Realistic missile acceleration

[bromdenlong]

(Note: I am only familiar with CT.)

Is anyone else really bugged that missiles can't accelerate any faster than ships? There are no squishy biological types on board, and no need for gravitics to protect them from high acceleration.

Do any of you use more realistic missile accelerations, say 10G - 60G, or even 100 - 600G? If so, how does it affect combat for you, in LBB2, HG, Mayday, etc?

I do intend to game it out soon, but it isn't convenient just now.

If anyone is thinking that 100 - 600G is much too high, well, I'm not sure that it is. I saw a couple of Sprint ABM test launches when I was a kid, and I couldn't even begin to follow them with the naked eye. I might as well have tried to follow a .22-250 bullet coming out of a rifle. A poster in a previous thread wrote that current chemical rockets can reach 300G, and I am inclined to believe it.

Also, do later versions of Traveller have higher acceleration ratings for missiles?

 

[HG_B]

(Note: I am only familiar with CT.)

Get Mongoose Traveller.

 

[BlackBat242]

Get Mongoose Traveller.

WHY?

He asks a question about a specific rule-set, and your automatic, one-liner response is for him to shell out a lot of money on a different version.

If you have no knowledge of the version he is asking about, stay out of the conversation.

Otherwise, try to be helpful.

 

[The Oz]

I've always ignored the "official" missile accelerations. Since I never fought out any RPG battles with any maps or counters, it didn't matter what missile accelerations were. They were fast enough to have missiles catch ships after one (or two, at most) turns of flight, and that was enough for me and my gamers.

I suppose you could use STRIKER to build either grav vehicles or drone missiles and see what kind of accel you could get. The STRIKER acceleration table stops at 7Gs, but you could always extrapolate.

 

[Captain Midnight]

Also, do later versions of Traveller have higher acceleration ratings for missiles?

I can only really speak for GURPS Traveller, which has some fervent proponents and some equally fervent detractors. In that system, the maximum acceleration depends on the TL of the missile -- GTL 12 (equivalent to TTL 15) has a max acceleration of 10G, and if you get to GTL 13 (Darrians, or some GM fiat), you can get 55G. The "three turns at maximum acceleration" rule remains, but it's phrased as "you have (3 * max accel) in G-rounds of acceleration available)", so you can stretch it out if you need to; sensor ranges start coming into play then.

In practice, GT missile fights tend to play out like torpedo fights in a naval war game -- you can chase someone with the missile, and while he might see it coming, he's got to have a serious velocity differential to get away. It's interesting to me to see how people react to "vampires inbound" -- people whose background is from something different than whatever rule set you're using may have radically different reactions.

 

[HG_B]

If you have no knowledge of the version he is asking about, stay out of the conversation.

He asked for a later version with rules on higher Gs. I gave it to him.

Back off!

 

[aramis]

The snarking back and forth stops, gents.

One-liner "buy X" posts are generally unhelpful; one should explain the reasoning behind them.

 

[aramis]

Some semi-random thoughs in re the OP...

25-30G's transient g's is as much as current circuitry handles... past that the wiring gets unreliable, hardening can more than double that on a specific axis, but.... (Mind you, 30 G's is 294m/s/s or so... or 1058kph/s...)

Oh, and the AIM-9 has 20G's, and a total delta-V of 100G-seconds, is roughly 2.8m x0.127m diameter, and masses 86kg...

Thing is, in space combat, it's the total vector changes that matter, and a 2 seconds burn art 30G is far ess useful than 20s at 3G, unless the target is withing 2 sec burn range for the 30G... And the increased mass of a higher thrust engine reduces total delta-V a good bit...

If your initial vector change is more than the distance to target, you can legitimately direct fire those missiles; if not, then you stll have to account for missile maneuver.

If your 50+G missilies are having muti-turn endurace in CT space combat rounds, it's gonna snap the disbelief suspenders for many, simply because the exhaust velocities start to get dangerously high in order to keep the fuel volumes low enough to fit insinde the mass limit; this the begs the question of the poer source accellerating that fuel to that velocity out...

if you want to build realistic missiles, FF&S, or the non-traveller 3G3 + CORPS VDS, or the non-traveller EABA are good tools to do so; MT could be used, but really it's not designed for things that small... (Sidewinders are 0.04 Kl.. one could use the MT-HT drives with CT Bk 8 chassis and Striker/MT HE/HEAP warheads up to 20cm...)

 

[JustinInOz]

You are not the lone ranger in thinking that the misslile 6G limit is not sensible. I have always thought that it does not make much sense. I think that it is an artifact of the traveller board games. Not 100% sure there.

It could be a handwave, just like the reactionless maneuver drives. Maybe the reactionless drives can't produce more than 6G accelleration? Just like the jump drives can't go further than 6 parsecs. A lot of 6's keep showing up here. Hmm . . . .

I think to make it work, you have to do a bit of maths. If you are going to give them realistic accelerations, you have to give them realistic burn times. They accellerate because they are throwing stff out the back. So they can only get those enviable accellerations for a limited time.

The ships they are chasing while they don't accellerate nearly as fast can keep doing it all day and into next week. This is where the 15 minute turns and thousands of kilometre distances of Traveller battles come into play.

If you want to "do this right" I would be happy to work with you on the maths. If you are just looking for fellow travellers on the "missiles dont have realistic accelerations kick" then you have come to the right place.

 

[atpollard]

The HG MD progression of 1G=2%, 2G=5%, 3G=8%, 4G=11%, 5G=14%, 6G=17% can easily be extended to 7G=20%, 8G=23%, 9G=26%, 10G=29%, 11G=32%, 12G=35%, 13G=38%, 14G=41%, 15G=44%, 16G=47%, 17G=50% ... topping out at 33G=98%.
Personally, I would go with about 12G acceleration for missiles so that even if the target immediately fled at 6G, the missile could overtake it at 6G.

Using the Magic MD technology avoids range issues, just requiring turns of power to keep it running. If one wants to pursue reaction drives, then reaction mass will require 80%-90% of the missile volume and you will either be limited to low acceleration (ion drives) or short burn duration (chemical drives).

FWIW, 300G acceleration will require the thrust to be 300 times the mass of the missile - requiring VERY high thrusts (heat issues) or VERY light missiles (expensive materials).

 

[Colin]

Special Supplement 3 has extensive rules for handling missiles in Classic Traveller. While it doesn't provide any examples of greater than 6G, the rules could easily design a missile of greater acceleration.

All chemical rockets too.

 

[vitalis6969]

I know this is just a handwave and all, but the longest any missile takes in our games to reach the target is the following round. Close range, it hits at the end of the round it was fired in.

Flow of story and action to us is far more important than any mechanics.

-V

 

[mike wightman]

Don't try to equate modern air to air or air to surface missiles with Traveller space to space missiles.
As Aramis mentioned ship to ship missiles in Traveller have to be capable of minutes to hours of continuous thrust to match vectors with a target.

I always think of missiles as very small ships rather than chemically propelled, so however the maneuver drive works that's the tech the missile needs - SS3 just confuses the issue IMHO since chemically fueled missiles could not possible have the drive performance those rules present...

unless...

IMTU the maneuver drive on a ship uses the magic of gravitic technology to reduce the inertial mass of ship to make the relatively small thrust of the plasma drive (IMTU that's what the maneuver drive uses, not thruster plates) or a fusion rocket to produce the sustained multi-g acceleration they are capable of.

For missiles I imagine much the same inertial mass reduction system could be used with a chemically fueled rocket, but that the acceleration is therefore limited to the inertial mass reduction possible - max of allowing 6g.

Think of it this way, if a missile can break the 6g limit why can't a military ship be fitted with drives that also allow faster acceleration rating? Hence my need for a handwave that limits the acceleration.

 

[BlackBat242]

You know... that makes sense.

It also (in a round-about way) explains the difference between B2 and B5 maneuver drives.

B2 requires 10PN tons fuel for power plant & maneuver drive fuel, where HG only requires 1PN tons fuel (yes, B5 tends to require higher PNs, but you still end up with less than 1/3 of the PP/M fuel of an otherwise identical B2 design).

B2 seems more appropriate for a "inertia dampened reaction thruster" and B5 seems to fully incorporate the "grav thruster plates" model.


Hmmmm... I'll have to think about that.

 

[aramis]

Actually, BB, the larger ships wind up with LOWER fuel requirements under Bk2

At 1000Td, PP6 is 60 Td either weay... at 2000Td, Bk2 is still 60Td, but B5 is 120Td PP fuel...

 

[saundby]

25-30G's transient g's is as much as current circuitry handles... past that the wiring gets unreliable, hardening can more than double that on a specific axis, but.... (Mind you, 30 G's is 294m/s/s or so... or 1058kph/s...)

Oh, and the AIM-9 has 20G's, and a total delta-V of 100G-seconds, is roughly 2.8m x0.127m diameter, and masses 86kg...

Actually, current circuitry can go way beyond this. There are some strict mechanical design rules, and semiconductors are specially packaged (we usually buy dice and do it ourselves.) But I've worked on systems that operate under much higher g-loads for about 30 years now. Tank shells, gel-prop missiles, missile interceptor KVs, etc.

OTOH, Sidewinder, Hawk, AMRAAM, Maverick...they're pussycats.

How this relates to Traveller tech is up to the ref.

 

[aramis]

As I said, hardening. I've some friends who worked on similar projects. There's a DARPA paper from about 1995 that discusses the difficulty with guided warheads on 5" arty... the 200+G's acceleration of some rounds being routinely fatal to the electronics being the big issue. It requires very special techniques, and those were hardened for high transient G's.

As long as the accelleration is smooth, most soldered stuff can easily handle 10-12 G's smothly applied G's. But transient G-loading is gonna be hell on wiring (and always is)... and given that Traveller missiles in the late 3I are, canonically, mix-n-match parts... that's either contacts or wires. In either case, a significant point for failure.

There is also the vibration issue... it's doable, it's not "off the shelf" tech. It might be in Traveller, but somehow, I doubt it. The physics of the delta V issue make it a non-issue.

 

[far-trader]

But transient G-loading is gonna be hell on wiring (and always is)... and given that Traveller missiles in the late 3I are, canonically, mix-n-match parts... that's either contacts or wires. In either case, a significant point for failure.

What about beamed optical or wireless?

 

[aramis]

What about beamed optical or wireless?

Wireless can be jammed; optical has the same issues with vibration as wired, but not the transient G-load.

 

[nyrath]

As long as the accelleration is smooth, most soldered stuff can easily handle 10-12 G's smothly applied G's. But transient G-loading is gonna be hell on wiring (and always is)... and given that Traveller missiles in the late 3I are, canonically, mix-n-match parts... that's either contacts or wires. In either case, a significant point for failure.

Agreed. I ran across this when somebody was explaining why using fiber optic control cables (to harden the missile or ship against EMP) created new problems.

Fiber optic cables are immune to EMP, unfortunately they are not shock tolerant. Specifically they have poor shear tolerance. Fiber can withstand a certain amount of flex, but it's resistance to "instantaneous flex" (like you'd see with a conventional missile hit) is not good. Ordinary twisted pair wires will stretch with the displacement from the explosion (assuming a hit close enough to warp the local supports but far enough not to directly break the cables) but are vulnerable to EMP. A sharp strike, bend or flex to fiber optic cable will shatter the individual strands across the grain, and destroy the cable.