer radius
into the ramscoop magnetic collection field. The ioned hydrogen gas
then enters the magnetic plasma engine, where enough microwave emmitters can heat it to fusion range range temperatures of perhaps
100,000,000 celcius .Then the plasma is expelled through a
magnetic nozzle to produce thrust. If you have enough antimatter
availible you can inject it into the ramjet plasma vortex,
where it will be annhilated and then further heat the hydrogen gas
exchaust of the ramjet. In the plasma engine the magnetic field
also creates a magnetic bottle to contain the plasma.

This will not result in nuclear fusion, but it can provide a
plasma drive that can generate fusion range propulsion
performance. This ramjet can theoreticly approach the velocity
of light, and it is probably a feasible design.

There are two key issues however that can limit the velocity
actually achieved by the ramjet in practice.This are the thrust to
mass ratio of the ramjet, and the longevity of the operation of
the ramjet propulsion system , and its power sources.

This determines the actual acceleration rate that can be
achieved by the ramjet.In order to get up to 72% of light speed within a 75 year acceleration period the ramjet must generate a thrust eqaul to 1 tenth the mass of the ramjet vehicle. This will yield a .01 g accleration rate. In order to generate a 1 g
acceleration you must generate a thrust equal to 10 times the mass
of the ramjet starship.This will get you .72% C in 9 months acceleration

To do this in 7.5 years you must generate a thrust equal
to the full mass of the ramjet. This will yield a .10 g
acceleration rate. If you generate a thrust eqaul to 1
hundreth of the ramjets mass, the accleration rate achieved
will be .001 g, and it will take 750 years to attain 72 % of
light speed, and during that time you will reach a distance of
270 light years from the solar system, but then it will take
another 750 years to decelerate down from 72 % of light speed
to mere interplanetary velocitys. So therefore the flight time
would be 1500 years, and you must travel at least 540 light years
from the solar system in the case of the .001g acceleration rate.
If the ramjet acclerates at .0001 g it will take 7,500 years to
attain 72% of light velocity, and you will go 2700 lightyears
during tha time. At .0001 g however you must go at least 5400
light years from the solar system because it will take 7500
more years to decelerate down from .72 light speed.

A burned out atomic reactor core will remain intensely radioactive
for more then 100, 000 years after the nuclear fission reaction
ends in the core . It also can generate about 100- 400 watts of electric power per pound of its weight from the radioactive decay heating of the plutonium 239 left in the burned out atomic core,
if you use it as a giant RTG (radioistope decay powered
electric generater) for the next 100,000 years or so.

The gamma factor eqaution is Y= )1 - (V*V/C*C) raised
to the -1/2 power. We thus find that at .72 C Y = about
1.414 which is the sqaure root of two.
So your time dilation factor, spacetime contraction factor,
and relavestic mass increase is a factor of 1.414 at .72 C.
Your practical velocity because of relatavity is thus .72C * 1.414
which is 1.00 C (light speed). If you get closer to light speed
then .72 C then you can effectively achieve faster then light
speed travel for the ramjet starship in practical velocity:
(But only for those who go on the ramjet journey to the stars ).
Here is a few interesting numbers :
At .90 C Y = 2
at .94 c y =3.34
at .99 c y = 7
at .999 C y = 27
at .9999 c y = 70
This is probably the only kind of ftl travel that any civilization
no matter how advanced it is, can realisticly aspire to achieve:
throughout albert einstein's universe in which we live literally.
Notice that .99 C is almost equivelent to the science fiction
warp factor of warp 2 in star trek science fiction, and that
.72 c is effectively equivelent to warp 1 because of relatavity.
.999c is effectively equivelent to warp 3, and .9999 c is
effectively equivelent to warp 4 because of relatavitys effects.

All though the einstein equations theoreticly allow two other
types of ftl travel via using rapidly rotating/spinning wormholes
in curved spacetime (hyperdrive ), and via the superliminal
expansion of a bubble of space time (the albuirre warp drive)
these solutions to the einstein equations are probably not (physical), which means they are ( non-emperical) in physics
slang. Nonemperical means that they can not be realized in practice, plus they could also violate the C.O.P. postulate
in physics. This is the casuelty paradox.

My research into feasible ramjets indicate that
a fission powered nuclear electric propulsion ramjet can
achieve an acceleration in practice of only .0001 g to
.001 g .A feasible fusion powered ramjet can achieve only
.001 g to .01g in acceleration, and that only a
matter-antimatter annhilation powered ramjet can achieve accelerations in the range of .01 g to 1 g. So if you
want to acclerate up to lightspeed within 1-10 years
and then go cruise the galaxy at near the speed of light,
you need to build an interstellar ramjet that is powered
by the annhilation of matter and antimatter in its
ramjet engines. For the rocket propulsion part of the
vehicle you can use annything from nuclear electric
engines, to fusion microexplosion engines, or even
antimatter - matter annhilation powered rocket engines.

Timothy J Mayes

OK, point by point:

1. Protium fusion is not an achievable goal eh? I'll try to remember that the next time I look at the sun...

2. "2. Dueterium-dueterium fusion, and dueterium -tritium
fusion is an achievable goal."

We agree on that, at least...

"Matter-antimatter annhilation is also an achievable goal."

More like "an unavoidable physical reality" I'd have said, but it's completely irrelevant anyway because you can't collect the antimatter as you go along because there isn't any.

"A feasible ramjet must carry onboard fission, fusion, or matter-antimatter reactors"

Ah, no. Wrong. It *must* carry an onboard FUSION reactor. The WHOLE POINT of this gadget is that it picks its fuel up as it goes along, and there's nothing fissionable in the space between the stars. There's also no (or certainly not enough) antimatter. So, a fusion reactor, ONLY. (Unless you wanna carry a fission reactor to power stuff when you're not ramming - but why bother? Just slush some deuterium into tanks.)

" and the fuel for them as its power source"

Er, have you even read this entry at all? The whole bloody point of this thing is that you DON'T carry the fuel, you collect it as you go along. (unless, as I say, you mean fuel for when you're NOT ramming)

", unless a laser/maser electric ramjet is used."

Absolutely no idea what you mean by that, please explain.

"3. A feasible ramjet will probably be able to collect only
a few grams of reaction mass per second.

See below for comments on the use of the word "feasible".

Collection rate based on what? The variables are
(a) density of interstellar hydrogen
(b) area of collection field
(c) velocity of collection field through interstellar hydrogen.

Assume (a) is 1 atom per cubic centimetre (conservative estimate, I think)
Assume (b) is for a *small* collection field of say 10,000km diameter, which is 7.85x10^17cm2.
Assume (c) is 1% of lightspeed, i.e. 3x10^8 cm/s.

You collect 2.36x10^26 atoms of hydrogen per second - which is well over a kilogram, I think. This assumes a small field which is only just reaching ramjet velocities. Fusing several kilograms of hydrogen per second would produce quite a bit of energy...

" A ten tesla (100,000 gauss) electromagnetic field ramscoop can collect at least 1 gram of mass per second."

As I say, that depends on the collection area, the density and the velocity...

"4. Assume a 1,000,000 kilogram mass ramjet vehicle, that has
a 2/1 mass ratio. It has both a ramjet propulsion system,
and a rocket propulsion system."

I balk a bit at the term "rocket", because it carries implications of present technologies, which are unlikely to be able to accelerate a ship to ramjet velocities - I'd prefer something like an ion drive, a solar sail/laser launcher or even some sort of space-based railgun arrangement...

"It might resemble a star trek
science fiction vessel a liitle bit."

I'm all for that!

"It could have a cylindrical
body with a rotating crew habitat,"

Why bother? By definition the thing is going to be under acceleration for almost all of its journey (apart from turnover) so why not just build it like an office building with multiple floors and a single, identifiable "down"? (unless you're designing for tiny accelerations... in which case you might as well use a lightsail)

"and two cylindrical ramjet propulsion modules attached to it."

Two? Why two? You just need one.



Most of the rest of what you've written is (as far as my amateurish knowledge of this stuff goes) technically accurate, but I can't help thinking that this sort of speculation is similar to Victorian engineers swapping theories about why heavier than air flight is and always will be impossible...

But nevertheless, thanks for reading and commenting. I love feedback!

H.

(btw, you should write something in your personal space, people can drop by and say hi, and you can write entries and have actual conversations and stuff. This site is extremely entertaining, and not everything on it is tedious speculative sf guff like my Bussard entry! )

I don't understand how you can even consider building a ramjet based on antimatter/matter annihilation...

Where does the antimatter come from? It's not just lying about in space, so unless you've got some kind of quantum charge reversal device which allows you to just flip matter into antimatter then let it annihilate, you're going to have to carry all your antimatter around with you - which defeats the point of the ramjet, which was to overcome the rocket economics problem.

And the thing about apparent "faster than light" travel that it's important to say is that it's *only* apparently faster than light for the people *on* the ship. For the people left at home, it's emphatically SLOWER than light (although not necessarily by much). People on the ship appear, to themselves, to get from A to B in, say, 20 years. People back home see them get there in 200, or 2000, or whatever.

Fascinating stuff.

H.

Protium fusion can be achieved by nature but not by human
technology. The goal of a ramjet is to get around the limits of interstellar rocketry which are imposed by the rocket eqaution.
It would be good if we could achieve protium fusion
but this requires temperatures, and pressures far higher
then those required for more conventional fusion, and the
protium fusion reaction proceeds to slowly to be practical
in a compact lite weight starship engine.You would have to carry
your fuel with you on a feasible ramjet starship, due to the fact
that protium fusion is not an attainable goal.This is true whether
your fuels are U 235 Pu 239 Duterium ,Tritium or Lithium.or some
form of antimatter. Only celestial bodies that have a a lot of
water have much dueterium on them.No known celestial bodies
have antimatter on them. That is why antimatter must be made in
particle acclerators and stored in magnetic bottles for use as
fuel.Many celestial bodies however have uranium, and thorium
ores on them from which fission fuel can be extracted, or made,
and refined. Many celestial bodies also have lithium ores
on them from which tritium can be made in a nuclear reactor.
A feasible starship must be able to live off the celestial
enviroment and its resources. Therefore it must mine certian
nuclear fuels from celestial bodies and it will use the gas
that floats between the stars as propellant.Using atimatter-matter
antimatter annhilation to power a ramjet allows the gas collected
by the ramscoop to be used as fuel in two ways.
1. When you mix antimatter with matter(such as propellant collected
by the ramscoop) the mass of both is converted completely into
energy.
2.The gas collected by the ramscoop can be used to make antimatter
in particle acclerators on the starship. Then the antimatter
is stored for later use in electromagnetic bottles or
electro magnetic storage rings.
3. Matter antimatter annhilation releases 100 times more
energy per unit of mass then does nuclear fusion.
4. The rocket equation is that v = exchaust velocity *
the natural logarithim of the mass ratio.
Using a ramjet allows you to get around the mass ratio limits of
rocketry no matter what the ramjets exchaust velocity is.
5.The mass collected by a pure magnetic ramscoop per second
is :
1. The condition for an ion to be collected by a magnetic ramscoop
is where the sqaure root of the ramscoop magnetic flux B in gausses
is = or > then the interstellar magnetic field of 10 to the -6
gauss.
2.The magnetic flux b of a soleniod with a a hollow iron or steel
core is = N * (the number of solenoid coils) * I
(the electric current) / the square root of R
(radius of the solenoid) for the magnetic field at the center
of the of the inside of the solenoid coils, and it is b= n* I /the sqaure of the distance d from the magnetic field
3. If we assume that the density of gas in space is 1 ion per
cubic centimeter then 100 cm *100cm*100 cm means there is
1,000,000 ions per cubic meter of space to be collected
by the ramscoop for each cubic meter of space in which
b is greater the 10 to the -6 gauss within the ramscoop
field.
4. If we use a 100,000 gauss magnetic field then the ion
collection radius in meters = the sqaure root of 100,000
* 1,000,000.
This is the sqaure root of 100,000,000,000 meters which is
about 316,000 meters which is 316 kilometers.
1 kilometer = 1000 meters
to find the number of cubic meters within the ramscoop field
we can treat the collection volume as a cube to simply the
calculation
316,000 cubed is 3.16 * 10 to the 16 power cubic meters.
Now we multiply this number by 1,000,000 to find how many ions
are in the scoop field. We find that this number of ions
is 1 * 10 to the 24th power ions. Avagadros number is 6.02 * 10 to the 23rd power . Using the mole atom law in chemistry
1 mole of hydrogen 1 ions is 6.02 * 10 to the 23rd power ions
which has a mass of 1 gram 1 * 10 to the 24 power/ 6.02 *
10 to the 23rd power = 1.66 grams of mass .
If however the ramjet were moving at 3160 km/sec which is about
.01 C (light velocity) then the amount of ions collected will
increase about 100 fold and the mass collected by the ramjet per second would be about 166 grams .
Tim

This means that the mass collected by the ramscoop per second
should increase expoentially as the ramjets velocity through
space increases. This what theoreticly allows a ramjet vehicle to aproach the speed of light closely given enough time, as the
American nuclear engineer Bob Bussard calculated in 1960 and
wrote in his paper on interstellar ramjets.
Tim

Note * the 1.66 grams of mass per second qouted previosly
assumes that the ramjet is operating at velocity of 316 kilometers per second or less when the ramjet is activated
Tim.

Tim, me old china, WRITE SOMETHING in your personal space, will you? I'll write an actual reply to the above in a moment, but in the meantime put something on your personal space even if it's just a plaintext "hello", please?

Thanks

H.

"Protium fusion can be achieved by nature but not by human technology."

Possibly you missed the reference above to heavier than air flight. At various times through history it has been pronounced physically impossible to fly, to fly a heavier than air craft, to fly faster than sound (hence the holdover phrase "sound barrier" - there IS no barrier, of course) and to fly into space. In every case there was no reason in physics why we shouldn't do it, the problem was merely (!) technological. And yet people more knowledgable than yourself pontificated publicly that such things were impossible. Those people now, of course, look very stupid.

Is there a PRINCIPLE that you can state which says precisely WHY this process - hydrogen fusion - while very, very obviously possible from a simple inspection of the sky on a clear day, is for some reason IN YOUR OPINION never going to be possible for our technology? What is stopping us?

Precision now - I couldn't build a ringworld a hundred thousand miles across for good, physical reasons - the strength of interatomic bonds would prevent me from making a material strong enough to stand up to the stresses induced in spinning the thing fast enough to generate 1g radial acceleration on the inner surface - that really will never happen in this universe, and I can explain why.

By contrast, your argument for why we'll never achieve controlled hydrogen fusion is that YOU, personally, don't know how we'll do it. Pardon me, but that's not really a convincing argument. Got any better ones?

"It would be good if we could achieve protium fusion
but this requires temperatures, and pressures far higher
then those required for more conventional fusion,"

So? Fusion requires far higher temperatures and pressures than fission, and yet we build hydrogen bombs, and you don't seem to have a problem picturing a future where we can generate SOME fusion in a controlled way. What's so incredible about being able to go further and fuse hydrogen?

"protium fusion reaction proceeds to slowly to be practical in a compact lite weight starship engine."

Now you're just being a bit silly. You talk further on about manufacturing anti-matter in a particle accelerator to make fuel, and yet you object to fusion reactors on grounds of *size*??? Have you SEEN a particle accelerator? Their diameters are measured in MILES. And besides, these ships will never land. They will only ever travel in a vacuum. Regardless of their initial mass, there is no theoretical limit to their eventual approach to lightspeed. The only thing which is affected by their mass is their peak acceleration. So, accepting for a moment your failure of imagination in being unable to picture a fusion reactor that would fit inside, say, a 100 metre sphere, what does it matter?

"You would have to carry your fuel with you on a feasible ramjet starship"

You keep using that word "feasible", as though you somehow know everything that's required to build one, when you manifestly don't. You really do sound like those people who announced gravely that railway travel should be strictly controlled because any human travelling at over 25 mph would suffocate...

", due to the fact that protium fusion is not an attainable goal."

Let me rephrase that - "protium fusion is not an attainable goal FOR YOU, because you've no idea how to do it so you've already given up".

"Only celestial bodies that have a a lot of water have much dueterium on them."

Rubbish. Complete nonsense. Any body with a large quantity of hydrogen IN ANY FORM is going to have a proportion of deuterium in it. Jupiter, for instance, incredibly thick atmosphere mostly methane, methane of course four hydrogen atoms per molecule, and for every 6700 or so of those hydrogen atoms, there's a deuterium atom. That proportion applies also to the interstellar gas. So there's deuterium EVERYWHERE, in every direction, even in "empty" space. Just not very much of it, comparatively. Water, and specifically sea water, just happens to be the most convenient source for deuterium that we have on this planet. But this just demonstrates the limitations of your imagination again...

"No known celestial bodies have antimatter on them."

Well, apart from the earth...

"That is why antimatter must be made in particle acclerators"

You want a lightweigt, compact engine, but you're going to lug around a particle accelerator to generate anti matter??? Those things are HUGE, and for reasons of basic principle couldn't be made smaller. That's why I speculated on a "quantum charge reversal device" for manufacturing anti matter. OK, so I nicked the term from the Star Trek Next Generation Technical Manual but the point is, particle accelerators are huge, impractical things NOW, and the biggest most powerful ones we have can make antimatter at rate so slow that they'd make enough fuel to get to the moon and back if they ran continuously for about a million years. And like I say, they're only going to get BIGGER. This process is not something you can miniaturise.

"1. When you mix antimatter with matter(such as propellant collected by the ramscoop) the mass of both is converted completely into energy.

E=mc^2. I know, I've heard of it.

"2.The gas collected by the ramscoop can be used to make antimatter in particle acclerators on the starship. Then the antimatter is stored for later use in electromagnetic bottles or electro magnetic storage rings."

Quick question - how do you store an atom, which is electrically neutral and therefore non-magnetic, in a magnetic bottle? Serious question.

"3. If we assume that the density of gas in space is 1 ion per cubic centimeter"

It's one ATOM per cc. How are you proposing to ionise all that?

"... mass collected by the ramjet per second would be about 166 grams"

And blah blah blah I did this calculation above, what's your point?

H.

"This means that the mass collected by the ramscoop per second should increase expoentially as the ramjets velocity through space increases. This what theoreticly allows a ramjet vehicle to aproach the speed of light closely given enough time, as the American nuclear engineer Bob Bussard calculated in 1960 and wrote in his paper on interstellar ramjets."

Um... yeah. I know. Isn't that what I SAID in the entry? Didn't I mention Bussard? Didn't I say, 1960? Didn't I say it could approach lightspeed? Do you have *point*, at all?


H.

1. Antimatter merely requires a 2 gev high proton current
linear particle accelerator to manufacture it by colliding
proton beams or by slamming proton beams into metal targets.
Un-ionized, and electricaly neutral Antihygrogen can be
be stored in a magnetic bottle because hydrogen has a
property called diamagnetism which causes it to collect
in the center of a magnetic field where it can form a solid ball
of antihydrogen ice.You make neutral antihydrogen by combining
a beam of antiptotons with a beam of positrons after using a laser beamto decelerate antiprotons for capture in a magnetic bottle.

2. Magetic bottles holding antihydrogen ice could be loaded on to ramjet starship before it ever left leo. Burning it driectly in a rocket/ramjet exchaust would require enormus amounts of antimatter. If however you use it generate electricity inside a controled matter-antimatter annhilation reactor you may need only a few hundred kilograms of it for use as starship fuel.

3.If you examined my earlier postings you would see that the ramjet engines are electric ion or plasma propulsion engines. You will also see that electric ion or plasma rocket engines, or fusion engines or antimatter rocket engines are used to acclerate the ram ship up to ramnjet take over velocity on a solar system escape velocity.

4. A feasible ramjet will likely acclerate at only a small fraction
a G. For this reason a rotating crew habitat is needed to provide artificial gravity on a ram ship.

5. The lawson criterion determines the condition required to
achieve thermonuclear ignition in a fusion plasma. In a plasma
made of protium rather then of pure dueterium ,or a mixture of dueterium and tritium plasma gases, the conditions required to achieve thermonuclear ignition are a 1000 times more extreme,
and the the protium fusion reaction proceeds at a far slower
rate.
7. 99.97 Percent of all the hyrogen in the universe is protium.
That is why you need a water rich planet like earth in order to extract large amounts of duterium. Tritium must be made inside
of a nuclear reactor, or inside of a Hydrogen Bomb.

8. Atomic (fission ) fuel is far more common in nature in the
cosmos then is fusion fuel. As I said a starship must live off the country. If you use breeder type fission reactors one very large
reactor fuel load can breed enough U 233 or Pu239 to keep the
fission reaction going on for a least a period of centurys.

9. The radioative decay heating of spent reactor core can turn it into a giant (rtg) radioistope decay powered electric generator that can provide large amounts of electric power to the ram ship for 10s of thousands of years.
10 A very large ultra high power breeder type fission reactor
is required from the beginning to provide electric power to the ramship, and to provide power to kindle, and confine a fusion reaction, in a fusion reactor, or to contain and control a
matter-antimatter annhilation in a mama reactor. It is also
required to power the electric ion or plasma rocket part of
the vehicle, to generate laser beams to ionize hydrogen gas
in the path of the ramjet, for microwave radio, and television communicatons, life support systems, power the magnetic bussard
ion collectors, and any laser weapons, particle beam weapons,
or power guided missile, rocket/torpedo launch systems etc.
Tim

Point 1. "merely"

Point 2. For spectators, leo = low earth orbit.

Point 3. I *have* examined your earlier postings. I'm still struggling to see if you have a straightforward point to make. You use the phrase "are used" as though this is already going on. How about "might be used"? Or "might be used if we don't think of something better by the time we're in a position to build something like this..."?

Point 4. There you go again, a "feasible ramjet". There ain't no such thing, yet, so you're describing science fiction. You might just as well talk about a feasible warp drive, or a feasible wormhole generator. Kerr developed the equations for the latter in the seventies, but I still can't cross the Atlantic in a single step, annoyingly.

Point 5. Once again, you make an observation which is factually correct and state it baldly as though it in some way supports your point. A hundred years ago one might equally have pointed out that fusion requires such temperatures and pressures that we'd never be able to achieve it on earth - but we have, thanks to new materials and techniques.

Point 6. There is NO.... point 6.

Point 7. Again, unwarranted assumptions based on correct facts. Yes, 99.97% of hydrogen is protium. That leaves 0.03% deuterium, which doesn't sound like much. But it's 0.03% of 1 atom per cubic centimetre, and as the late great Douglas Adams once said, "space is big. REALLY big." 10% of nothing is still nothing, but 0.03% of something the size of the space between here and even the nearest star is, for want of a better term, f*****g HUGE.

Point 8. Ooh, unusual. You're actually factually wrong. Protium is fusion fuel. Like I said, look at the sun... Hydrogen is by far the most common substance in the universe. 90% of ALL matter is hydrogen. So if you make the not unreasonable assumption that it will one day be possible to sustain and control the kind of reaction which fuels the sun, then 90% of the entire universe is your fuel tank.

Point 9. Correct, but I wouldn't want to be anywhere near it, and in any case, see point 8.

Point 10. All of that assumes that your initial propulsion system has to be based on the ship. Why bother? Why not just build a massive solar powered laser array in one of Mercury's Trojan points, focus it with an array in the asteroid belt and pump power in that way? No need for bulky, and more to the point HEAVY, equipment on board then. You could even use the same equipment to decelerate at your target system, assuming of course that your destination is a stellar system (which it would be for the first few of these journeys, since they'd most likely be exploration/colonisation missions).

I'm still struggling to see what your problem is with my entry here.

H.

1. Laser electric, or maser electric ramjets beam power to a ram
ship with a solar powered laser or maser array, so that a
ramjet does not have to carry its power source along with it.
2. D+D type fusion reactors, and D+T type fusion reactors
can be created as hardware. P+P+P+P type fusion reactors
can not be acieved from the prospective of practical
nuclear engieering. Matter-antimatter annhilation releses 100
times more energy then does nuclear fusion. A mama powered
ramjet starship is therefore vastly superior to any fusion
powered ram ship, if you can get enough antimatter stored
in magnetic bottles to take with you for use as ram ship fuel.
Tim

For we americans the following advanced spacecraft propulsion
technologys exist as successfully demonstrated space propulsion
hardware: in that they have already been successfully
ground tested, or flight tested in hardware form in the past.

1.Solid core Nuclear thermal rocket engines .
Maximium currently achievable specific impulse (SI)
1000 seconds demonstated 1958-1972

2. External explosion powered pulse rockets.
Max potential SI = 3,000,000 seconds,using
thermonuclear explosives
The maximium present demonstated SI = 1000 seconds
using chemical high explosives demonstrated 1963

3. solar sails Si = 30,000,000 seconds
Demonstated on the ground 1977 - 2002 and soon to be
flight tested in space by the planetary society

4. Electric ion rocket engines
The maximium potential SI is 29,000,000 seconds +
Maximium demonstated SI = 10,000 seconds at present
Demonstrated on space probe deep space 1 2009
and demonstrated on ground and in earth orbit many
times from 1958 to present
5. Electric plasma rocket engines vasimir engine demonstrated
in the present on the ground, other plasma engines demonstrated on the ground and in earth orbit many times 1958 to present
Maximium potential Si = 3,000,000 seconds
Max demonstated SI at prsent = 3000 seconds

6. Electric arc jet rocket engines
max Si demonstated = 1500 seconds
Have been demonstrated many times
in earth orbit, and on ground from 1958 to present
7. Electric Resistojet rocket engines
Si = 1000 seconds
Have been demonstrated many time in erth orbit and
on ground 1958 to present.

* Maximium actual manned spaceflight technological
capability currently , manned voyages to all the
9 planets of the solar system possible when ever
desired. Maximium current potential manned capability
Manned starflight at .10 C using nuclear fusion pulse drive interstellar rockets .Maximium thus far actually done
manneed landings on the moon 1969 to 1972.
Maximium potential U. S. robotic spaceflight capability.
Robot star probes at near light velocity using laser/maser
/solar photon sails to nearby star. Maximium so far done
robot space probes that have reached the keiper belt

* Please excuse the typing errors in the above postings
by me.

"1. Laser electric, or maser electric ramjets beam power to a ram
ship with a solar powered laser or maser array, so that a
ramjet does not have to carry its power source along with it."

Um... BY DEFINITION a ramjet doesn't have to carry its power source along with it. Have you actually read the entry this is attached to at all?

"2. D+D type fusion reactors, and D+T type fusion reactors
can be created as hardware. P+P+P+P type fusion reactors
can not be acieved from the prospective of practical
nuclear engieering."

Here we go again. Says who? Says you, sitting in your Texan home in 2002. Is there a PHYSICAL PRINCIPLE which you can state in a single sentence which explains why plain hydrogen fusion is not possible in a controlled reactor? Don't give me any garbage about current technology, either. I couldn't build a Ringworld 200 million miles in diameter with current technology, but there's nothing PHYSICALLY impossible about one. There IS however something physically impossible about a Ringworld, say, five thousand miles in diameter - the very strength of interatomic bonds in this universe makes it impossible to build a structure which could stand up to the kind of stress it would experience if you spun it fast enough to generate 1g on the interior surface. So there is a a physical reason. I know of no such principle which prevents hydrogen fusion, and as I'll keep on saying until I'm blue in the face LOOK AT THE SUN. This is not a rare reaction we're talking about.

"Matter-antimatter annhilation releses 100
times more energy then does nuclear fusion. A mama powered
ramjet starship"

For spectators, "mama" is "mutual annihilating matter/antimatter".

A mama powered ramjet is a contradiction in terms. You might just as well talk about a rocket-powered jet. If your ship is powered by antimatter, then you need to carry all the fuel you'll need. No matter how concentrated it is as an energy source (and it can't get any more concentrated than anti-matter, as far as I know), you've STILL got the problem of rocket economics, in that you're using some of your fuel accelerating fuel. It's difficult to see how you could have missed the point of this entry any further...

" is therefore vastly superior to any fusion powered ram ship, if you can get enough antimatter stored in magnetic bottles to take with you for use as ram ship fuel."

See above. Superior according to what criteria?

H.

"For we americans"

I love this. So effortlessly arrogant, so beautifully uncapitalised, so marvellously self-regarding while simultaneously being so devoid of introspection.

"the following advanced spacecraft propulsion
technologys exist as successfully demonstrated space propulsion
hardware: in that they have already been successfully
ground tested, or flight tested in hardware form in the past."

The statement that the nation is so very, very advanced in its development of spaceflight technology, begs a question along the lines of "if you're so smart, how come you ain't rich?". According to you, the US has an embarrassment of riches when it comes to propulsion technolgies, yet still we see the fairly rare launches struggling into low earth orbit and crawling round the solar system using conventional chemical rockets not much more advanced in principle than Goddard's. Why?

* Maximium actual manned spaceflight technological
capability currently , manned voyages to all the
9 planets of the solar system possible when ever
desired.

Yeah, right. I won't hold my breath...

"Maximium potential U. S. robotic spaceflight capability.
Robot star probes at near light velocity using laser/maser
/solar photon sails to nearby star."

LOL. Again, I won't hold my breath.

"Maximium so far done robot space probes that have reached the keiper belt"

It's "Kuiper". And they got there with standard, Goddard type chemical rockets.

I'll ask again. Do you have an actual point?

H.

Only politics has prevented we americans from
doing more then the actual space missions
that have occured. We would be launching
practical robot starprobes right now
to nearby stars if it were not for politics.
We would have already landed men on mars 20 years
ago if it were not for politics. We would already
have both moon bases and mars bases if it were not
for politics .When we say that protium fusion is not
an achievable goal. We mean that protium fusion reactors
can be not be made technologicly practical ,
in terms of practical nuclear engineering.
Tim

"Only politics has prevented we americans from
doing more then the actual space missions
that have occured."

Interesting use of the word "only". What you're saying is, someone failed. Who, in your opinion, was to blame?

- the engineers in the space programme for failing to design more economic launching systems?
- the leaders of the space programme, for failing to argue their case persuasively with the government?
- the politicians in charge of budgets, for their shortsightedness and failure of imagination when they cut funding to the space programme?
- or the American people themselves - YOURselves, I should say - for getting bored and not wanting to fund the future of our species any more?

Or was it someone else? I'm interested in your opinion.

"We would be launching
practical robot starprobes right now
to nearby stars if it were not for politics."

See above.

"We would have already landed men on mars 20 years
ago if it were not for politics."

Um... how would you be planning to protect the crew from the effects of solar radiation bursts? Moon missions lasting a few days are OK, you can slot them in between such events, but if you're going to Mars the crew is going to be outside the protection of the atmosphere for a period of MONTHS. What technology did we have in 1982 (i.e. the year after the very first, much delayed launch of the Space Shuttle) which would protect a large crew from such risks in open interplanetary space for a period of over a year? Forcefields? Ultralight yet radiation-opaque shielding? Incredibly powerful engines which could push a lead-shielded ship full of fuel for the return journey to Mars in a reasonable time? I'm honestly interested to know how you think this could have been achieved - Mars is a quite different proposition to the moon. We need REAL spaceflight capability for that, not cramped, fragile, disposable tincans only usable by test pilots.

"We would already have both moon bases and mars bases if it were not for politics."

Now you're talking. But see above for objections to that. I'm really interested in the answers. We have, thanks the Soviet Union, a lot of data on the effects of prolonged weightlessness. We have NO data on the effects of extended (i.e. more than a week or so) interplanetary travel.

"When we say that protium fusion is not
an achievable goal."

Er... who is "we"?

"We mean that protium fusion reactors
can be not be made technologicly practical ,
in terms of practical nuclear engineering."

I've asked you more than once to justify that statement. Just drawling "nope, cain't be done" over and over again doesn't make you right, you know. Give me one reason, one PHYSICAL PRINCIPLE which backs up your statement. To be clear, I'm NOT interested in anything you have to say about the current state of nuclear technology, because it is irrelevant. If you are aware, on the other hand, of a basic principle of physics which means that for some reason the reaction that powers the sun, and which humans can create any time they want on earth by detonating a hydrogen bomb, cannot be harnessed for power generation - bring it on. I *want* to know about it. So far I've asked you at least twice and all you keep saying is "we can't do it because we can't do it." That's not an answer.

There's an interesting contrast here between your apparent inability to conceive of a technology to do hydrogen fusion and your belief that despite all the technical hurdles we'd be on Mars if it weren't for "politics".

You're obviously as enthusiastic as I am about the driving need for the human race to get off this planet as fast as possible. You CLAIM that if it were not for politics, we'd already have a base on Mars. Setting *foot* on the Moon took your nation ten years and some significant portion of its collosal GDP to achieve. Establishing a base on the Moon would undoubtedly have been a MUCH bigger undertaking, because the Saturn V launch system was totally unsuited to doing that. So designing, pretty much from the ground up, a totally different launch system suitable for ferrying men and materials to the Moon would likely take even longer. Let's say your nation didn't give up on spaceflight in 1972, but instead actually decided "we're going to the moon, and this time we're staying". I simply cannot imagine how you could have achieved a first landing with the new launch system realistically any time before about 1985. (and I'm being VERY generous here). There's just too much to design and test to be able to get it done in less than that time, and we have the example of the Apollo programme for comparison. It took till 1981 to get the shuttle up, for Bod's sake, and that's just a flatbed truck which goes to leo.

So, you're the first back to the moon with a bulldozer and some water in 1985 - how long to build a base? Looking at the ISS (another merely leo construction), a base supporting a permanent presence would surely take at least ten years to establish, possibly more. Be incredibly generous again. So we're at 1995. It's only then we can sensibly think about even *starting* to make the leap to Mars - which as I say makes the whole Moonbase thing look like childsplay.

I'm not saying you're wrong. It is *physically* possible (I think - I don't know the answer to the radiation shielding problem, and neither, I suspect, do you) that we could have a Mars base by now - but you would have needed to start designing it in 1972 and put every competent scientist and engineer in the Western world on the payroll for thirty years. It's physically possible, but it's just wildly unrealistic in that timescale.

I've put no timescale on hydrogen fusion. I know of no reason why it's not physically possible. Do you?

H.