Kind of lore/headcanon question. - How fast are ASF's?

[marauder648]

I've seen multiple speeds over the years including them being near hypersonic if they really give it the beans or are a speed focused design, down to more reasonable Mach numbers. 
So what do you folks think? Do we have any actual numbers?  To go from group to space the'd need to have some kind of thruster setting that is just 'point up and GO HELLA FAST' possibly with droppable fuel tanks to sustain this hugely inefficient thrust method to get out of the atmopshpere, but in a typical Earth like atmosphere, how fast are we talking? 

[Elmoth]

Both. if you look at their speed profiles 8at least in Apha strike) there are a lot of designs that are more or less the same spoeed as conventional fighters. Medium and heavy designs, especially.

However, Interceptors (light ASF like the thrush, Sabre, Centurion, Cheetah or Sparrowhawk) are WAY faster. Those could be hipersonic easily if the pilots push their frames.

[Weirdo]

Velocity 7 on the Low Altitude map is roughly Mach 1. That should give you a benchmark to work from.

[Elmoth]

Wow. Conventional fighters in BT (alpha strike) do not reach Mach 1?

[Weirdo]

They do, and quite easily. Anything with a Thrust Rating of 4/6 or higher in TW can manage it. 3/5s can do it in a dive, but it's not safe, requiring at least one piloting skill roll to avoid damage or loss of control.

I know of no Conventional Fighters that are slower than 4/6. I think you have to start looking at Support Aircraft for that.

[Elmoth]

Ah. Must be the Alpha Strike conversion. All conventional fighters move between 5 and 7 points of movement there. Does not seem to have a direct correspondence with what you are talking about here :) I have no rral knowledge of traditional BT except for having played the rulebook like 20 years ago a few times. Never used more than a few mechs there.

[Weirdo]

Alpha Strike does not give real-world figures for speed or distance, and if the writers are wise, it never will.

When looking at aeros, the Alpha Strike thrust will be the Safe Thrust in TW. So something with 5 Thrust in Alpha Strike is a 5/8 in Total War.

[Tai Dai Cultist]

Keep in mind it's not 7 thrust that is roughly equal to MACH 1 but 7 velocity.

Atmospheric flight has air resistance so you don't have unlimited potential velocity, but you still can reach velocities in excess of your thrust rating.

[Weirdo]

Bingo, that's how 4/6 units can hit 7. I *think* a 3/5 can hit it in a dive, but I haven't worked it out precisely.

[Tai Dai Cultist]

IIRC aeros lose 2 velocity per turn in atmospheric flight, so even 3 thrust would be sufficient to attain the necessary velocity to go supersonic in level flight.  So long as you don't need to turn...

[AdmiralObvious]

Last I checked, can't ASFs get up to double their safe cruise in velocity before they start to fall apart? A 3/5 can probably hit Mach 1, you're just about to snap the wings off though.

[Tai Dai Cultist]

Last I checked, can't ASFs get up to double their safe cruise in velocity before they start to fall apart? A 3/5 can probably hit Mach 1, you're just about to snap the wings off though.

If that's true, 3/5 is just short of making a sonic boom but 4/6 is comfortably capable.

[AdmiralObvious]

Alright, I went and had a look at the charts in the book. Max safe velocity is dependent on altitude when in atmosphere, but if you try a maneuver that's double the safe cruise or more, then you might take structural damage.

So, they're two different things. In theory, any ASF can reach Mach 1, provided they're either in space (where there will be no sonic boom) or in an atmosphere above 54 km. They must fly in a straight line, but in theory you can go as fast as you want, as long as the atmosphere doesn't start ripping parts off the craft. You won't be able to turn (or do much of anything else) safely though till you slow down.

[AldanFerrox]

Well, they have to be at least fast enough to reach escape velocity, because I was always under the impression that all ASF's are able to reach orbit unassisted.

[Weirdo]

They may simply have not built an ASF slow enough...yet.

...aeros lose 2 velocity per turn in atmospheric flight...

50% of velocity.

[I am Belch II]

I know its way off but I always thought that it was a 180 kph for 1 mp on the low altitude chart. Which would put the fast 21mp  at around Mach 3.5.

[cray]

I've seen multiple speeds over the years including them being near hypersonic if they really give it the beans or are a speed focused design, down to more reasonable Mach numbers. 

Do we have any actual numbers?

We have the rules, which are linked to hexes defined in meters and turns defined in seconds. The answer depends on altitude.

The following I've copied and pasted from a Sarna primer on fuel usage, so the wording is a bit off from a velocity discussion.

Low altitude

Per Total Warfare p.81-85, The low altitude map uses hexes that are 1 BT ground map board across (i.e., 500 meters) and turns that are 10 seconds long. Per p. 85, winged units do NOT travel like ground units. Instead of spending thrust points to cross hexes, you spend thrust points to change velocity.

A 'Mech or VTOL on the ground map will spend 9 MP to travel across 9 flat, simple ground hexes. A fixed wing vehicle on the low altitude map expends thrust to change velocity, so a fighter that spends 9 thrust (and thus 9 fuel) reaches a velocity of 9 and covers 9 hexes that turn.

"But wait, didn't you just say it doesn't move like ground units...?"

Hold on a second, I'm getting to it.

On turn number 2, that fighter traveling at 9 hexes per turn doesn't have to spend 9 thrust points to maintain its velocity. Instead, per p. 84 TW, they have to pay half their velocity in thrust points (round down) to maintain their current speed (if they want to). That fighter traveling at 9 hexes per turn only needs to spend 4 thrust points (and thus 4 fuel points) to continue traveling at 9 hexes per turn.

Hence a 4/6 conventional fighter could peak at velocity 12 on the low altitude map.

12 hexes (6 kilometers) per 10-second turn is 600 meters per second, or just under mach 2.

High altitude

High altitude movement (in rule terms) is more like moving in space, but with annoying atmosphere effects, and is covered from p. 79 to 80 in Total Warfare.

High altitude movement turns are the same as space turns (60 seconds long) and the hexes are 18,000m across. You're going to go a lot further on a tank of gas in high altitude movement mode.

Also, you do not lose half your velocity per turn on the high altitude map. Instead, you lose 1 velocity point per turn, period (unless you pop your air brakes). It takes 2 thrust points to accelerate.

Finally, there are safe velocity limits depending on altitude. (Altitude 0, ground row/low altitude: 2 hexes per turn. Row 1 [18-35km altitude]: 3 per turn. Row 2 [36-54km]: 6. Row 3: 9. Row 4: 12. Space interface: 15.)

Since you're only losing 1 velocity per turn and spending 2 thrust points (2 fuel points) to offset that drag, it quickly becomes apparent that "faster is more fuel efficient, and faster means higher altitude."

However, conventional fighters (and support vehicles) are limited to rows 0 and 1. The only thing traveling higher and faster are aerospace fighters and other spacecraft, who don't need to fart around in the atmosphere. For about 1 ton of fuel, they can pop into orbit (above the interface, and about 30 hexes/turn) and reach anywhere on an Earth-like planet in 45-50 minutes.

Therefore, I'll only calculate range for high altitude movement in row 1 (~60,000ft altitude, 18km). The safe limit there is 3 hexes per turn. At high altitude, 1 hex per turn (18km / 1 minute) is about mach 1. So, this scenario is looking at traveling at about mach 3 at about the cruising altitude of an SR-71.

You're covering 3 hexes per turn using 2 thrust points to maintain velocity. That 2 fuel points per turn. Figuring you set aside 1 ton for takeoff and landing, that's 400 fuel points again. 400 fuel points will last 200 turns.

During each of those 200 turns, you cover 3 hexes. Total range: 600 hexes. Size of a hex: 18km. 600 x 18km = 10,800km (~6500 miles.)

Note: 1 hex per turn = mach 1 on the high altitude map.

  To go from group to space the'd need to have some kind of thruster setting that is just 'point up and GO HELLA FAST' possibly with droppable fuel tanks to sustain this hugely inefficient thrust method to get out of the atmopshpere, but in a typical Earth like atmosphere, how fast are we talking?

You wouldn't need drop tanks. Per the Takeoff rules, it only takes a ton of fuel to get into orbit.

Further, you wouldn't need to go very fast. You're not battling severely inefficient engines like a chemical rocket. It'd be reasonable to head upward at 2-3 hexes per turn (mach 2-3) to clear the atmosphere rows in a few turns, then you could sprint to orbital velocity (about 26-27 hexes per turn) in a vacuum without worrying about atmospheric effects.

Note Strategic Operations has a whole section on long distance planetary aerospace travel.

[Daryk]

Cray, thanks for the VERY detailed explanation!  :thumbsup:

[cray]

Cray, thanks for the VERY detailed explanation!  :thumbsup:

You made the example of powered fighter descent, right?

[Daryk]

I think that was Weirdo, but thanks for thinking of me!  :)

[Weirdo]

Yeah, I've made detailed powered descents plenty of times. Survived all the ones that happened in real life! :thumbsup:

[Daryk]

Aren't all commercial airliner landings technically "powered descents"?

[cray]

Aren't all commercial airliner landings technically "powered descents"?

:P I was thinking more of using fusion rockets to slow well below orbital velocity before entering an atmosphere, but you're not wrong. :D

[marauder648]

Fascinating stuff Cray :) I asked this question because i'm just trying to write/produce something and in it i've got a max/cruising speed of some ASF's and had a 7/11 55 tonner able to cruise along at Mach 1.81 and go to Mach 3.68 when they give it the beans.  A 6/9 85-tonner's cruising at Mach 1.14 and Mach 2.38 at full throttle. 

Does that sound about the ball park ish for folks?

[Nebfer]

Fascinating stuff Cray :) I asked this question because i'm just trying to write/produce something and in it i've got a max/cruising speed of some ASF's and had a 7/11 55 tonner able to cruise along at Mach 1.81 and go to Mach 3.68 when they give it the beans.  A 6/9 85-tonner's cruising at Mach 1.14 and Mach 2.38 at full throttle. 

Does that sound about the ball park ish for folks?

The Short of it is using Low altitude rules which translates to 180kph per hex, for a 6/9 the max speed is 12 hexes per turn or 2,180kph. High altitude it Ironically is the same for 0-18km of altitude, above that you start getting faster speeds, as under high altitude rules each hex traveled is equivalent to a speed of 1,080kph, as such the ultimate airspeed under the rules with this rule set is 12,960kph (at ~55-72 km).

So for low altitude the following speeds will be achievable
4/6..... 8 hexes or 1,440kph or Mach 1.18 at sea level 
5/8..... 10 hexes or 1,800kph or Mach 1.47
6/9..... 12 hexes or 2,160kph or Mach 1.76
7/11... 14 hexes or 2,520kph or Mach 2.06
8/12... 16 hexes or 2,880kph or Mach 2.35
9/14... 18 hexes or 3,240kph or Mach 2.65
10/15. 20 hexes or 3,600kph or Mach 2.94
11/17. 22 hexes or 3,960kph or Mach 3.23
12/18. 24 hexes or 4,320kph or Mach 3.53
13/20. 26 hexes or 4,680kph or Mach 3.82
14/21. 28 hexes or 5,040kph or Mach 4.11
15/23. 30 hexes or 5,400kph or Mach 4.41

A few things to note, as noted the Mach number is for Sea level, at 12 to 20 km the speed of sound is only 1,063kph and not 1,225kph it would be at sea level, as such a Generic "dog fighter" ASF (typically 6/9) would be capable of traveling at Mach 2.03 at thoughs altitudes. Using the High altitude rules all ASFs are capable of 2,160kph at these speeds. Though at 19-20km altitude one could use the high altitude rules and travel at 3,240kph or mach 3.05... An interesting fact, spheroid Dropships at high altitude can travel one hex laterally per turn so yeah you can have an Overlord traveling at supersonic speeds sideways...

If you want something more fluffy from the Novels their are three references (AFAIK) of ASFs traveling at hypersonic speeds (in atmosphere), as low as 500m above the ground, interestingly one of them I believe was a 5/8. So in universe ASFs are a bit faster in an atmosphere than what the game would go with (also in the novels are a few references to bombing at supersonic speeds, which I believe is something they can do in game, and is done in real life).

Endurance is fairly simple, each point of fuel is 36km using the high altitude rules, though only if your using just one fuel point per turn and or cruising with an even number of movement points (I.e. moving is 2, 4 or 6... hexes per turn and not 3 or 5...), as odd numbers cut the distance you travel in by a fair bit (by up to 25%). So the typical 5 ton fuel tank is enough for between 7,200 and 14,400km (on average it would seem closer to the 14,000km figures). Even crazier is the fact that Conventional fighters have twice this range, and if you use the optional rules in Strat ops quadrupled, it's not to hard to get an conventional to be able to fly around the earth once or twice (Meteor HSF with max external fuel supposedly can fly for some 86,000km (unless conventional fighters using external only get 40 points per tank...))!

Using the high altitude rules the speed "limits" are as such
0 to 18 km 2 hexes per turn or 2,160kph
19 to 36 km 3 hexes per turn or 3,240kph
37 to 54 km 6 hexes per turn or 6,480kph
55 to 72 km 9 hexes per turn or 9,720kph
73 to 90 km 12 hexes per turn or 12,960kph
91 to 108 km 15 hexes per turn or 16,200kph
After this your suborbital (in space), unless you speed up to ~27 hexes per turn and enter orbit.

[cray]

Fascinating stuff Cray :) I asked this question because i'm just trying to write/produce something and in it i've got a max/cruising speed of some ASF's and had a 7/11 55 tonner able to cruise along at Mach 1.81 and go to Mach 3.68 when they give it the beans.  A 6/9 85-tonner's cruising at Mach 1.14 and Mach 2.38 at full throttle. 

Does that sound about the ball park ish for folks?

Only if they're in low altitude combat mode, where they'll also run out of fuel in a few hundred kilometers. Either of those ASFs or, a hypothetical 2/3 ASF, could cruise at mach 3 at high altitude row 1 for thousands of kilometers and go hypersonic at higher altitudes.

[The_Caveman]

If you want something more fluffy from the Novels their are three references (AFAIK) of ASFs traveling at hypersonic speeds (in atmosphere), as low as 500m above the ground, interestingly one of them I believe was a 5/8. So in universe ASFs are a bit faster in an atmosphere than what the game would go with (also in the novels are a few references to bombing at supersonic speeds, which I believe is something they can do in game, and is done in real life).

I think this is a case of the writer not truly understanding the difference between supersonic and hypersonic.

Sonic booms from aircraft doing moderate supersonic speeds in the stratosphere can break windows on the ground. If you could do Mach 5 at sea level, you wouldn't need bombs!

(According to an estimate based on this report, the bow-shock overpressure from a 100-ton fighter doing Mach 5, 500m off the ground would be in the range of 42 psi, which is comparable to being 100 meters away from a 1-kiloton nuclear detonation. It would annihilate anything under its ground-track.)

[Nebfer]

I think this is a case of the writer not truly understanding the difference between supersonic and hypersonic.

Sonic booms from aircraft doing moderate supersonic speeds in the stratosphere can break windows on the ground. If you could do Mach 5 at sea level, you wouldn't need bombs!

(According to an estimate based on this report, the bow-shock overpressure from a 100-ton fighter doing Mach 5, 500m off the ground would be in the range of 42 psi, which is comparable to being 100 meters away from a 1-kiloton nuclear detonation. It would annihilate anything under its ground-track.)

The accounts do mention shattering of glass for kilometers along the path, toppling of pedestrians along the flight path with the leading edges glowing bright yellow, in one case the passage of the aircraft was enough to topple a large monument, the aircraft also is mentioned to have left very long glowing ionization trails.
One such aircraft mentioned was a Scytha with Sholagars and Vandals also mentioned in another passage.

From what I can gather no the writer dose not seem to be inherently mistaking hypersonic for supersonic. The writer dose seem to understand that these speeds will leave a fair bit of destruction, though he might of not fully known the strength or downplayed it, at the lest their being a bit hyperbolic, as it would seem the writer intended them to be notably faster than just mere supersonic. Considering that a well known 70ish ton aircraft only gets to around 550-600 C at around Mach 3.2, one would wonder at what speed a Scytha would have to be to reach 1,000-1,100ish C (Bright yellow AFAIK would indicated around 1,000 to 1,200 degrees C).

Though moving at 1.7km/s+ at sea level would be risky in any event as even slight deviations downward could cause one to crash in mere seconds or less.
None the less I would think even if you go with hypersonic being a bit hyperbolic I would think the indications is clear that their going notably faster than what the game would imply them to have at these altitudes.

[Wolf72]

well, those speed numbers now explain why the star wars fighters got crap speed in Nebulae California.  iirc most of the fighters in WEG listed their atmo speed somewhere around 1,000 kph ... less than a 4/6 ASF.

[The_Caveman]

From what I can gather no the writer dose not seem to be inherently mistaking hypersonic for supersonic. The writer dose seem to understand that these speeds will leave a fair bit of destruction, though he might of not fully known the strength or downplayed it, at the lest their being a bit hyperbolic, as it would seem the writer intended them to be notably faster than just mere supersonic. Considering that a well known 70ish ton aircraft only gets to around 550-600 C at around Mach 3.2, one would wonder at what speed a Scytha would have to be to reach 1,000-1,100ish C (Bright yellow AFAIK would indicated around 1,000 to 1,200 degrees C).

The thing to keep in mind here is, they're supposedly doing it near sea level. There isn't an aircraft in the world today that can do Mach 2 at sea level (few can even break Mach 1), let alone Mach 5+. The SR-71 has to climb up above 99% of the atmosphere, almost on the edge of space, to hit Mach 3. Doing Mach 3 at sea level the temperature rise is almost 500 degrees higher than it is in the upper stratosphere because the air is thicker (and ground speeds are higher since the speed of sound drops off with altitude).

The Sprint missile, doing close to Mach 10, had leading-edge temperatures around 3k Celsius in the upper stratosphere where there ain't much air left to heat things. It glowed white.

FWIW the results listed sound comparable to mid-high supersonic less than 1km off the ground, aside from bringing down the stone monument. Project Pluto, the nuclear ramjet "missile from Hell", was estimated to produce 162 dB shockwaves doing Mach 3 near the surface (doable for Sholagars and Vandals), which would have caused structural damage to buildings. Its surface would almost certainly have glowed red/yellow.

Best estimate for leading-edge temps at Mach 5 near the surface would be somewhere in the range of 1700C, which is higher than the melting point of most steels. They'd really be putting BT's magic armor to the test.

Any ionization trails would be from the fusion engine exhaust, since ionizing air to the point of glowing requires temperatures several thousand degrees higher than we're talking about.

If you really wanted to be destructive, though, fly an aerodyne DropShip near the surface at high supersonic speeds. The shockwave pressure level scales with the size of the object, so a multi-thousand-ton DropShip would be a weapon of mass destruction.

[AdmiralObvious]

There are maximum safe speeds for ships and ASF's at different levels of atmosphere. You might be able to get a dropship to do Mach 1 at sea level in an "earth like" planet, but the ship will probably have disintegrated before it reaches height 3 on the low altitude map at that speed. Going above those safe limits goes directly into the SI for the craft. Doesn't matter how fancy the armor is if the whole thing collapses into a fireball.

[The_Caveman]

There are maximum safe speeds for ships and ASF's at different levels of atmosphere. You might be able to get a dropship to do Mach 1 at sea level in an "earth like" planet, but the ship will probably have disintegrated before it reaches height 3 on the low altitude map at that speed. Going above those safe limits goes directly into the SI for the craft. Doesn't matter how fancy the armor is if the whole thing collapses into a fireball.

Not quite.

Max safe speed for the "ground" row of the high altitude map, which corresponds to the play space of the low-altitude map, is 2 high-altitude/space hexes a turn, which is Mach 2-ish. On the low altitude map, maximum safe speed is twice a ship's safe thrust. There are canon aerodyne DropShips (Avenger comes to mind) that can reach moderate supersonic speeds at low altitude without risking structural damage.

[BloodRose]

A 'Mech or VTOL on the ground map will spend 9 MP to travel across 9 flat, simple ground hexes. A fixed wing vehicle on the low altitude map expends thrust to change velocity, so a fighter that spends 9 thrust (and thus 9 fuel) reaches a velocity of 9 and covers 9 hexes that turn.

"But wait, didn't you just say it doesn't move like ground units...?"

Hold on a second, I'm getting to it.

On turn number 2, that fighter traveling at 9 hexes per turn doesn't have to spend 9 thrust points to maintain its velocity. Instead, per p. 84 TW, they have to pay half their velocity in thrust points (round down) to maintain their current speed (if they want to). That fighter traveling at 9 hexes per turn only needs to spend 4 thrust points (and thus 4 fuel points) to continue traveling at 9 hexes per turn.

A great explanation but for one thing - 1 Velocity actually equals 16 hexes of movement. So a Mech that spends 4 movement will move 4 hexes, but a ASF or CF that expends 4 Thrust to reach Velocity 4 will move 64 hexes in that turn.

[Daryk]

16?  I thought map sheets were 17 hexes long...

[Weirdo]

They are. If you're using normal movement rules, an aero hex is equivalent to one mapsheet. If you're brave enough to try the Aero Units on Ground Mapsheets rules, one point of velocity moves you sixteen ground hexes. No, the two don't match exactly.

[Daryk]

Ah, I see... thanks Weirdo!  :thumbsup:

[BloodRose]

On a side note, this is why you have to either use the Radar map, an Aero map or have some abstracted turn-around system if you are not using masses of maps but want air support.

[Weirdo]

Using an aero map is so easy, I genuinely can't imagine going back to the ground map rules. Once you get to the ground map area, you can strike every turn if you want, and the only fancy flying you need to do is be able to maintain a velocity of six and be able to turn. Either direction, it doesn't matter.

[RifleMech]

So if I understand this right, and I probably don't, a 2/3 Prop fighter can hit mach speeds?

[Weirdo]

No. Propeller-driven craft are explicitly forbidden from going that fast, on low altitude maps, at least. I think on the high-altitude map they're allowed to move one hex per turn, which might be supersonic, but it's abstracted so that they can do any movement at all up there. Same for airships.

[RifleMech]

No. Propeller-driven craft are explicitly forbidden from going that fast, on low altitude maps, at least. I think on the high-altitude map they're allowed to move one hex per turn, which might be supersonic, but it's abstracted so that they can do any movement at all up there. Same for airships.

Sorry I'm still don't understand. I can understand the abstraction on the high-altitude map but how fast can props go on the low-altitude map? TechManual says they go out of control at 8+. That would be a max velocity of 7, right? But doesn't that come out to something like 1,209.6kph or Mach 1.12?  ???

[Tai Dai Cultist]

Sorry I'm still don't understand. I can understand the abstraction on the high-altitude map but how fast can props go on the low-altitude map? TechManual says they go out of control at 8+. That would be a max velocity of 7, right? But doesn't that come out to something like 1,209.6kph or Mach 1.12?  ???

If breaking the sound barrier is an issue, just hand-waive it that in this particular world's atmosphere and/or at that particular altitude, velocity 7 works out to be just under the sound barrier.

[RifleMech]

That'd only work for some planets though.

[Thatguybil]

Prop planes can hit / exceed the sound barrier for short periods during steep dives.

[marauder648]

Prop planes can hit / exceed the sound barrier for short periods during steep dives.

I've never heard of a prop plane breaking the speed of sound, but I don't doubt that its possible, if you went up as high as you could in a fast prop and dove as hard as you could.  Pulling out of that dive however...

[Daryk]

I believe it happened as far back as WWII, in isolated cases.

[AdmiralObvious]

I'm fairly sure the first prop driven plane to break the sound barrier "officially" was either a Helldiver or a Bearcat, some time way after WWII.

You've got pilots from the Battle of Britain who claimed otherwise though, but nobody could prove it because nobody could actually verify the claim.

[Ruger]

I believe it happened as far back as WWII, in isolated cases.

I've heard that too, but only in extreme dives with something like a P-51 or P-37...

Ruger

[RifleMech]

According to wiki claims of reaching supersonic speeds were always in emergency dives and were never confirmed. It also says the fastest speed a prop plane is alleged to have reached is 690 mph (1110 km/h, Mach 0.96) in Spitfire. Almost but not quite breaking the sound barrier.

Wiki also says the record for fastest prop plane is the Tupolev Tu-114 with a maximum speed of 878 km/h (540 mph, Mach 0.73) I think that works out to Velocity 5?

I suppose modern BT prop aircraft can hover around mach speed in normal flight at sea level. I also suppose older planes can hit velocity 7 in emergencies. But would they have room to pull up and what about normal flight? 

[glitterboy2098]

actually it is theoretically possible to go supersonic in level flight with the right engine and props, but it hasn't been actually achieved yet, mostly because it has been too expensive for small scale private industry and individuals, and big business and governments generally aren't interested.

[RifleMech]

actually it is theoretically possible to go supersonic in level flight with the right engine and props, but it hasn't been actually achieved yet, mostly because it has been too expensive for small scale private industry and individuals, and big business and governments generally aren't interested.

So that would leave room for more advanced tech planes to hit velocity 7 while older tech planes are limited to velocity 6?

[Alsadius]

actually it is theoretically possible to go supersonic in level flight with the right engine and props, but it hasn't been actually achieved yet, mostly because it has been too expensive for small scale private industry and individuals, and big business and governments generally aren't interested.

Given how RL prop engine designers worry about prop tips going supersonic, I'd shudder to think of what's happen if the whole plane did. It's well within the BT universe's capabilities, I'm sure, but the engines would probably have painfully short service lives even there.

I'm actually pretty impressed by this thread, tbh. Everything is worked out in ways that seem pretty logical, realistic for the setting, and still playable.

[RifleMech]

So if I wanted to make a replica of an F-14 it'd have a max speed of 8/12 it would have a thrust rating of 4/6? Is that right or is jets have a top speed?

[BloodRose]

So if I wanted to make a replica of an F-14 it'd have a max speed of 8/12 it would have a thrust rating of 4/6? Is that right or is jets have a top speed?

Thrust 4/6 would give it 4 regular or 6 'full burn' points to move per turn. Assuming you take off at safe and climb to ceiling then start to accelerate you will start off moving at 2 aero (32 ground) and gradually accelerate as you climb (assuming 2 levels/turn) by 1 aero (16 ground) unless you throttle back or climb faster. If you dont then you will reach 3 aero (48 ground) and stay there. Assuming you climb for 4 turns (to height 8) you will be going at speed three, then you level out. With no other altitude changes and going at full safe burn you will reach Speed 8 (128) in three turns and be able to maintain it easily, unless you climb or perform a maneuver that costs thrust.
Now, if you hit full burn once you level out you will jump straight to 6 (96) on turn one of leveling out, 10 on the second and then creep to 11 before finally hitting 12 on the fourth turn. At that point you are burning fuel rapidly though, and will lose speed on any maneuver that does not cost you at least 3 altitude.
4/6 is good enough for a "modern day" conventional fighter, but do not expect to be outrunning a later design (Although you could out punch them).

[RifleMech]

Thrust 4/6 would give it 4 regular or 6 'full burn' points to move per turn. Assuming you take off at safe and climb to ceiling then start to accelerate you will start off moving at 2 aero (32 ground) and gradually accelerate as you climb (assuming 2 levels/turn) by 1 aero (16 ground) unless you throttle back or climb faster. If you dont then you will reach 3 aero (48 ground) and stay there. Assuming you climb for 4 turns (to height 8) you will be going at speed three, then you level out. With no other altitude changes and going at full safe burn you will reach Speed 8 (128) in three turns and be able to maintain it easily, unless you climb or perform a maneuver that costs thrust.
Now, if you hit full burn once you level out you will jump straight to 6 (96) on turn one of leveling out, 10 on the second and then creep to 11 before finally hitting 12 on the fourth turn. At that point you are burning fuel rapidly though, and will lose speed on any maneuver that does not cost you at least 3 altitude.
4/6 is good enough for a "modern day" conventional fighter, but do not expect to be outrunning a later design (Although you could out punch them).

So that's a yes to an F-14 hitting a max velocity of 12?  And fuel usage depends on altitude with the higher you go the less you use?

[Weirdo]

Bear in mind that all aero units have a top speed limit of twice their safe thrust, and exceeding this forces you to make increasingly difficult control rolls. (TW, p. 84) A hypothetical 4/6 F-14 trying to fly at velocity 12 is highly likely to tear itself apart in an incredibly short span of time.

[RifleMech]

Still haven't quite figured out velocity but it's good to know that there re maximums.  This thread has been quite educational. Thanks everyone!  :thumbsup:

[Nebfer]

Bear in mind that all aero units have a top speed limit of twice their safe thrust, and exceeding this forces you to make increasingly difficult control rolls. (TW, p. 84) A hypothetical 4/6 F-14 trying to fly at velocity 12 is highly likely to tear itself apart in an incredibly short span of time.

Ignoring the fact that few Real fighters even reach 1.5Gs of straight line acceleration...

So technically modern fighters would be 2/3 or 3/5 if you want to be a bit generous, but their top speeds is would be notably higher than what the game would indicate from their thrust profiles. Even so most modern fighters rarely even go supersonic spending most of their time subsonic (IIRC many pilots could count the number of times they went supersonic on their hands in their entire careers).

Considering that most real fighters only travel around at mach 0.8 ish in comparison to B-techs notably higher cruising speeds of around mach 2ish, so B-tech fighters are on average twice as fast.

[BloodRose]

Bear in mind that all aero units have a top speed limit of twice their safe thrust, and exceeding this forces you to make increasingly difficult control rolls. (TW, p. 84) A hypothetical 4/6 F-14 trying to fly at velocity 12 is highly likely to tear itself apart in an incredibly short span of time.

IIRC the maximum speed for atmo flight is Velocity 12, and exceeding it makes bad things happen.

[RifleMech]

Ignoring the fact that few Real fighters even reach 1.5Gs of straight line acceleration...

So technically modern fighters would be 2/3 or 3/5 if you want to be a bit generous, but their top speeds is would be notably higher than what the game would indicate from their thrust profiles. Even so most modern fighters rarely even go supersonic spending most of their time subsonic (IIRC many pilots could count the number of times they went supersonic on their hands in their entire careers).

Considering that most real fighters only travel around at mach 0.8 ish in comparison to B-techs notably higher cruising speeds of around mach 2ish, so B-tech fighters are on average twice as fast.

Are you talking cruising speeds? I was going by the top speed listed in Wiki. If I did it right, it works out to 4/6 for the F-14. If I'm doing this right, an F-4 would be 3/5 with a max velocity of 10.  But that's if I'm doing things right. Also if I'm doing things right a P-51 will have a max 3 and a Sopwith Camel a max thrust of 1. I'm not sure what the thrust ratings would be. I'm even less sure about how one would make such vehicles in BT right now. So I'm back to being lost again.  :(

[The_Caveman]

The rules were not designed to reproduce real-world 20th century aircraft in any way, shape, or form. You're not going to get anything satisfactory. Garbage in, garbage out.

[Tai Dai Cultist]

The rules were not designed to reproduce real-world 20th century aircraft in any way, shape, or form. You're not going to get anything satisfactory. Garbage in, garbage out.

This is absolutely true.

Still, the OP may be interested in checking out TRO:1940 regardless.

[RifleMech]

The rules were not designed to reproduce real-world 20th century aircraft in any way, shape, or form. You're not going to get anything satisfactory. Garbage in, garbage out.

I know that but I should be able to make something sort of close. The problem for aircraft is the speed/thrust system doesn't work well at slow speeds. Unfortunately, there's no legal mechanism for building airplanes with fractional thrust points.

This is absolutely true.

Still, the OP may be interested in checking out TRO:1940 regardless.

I love XTRO:1945!  :smitten:  Unfortunately, it isn't legal. :'(  If it were I'd used it and not have a problem.  :)

[The_Caveman]

I know that but I should be able to make something sort of close.

Why should you? There is nothing in BattleTech that's even kind-of-sort-of like an F-14, much less a Sopwith Camel. Would you expect the Mobile Structure rules to give you a good approximation of a medieval siege tower?

BT just isn't meant to be an anything-simulator. It's intended for pitting fantasy-tech units from a very particular vision of the far future, which are more or less evenly matched in terms of technology, against one another. If you try to do anything outside of that, you're going to get weird results.

Your best bet is to try to create something that has the "feel" of its real-life counterpart rather than attempting to duplicate the actual stats. For an F-14, we'd need a heavy turbine conventional fighter that is somewhat maneuverable, has lots of fuel, and carries a big payload of long-range missiles. Say, a 40-tonner with 6/9 thrust and an LRM-15.

[Daryk]

Or even an Extended LRM, or maybe a Thunderbolt launcher, depending on how you want to get the feel of an AIM-54...

[Kovax]

Responding to a couple of older posts in the thread, I was under the impression that several prop planes were strongly believed to have exceeded the speed of sound in a dive, probably with structural damage in the process of breaking that barrier, but were then destroyed in the process of dropping back below the threshold.  Basically, it's likely to have happened, but nobody lived to tell about it.

That doesn't mean it can't be done, but it's never been worth the engineering, cost, and mortal risk to try to push a prop plane to those speeds when a jet powered craft can be built to do so more easily and affordably.

[RifleMech]

Why should you? There is nothing in BattleTech that's even kind-of-sort-of like an F-14, much less a Sopwith Camel. Would you expect the Mobile Structure rules to give you a good approximation of a medieval siege tower?

BT just isn't meant to be an anything-simulator. It's intended for pitting fantasy-tech units from a very particular vision of the far future, which are more or less evenly matched in terms of technology, against one another. If you try to do anything outside of that, you're going to get weird results.

Your best bet is to try to create something that has the "feel" of its real-life counterpart rather than attempting to duplicate the actual stats. For an F-14, we'd need a heavy turbine conventional fighter that is somewhat maneuverable, has lots of fuel, and carries a big payload of long-range missiles. Say, a 40-tonner with 6/9 thrust and an LRM-15.

Its the last part that I'm trying to do. Something similar with the same feel. So I'm ok with a 4/6 jet fighter. Prop fighters are a little more complicated but I can house rule XTRO:1946 rules are in play. WWI fighters though...the speeds are so slow it be easier to use no than thrust? And why can't I use Sopwith Camels armed with pulse lasers to hunt for flying infantry? Or just as an alternative to VTOL?

[Daryk]

Fixed-wing Support Vehicles are what you want for Camels.  They just don't operate on the same scale with ASFs.

[Tai Dai Cultist]

I'd venture another suggestion.  Treat them as VTOL infantry, in the same way that you'd treat a bunch of halftracks as some form of mechanized infantry rather than bothering to build vehicle stats for them.

They're agile and slow enough, VTOLs would be a more or less appropriate rules depiction.  If necessary, maybe add a restriction that they can't hover.

[RifleMech]

Fixed-wing Support Vehicles are what you want for Camels.  They just don't operate on the same scale with ASFs.

They still use thrust point though and at these speeds they should use MPs.

I'd venture another suggestion.  Treat them as VTOL infantry, in the same way that you'd treat a bunch of halftracks as some form of mechanized infantry rather than bothering to build vehicle stats for them.

They're agile and slow enough, VTOLs would be a more or less appropriate rules depiction.  If necessary, maybe add a restriction that they can't hover.

If I wanted that level of abstraction I would but I'd like to build the vehicle.

Itd be nice if airplanes operating at low speeds could be built using MPs and then abstracted or converted up to thrust points. (Same for VTOL and Aairships but that's another problem.) Unfortunately that isn't legal. :'(

[The_Caveman]

Responding to a couple of older posts in the thread, I was under the impression that several prop planes were strongly believed to have exceeded the speed of sound in a dive, probably with structural damage in the process of breaking that barrier, but were then destroyed in the process of dropping back below the threshold.  Basically, it's likely to have happened, but nobody lived to tell about it.

That doesn't mean it can't be done, but it's never been worth the engineering, cost, and mortal risk to try to push a prop plane to those speeds when a jet powered craft can be built to do so more easily and affordably.

So, this is one of those things that probably never happened, but they thought it did because of the limited understanding of the time. There were some planes such as the P-38 and Spitfire that had high enough critical Mach numbers (above 0.8 ) that they could get into the compressibility region in a steep dive. Once the air starts compressing near the speed of sound, it makes airspeed indicators (which rely on ambient air pressure) unreliable. In the 1940s the knowledge of compressible aerodynamics was very limited and instruments weren't designed to compensate. The airspeed indicator could read a speed faster than sound while the aircraft was still subsonic.

Prop aircraft can't really exceed the speed of sound because the drag produced by a propeller increases exponentially near sonic speeds, and a prop which is capable of cutting through the shockwaves in the transonic region would be too thin and short to produce sufficient takeoff thrust. Very fast prop aircraft usually have their blade tips already going supersonic, and the outer part of the prop actually produces slight negative thrust due to Mach effects. The faster you go, the more of the blade is supersonic and the less thrust it can produce.

Early attempts at penetrating the sound barrier usually ended tragically because the shockwaves produced control flutter that made it impossible to pull out of a dive--or worse, would rip the wing apart. Safe supersonic flight required the development of stiffer wings and better control surface design.

[The_Caveman]

I'd venture another suggestion.  Treat them as VTOL infantry, in the same way that you'd treat a bunch of halftracks as some form of mechanized infantry rather than bothering to build vehicle stats for them.

They're agile and slow enough, VTOLs would be a more or less appropriate rules depiction.  If necessary, maybe add a restriction that they can't hover.

VTOL infantry for WW1 planes is a great suggestion. Especially since their weapons would be infantry MGs by BattleTech standards and do less than 1 point of damage apiece.

They still end up being too slow, but this is a general problem with VTOLs in BattleTech. No VTOL except maybe the Ferret has a realistic flight speed.

[RifleMech]

But you can also mount infantry weapons on small support vehicles. I'd like to build the vehicle version of the abstracted infantry.

The thing is motorized/mechanized infantry and vehicles operate under different rules. Aerospace adds further complications.

[The_Caveman]

I'd like to build the vehicle version of the abstracted infantry.

I don't know what to tell you. Go back in time and talk to the guys that wrote the support vee rules before they were published?

You can get most of the way there with the support vehicle rules, but you need to increase the weight to about 5 tons to have enough fuel to be useful.

[RifleMech]

I don't know what to tell you. Go back in time and talk to the guys that wrote the support vee rules before they were published?

You can get most of the way there with the support vehicle rules, but you need to increase the weight to about 5 tons to have enough fuel to be useful.

I'm not having problems with support vehicles rules so much. It's having to use thrust speeds and that aerospace always flies higher. Thrust makes sense after you get to a certain speed but below that it doesn't. Thrust also works higher up but not down low.

I also don't expect range to be huge. It'd be enough for a short combat. I think. I still haven't completely figured out the velocity thing anyway. I usually just end up abstracting a couple passes.

[The_Caveman]

I'm not having problems with support vehicles rules so much. It's having to use thrust speeds and that aerospace always flies higher. Thrust makes sense after you get to a certain speed but below that it doesn't. Thrust also works higher up but not down low.

I also don't expect range to be huge. It'd be enough for a short combat. I think. I still haven't completely figured out the velocity thing anyway. I usually just end up abstracting a couple passes.

You've run head-on into the problem with the VTOL movement rules being a crude kludge based on jump MPs: they massively fail to bridge the gap between ground units and aerospace units.

What's needed is a third layer of movement, but adding one is only going to add to the chug of an already glacially-paced game.

[RifleMech]

The VTOL movement is ok but you're right. It doesn't bridge ground and aerospace. I don't think any of the TPTB thought players would want to play with such slow moving airplanes though.

I think the best fix would be for all aircraft operating below a certain speed to use MP and to use TP above that. I would also say that all aircraft flying above a certain elevation be treated as aircraft and those below as ground units. That way aircraft of all kinds can dog fight or be staffed depending on the stituation.


Back on topicish. The max velocity for a prop plane is 9, right?

[RifleMech]

(Sigh) I am remembering why we house ruled aerospace.

If nebfer's post https://bg.battletech.com/forums/index.php?topic=63990.msg1472345#msg1472345 is right an aerospace unit should be able to a max of 23 hexes.  A top speed of 5,400kph or Mach 4.41.  But isn't to max movement 2 hexes, or 360kph or Mach .29?

[The_Caveman]

(Sigh) I am remembering why we house ruled aerospace.

If nebfer's post https://bg.battletech.com/forums/index.php?topic=63990.msg1472345#msg1472345 is right an aerospace unit should be able to a max of 23 hexes.  A top speed of 5,400kph or Mach 4.41.  But isn't to max movement 2 hexes, or 360kph or Mach .29?

You're confusing high and low altitude hexes. Low altitude hexes are 500m, high altitude hexes are 18km.

I think what you're looking for is "aerospace units on ground maps" rules where every point of (low altitude) AS velocity translates to 16 ground MP.

[RifleMech]

You're confusing high and low altitude hexes. Low altitude hexes are 500m, high altitude hexes are 18km.

I think what you're looking for is "aerospace units on ground maps" rules where every point of (low altitude) AS velocity translates to 16 ground MP.

Well I am confused.

His post said those were the speeds for low altitude. That's altitudes 0 and 1 right?  :-\

[Weirdo]

Low Altitude is when the map is parallel to the planet's surface, and encompasses Altitudes 1-10. High Altitude is when your map is perpendicular to the surface, one hexrow is the ground, you have a few hexrows of atmosphere, and then space. The lowest non-ground hexrow on the High Altitude map encompasses all of Low Altitude. Low Altitude hexes are 500 meters across, High Altitude hexes are 18 kilometers across. Combat at Low Altitude uses ten-second turns, High Altitude and Space operations use sixty-second turns. Between those figures and Total War, all your velocity questions are easily answered.

The rules for all of this can be found in Total War. Low Altitude is on pages 80-88, and High Altitude/Space Movement is on pages 76-80. It is not possible for text to convey sufficiently strongly that you stay the hell away from the Aerospace Units on Ground Mapsheets rules on pages 91-92. Seriously, they will only bring you pain.

[RifleMech]

Low Altitude is when the map is parallel to the planet's surface, and encompasses Altitudes 1-10. High Altitude is when your map is perpendicular to the surface, one hexrow is the ground, you have a few hexrows of atmosphere, and then space. The lowest non-ground hexrow on the High Altitude map encompasses all of Low Altitude. Low Altitude hexes are 500 meters across, High Altitude hexes are 18 kilometers across. Combat at Low Altitude uses ten-second turns, High Altitude and Space operations use sixty-second turns. Between those figures and Total War, all your velocity questions are easily answered.

The rules for all of this can be found in Total War. Low Altitude is on pages 80-88, and High Altitude/Space Movement is on pages 76-80. It is not possible for text to convey sufficiently strongly that you stay the hell away from the Aerospace Units on Ground Mapsheets rules on pages 91-92. Seriously, they will only bring you pain.

Sorry. Still lost. :(  I can't even figure out the tables. The High-Altitude Table has the ground row being up to 17 km with a safe velocity of 2. The Low Altitude Table has Altitude 10 at a max height of 18,000 meters. Doesn't 18,000 m = 18 km? So which table do I use when flying at 17.5 km?

Page 81 also says that any unit prohibited from operating ins space can't move from Altitude 10 to Altitude 11 (Row 1). So how does a conventional fighter or support vehicle travel in Row 3 at mach 3?

I'd only want to use really slow aircraft on the ground mapsheet but the other rules give me enough pain. I'm pretty sure I had VCR instructions that were easier to understand. :'(

[Weirdo]

Sorry. Still lost. :(  I can't even figure out the tables. The High-Altitude Table has the ground row being up to 17 km with a safe velocity of 2. The Low Altitude Table has Altitude 10 at a max height of 18,000 meters. Doesn't 18,000 m = 18 km? So which table do I use when flying at 17.5 km?

As the prior post says, Low Altitude and High Altitude overlap a bit. It is your choice as to which map you choose to operate the unit on.

[RifleMech]

I'm sorry I'm still lost. :(


High altitude row 1 has a max speed of mach 3, and Row 0 /low altitude has a max speed of mach 2. Right?  So how does an aircraft reach mach 4.4 on the low altitude map/row 0?  Doesn't that exceed the safe thrust/velocity limit?

[The_Caveman]

I'm sorry I'm still lost. :(


High altitude row 1 has a max speed of mach 3, and Row 0 /low altitude has a max speed of mach 2. Right?  So how does an aircraft reach mach 4.4 on the low altitude map/row 0?  Doesn't that exceed the safe thrust/velocity limit?

High and low altitude rules don't overlap even though the maps do. Aerospace craft that drop onto the low-altitude map are like banditos that make it across the border before the sheriff catches them. Whole different set of laws apply.

Ground, low-altitude, and high altitude rules use different levels of abstraction, going from most detailed (ground) to least (high altitude/space). The high altitude rules don't take safe thrust into account for atmospheric speed limits for the sake of simplification.

[marauder648]

all these rules sound a tad complex :S

[The_Caveman]

all these rules sound a tad complex :S

It's what happens when you take a hex-based 2D wargame designed for walking tank battles and try to project it onto 3D aerospace battles. The entire paradigm of Aerotech is misaligned and has been from the start. About the only upside to it is the game mechanics are similar enough that players don't have to learn an entirely new system.

[RifleMech]

High and low altitude rules don't overlap even though the maps do. Aerospace craft that drop onto the low-altitude map are like banditos that make it across the border before the sheriff catches them. Whole different set of laws apply.

Ground, low-altitude, and high altitude rules use different levels of abstraction, going from most detailed (ground) to least (high altitude/space). The high altitude rules don't take safe thrust into account for atmospheric speed limits for the sake of simplification.

So aerospace using ground, low-altitude rules can go as fast as twice their max thrust, whatever that may be?

[The_Caveman]

So aerospace using ground, low-altitude rules can go as fast as twice their max thrust, whatever that may be?

Twice as fast as their safe thrust, unless that has changed recently.

[Weirdo]

Well, I suppose you can manage to hit twice your max thrust, if you can pass a large number of very difficult piloting skill rolls, with failing even a single one being a Very Bad Thing.

[RifleMech]

Twice as fast as their safe thrust, unless that has changed recently.

So you can go faster on the low altitude map than you can at the same height on the high altitude map?    ???   No wonder I'm lost. I flew into the twilight zone.  xp. Thanks  ;)

Well, I suppose you can manage to hit twice your max thrust, if you can pass a large number of very difficult piloting skill rolls, with failing even a single one being a Very Bad Thing.

Not likely.   :)     so this is where the 5 points of damage to the nose comes in?

[The_Caveman]

So you can go faster on the low altitude map than you can at the same height on the high altitude map?    ???   No wonder I'm lost. I flew into the twilight zone.  xp. Thanks  ;)




Not likely.   :)     so this is where the 5 points of damage to the nose comes in?

When you consider that most aerospace craft are between 3/5 and 8/12 thrust, capping the speed in the lowest row to Mach 2 is not an unreasonable abstraction. It only breaks down for edge cases like light fighters that are all engine.

[RifleMech]

When you consider that most aerospace craft are between 3/5 and 8/12 thrust, capping the speed in the lowest row to Mach 2 is not an unreasonable abstraction. It only breaks down for edge cases like light fighters that are all engine.

It makes me wonder why have a cap if you're allowed to go faster than the cap?

[Weirdo]

Well, given that we're talking about a game...maybe for gameplay reasons?

[RifleMech]

Still, why say you can't and then say you can?

[Weirdo]

Dunno, not invested enough in the fluff-only details to find out. My closing advice: Learn one of them. High Altitude or Low Altitude, pick one. For the sake of your mind, assume the other does not exist.

[RifleMech]

I'll go low. Not that my mind cares. It left me long ago. :D

Thanks :)

[Wolf72]

Memory Jog, please ...

What is the relatively safest thrust for conventional fighters?

I just went through some old word.docs and found a simple trainer design I had ... 4 tons, 40 fuel cell engine, 10/15 movement ... but I think it's more of death trap.  I mean, my '94 Mazda 323 went to 140 on the speedometer, I don't think it would have been wise to push it that far.

[snewsom2997]

Responding to a couple of older posts in the thread, I was under the impression that several prop planes were strongly believed to have exceeded the speed of sound in a dive, probably with structural damage in the process of breaking that barrier, but were then destroyed in the process of dropping back below the threshold.  Basically, it's likely to have happened, but nobody lived to tell about it.

That doesn't mean it can't be done, but it's never been worth the engineering, cost, and mortal risk to try to push a prop plane to those speeds when a jet powered craft can be built to do so more easily and affordably.

IRL, It has to do with the propeller tips exceeding the speed of sound apparently they cannot generate thrust when doing so.

[Wolf72]

IRL ...

that makes sense,

but how 'bout some B(attle)T(ech)L(ife) though? ...   :P