Pretty unbelieveable...

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Skipjack
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Post by Skipjack »

Where did you get this from? If my understanding of the Mach Effect (ME) is accurate, you have to have a change in the internal energy of the "mass" in order to "see" or "use" the ME.
Mhmm, so maybe I missunderstood this. To be honest, I have not even the slightest idea about the physics of this. I also dont have the time to read up on this in depth. I wished I could. The presentation on the Nextbigfuture blog was a bit sketchy about this too and maybe missleading.
Last edited by Skipjack on Tue Sep 15, 2009 12:41 pm, edited 1 time in total.

MSimon
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Post by MSimon »

ltgbrown wrote:
an engine that "makes the mass of the ship and anything in it negative"
Where did you get this from? If my understanding of the Mach Effect (ME) is accurate, you have to have a change in the internal energy of the "mass" in order to "see" or "use" the ME. The internal energy of the ship is not being changed, so the mass of the ship is not changing. Only the dielectric in the "ME Drive" is changing. The thrust comes from the ME Drive and is applied to the structure of the ship to accelarate the ship. That accelaration would feel the same to the ship and the humans onboard whether it was a chemical rocket, nuclear rocket, ion drive, or ME drive. (Of course, I could be completely wrong! :oops: )

Also, Pfrit is saying if a 100 lb ship got 10 lbs of thrust from a ME Drive, that would be great. MSimon is saying the same 100 lb ship gets 110 lbs of thrust. Two different things.
I agree

The only thing I would add is that my statement was not an assertion but a hypothetical.
Engineering is the art of making what you want from what you can get at a profit.

D Tibbets
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Post by D Tibbets »

I know next to nothing on this topic, but...
Is this system producing effective thrust through the expendature of energy, without an intermediary reaction mass being ejected out the back?
If so, you would still need fuel- eg hydrogen and boron11 to fuel the Polywell reactor. So you would have an effective ISP depending on the efficiencies of your power generating and applying systems. Would this provide effective ISP's approaching a photon drive (several hundred million?)?

Dan Tibbets
To error is human... and I'm very human.

djolds1
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Post by djolds1 »

D Tibbets wrote:I know next to nothing on this topic, but...
Is this system producing effective thrust through the expendature of energy, without an intermediary reaction mass being ejected out the back?
If so, you would still need fuel- eg hydrogen and boron11 to fuel the Polywell reactor. So you would have an effective ISP depending on the efficiencies of your power generating and applying systems. Would this provide effective ISP's approaching a photon drive (several hundred million?)?

Dan Tibbets
Yes, you still burn fuel for the electrical generator. Paul March calculates the effective Isp as being 13 to 26 Teraseconds.
Vae Victis

Skipjack
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Post by Skipjack »

Yeah and that at much more thrust...
At least from what I understand. Pretty cool if it works. Still, you are effectively limited in the amount of acceleration you can do (for manned flights anyway) with it. E.g. you wont be doing much more than 1 g for polonged periods of flight.
You might be able to do 4 or 5 g for shorter periods though, but that would not really make that much a difference (only for shorter distances with short travel times).
To bad, had it been a truly reactionless drive, then I guess you would not feel any acceleration forces at all (or even inverse ones as in anti gravity drives from science fiction, e.g. the Impulse engines).

tombo
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Post by tombo »

Paul March calculates the effective Isp as being 13 to 26 Teraseconds.
Yea, but he does it by assuming complete conversion of fuel mass to energy.
A real Isp would require calculating the mass of, say, Boron & Hydrogen burned to generate that power.


Even 0.1 G would get you off the ground with wings.
If it is sustained it should be possible to spiral all the way to orbit.
Once there, you are half way to anywhere.
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

93143
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Post by 93143 »

Technically, though, if you keep the reaction products on board, using m=E/(c^2) does satisfy the rocket equation...

I complained about this on the nasaspaceflight Advanced Concepts board, thusly:
93143 wrote: I think it's kinda silly to calculate Isp based on mass-energy expenditure, unless you're powering your thruster with a total conversion plant. Sure, it satisfies Tsiolkovsky's equation, but with modern energy supplies like hydrogen/oxygen fuel cells (or even hydrogen/boron-11 fusion reactors) you have to bring a preposterous amount of fuel to get a significantly non-unity mass ratio that way, so it's not really an informative representation...
[I'm not sure what I was thinking; even with a spacecraft nearly 100% LOX/LH2, the mass ratio is only going to approach 1.000000000167 or so. With p-11B it approaches 1.00078 or something like that. So the mass-energy method is even more uninformative than my careless wording implied...]
93143 wrote:If you assume expended fuel is dumped overboard, a reasonable estimate can be obtained for WarpStar 1 using conventional procedures. At 1 N/W, we get

(1 N.s/J)*(1.504e7 J/kg)/(9.80665 N/kg) = 1.534e6 s

Still not bad - according to Wikipedia, that's 15 times as high as the theoretical maximum for an Orion...

If you keep expended fuel on the ship (possibly a better alternative than wasting all that water, even though performance suffers a bit), it gets complicated. Technically the mass-energy method is more correct, but as mentioned above it's uninformative. It also reaches a singularity with a solar-powered thruster, where (except for solar panel ablation and such) no mass at all is expended.

For a solar-powered thruster, or even a thruster-on-a-flywheel-powered thruster, perhaps we could back-calculate an effective Isp out of Tsiolkovsky's equation using the power system mass and mean time between failures:

dV = F*t/m -> F*t/(m*g*ln(MR)) = Isp

where t is the MTBF for the power system, m is the total mass and MR is the ratio between m and the non-power-system mass. This should also work reasonably well for a fueled thruster if you take t as the fuel exhaustion time and MR as the familiar fueled/dry mass ratio:

WarpStar 1: (3.2e10 N.s)/((26465 kg)*(9.80665 N/kg)*ln(1.087)) = 1.47e6 s

which is fairly close to the water-dumping maximum calculated above, probably due to the near-unity mass ratio. Of course, this method results in an Isp that depends on spacecraft parameters... Isp really wasn't designed to deal with propellantless thrusters...

djolds1
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Post by djolds1 »

Skipjack wrote:Yeah and that at much more thrust...
At least from what I understand. Pretty cool if it works. Still, you are effectively limited in the amount of acceleration you can do (for manned flights anyway) with it. E.g. you wont be doing much more than 1 g for polonged periods of flight.
You might be able to do 4 or 5 g for shorter periods though, but that would not really make that much a difference (only for shorter distances with short travel times).
To bad, had it been a truly reactionless drive, then I guess you would not feel any acceleration forces at all (or even inverse ones as in anti gravity drives from science fiction, e.g. the Impulse engines).
Woodward claims that artificial gravity fields should be achievable in the medium term - that means acceleration compensators.
tombo wrote:Even 0.1 G would get you off the ground with wings.
If it is sustained it should be possible to spiral all the way to orbit.
Once there, you are half way to anywhere.
True. Scamjets (NOT sp) have left me jaded wrt winged lifters, but a spiral out is possible given constant acceleration.
Vae Victis

EricF
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Post by EricF »

Would a fractional output of the drive to allow for a slowed descent help with the heat issue of reentry?Perhaps those flimsy ceramics that keep getting damaged on the space shuttle would no longer be needed?

Betruger
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Post by Betruger »

djolds1 wrote:
tombo wrote:Even 0.1 G would get you off the ground with wings.
If it is sustained it should be possible to spiral all the way to orbit.
Once there, you are half way to anywhere.
True. Scamjets (NOT sp) have left me jaded wrt winged lifters, but a spiral out is possible given constant acceleration.
So the sci-fi winged space/air craft (e.g. Star Wars') would be feasible and interesting design schemes after all.. Nuts.

93143
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Post by 93143 »

EricF wrote:Would a fractional output of the drive to allow for a slowed descent help with the heat issue of reentry?Perhaps those flimsy ceramics that keep getting damaged on the space shuttle would no longer be needed?
That depends on the achievable thrust efficiency and thrust-to-weight ratio. The proponents mention 1 N/W as an achievable thrust efficiency, and I've been informed that a T/W of 10:1 is "more than conservative" - I believe there are notional thrusters that approach 50:1. So that's the optimistic expectation.

If, on the other hand, the drive were proven to work and developed, but with no advances beyond elimination of the observed thrust die-off, ground launch and propulsive entry would be ruled out. The thrust efficiency and T/W that Paul March seems to have already observed experimentally would make for a better space drive than VASIMR, but that's all it would be good for...

Polywell-powered QED engines could probably do propulsive entry. Certainly if Bussard was right, Polywell is what you'd call a "game-changer" in a lot of ways.

But if Mach-effect technology works, and works as well as the proponents hope, it's much more than just a game-changer. Fully propulsive landing on (and launch from) every terrestrial planet and moon in the solar system, in sequence, repeatedly, without refueling, would not be impossible. High-thrust trajectories would yield transit times measured in days rather than months or years. Radiation shielding could be as heavy and bulky as you wanted. This technology could render most science fiction obsolete. It would revolutionize not just space travel, not just air travel, but also power generation and even ground travel. That last probably requires some explanation:

I have a car. It has an IC engine, rated at 114 hp (85 kW). Fully loaded (and it's been pretty full), the car is probably about two metric tonnes. If, instead of accelerating by exploiting the static friction between the tires and the road, I simply used a Mach-effect thruster with a thrust efficiency of 1 N/W, this vehicle would go from 0 to 60 mph in a little over half a second.

The reason is (presumably) that over most of the acceleration curve, there's a significant amount of mass in the universe that has a velocity much closer to the velocity of the car than the velocity of the road is, resulting in the v in P = F·v being really small, so that for a given P, F is large (or for a given F, P is small). So the thrust efficiency could theoretically be significantly higher than that of a wheeled vehicle.

There's another way it could help, but I won't get into that because I already sound too much like a free-energy nutjob...
Betruger wrote:So the sci-fi winged space/air craft (e.g. Star Wars') would be feasible and interesting design schemes after all.. Nuts.
Yep. You could even use the wings as radiators in space - with enough thrust efficiency, the power dissipation rate should be quite low even for high-thrust operation, so you wouldn't need the proverbial football field...

Actually, a saucer-shaped craft has advantages too, if the available acceleration exceeds 1 gee...

TallDave
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Post by TallDave »

I have a car. It has an IC engine, rated at 114 hp (85 kW). Fully loaded (and it's been pretty full), the car is probably about two metric tonnes. If, instead of accelerating by exploiting the static friction between the tires and the road, I simply used a Mach-effect thruster with a thrust efficiency of 1 N/W, this vehicle would go from 0 to 60 mph in a little over half a second.
Heh, I had to read that a couple times before I got it. That's a very interesting point.

Skipjack
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Post by Skipjack »

That is exactly why the possibilities are getting me so excited.
If and that is a big if it works. The thing is that this is one of those "high risk, large potential gain" investments. If someone was to invest into it.
Now, I am just impatient as hell and would really like to know now. Same goes with Polywell (as 93143 said).
Lets just hope and maybe science fiction will be yesterday.
:)
Woodward claims that artificial gravity fields should be achievable in the medium term - that means acceleration compensators.
Ok, so there wont be any acceleration forces after all? Because that was my initial question.
I am confused now. This is unrelated to the Mach effect thruster? Or is that a derived development?

As I would understand it a "gravity compensation" in one direction would result in acceleration in the other direction. So it basically is Munchhausen pulling himself out of the swamp by his hair.
That was what I was wondering about in regards to the Mach effect thruster. So now I am again where I was with my question earlier in the thread ;)

AcesHigh
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Post by AcesHigh »

Im quite scared of ships travelling at lightspeed... specially if they have the potential (with this technology) to be so common.

I mean... think of a 9/11, but with a terrorist hitting Earth with a 1000 tons spaceship, at 0.99999% c.

Can anyone calculate the power of such impact?

Security would be even more important in such a universe... maybe robot guided ships, that dont give a darn about the passengers and will self-destruct if anyone announces a "hi-jacking"...

AcesHigh
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Post by AcesHigh »

lets not forget that fuel for electricity generation FOR PROPULSION is just a small part of what is needed... travelling at such high speeds, I would guess that we would need another fusion reactor only to create very large electromagnetic shields, very distant from the ship, to prevent collision with minor particles at near c speeds.

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