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Author Topic: Kind of lore/headcanon question. - How fast are ASF's?  (Read 6054 times)

marauder648

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Kind of lore/headcanon question. - How fast are ASF's?
« on: 07 January 2019, 08:12:25 »
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? 
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Elmoth

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #1 on: 07 January 2019, 08:18:46 »
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.

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #2 on: 07 January 2019, 14:26:07 »
Velocity 7 on the Low Altitude map is roughly Mach 1. That should give you a benchmark to work from.
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Elmoth

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #3 on: 07 January 2019, 16:39:49 »
Wow. Conventional fighters in BT (alpha strike) do not reach Mach 1?

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #4 on: 07 January 2019, 18:24:08 »
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.
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Elmoth

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #5 on: 07 January 2019, 18:33:23 »
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.
« Last Edit: 07 January 2019, 18:35:53 by Elmoth »

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #6 on: 07 January 2019, 18:52:39 »
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.
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Tai Dai Cultist

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #7 on: 07 January 2019, 18:59:59 »
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.

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #8 on: 07 January 2019, 20:52:41 »
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.
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Tai Dai Cultist

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #9 on: 07 January 2019, 21:06:44 »
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

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #10 on: 07 January 2019, 21:10:27 »
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.

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #11 on: 07 January 2019, 21:25:01 »
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

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #12 on: 07 January 2019, 21:59:46 »
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

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #13 on: 07 January 2019, 22:02:33 »
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.
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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #14 on: 07 January 2019, 22:20:38 »
They may simply have not built an ASF slow enough...yet.

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

50% of velocity.

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I am Belch II

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #15 on: 08 January 2019, 16:51:40 »
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.
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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #16 on: 08 January 2019, 18:04:26 »
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.

Quote
  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.

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #17 on: 08 January 2019, 19:28:01 »
Cray, thanks for the VERY detailed explanation!  :thumbsup:

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #18 on: 08 January 2019, 19:41:41 »
Cray, thanks for the VERY detailed explanation!  :thumbsup:

You made the example of powered fighter descent, right?
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**"Well, the first class name [for pocket WarShips]: 'Ship with delusions of grandeur that is going to evaporate 3.1 seconds after coming into NPPC range' tended to cause morale problems...." --Korzon77
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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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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #19 on: 08 January 2019, 19:47:10 »
I think that was Weirdo, but thanks for thinking of me!  :)

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #20 on: 08 January 2019, 19:59:49 »
Yeah, I've made detailed powered descents plenty of times. Survived all the ones that happened in real life! :thumbsup:
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Daryk

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #21 on: 08 January 2019, 20:04:17 »
Aren't all commercial airliner landings technically "powered descents"?

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #22 on: 08 January 2019, 20:16:12 »
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
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**"Well, the first class name [for pocket WarShips]: 'Ship with delusions of grandeur that is going to evaporate 3.1 seconds after coming into NPPC range' tended to cause morale problems...." --Korzon77
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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.

marauder648

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #23 on: 09 January 2019, 06:57:39 »
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?
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Nebfer

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #24 on: 09 January 2019, 23:37:41 »
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

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #25 on: 10 January 2019, 06:50:11 »
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.
Mike Miller, Materials Engineer

**"A man walks down the street in that hat, people know he's not afraid of anything." --Wash, Firefly.
**"Well, the first class name [for pocket WarShips]: 'Ship with delusions of grandeur that is going to evaporate 3.1 seconds after coming into NPPC range' tended to cause morale problems...." --Korzon77
**"Peace is that brief glorious moment in history when everybody stands around reloading." --Thomas Jefferson, or not

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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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #26 on: 10 January 2019, 11:39:52 »
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.)
« Last Edit: 10 January 2019, 12:08:05 by The_Caveman »
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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #27 on: 10 January 2019, 22:11:40 »
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.
« Last Edit: 10 January 2019, 22:13:44 by Nebfer »

Wolf72

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #28 on: 10 January 2019, 22:14:03 »
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.
War does not determine who is right, only who is left. -- said no Clanner ... ever!

The_Caveman

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Re: Kind of lore/headcanon question. - How fast are ASF's?
« Reply #29 on: 11 January 2019, 01:18:31 »
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.
Half the fun of BattleTech is the mental gymnastics required to scientifically rationalize design choices made decades ago entirely based on the Rule of Cool.

The other half is a first-turn AC/2 shot TAC to your gyro that causes your Atlas to fall and smash its own cockpit... wait, I said fun didn't I?