Ion engine shenanigans

[His Divine Shadow]

And I don't like to kick you in the head with facts again... but do you even have the *foggiest* idea of what an ion wash on that scale would look like? Christ, after the burn made by the Imperial fleet at Endor, the whole damned sky of the planet should have been awash... there'd be a glowing trail thousands of km long tailing the Imperial fleet like the mother of all contrails. Worse, do you know how much mass would have to be spewed out of the back of those ships at near light-speed to manage that? The numbers ain't pretty...

Now E1701 do make alot of these claims, especially in the past I remember him doing them infront of DasBastard.
My claims was that the exhaust wash of an ISD would be around 1e23watts or so, using the common mass of 50e9kg and an exhaust speed of .9c for the ion wash.

That is his counter claims, he has provided no math and I have pointed this out, but it woud indeed be sweet to play his game and turn it against him.

[Ender]

Unless I've got a gross concept error here, there is an easier way to get numbers.

Mass: 50 million tons (though I've done some stuff that suggests to me that 13 trillion tons might be more accurate)

Aceleration: 3000 G around Endor.

KE required for this:

.5 * (5E7*907.1848) * ((3000*9.8m/sec^2)* 1 sec)^2 = 1.96E19 joules

That much energy must be shot out the back of the ISD to propel it (unless I'm leaving off something because the ions have mass and thus momentum, I'm hazy at that part)

Thus each of the main engines would need to be able to withstand atleast 1.5 GT

So torp up the tailpipe is pointless.

[His Divine Shadow]

Well if you wanna argue that, go ahead, I just want someone to confirm/debunk E1701's claims about what it ought to look like.

[NecronLord]

http://bbs.stardestroyer.net/viewtopic. ... 546#543546

Finding fuel won't be a problem.

50e9kg

Is this the mass of an Imperator? And shouldn't it be 5e10?

[Connor MacLeod]

Actually Ender I think what you need to do is figure out the required force (to simplify, as I usually do, assume the time is equal) to be imparted on the ISD by the reaction mass, estimate/calculate the reaction mass.

For example, a 5e10 kg ISD x 30,000 m/s^2 should give us a total force of 1.5e15 newtons (Remember that Force = Mass x acceleration. Anyone wants to check those calcs, they can.

To impart equal force to the ISD, the reaction mass of an ISD, assuming .99c velocity (~297,000,000 m/s ~3e8 m/s) would have to mass about 5e6 kilograms (roughly 5,000 tons).

However, we should note that this "mass" could be real mass, or relatavistic mass. At .99c I believe the ratio of relatavsitic mass to "real" mass is roughly 7:1, so we're *actually* dealign with less than 704,000 kg of mass per second.

Also, according to Mike's relatavity calculator, a 5 million ton mass traveling at .99c should have about 3.891E+23 joules (Enter 710000 as mass in kg, 297000000 as mass in meters per second, and calculate. Relatavistic mom entum should be about 1.495e15 kg*m/s)

Further, there is nothing that says an ISD could not accelerate its reaction mass to say, .9999c or more, for example, provided they have the requisite energy (which they do.) They can decrease the mass requirements for reaction mass by increasing the relatavistic mass (although there is probably a limit to which they can do this.) E seems to
ignore this little possibility, though (I wonder why.)

I also question why he assumes it would be "visible" - A substantial amount of mass being ejected out MIGHT be visible, but if the reaction mass has a substantial relatavistic mass component to it, it will not neccesarily be easily visible, unless it is somehow emitting energy like some kind of plasma. Simple charged particles would not be visible, neccesarily. Perhaps you could ask E to cite his "proof/rationale" for why the exhaust should be visible.

[Connor MacLeod]

Ender: The problem in your calcs is that the engines would only absorb a small fraction of their energy on being emitted. If the thrusters actually absorbed MORE, the ISD's propulsive abilities would descrease. It does suggest approximately the rough "order of magnitude" energy level its required to endure, though.

It should also be noted that mass could be several orders of magnitude higher, due to the fuel stored on an ISD (which if similar to the acclamator, is "orders of magnitude" more dense than the ship itself.)

We should also note that the exhaust of the engines would represent a danger to any small object (fighter, missile, otherwise) approaching it. The projectile in question woudl be REQUIRED to endure the energy output stated (to probably say nothing of the associated momentum/force) to survive and penetrate.

[Lord Poe]

Ask this idiot why the space around the Dyson sphere wasn't "awash with light" when the E-D fought madly to resist the Sphere's tractor beam? It was still THERE, as Scott and LaForge detected it, but couldn't be seen.

[The Yosemite Bear]

I'm just picturing the evil thoughts of trying to explain the Kzin Patriarchy to idiots like this....

Gee haven't they heard of the old school sci fi concept of using a very big series of fusion bombs to propell a ship.

[PainRack]

Alternatively,this might be an excellent time to talk about the existence of gravitic drives in Star Wars or some other form of exotic drive.

After all,there must be something that's deccelerating the Rebel ships at Endor and it ain't the ion drive.

[Mad]

My claims was that the exhaust wash of an ISD would be around 1e23watts or so, using the common mass of 50e9kg and an exhaust speed of .9c for the ion wash.

Wha--? 1E23 W as in a 2.2 second burn would require enough energy to meet the gravitational binding energy of a planet?

[Mad]

Whoops, nevermind... I transposed the 2 and 3 in 32... Now I wish I could just delete that.

[Ender]

Does anyone have the formulas used in the relativity claculator handy? I'd like to build my own into what I'm working on here.

[XaLEv]

Does anyone have the formulas used in the relativity claculator handy? I'd like to build my own into what I'm working on here.

Well, relativistic kinetic energy = mc²(x - 1), where x = 1/sqrt [1 - (v²/c²)]

Not sure about what others he used.

[His Divine Shadow]

Does anyone have the formulas used in the relativity claculator handy? I'd like to build my own into what I'm working on here.

Well, relativistic kinetic energy = mc²(x - 1), where x = 1/sqrt [1 - (v²/c²)]

Not sure about what others he used.

Could you help me out with an example?

[XaLEv]

Could you help me out with an example?

What do you mean? Write out the derivation of some mass's RKE, showing all the math and everything?

[Ender]

Dammit, I found a formula for relativistic mass, but my spreadsheet formula of it is off by a single order of magnitude.

=(B1*907.1848)/((1/(POWER((1-(POWER((B2*9.,2)/9E16)), 0.5)))-1)

B1 is normal mass, B2 is acceleration

Can anyone tell me what is wrong here?

[Howedar]

There's a smile in it

[Ender]

Dammit, that is suppossed to be "8 )"

[His Divine Shadow]

Could you help me out with an example?

What do you mean? Write out the derivation of some mass's RKE, showing all the math and everything?

As in putting some numbers in there, showing how you use the formula.

Allow me to show you my understanding of the formula so far:

KE = mc²(x - 1), where x = 1/sqrt [1 - (v²/c²)]

Calculating x:
x = 1/sqrt [1 - (v²/c²)]

This is where I am stumped, I get negative numbers if I use 2e8² for v² and 3e8² for c²

So clearly I am friggin stupid.

[XaLEv]

Well that certainly shouldn't happen.

Okay, using your numbers:

Code: Select all

x = 1/sqrt [1 - (v²/c²)]
           [1 - (4e16/9e16)]
           [1 - 0.44444]
      sqrt 0.55556
    1/0.74536
x = 1.34163

[His Divine Shadow]

Gah, stupid me, I had this part: [1 - 0.44444] reversed.

OK, så now we have(say mass if 50kg):

Code: Select all

KE = mc²(1.34163 - 1)
     mc²(0.34163)
     4,5e18(0,34163)
KE = 1,537e18j

And MW's calculator agrees.

[His Divine Shadow]

You might notice some odd usage of dots and commas, thats because we use commas instead of dots, I tried to turn commas into dots but I forgot some, so here's a cleaned up version.

Code: Select all

KE = mc²(1.34163 - 1)
     mc²(0.34163)
     4.5e18(0.34163)
KE = 1.537e18j

[YT300000]

Just Fuck off you little cocksuckers.

[Ender]

Just Fuck off you little cocksuckers.

Well that was fucking random

[Howedar]

No it wasn't, the above post just got cut. Speak no more of it.