adamwehn
Corporal
Reged: 06/27/06
Posts: 67
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Aerospace fighters speed...
#133148 - 06/27/06 09:18 PM (66.211.72.162)
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I'm just curious how I would know an aerospace fighters speed, not in hexes or MP and such but Km/H, like when you view a tech readout for mechs. I'm looking at the Xerxes Aerospace fighter, but don't have Aerotech rules, this is for a conversion game I'm doing.
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Toontje
Colonel
Reged: 01/18/04
Posts: 2578
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Re: Aerospace fighters speed...
[Re: adamwehn]
#133158 - 06/28/06 01:05 AM (84.24.165.226)
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Depends. Atmospheric I presume, as space velocity is more or less unlimited.
Not really clear to me, there is a max safe velocity somethnig equal to safe trustx5, in mapsheets 1 km wide, per 10 seconds or 1 minute.
Say for a trush (fast one 10/15 iirc), that would boil down to 50 km every minute (otherwise 300 km/minute.. mach 14). mach 2.3, should be about right, or 3000 km/h.
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Rather to blow up, then.
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Cray
General
Reged: 07/27/01
Posts: 4131
Loc: North America
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Re: Aerospace fighters speed...
[Re: adamwehn]
#133164 - 06/28/06 05:45 AM (147.160.136.10)
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Quote:
I'm just curious how I would know an aerospace fighters speed, not in hexes or MP and such but Km/H, like when you view a tech readout for mechs. I'm looking at the Xerxes Aerospace fighter, but don't have Aerotech rules, this is for a conversion game I'm doing.
That depends on the scale you're using.
IN THE ATMOSPHERE
In Close Air Support
When engaging targets on Battletech maps, each Aerotech hex is equal to one BT map, and a BT map is about 0.5km across. A turn at this scale is 10 seconds. Thus, each hex moved per turn equates to 180kph.
Note that thrust ratings and overthrust ratings do not translate directly to movement. Instead, the fighter suffers drag equal to half its current speed at the end of the turn. This means you can eventually get a fighter moving at twice its overthrust rating. A 12/18 fighter could move 36 hexes per turn, which is 6480kph.
On The Space Map, In The Atmosphere
AT2 Space Maps have several rows of atmosphere where spacecraft can flirt with re-entry and other such fun. Speeds are different on this map than in ground support mode (which technically occurs at "row 0" on the space map.)
Here, you're now using the space scale, which is about 18km per hex (17,640m, if you round 1G to 9.8m/s/s), and 60 seconds per turn.
In this case, each hex moved per turn equates to ~300m/s (more specifically 294m/s), or roughly 1 mach, 1080kph.
Further, drag is different at these rarefied altitudes. Basically, it takes an aircraft 2 thrust points to accelerate by 1 point, but then the speed is maintained for a continuous expenditure of 2 thrust points. You can, in theory, move at 50 hexes/turn by spending only 2 thrust points per turn.
However, there are speed limits representing atmospheric friction. Exceeding the limit causes gruesome damage. The limits vary with altitude, getting up to about 17 hexes/turn at the "interface" row and as low as 2 hexes/turn at row 0 and 3 hexes/turn at row 1.
ICE aircraft are limited to row 0; fusion-powered conventional fighters are limited to row 1. This means the top speed of ICE conventional fighters is mach 2, and the top speed of fusion conventional fighters is mach 3. Aerospace fighters have no trouble going hypersonic at higher altitudes.
Indeed, using the space map is a very fuel efficient way to travel long distances. People have often bemoaned the short range of BT aircraft, but using the atmosphere rows of the space map allows pretty good range at supersonic speeds. An ICE aircraft at mach 2 (2 hexes/turn) consumes 1 fuel point per 18km; a conventional ICE fighter with a typical 5-ton fuel load has a 14400km unrefueled range.
IN SPACE
Once you get out of the atmosphere, you can really rocket ahead (pun intended). Again, you're using the space scale, which is about 18km per hex (17,640m, if you round 1G to 9.8m/s/s), and 60 seconds per turn.
There's no upper limit to speed except fuel exhaustion. You generally want to burn no more than half the fuel on a spacecraft so you have enough go-juice to stop at the end of a flight. Thus, a typical aerospace fighter (limited to tactical fuel consumption and having 5 tons of fuel) can accelerate to 200 hexes/turn, or 60,000m/s, or 216,000kph.
(Incidentally, if you just use strictly realistic delta-V expenditures rather than thrust points, a 100-ton aerospace fighter can accomplish with about 0.5 tons of fuel what the 100-ton US space shuttle accomplishes with 2000 tons of fuel.)
However, there are better fuel consumption modes out in BT. "Strategic fuel consumption" shifts to a higher efficiency engine operation mode that is unsuited for the hard maneuvering and accelerations of combat. This mode is available to smallcraft, dropships, jumpships, space stations, and warships. For military dropships, fuel consumption is 1.84 tons of fuel per full day spent at 1G. Each 3-4 days spent accelerating at 1G changes your speed by 1% of light speed, roughly, so normal transits from jump points to planets often involve dropships reaching a small percentage of light speed (1% light speed = 10,800,000kph). A large military dropship only needs about 700 tons of fuel to almost reach light speed, or about 1400 tons to reach it and brake to a halt. The largest warship (2.5 million tons) would only need about 30,000 tons of fuel to accomplish the same feat.
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Mike Miller, Materials Engineer
Disclaimer: Anything stated in this post is unofficial and non-canon unless directly quoted from a published book. Random internet musings of a BattleTech writer are not canon.
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sdog
Lieutenant Colonel
Reged: 09/01/03
Posts: 1791
Loc: europe
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Re: Aerospace fighters speed...
[Re: Cray]
#133173 - 06/28/06 09:40 AM (139.174.165.124)
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the kinetic energy of the 100t spacecraft would be
1e+5 kg / 2 * (6e+4)^2 = 1.8e+14 J
at 1 g it takes 6000 s for the acceleration to 60km/s
P=30 GW
the accelerating force:
F=m*a= 1e+5 kg * 10 m/s^2 = 1 MN
it burns 2.5t of fuel in 6000 s
dm_f/dt = 2500/6000 kg/s= 0.4 kg/s
for 1 g the impulse of 0.4 kg fuel must be
p = 1e+5 kg * 10 m/s = 1e+6 kg m/s
the average relative velocity of the fuel
v = p/m = 1e+6 / 0.4 m/s = 2.5e+6 m/s
this is about 1% c a non relativistic velocity.
what fuel are BT aerospace fighter "burning"?
hydrogen/protons?
atomic mass 1*1.7e-27 kg
the kinetic energy is 1e-14 J (or 60keV)
this would equal a temperature
T = E / k = 1e-14 J / 1.4e-23 J/K = 1e9 K (1000 million K)
so it's clearly not just heating hydrogen.
Natrium has an atomic mass 23 au, 50 million K. still to much.
accelerating protons to 60keV is not a problem however, an Ion drive could do it. 0.4kg/s is a hell lot for one however!
this would cause problems with the drive geting charged while ionising the hydrogen.
hydrogen atoms per second
dN/dt = 0.4/1*1.7e-27 kg = 2e+26
current I = Q/s = 2e26*e = 39 kA !!!
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I realised soon that the fun part of playing a military game is that we have lots of lifes and in the end knowone dies, ...
- Skaven, ArmA modding community
Edited by sdog (06/28/06 09:41 AM)
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adamwehn
Corporal
Reged: 06/27/06
Posts: 67
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Re: Aerospace fighters speed...
[Re: sdog]
#133174 - 06/28/06 09:47 AM (66.211.72.162)
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Quote:
the kinetic energy of the 100t spacecraft would be
1e+5 kg / 2 * (6e+4)^2 = 1.8e+14 J
at 1 g it takes 6000 s for the acceleration to 60km/s
P=30 GW
the accelerating force:
F=m*a= 1e+5 kg * 10 m/s^2 = 1 MN
it burns 2.5t of fuel in 6000 s
dm_f/dt = 2500/6000 kg/s= 0.4 kg/s
for 1 g the impulse of 0.4 kg fuel must be
p = 1e+5 kg * 10 m/s = 1e+6 kg m/s
the average relative velocity of the fuel
v = p/m = 1e+6 / 0.4 m/s = 2.5e+6 m/s
this is about 1% c a non relativistic velocity.
what fuel are BT aerospace fighter "burning"?
hydrogen/protons?
atomic mass 1*1.7e-27 kg
the kinetic energy is 1e-14 J (or 60keV)
this would equal a temperature
T = E / k = 1e-14 J / 1.4e-23 J/K = 1e9 K (1000 million K)
so it's clearly not just heating hydrogen.
Natrium has an atomic mass 23 au, 50 million K. still to much.
accelerating protons to 60keV is not a problem however, an Ion drive could do it. 0.4kg/s is a hell lot for one however!
this would cause problems with the drive geting charged while ionising the hydrogen.
hydrogen atoms per second
dN/dt = 0.4/1*1.7e-27 kg = 2e+26
current I = Q/s = 2e26*e = 39 kA !!!
I ain't a freakin physicist here, I just need to know how to come up with the speed of an aerospace fighter with a simple, 1 speed unit in game is equal to X real world speed.
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sdog
Lieutenant Colonel
Reged: 09/01/03
Posts: 1791
Loc: europe
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Re: Aerospace fighters speed...
[Re: adamwehn]
#133175 - 06/28/06 10:34 AM (139.174.165.124)
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that's been answered in crays posting already. and it's a pretty good answer.
however, there were some interesting questions open.
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I realised soon that the fun part of playing a military game is that we have lots of lifes and in the end knowone dies, ...
- Skaven, ArmA modding community
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adamwehn
Corporal
Reged: 06/27/06
Posts: 67
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Re: Aerospace fighters speed...
[Re: sdog]
#133177 - 06/28/06 11:43 AM (66.211.72.162)
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Quote:
that's been answered in crays posting already. and it's a pretty good answer.
however, there were some interesting questions open.
Yeah it may have been, but it's surrounded by so much detail/garbage that I can't find it. My head hurts just looking at all the other posts.
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Toontje
Colonel
Reged: 01/18/04
Posts: 2578
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Re: Aerospace fighters speed...
[Re: adamwehn]
#133178 - 06/28/06 11:49 AM (84.24.165.226)
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Try putting an electron cannon next to the ion engine, that should help keep things at zero net charge.
Come to think of it, does a relativistic effect not come into play when nearing .9c? I mean, the accelerated proton/electron gains weight. Doubling the potential on the coils, would either result in:
A/ double thrust. (since that would be 1.3c asuming .9c electron velocity at initial potential, might have a problem there.)
B/ double thrust (relativistic mass increase due to the electrons increase in mass).
C/ neither.
As you, sdog, are a physics student iirc (well, roughly), and this should be more or less your area, chew on that, and enlighten the crowd.
--------------------
Rather to blow up, then.
Edited by Toontje (06/28/06 11:56 AM)
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Cray
General
Reged: 07/27/01
Posts: 4131
Loc: North America
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Re: Aerospace fighters speed...
[Re: adamwehn]
#133184 - 06/28/06 02:29 PM (147.160.136.10)
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Quote:
Yeah it may have been, but it's surrounded by so much detail/garbage that I can't find it. My head hurts just looking at all the other posts.
Look for posts by me in this thread. If it helps, switch to Threaded View mode and just click on my posts in the thread tree.
Now, on to some other comments...
Quote:
what fuel are BT aerospace fighter "burning"?
hydrogen/protons?
Yes. Hydrogen fusion.
Quote:
atomic mass 1*1.7e-27 kg
the kinetic energy is 1e-14 J (or 60keV)
this would equal a temperature
T = E / k = 1e-14 J / 1.4e-23 J/K = 1e9 K (1000 million K)
so it's clearly not just heating hydrogen.
Let me suggest another approach: look at fuel consumption per unit time vs thrust. This is how you can figure out the specific impulse of chemical rockets.
1 thrust point of fuel (12.5kg) delivers a delta-V of 294m/s over the course of 60 seconds to a 100-ton aerospace fighter, or 0.417kg/s. The acceleration (0.5G) calls for 490,000 Newtons of thrust.
Yech...sorry, I do this better with pounds. That's 0.92 pounds of fuel per second to generate 110,000lbs thrust, or a Specific Impulse of (110,000lb / 0.92lb/s) = 120,000 seconds.
Exhaust velocity is Specific Impulse x G, or 1,176,000m/s, or 0.392% of light-speed.
As I understand, engineering studies of fusion rockets say specific impulses of 2500 to 2 million seconds are feasible, so 120,000 seconds should be possible.
The exhaust velocities of larger spacecraft in strategic fuel mode are just insane.
--------------------
Mike Miller, Materials Engineer
Disclaimer: Anything stated in this post is unofficial and non-canon unless directly quoted from a published book. Random internet musings of a BattleTech writer are not canon.
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sdog
Lieutenant Colonel
Reged: 09/01/03
Posts: 1791
Loc: europe
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Re: Aerospace fighters speed...
[Re: Toontje]
#133186 - 06/28/06 02:57 PM (139.174.165.124)
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the relativistic mass is:
m_rel = m_0 * \gamma = m_0 (1 - v^2/c^2)^(-1/2)
the Lorentz factor gamma depends on the square of the ratio of v and c.
but for the protons we got only v/c 0.01, squared it's 0.001
1-0.001 is in very good approximation 1 so the Lorentz factor is 1. the relativistic mass = rest mass
for a Lorentz factor of 1.1 e.g. 10% difference v needs to be about 0.4*c
you're right for 0.9 c gamma would be approximately 2. but the electron
mass is 1/2000 of the proton mass.
the kinetic energy of electrons accelerated to velocities where gamma is 2000 ( 0.9999999 c) would be
E=\gamma m_0*c^2 = 2000 * 0.5 MeV = 1GeV
that's not much (i think such energies have been achieved with betatrons in the 40s and 50s. todays accelerators get to the TeV order for electrons.)
i'm to lazy to calculate the values, but i think you could get half the thrust by accelerating the protons, and half by accelerating the electrons with a second accelerator.
i'm not very competent with relativistic physics, and don't know anything about accelerator physics. you could ask the owner of Hart Industries [DEST], he's doing his PhD at a DESY (a leading accelerator lab)
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I realised soon that the fun part of playing a military game is that we have lots of lifes and in the end knowone dies, ...
- Skaven, ArmA modding community
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sdog
Lieutenant Colonel
Reged: 09/01/03
Posts: 1791
Loc: europe
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Re: Aerospace fighters speed...
[Re: sdog]
#133187 - 06/28/06 04:02 PM (139.174.165.124)
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oh, btw
imo both accelerators definitely won't work in atmosphere!
the electron accelerator needs ultra high vacuum, the vacuum of space is actually not a vacuum at all, but just a thin gass. far to dense for such things.
maybe you could put some very high power vacuum pumps at the opening for the electron beam. i haven't got enough experience with vacuum technology to even guess if it could work. in outer space it could maybe...
if the accelerators run, they could maybe transfer enough impulse to intruding gas particles to push them out of the accelerator's opening.
as the gas get's ionized electrostatic pumps could be used very easily.
if the drives would work in atmosphere. the electron beam would cause some heavy x-ray radiation (bremsstrahlung) most likely much more deadly than it's weapon systems.
there's a big bug in my first posting!
it can't be 30 GW. i have to do it differently
the power is the time derivative of the kinetic energy
P= dT/dt
T= 1/2 m v^2
P= 1/2 m 2 v dv/dt = m*v*a
we got a only. thus we have to integrate over a to get v
a is constant however.
for 1g
P= 10 m/s^2 * 10 m/s * 10^5 kg = 10 MW
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I realised soon that the fun part of playing a military game is that we have lots of lifes and in the end knowone dies, ...
- Skaven, ArmA modding community
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sdog
Lieutenant Colonel
Reged: 09/01/03
Posts: 1791
Loc: europe
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Re: Aerospace fighters speed...
[Re: Cray]
#133188 - 06/28/06 04:04 PM (139.174.165.124)
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ah, thanks. we've been writing at the same time...
Quote:
Let me suggest another approach: look at fuel consumption per unit time vs thrust. This is how you can figure out the specific impulse of chemical rockets.
1 thrust point of fuel (12.5kg) delivers a delta-V of 294m/s over the course of 60 seconds to a 100-ton aerospace fighter, or 0.417kg/s. The acceleration (0.5G) calls for 490,000 Newtons of thrust.
Yech...sorry, I do this better with pounds. That's 0.92 pounds of fuel per second to generate 110,000lbs thrust, or a Specific Impulse of (110,000lb / 0.92lb/s) = 120,000 seconds.
Exhaust velocity is Specific Impulse x G, or 1,176,000m/s, or 0.392% of light-speed.
i've used 1g, and got the same results, if i apply a factor of 2 or respectively 1/2 except for the fuel consumption.
but this was caused by missunderstanding your posting, i thougt it you calculated only with half to the fuel, saving the other half for deceleration.
this is only a factor of two however, so no fundamental changes for the particle velocities. (where we both are in the same order of magnitude >1% c)
Quote:
As I understand, engineering studies of fusion rockets say specific impulses of 2500 to 2 million seconds are feasible, so 120,000 seconds should be possible.
The exhaust velocities of larger spacecraft in strategic fuel mode are just insane.
this is interesting, the propelant fuel is also the fusion fuel?
correcting my earlier mistake the temperature should be about 500 million K (half the thrust) that's in the range of fusion plasmas i think. however when i remember correctly the electron temperatures are considerably higher then the temperature of the hydrogen ions.
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I realised soon that the fun part of playing a military game is that we have lots of lifes and in the end knowone dies, ...
- Skaven, ArmA modding community
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adamwehn
Corporal
Reged: 06/27/06
Posts: 67
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Re: Aerospace fighters speed...
[Re: Cray]
#133189 - 06/28/06 04:22 PM (66.211.72.162)
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Cray, that post is the one I was talking about, there is so much technical garbage there that my head spins just reading a few sentences. Simplify it for me.
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sdog
Lieutenant Colonel
Reged: 09/01/03
Posts: 1791
Loc: europe
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Re: Aerospace fighters speed...
[Re: adamwehn]
#133190 - 06/28/06 04:28 PM (139.174.165.124)
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In Space
Quote:
There's no upper limit to speed except fuel exhaustion.
Quote:
... 5 tons of fuel) can accelerate to 200 hexes/turn, or 60,000m/s
mate, have you tried readin already?
if you want to know it for atmosphere it's all there...
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I realised soon that the fun part of playing a military game is that we have lots of lifes and in the end knowone dies, ...
- Skaven, ArmA modding community
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adamwehn
Corporal
Reged: 06/27/06
Posts: 67
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Re: Aerospace fighters speed...
[Re: sdog]
#133191 - 06/28/06 04:49 PM (66.211.72.162)
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Quote:
In Space
Quote:
There's no upper limit to speed except fuel exhaustion.
Quote:
... 5 tons of fuel) can accelerate to 200 hexes/turn, or 60,000m/s
mate, have you tried readin already?
if you want to know it for atmosphere it's all there...
Yeah and like I told you before, I ain't a freakin physicist, and everything that's there is a bunch of gobbley gook that makes my head hurt! I ain't a god damn genius!
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Cray
General
Reged: 07/27/01
Posts: 4131
Loc: North America
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Re: Aerospace fighters speed...
[Re: adamwehn]
#133195 - 06/28/06 06:58 PM (68.200.109.191)
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Quote:
Yeah and like I told you before, I ain't a freakin physicist, and everything that's there is a bunch of gobbley gook that makes my head hurt! I ain't a god damn genius!
I'll repeat and clarify my first answer, with the important points underlined. If you don't understand the bulk of the reply, just focus on the underlined points. If there's something you don't understand, quote the section and ask a question about it.
Basically, there are 3 environments that a fighter can operate in in Battletech.
Environment 1: In Close Air Support
When engaging targets on Battletech maps, each Aerotech hex is equal to one BT map, and a BT map is about 0.5km across. A turn at this scale is 10 seconds. Thus, each hex moved per turn equates to 180kph.
Note that thrust ratings and overthrust ratings do not translate directly to movement. Instead, the fighter suffers drag equal to half its current speed at the end of the turn. This means you can eventually get a fighter moving at twice its overthrust rating. A 12/18 fighter could move 36 hexes per turn, which is 6480kph.
Environment 2: On The Space Map, In The Atmosphere
AT2 Space Maps have several rows of atmosphere where spacecraft can flirt with re-entry and other such fun. Speeds are different on this map than in ground support mode (which technically occurs at "row 0" on the space map.)
Here, you're now using the space scale, which is about 18km per hex (17,640m, if you round 1G to 9.8m/s/s), and 60 seconds per turn.
In this case, each hex moved per turn equates to ~300m/s (more specifically 294m/s), or roughly 1 mach, 1080kph.
Further, drag is different at these rarefied altitudes. Basically, it takes an aircraft 2 thrust points to accelerate by 1 point, but then the speed is maintained for a continuous expenditure of 2 thrust points. You can, in theory, move at 50 hexes/turn by spending only 2 thrust points per turn.
However, there are speed limits representing atmospheric friction. Exceeding the limit causes gruesome damage. The limits vary with altitude, getting up to about 17 hexes/turn at the "interface" row and as low as 2 hexes/turn at row 0 and 3 hexes/turn at row 1.
ICE aircraft are limited to row 0; fusion-powered conventional fighters are limited to row 1. This means the top speed of ICE conventional fighters is mach 2, and the top speed of fusion conventional fighters is mach 3. Aerospace fighters have no trouble going hypersonic at higher altitudes.
Indeed, using the space map is a very fuel efficient way to travel long distances. People have often bemoaned the short range of BT aircraft, but using the atmosphere rows of the space map allows pretty good range at supersonic speeds. An ICE aircraft at mach 2 (2 hexes/turn) consumes 1 fuel point per 18km; a conventional ICE fighter with a typical 5-ton fuel load has a 14400km unrefueled range.
ENVIRONMENT 3: IN SPACE
Once you get out of the atmosphere, you can really rocket ahead (pun intended). Again, you're using the space scale, which is about 18km per hex (17,640m, if you round 1G to 9.8m/s/s), and 60 seconds per turn.
There's no upper limit to speed except fuel exhaustion. Each fuel point gives 300m/s or 1080kph. You generally want to burn no more than half the fuel on a spacecraft so you have enough go-juice to stop at the end of a flight. Thus, a typical aerospace fighter (limited to tactical fuel consumption and having 5 tons of fuel) can accelerate to 200 hexes/turn, or 60,000m/s, or 216,000kph.
(Incidentally, if you just use strictly realistic delta-V expenditures rather than thrust points, a 100-ton aerospace fighter can accomplish with about 0.5 tons of fuel what the 100-ton US space shuttle accomplishes with 2000 tons of fuel.)
However, there are better fuel consumption modes out in BT. "Strategic fuel consumption" shifts to a higher efficiency engine operation mode that is unsuited for the hard maneuvering and accelerations of combat. This mode is available to smallcraft, dropships, jumpships, space stations, and warships. For military dropships, fuel consumption is 1.84 tons of fuel per full day spent at 1G. Each 3-4 days spent accelerating at 1G changes your speed by 1% of light speed, roughly, so normal transits from jump points to planets often involve dropships reaching a small percentage of light speed (1% light speed = 10,800,000kph). A large military dropship only needs about 700 tons of fuel to almost reach light speed, or about 1400 tons to reach it and brake to a halt. The largest warship (2.5 million tons) would only need about 30,000 tons of fuel to accomplish the same feat.
Now, where do you need clarification? If you don't know where to start, throw some questions out there and we'll figure something out.
BTW, What game system are you converting to? I might be able to do the conversion for you.
Edited by Cray (06/28/06 07:01 PM)
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adamwehn
Corporal
Reged: 06/27/06
Posts: 67
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Re: Aerospace fighters speed...
[Re: Cray]
#133196 - 06/28/06 07:50 PM (66.211.72.162)
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Thank you! Your underlining the pertinent information was immensely helpful. Now I understand how to calculate it.
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Toontje
Colonel
Reged: 01/18/04
Posts: 2578
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Re: Aerospace fighters speed...
[Re: sdog]
#133227 - 06/30/06 02:02 AM (84.24.165.226)
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Quote:
oh, btw
imo both accelerators definitely won't work in atmosphere!
the electron accelerator needs ultra high vacuum, the vacuum of space is actually not a vacuum at all, but just a thin gass. far to dense for such things.
maybe you could put some very high power vacuum pumps at the opening for the electron beam. i haven't got enough experience with vacuum technology to even guess if it could work. in outer space it could maybe...
if the accelerators run, they could maybe transfer enough impulse to intruding gas particles to push them out of the accelerator's opening.
as the gas get's ionized electrostatic pumps could be used very easily.
if the drives would work in atmosphere. the electron beam would cause some heavy x-ray radiation (bremsstrahlung) most likely much more deadly than it's weapon systems.
Any possible intruding particles would most likely have too high velocities to be affected by a vacuum pump. More effect to shield the accelerator from any intruding particles would be to bend the exhaust by a magnetic/electric field. Since teh curvature fo a particle in a field is dependant on charge, mass and velocity, most would have a different path than the exit particles. Two times a small hole on either end of the field, would eliminate most of those problems. (ok that is more or less the electrostatic pump you described.. my fault)
Always thought particle accelerators require such high vacuum since you want to observe what happens with a few foreign particles in the system as posible, maybe for impulse transfer it does not matter that much?
--------------------
Rather to blow up, then.
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sdog
Lieutenant Colonel
Reged: 09/01/03
Posts: 1791
Loc: europe
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Re: Aerospace fighters speed...
[Re: Toontje]
#133230 - 06/30/06 03:20 AM (139.174.165.124)
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i didn't think about bending the beam. the electrostatic pump is something different, just a charged plate where charged particles get pulled to, then removed by another pump.
your suggestion would solve the problem.
however you'll need considerable power for it. and you will get a lot of synchrotron radiation, this energy will be lost from the beam energy, e.g. propulsion.
you don't want the particles in your beam to colide with 'dirt' as this means loss. if the average mean free path is as long as the accelerator is long, half of the beam should be lost. (and your vacuum get's worse by those collisions, as you got the collision products flying around there.)
however geting the mean free path for this is a bit more difficult cause the collision cross sections are completely different for such high electron energies.
were geting into an area where we would need to calculate/ approximate values. but where it becomes a bit more difficult as a lot of special knowledge is required. doesn't make the thread less interesting though. and so what, we're talking about a SciFi spacecraft.
--------------------
I realised soon that the fun part of playing a military game is that we have lots of lifes and in the end knowone dies, ...
- Skaven, ArmA modding community
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Toontje
Colonel
Reged: 01/18/04
Posts: 2578
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Re: Aerospace fighters speed...
[Re: sdog]
#133233 - 06/30/06 04:19 AM (84.24.165.226)
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Not so much fiction, it is rather doable with current tech. But for bending, not that much power is required, I think you can manage with a permanent magnet. Space is not an issue in space, the components do not have to be pressurised after all (and if it needs a higher vacuum than interstellar vacuum, pressure will not be high so simple construction would do), so path length to get sufficient seperation is not hard to find.
But you were right on the not needing a cyclotron, maybe if you really need to get the maximum possible out of the reaction mass, but in general a linear accelerator should be fine for now.
Assuming similar operation as a cathode ray tube, (charge on one end, expell plasma on the other), all you need is:
A/ A plasma
B/ An electric field
C/ Power to provide A and B
Foreign particles would not disturb either, or get charged and expelled as you said. With fusion power (not such a long shot), the 39 kA at 60 kV should not be a problem.
If the 60 kV is a problem, maybe 30 kV with double valency ions, such as Be, Mg, Ca? Being heavierwould only detract in the sense the not-yet-used reaction mass is heavier than protons.
Actually, the valency will never be a problem, with enough energy you can strip them of all electrons if need be... But power requirements will remain the same.
Of cause, the way to get A down to prevent charge buildup, from VA is to get V up.. I am unaware of practical problems in this area (thus at what time a short circuit is induced in vacuum, or leakage becomes to high.)
kV is surely not much of a problem, the high voltage grid is something like 100kV. After checking, 380 kV is the paneuropean norm from what I get out of it. (http://de.wikipedia.org/wiki/Hochspannungstechnik)Damn those amperes, up the voltage! 
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Rather to blow up, then.
Edited by Toontje (06/30/06 04:21 AM)
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