Frag gernades in Zero-G

[Woas]

Lets say some characters are engaged in combat in Zero-G. One of them busts out a frag 'nade. On page 101 is states that the blast radius is 3/6/9 meters. In Zero-G would this be near limitless (until the fragments hit something)? So for example in a huge cargo bay (say 50 meters measuring length, width and height) or other such large room with a Zero-G environment, throw a 'nade in the middle and it will eventually 'touch' the whole room.
Or do you think that after the 9m distance is reached the fragmentations have become diluted in space (although they would still be traveling very fast) to not warrant much danger? Or perhaps a middle ground and say, double or triple the blast radius just as an off the top of my head number as the 'effective' radius?

 

[Strangelove]

At 10 meters from the center the field density would be 1/8 of the density at 5 meters. So while you are right that the fragments would eventually hit the walls they would do so at such a low concentration that it would be a 1 in a thousand chance to actually be hit with a piece if you were standing there.

A bigger concern would if the room is pressurized or a vacuum. In a vacuum the gas expelled from a grenade would not be a problem because it has the whole room to fill. If the room was already pressurized then the effect could be quite messy unless the blast could penetrate the room to allow the pressure to escape. I would have to know what type of explosive is in the grenade to do the math and see how many psi of overpressure you'd experience. Also consider the possibility that if the pressure seals of the room held up to the pressure wave then all the breathable atmosphere could be burned up, including what's in the occupants lungs.

All things considered, the fragments are likely the least of your worries in a pressure sealed room at zero gee.

 

[BP]

Beside gravity - air pressure exerts force - so no to 'near limitless' unless the environ is near vacuum...

Interesting question from a rules standpoint... and the 'diluted' effect should definitely be factored in. Perhaps expanded range for ballistic style kinetic weapons needs to take this into account.

Also the fact that this may make the characters vulnerable as well...

Hope they have Zero-G skill when busting out those 'nades... :twisted:

[Strangelove beat me to it and made some better points... though overpressure from a fragmentation grenade probably won't increase the effective casualty radius and no extra advantage due to Zero-G - not to mention low pressure/vacuum]

 

[Dave Chase]

Riccohet (bouncing off the walls, structures)
The bang, concussion of the grenade
And the surprise and fear that a grenade can cause

These are some other considerations besides those good points already made.

Dave Chase

 

[alex_greene]

It would cause damage twice. First time from the expanding blast front; the second time, from the repercussive "echo" of the pressure wave reflecting back from all the walls.

 

[EDG]

I'm not sure what a normal frag grenade would do in zero g vacuum, would it even explode? If it did though, it'd be pretty nasty - all the fragments would fly out at their initial velocity and fill the room, then bounce off the walls, and they'd keep bouncing until the ricochets and collisions with other fragments sapped their kinetic energy. I think it'd take a long time for that to happen.

 

[Strangelove]

I'm not sure what a normal frag grenade would do in zero g vacuum, would it even explode? If it did though, it'd be pretty nasty - all the fragments would fly out at their initial velocity and fill the room, then bounce off the walls, and they'd keep bouncing until the ricochets and collisions with other fragments sapped their kinetic energy. I think it'd take a long time for that to happen.

Well usually the oxidizer is already bound into the chemical make-up of the explosive so it wouldn't require any external oxygen for combustion. As long as the detonator functioned the explosives would work. For example:

A common hand grenade makeup is Composition "B" [60%RDX and 40%TNT] inside a steel shell with a mechanical detonator that when activated usually detonates a PETN charge via friction.

PETN [C5-H8-N4-O12] is a very unstable explosive that is usually only used as an ignition source.

RDX [C3-H6-N6-O6] is a very stable explosive but it will sublimate (or pass from solid to gas without a liquid transformation) in a vacuum. This would mean the grenade shell would need to be sealed or you would end up gas. It also has trouble below -4C remaining stable.

TNT [C7-H5-N3-O6] the cheaper part of the mixture that is ultra-stable and helps with the "plasticity" of the mixture. It won't absorb or dissolve in water which makes a nice sealing agent for other explosives that will.

As you can see in each of the chemical compositions above the oxidizer is already present in the mixture and will generate a fireball even in a vacuum. The funny thing is in normal atmosphere the heat of blast is quickly diluted by the rest of the atmosphere through convection and conduction. In a vacuum it only loses energy through radiation which is much slower and basically lets the blast sphere expand until the density is so low that there is sufficient surface area to radiate the heat from the reaction.

 

[Sevya]

It would cause damage twice. First time from the expanding blast front; the second time, from the repercussive "echo" of the pressure wave reflecting back from all the walls.

Doesn't this happen anyway? A fragmentation grenade's primary damage is caused by the fragments. The explosion just accelerates them. However, the explosion can still cause damage on its own.

Sevya

 

[alex_greene]

It would cause damage twice. First time from the expanding blast front; the second time, from the repercussive "echo" of the pressure wave reflecting back from all the walls.

Doesn't this happen anyway? A fragmentation grenade's primary damage is caused by the fragments. The explosion just accelerates them. However, the explosion can still cause damage on its own.

Sevya

It's the pressure waves echoing from the walls. The combination of pressure inside and out is sometimes enough to liquefy the organs of victims of blasts.

 

[BP]

The use of a fragmentation grenade in Zero-G vacuum might have more effect as a distraction than anything...

Since adversaries are likely in some kind of space suit - damage is likely to be limited as suits have to be able to handle high kinetic energy impacts anyway. (If they are not - well a grenade seems kinda melodramatic unless they are an adapted alien :roll: )

And throwing a grenade with any accuracy should require some degree of Zero-G skill (bounce back from the over enthusiastic lobbing could be a real pain ).

The creative character might turn the grenade into a sticky bomb (being very careful with the sticky).

Of course, the issue of whether the grenade would detonate - or worse, pre-detonate! - should probably be accounted for *(assumes TL of grenade does not automatically make vacuum hardened devices). Explosive out gassing and sublimation (as pointed out by Strangelove) could definitely encourage a Referee to apply some DMs here.

(A long time ago I went on a high-tech binge which included an EMP grenade for use in space combat...)

 

[Klaus Kipling]

In terms of game mechanics, there would probably be little difference.

In a confined space, ricochet would be just as prevalent in zero G and vacuum as pressurised and gravitated.

Only difference in vac, blast would be not as effective, but at those ranges, in terms of mechanical damage, it probably hardly matters.

 

[atpollard]

Traditionally, interior walls are as soft as the interior walls in a typical home or office. the fragments will prnetrate and not bounce off the walls.

Engineering would be an exception where heavy bulkheads are the norm.

Warships would be compartmentalized into large sections (per MgT rules)so it should bounce off some walls and pierce others.

 

[BP]

The attentive Referee should also have fun with high pressure piping, duct work and combustibles.

 

[lastbesthope]

In a confined space, ricochet would be just as prevalent in zero G and vacuum as pressurised and gravitated.

No, in zero G vacuum, there is no gravity to alter the direction of shrapnel, and no air resistance to slow it, increasing the likelihood of ricochet, and the effectiveness. The thing most affecting ricochet apart from atmosphere and grav is contact surface and angle.

LBH

 

[Infojunky]

It would cause damage twice. First time from the expanding blast front; the second time, from the repercussive "echo" of the pressure wave reflecting back from all the walls.

That really depends on the size of the space it goes off in. Yes, there would be "extra" effect from the detonation, but a lot of that is going to depend on the topology of the location. In general the smaller the enclosed space the more effect.

As a another point to be considered Fragmentation grenades have relatively small bursting charges, as the fragmentation shell is the primary wounding vector, not the explosive charge.

 

[Infojunky]

Engineering would be an exception where heavy bulkheads are the norm.

Engineering spaces tend to have sound damping material on the exterior walls of the space, or at least in current surface ships.

Couple that with a lower concern about exposed angle iron many engineering spaces are filled with lots of loverly shot traps.