Flight Termination System

[Swamp1983]

I have been combing the forums and have yet to find an actual answer to this question. What is utilized in the Flight Termination System to cause the vehicles to detonate? (i.e. C4, TNT, ...) All searches I have found just point to Safe and Armed System but not what actuatly detonates the vehicle.

[Jim]

shaped charges

[Asteroza]

shaped charges

Is there a preference for point detonation shaped charges, or linear shaped charges for a zipper effect?

[eriblo]

The point of the FTS charges is not to "detonate" the vehicle, that is actually specifically to be avoided. The goal is to disable any propulsive elements and disperse any liquid propellant.

Liquid propellant tanks and at least some SRBs are "unzipped" with linear shaped charges like this: https://psemc.com/products/linear-shaped-charge/

[Jim]

shaped charges

Is there a preference for point detonation shaped charges, or linear shaped charges for a zipper effect?

Depends on the tank/motor size

[Nomadd]

 I've wondered this myself. Poking holes with high velocity charges like C-4 might not do the job very well, but that 4mm stainless is a lot tougher than people realize, and you'd need a lot of something like Comp B to retire those big tanks. Unzipping them with det cord or the like isn't as easy as it sounds.
 In other words, I don't have a clue, and people who know aren't talking.
 
 Glad I could pretend to help.

[Tomness]

I've wondered this myself. Poking holes with high velocity charges like C-4 might not do the job very well, but that 4mm stainless is a lot tougher than people realize, and you'd need a lot of something like Comp B to retire those big tanks. Unzipping them with det cord or the like isn't as essy as it sounds.
 In other words, I don't have a clue, and people who know aren't talking.
 
 Glad I could pretend to help.

I am sure the Army Corp of Engineers, Air Force and Space Force are working with SpaceX and any other party on solving these issues.

[AllenB]

Don’t feel bad. Even SpaceX and associated experts apparently got it wrong for IFT 1.

Aside: pretty amazing what’s available “off the shelf” in 2023 if you’ve got the requirement and the funds.

[Jim]

I've wondered this myself. Poking holes with high velocity charges like C-4 might not do the job very well, but that 4mm stainless is a lot tougher than people realize, and you'd need a lot of something like Comp B to retire those big tanks. Unzipping them with det cord or the like isn't as essy as it sounds.
 In other words, I don't have a clue, and people who know aren't talking.
 
 Glad I could pretend to help.

I am sure the Army Corp of Engineers, Air Force and Space Force are working with SpaceX and any other party on solving these issues.

Why would COE be involved?

[eriblo]

Don’t feel bad. Even SpaceX and associated experts apparently got it wrong for IFT 1.

Aside: pretty amazing what’s available “off the shelf” in 2023 if you’ve got the requirement and the funds.

Indeed, the explosive part of the FTS is not rocket science and this is not a particularly difficult use case (as far as we know it worked fine for IFT-1)

Just a quick search of some literature suggest that a 800 grain/ft lead/RDX LSC from the vendor I linked above could handle something like an inch of 304 SS.

[Zed_Noir]

The point of the FTS charges is not to "detonate" the vehicle, that is actually specifically to be avoided. The goal is to disable any propulsive elements and disperse any liquid propellant.

Liquid propellant tanks and at least some SRBs are "unzipped" with linear shaped charges like this: https://psemc.com/products/linear-shaped-charge/

As the size of the vehicle gets bigger, the probability of a flight termination system able to break up the vehicle without aerodynamic stresses seems iffy after Max-Q without full up testing inflight.

[Tomness]

I am sure the Army Corp of Engineers, Air Force and Space Force are working with SpaceX and any other party on solving these issues.

Why would COE be involved?

They would be great resource in structural integrity, demolition simulation, demonstration and FTS.

[Jim]

I am sure the Army Corp of Engineers, Air Force and Space Force are working with SpaceX and any other party on solving these issues.

Why would COE be involved?

They would be great resource in structural integrity, demolition simulation, demonstration and FTS.

Not really.  This isn't bridge or dam.  SpaceX would know its vehicle better and has structure experts.  COE doesn't deal with FTS or flight demolitions.  This is way out of the COE wheel house.   There are plenty of range safety experts from the Space Force and other DOD ranges.