Shrike in vacuum

[Burke]

There might be some very interesting gameplay on worlds with virtually no atmosphere. Specifically, the Shrike's rocket motor will continue to provide a force and the projectile will never reach a terminal velocity (assuming this is modeled correctly in the game).

Out of curiosity I tried to estimate the impact velocity we could see from this type of rocket, assuming it was generally similar to, say, a TOW. With similar weight, exhaust velocity, etc a Shrike rocket engaging an enemy 1km distant could probably reach an impact velocity in excess of mach 7 (2500 m/s). Compare this to the muzzle (not impact) velocity of our best APFSDS kinetic energy anti-armor rounds, which is around 1800 m/s.

The rocket wouldn't mechanically be designed to deliver the same type of pressure as a depleted uranium APFSDS or something, but it would close with the target extremely quickly, have enough KE to punch through many AFVs, and deliver high explosives on top of this.

The different atmospheres should definitely add a new and interesting element to armored combat.

[Tarquelne]

Originally posted by Burke:

[QB] There might be some very interesting gameplay on worlds with virtually no atmosphere. Specifically, the Shrike's rocket motor will continue to provide a force and the projectile will never reach a terminal velocity (assuming this is modeled correctly in the game).

Maybe more use of cannons? I seem to remember reading that air resistance is a big part of why missiles came into use in the first place, in place of projectiles. (This may have just been with regard to extremely long-range fire, though.)

More use of energy weapons/particle beams? All that messy gas out of the way...

I dunno, while you're admiring the flight of your missiles your opponent may be enjoying the impending impact on your position of his rarely-used, but oh-so-effective, zero-pressure weapons.

Besides, missiles need something to push against.

[flamingknives]

Originally posted by Tarquelne:

Besides, missiles need something to push against.

No they don't.

[Burke]

Yeah, I was mainly just commenting on an interesting feature that could occur in zero-atmosphere. Cannon rounds will certainly be effective in that situation also, but even in a best case scenario they can only impact at their muzzle velocity.

Rockets, however, will continue to eject mass, and with no air resistance conservation of momentum requires that the rocket keep accelerating indefinitely. So you could get some unreal velocities with rockets over the distances we're talking about for DropTeam, which could mean the lowly Shrike is by far the deadliest weapon on near-vacuum worlds.

[Tarquelne]

Originally posted by flamingknives:

</font><blockquote>quote:</font><hr />Originally posted by Tarquelne:

Besides, missiles need something to push against.

No they don't. </font>

[Tarquelne]

Rockets, however, will continue to eject mass, and with no air resistance conservation of momentum requires that the rocket keep accelerating indefinitely.

Given an indefinite supply of fuel, yes. And anti-matter might effectively supply that.

Ok, I understand your point now: Maximizing velocity.

Hmm... it'd be interesting to have a missile launched at a tank 1k away travel 4k up, then 4k down just so it could build up enough kenetic energy to penetrate the target's armor. I suppose that could be necessary if all that energy couldn't be delivered in a all-at-once explosive package. Seems unlikely. OTOH, maybe an obscenely high velocity is the best way to get through the target's active defenses. And a relatively slowely-accelerating missile (compared to a projectile with the same velocity at target) could probably carry a more sophisticated payload.

[YankeeDog]

Some shaky assumptions here. At least IRL, projectiles not designed for KE penetration often do not benefit from hyper velocity.

Why? Fusing is one big reason. Hollow charge warhead fuses have to detonate as soon as the tip touches the target but must detonate the charge from the base in order for the munroe effect to work properly. As a result, if the projectile hits *too* fast, the detonation impulse can't travel from the nose to the detonator at the base of the charge quickly enough, and the shape of the hollow charge ends up being deformed before detonation, reducing performance. As anybody with high school physics will tell you, the speed which the detonation impulse can travel from the nose to the base detonator is theoretically limited by the speed of light. Once you start talking about projectiles moving 1000s of m/s, that actually becomes important. . .

And why doesn't it simply work as a KE penetrator, then? Well, Hollow Charge warheads are basically a large, empty cavity at the front, with some soft metail like copper and aluminium, and then more soft high-explosive, and finally the rocket motor at the rear, which is also not made of expecially dense material. So the warhead and rocket are nowhere near as strong as the steel (or ceramic composite, or whatever) of armor plating, and against any respectable amount of armor an extremely high velocity impacts by a warhead of this type would simply result in catastrophic failure of the warhead, not of the armor.

So, at least with the current anti-armor technologies we have, a warhead is either (a) a good low velocity CE penetrator, or ( a good high-velocity KE penetrator, but not both.

Of course, all of this assumes that CE anti-armor warheads in DropTeam use a hollow charge warhead with a design fundamentally similar to current ones. It's possible that in the world of DropTeam there is some radical new warhead type that is good at both CE and KE penetrations. And even if the warheads are based on technology similar to what we have today, there's no reason why we couldn't assume that the Shrike uses a different, dense-tip KE penetrator rather than a CE warhead for zero air resistance environments.

Actually, lack of air resistance is not a prerequisite for a rocket-accelerated KE penetrator. The US military is actually has a prototype rocket-accelerated anti-armor penetrator now that supposedly goes something like Mach 5, and has pretty impressive penetration stats. And there are other, even more intersting possibilities on the horizon. Rumor has it that one of the reasons the US Military is so interested in SCRAM-jet engines is the possibility of using them to create a long-range KE penetrator with a velocity of something like Mach 10. :eek: Of course, SCRAM-jets don't work at all without an atmosphere. . .

But as noted, currently the big limitation with these kind of systems is minimum range. Even without air resistance, it takes a while for the rocket to build up enough speed to become a good KE penetrator. Hypothetically, this problem could be solved by a composite, gun-launched, rocket-accelerated KE penetrator. . .

Cheers

YD

[Tarquelne]

Originally posted by YankeeDog:

[QB] Some shaky assumptions here. At least IRL, projectiles not designed for KE penetration often do not benefit from hyper velocity.

I was assuming a KE penetrator for a super-KE weapon.

Does (did?) the real-world Shrike have a HEAT warhead? What was it, an early HARM sort of missle? (I would look it up, but I've got no internet connection. Really. )

As anybody with high school physics will tell you, the speed which the detonation impulse can travel from the nose to the base detonator is theoretically limited by the speed of light. Once you start talking about projectiles moving 1000s of m/s, that actually becomes important. . .

You mean we can't have Faster-THan-Light technology in our missile fuses? Bother.

Actually, the I do think you bring up a good point. OTOH, Some FTL techs on the battlefield could be fun. And freaky.

Of course, all of this assumes that CE anti-armor

Do we know they'll be CE at all? I guess they probably will... with the exception of nasty nano-based weapons the only thing beyond CE would be fission, fusion, or anti-matter, yes?

I was wondering if they've got enough anti-matter to fuel the vehicles if they couldn't use some in weapons.

I could easily see them thinking that the sort of containment available for weapons, especailly projectiles, not being good enough.

But for anti-armor missiles? Maybe? The missle might end up costing up the wazoo, but so does a tank. Hyper-velocity wouldn't help with damage, but it might help you score a hit.

Actually, lack of air resistance is not a prerequisite for a rocket-accelerated KE penetrator.

I was thinking the heat caused by air resistance might be a major problem. But then if you've got dropship technology you might have some very clever ideas about such things...

Hypothetically, this problem could be solved by a composite, gun-launched, rocket-accelerated KE penetrator. . .

Do you think such a system would actually be practical?

[flamingknives]

If you get something moving at 10km/s, fusing is a moot point anyway. All your penetrating energy is going to be kinetic. The jet from a shaped charge 'only' reaches 8km/s.

Speed of projectile needn't be an issue for correct fusing of a shaped charge though - 8km/s plus whatever the projectile is doing - the fuse could just as easily be proximity or some form of laser rangefinder.

[YankeeDog]

AFAIK, virtually all active missile anti-armor systems that have been designed to date use a HEAT penetrator. There might be a few that use HESH, but it suffers from basically the same problems as HEAT with extremely high speed impacts. Fundamentally, in a straight-KE collision, if the materials in the warhead are weaker (in terms of tensile strength, hardness, etc.) than the stuff the armor's made of, it's the warhead that's going to fail catastrophically on impact, not the armor. . .

Other thing to keep in mind re: fusing and all is that the explosive reaction is not instantaneous, either, and takes some time to propegate from the detonation point thoughout the charge. Not a big deal for a missile moving 5000 m/s, but for one moving 5000 m/s, this might become a factor, too -- conceivably, the front half of the explosive charge could impact the armor and scatter, before the explosive reaction reached it!

Gun launched, Rocket Accelerated projectiles are already in existence, though AFAIK they are not presently used for anti-armor, DF weapons systems. The US military has a 155mm artillery shell that uses a gun launched projectile that then has a secondary acceleration from a rocket motor. Purpose there is to extend range, but there's no reason why you couldn't do the same thing to improve a KE penetrator.

And of course, in when you talk about the distant future there's all sorts on interesting possibilities -- Initial Magnetic launch (as in a rail gun), followed by secondary rocket acceleration, etc. Gun or magnetic launch, followed by particle beam acceleration, etc.

But anyway, my initial point was: under present technology, anti-armor warheads are either CE *or* KE. KE warheads benefit from acceleration. CE warheads don't, at least in terms of improved penetration (there may still be a better hit/accuracy). Anything's possible in the future, but at least for me it's hard to come up with a good Sci-Fi justification for a warhead that would be good at both KE *and* CE penetration. Fundamentally, KE penetrators rely having a really dense piece of something they shove through the armor at very high speed. Fundamentlly, CE penetrators rely on complex fusing and design of substance to create an explosive reaction focused into the armor.

Oh, and laser rangefinder/proximity fuses. Good idea. Only problem is that active broadcast fuse systems like this work both ways -- they would also alert any active defense systems on the target that there was an inbound missile, and reveal the missile's exact bearing. This could be a serious negative in a far future combat scenario, where presumable active defense systems would be much more advanced.

Cheers,

YD

[Redcon-5]

Three point to add to Yankee Dogs post.

1)The old Sheridan (yes I cant spell) also used a gun fired guided missle. Small charge to expel it then the rocket kicks in.

2)The M830A1 HEAT round or MPAT as it is called has a Chemical warhead with proximity fuse and a small KE penetrator.

3)You could not think of a use for a dual warhead missle? Just watch the news it is all about Bunker Bustin' these days. You have a KE head with a time delay fuse and a CE charge. KE punches a hole through the renforced wall and as it reaches the other side the CE charge goes off destroying the facility.

If it just so happens that it also makes a really good AT weapon in a vacuum so be it.

Side note: a rocket in vacuum will only accelerate to the speed of its exaust gasses at the nossel. Exception being Ion motors which are throwing out electrons (i think) at near light speed. Maybe with antimatter this would be a possiblity. NASA has one Ion motor in space but it accelerates really really slow.

[flamingknives]

Originally posted by YankeeDog:

AFAIK, virtually all active missile anti-armor systems that have been designed to date use a HEAT penetrator. There might be a few that use HESH, but it suffers from basically the same problems as HEAT with extremely high speed impacts. Fundamentally, in a straight-KE collision, if the materials in the warhead are weaker (in terms of tensile strength, hardness, etc.) than the stuff the armor's made of, it's the warhead that's going to fail catastrophically on impact, not the armor. . .

Once you get up to 2+km/s, the structure of the projectile doesn't really matter that much. It's moving far too fast for anything like strength to have any effect whatsoever. Density is about the only thing that matters from a material point of view.

You could also come up with a way to set a proximity fuse-type job that works off passive emissions, by pattern recognition or somefink. Or a long, telescopic probe that gives the fuse time to function.

Of course, a finned round wouldn't work so well in a vacuum, but then the prime cause of instability will be absent too. Nonetheless, any deviation on launch would cause a fin round to rotate so that, while it would fly straight, it might end up at the target backwards or sideways.

Fin control wouldn't work either - you'd need controlling rockets like the M47 Dragon.

[Tarquelne]

Originally posted by Redcon-5:

[QB] Three point to add to Yankee Dogs post.

1)The old Sheridan (yes I cant spell) also used a gun fired guided missle. Small charge to expel it then the rocket kicks in.

Thanks guys. And, come to think of it, there are probably a lot of tricks possible in the DropTeam universe involving such things.

[SSgt Viljuri]

Redcon-5 wrote:

NASA has one Ion motor in space but it accelerates really really slow.

Yes, although Nasa's Deep Space 1 was retired in 2001.

ESA's Smart-1 with its Ion (or rather plasma) engine is still operational and orbiting Moon. The craft is due to crash on the Moon in august 2006.

[Caseck]

Note that a HEAT type warhead is not considered a KINETIC ENERGY PENETRATOR... Those are apples and oranges, excepting the "Self-Forging Fragment" type of warhead, which is really just a flying "Platter Charge" which detonates at a preset radio/radar/laser fused distance. (Read SADARM [seek and Destroy Anti Armor Munition]or whatever that system evolved to in it's current incarnation. It's fielded under a different name, but I can't recall what it's called.)

Ablative armour would probably be the only defense against such weapons. You'd need greatly increased VOLUME of armour to offset the velocity. Bigger bulkier armour, not necessarily heavier. Again, NASA has experimented with such types of armour to defend against micrometeorites, which have similar characteristics to such extreme velocity weapons.

Comparing SHRIKE to an ATGM is not a good analogy, since SHRIKE is a mach 2+ missile, and TOW is subsonic. Totally different proportions of fuel and warhead as well. Just don't do it if you're crunching numbers, it'll mess with 'em.

[RSColonel_131st]

Google for the LOSAT program. That's the kinetic penetration missile mentioned above, and it seems far better at what it does than any hollow-charge warhead.

[flamingknives]

Again, NASA has experimented with such types of armour to defend against micrometeorites, which have similar characteristics to such extreme velocity weapons.

Yes, it's called a whipple shield, after Fred Whipple.

[John D Salt]

Originally posted by Caseck:

Note that a HEAT type warhead is not considered a KINETIC ENERGY PENETRATOR... Those are apples and oranges, excepting the "Self-Forging Fragment" type of warhead, which is really just a flying "Platter Charge" which detonates at a preset radio/radar/laser fused distance.

Certainly, you're right that it's not customary to designate HEAT warheads as KE penetrators. Nonetheless, it's kinetic energy that HEAT penetrators use to punch through armour. "Apples and oranges" isn't really true.

Below impact velocities of about 1km/sec, you can treat KE projectiles as being of constant mass.

Above that, they are likely to lose mass at the front of the projectile as penetration proceeds.

An explosively-formed penetrator (EFP) may have completed projectile formation before striking the armnour, and in that case will behave in much the same way as a classic monobloc penetrator, neither losing nor gaining mass during penetration.

HEAT is really a subclass of explosively-formed penetrators, with the additional complications that the penetrating jet is probably elongating in the course of formation. Depending on the standoff distance, the penetrator may still be forming, and thus adding mass at the penetrator base, as penetration proceeds.

It is quite possible, with current techniques, to design a warhead that forms two distinct penetrators from the same charge and liner; the first, a thin elongating "penetrator jet", and the second, a stubby non-elongating "cleaner" jet, which will widen the penetration made by the first.

This is in addition to the design of tandem or triple "follow-through" warheads, and such niceties as top-attack.

I expect by the timeframe of "Drop Team" things will have developed into a crazy mass of options for multi-axis, multi-stage warheads to defeat various exotic active armours and defensive aids suites, and high projectile velocity will be worth having if only to minimise the engagement time the target's defensive aids suite has to acquire, classify and neutralise the incoming projectile.

All the best,

John.

[Floydii]

Is it not possible that the propulsion system of these missles (with Heat warheads) using a inifinitely small reserve of Antimatter as the fuel, could be calibirated to take into account Vaccum conditions. Delivering alot less thrust so as to leave the warhead within the correct parameters to detonate properly? However, they would still travel somewhat faster than in atmosphere.

On the other hand, it would be cool to load out your units with ultra(hyper?)-sonic KE missile 'darts' which are only truly effective in Vaccum environments. In addition, 'overpenetration' could be modelled ala 'Steelbeasts', where the round may pass clean through light skinned vehicles, which just keep on rolling since it missed the critical systems.