Kinetic and Thermobaric Munitions

[BadEnoughDudeRescueRonny]

It seriously doesn't get any better than a discussion about the physics of a conceptual weapon  ;D.

AmmoTech90, is there any way to determine the terminal effects of a projectile besides the properties of whatever it hits? I agree that using joules to measure the force doesn't really describe anything in terms of effects and that's what I had the biggest issue with. It just seemed to me to be a number without any real meaning, which is why I tried converting it to explosive force values to try to make a guess as to the damage a THOR projectile could inflict.

Can you ever gauge a projectile's terminal effects based purely upon its kinetic energy value?

 

[GnyHwy]

Perhaps think of it in terms of how far it can penetrate cement or steel.  I recall an equation similar to the KE formula, but the length of the projectile gets multipled into it as well.

I'll have look for it tomorrow. 

 

[GnyHwy]

Found it.

For hyper velocity greater than 1200m/s. (Mach 3.5)

Penetration (P)=Length (L) x sqrt(density of penetrator(Dp)/density of target (Dt). 

P=L x sqrt(Dp/Dt).

Simply put, the length has alot to do with it but once the length to width ratio is greater than 7:1, it must be fin stabilized.

Not sure how that would be scaled up for higher machs in the teens.  It may not even matter.

 

[cupper]

Found this which goes into similar concepts while using the example of an asteroid colliding with earth.

http://muller.lbl.gov/teaching/Physics10/old%20physics%2010/chapters%20(old)/1-Explosions.htm

/RANT
Also, I hate to pick nits, but can y'all stop using the word cement, when you mean concrete. I apologize for making an issue of it, but as a structural engineer it drives me around the bend when people call concrete cement. Point of fact, cement is a constituent of concrete, along with sand, crushed rock, water, and other chemicals.
/rant.

 

[GnyHwy]

This reminds me of the bunker busters that were used in the first gulf war.  They were tank barrels with guidance systems attached.

UFI.  The time from conceiving the requirement to the time that the first one was dropped in operations was 3 weeks.  Kinda beats our procurement system.

 

[vonGarvin]

This reminds me of the bunker busters that were used in the first gulf war.

Were the bunkers cement bunkers?


>


(Apologies, cupper)

 

[Franko]

This reminds me of the bunker busters that were used in the first gulf war.  They were tank barrels with guidance systems attached.

UFI.  The time from conceiving the requirement to the time that the first one was dropped in operations was 3 weeks.  Kinda beats our procurement system.

Try to keep some perspective here.

When you have a defense budget of almost $400 billion and a President that wants someone dead, you get shit like that when you want it.

Regards

 

[Petard]

This reminds me of the bunker busters that were used in the first gulf war.  They were tank barrels with guidance systems attached.

UFI.  The time from conceiving the requirement to the time that the first one was dropped in operations was 3 weeks.  Kinda beats our procurement system.

A position awaits you on the ATWO, and an empty chair in DLR 2

 

[GnyHwy]

My procurement comment was meant with humour.  I have a fair grasp of what the procurement process entails and can appreciate the efforts that are involved. 

Some excellent examples of Canadian procurement would be the 777s and Leo 2s;  some of the pers kit that people hate wearing were excellent choices as well. 

Just to be clear, none of the above is sarcasm.

Cheers.

 

[cupper]

Were the bunkers cement bunkers?

Only if that's what they stored in it. :rofl:

(Apologies, cupper)

 

[GnyHwy]

A position awaits you on the ATWO, and an empty chair in DLR 2

Ok, sounds good.  When should I expect my message?  ;D

 

[a_majoor]

From Wikipedia (yes, I know....)

http://en.wikipedia.org/wiki/Kinetic_bombardment

Project Thor

Project Thor is an idea for a weapons system that launches kinetic projectiles from Earth orbit to damage targets on the ground. Jerry Pournelle originated the concept while working in operations research at Boeing in the 1950s before becoming a science-fiction writer.[1][2]

The most described system is "an orbiting tungsten telephone pole with small fins and a computer in the back for guidance". The weapon can be down-scaled, an orbiting "crowbar" rather than a pole.[citation needed] The system described in the 2003 United States Air Force (USAF) report was that of 20-foot-long (6.1 m), 1-foot-diameter (0.30 m) tungsten rods, that are satellite controlled, and have global strike capability, with impact speeds of Mach 10, and strike 25-foot accuracy.[3][4][5]

The time between deorbiting and impact would only be a few minutes, and depending on the orbits and positions in the orbits, the system would have a world-wide range.[citation needed] There is no requirement to deploy missiles, aircraft or other vehicles. Although the SALT II (1979) prohibited the deployment of orbital weapons of mass destruction, it did not prohibit the deployment of conventional weapons. The system is not prohibited by either the Outer Space Treaty nor the Anti-Ballistic Missile Treaty.[4][6]

The idea is that the weapon would inflict damage because it moves at orbital velocities, at least 9 kilometers per second. Smaller weapons can deliver measured amounts of energy as small as a 225 kg conventional bomb.[citation needed] Some systems are quoted as having the yield of a small tactical nuclear bomb.[5] These designs are envisioned as the ultimate bunker busters.[4][7]

The highly elongated shape and high density are to enhance sectional density and therefore minimize kinetic energy loss due to air friction and maximize penetration of hard or buried targets. The larger device is expected to be quite good at penetrating deeply buried bunkers and other command and control targets.[8] The smaller "crowbar" size might be employed for anti-armor, anti-aircraft, anti-satellite and possibly anti-personnel use.[citation needed]

The weapon would be very hard to defend against. It has a very high closing velocity and a small radar cross-section. Launch is difficult to detect. Any infra-red launch signature occurs in orbit, at no fixed position. The infra-red launch signature also has a small magnitude compared to a ballistic missile launch. One drawback of the system is that the weapon's sensors would almost certainly be blind during atmospheric reentry due to the plasma sheath that would develop ahead of it, so a mobile target could be difficult to hit if it performed any unexpected maneuvering.[citation needed] The system would also have to cope with atmospheric heating from re-entry, which could melt the weapon.[9]

While the larger version might be individually launched, the smaller versions would be launched from "pods" or "carriers" that contained several missiles.[citation needed]

The phrase "Rods from God" is also used to describe the same concept.[10] A USAF report called them "hypervelocity rod bundles".[11]

1 ^ Jonathan Shainin (10 December 2006). "Rods From God". New York Times. http://www.nytimes.com/2006/12/10/magazine/10section3a.t-9.html.
2 ^ Jerry Pournelle (6 March 2006). "Chaos Manor Mail". The View from Chaos Manor. http://www.jerrypournelle.com/archives2/archives2mail/mail404.html#Thor.
3 ^ Giuseppe Anzera (18 August 2005). "Star Wars: Empires strike back". Asia Times. http://www.atimes.com/atimes/Front_Page/GH18Aa01.html. Retrieved 25 May 2010.
4 ^ a b c John Arquilla (12 March 2006). "RODS FROM GOD / Imagine a bundle of telephone poles hurtling through space at 7,000 mph". San Francisco Chronicle. http://articles.sfgate.com/2006-03-12/opinion/17284306_1_rods-nuclear-weapons-outer-space-treaty. Retrieved 25 May 2010.
5 ^ a b Julian Borger (19 May 2005). "Bush likely to back weapons in space". The Guardian. http://www.guardian.co.uk/science/2005/may/19/spaceexploration.usnews. Retrieved 25 May 2010.
6 ^ Paul Reynolds (23 January 2007). "China's space challenge to the US". BBC News. http://news.bbc.co.uk/2/hi/asia-pacific/6290525.stm. Retrieved 25 May 2010.
7 ^ Jack Kelly (28 July 2003). "Rods from God". Pittsburgh Post-Gazette. p. A5.
8 ^ History Television, 'The Universe', season 4, episode 8, "Space Wars"; referring to rod from God
9 ^ Noah Shachtman (20 February 2004). "Pentagon Preps for War in Space". Wired. http://www.wired.com/science/discoveries/news/2004/02/62358?currentPage=2. Retrieved 25 May 2010.
10 ^ Michael Goldfarb (8 June 2005). "The Rods from God". The Weekly Standard. http://www.weeklystandard.com/Content/Public/Articles/000/000/005/700oklkt.asp. Retrieved 28 May 2010.
11 ^ Eric Adams (June 2004). "Rods from God". Popular Science. http://www.popsci.com/scitech/article/2004-06/rods-god. Retrieved May 2010.

(a 100kg projectile travelling at 7km/s would release about 2.5 gigajoules of kinetic energy, a tonne of TNT releases about 4.2 gigajoules)

The only comperable weapon would be hypervelocity railguns, such as the 42 Megajoule weapon being developed by the USN. Similar terminal effects can be calculated, including the idea of projectiles descending at high angles from near space trajectories...

 

[GnyHwy]

I just did it with the size of a real telephone pole.  I used 12m with a radius of 0.2m =  1.5 Sq metres ish.  With pure tungsten, that brings it in at about 18000 kg. 

This would produce 860,000,000,000 joules  or 860 gigjoules.

Wow, this is geeky.

Also, I did the penetration calculation with a 12m pole.  I couldn't find the density of cement.. er I mean concrete, so I used pure iron.

A 12m tungsten rod will pentrate 19m of pure iron.  I know 19m may not seem like a lot, but it is iron and chances are, the guys behind the iron would probably be a little unhappy.

 

[cupper]

FYI, concrete has a density of about 150 lb/cuft or 2400 kg / m3.

 

[a_majoor]

This reminds me of the bunker busters that were used in the first gulf war.  They were tank barrels with guidance systems attached.

UFI.  The time from conceiving the requirement to the time that the first one was dropped in operations was 3 weeks.  Kinda beats our procurement system.

Actually, I think they were surplus naval cannon barrels from 6" guns. Test articles were filled with concrete, and were able to penetrate test bunkers dug deep in the Nevada desert (including, I recall, ones which were made of reinforced concrete and surrounded by layers of gravel and earth to dissipate shock waves).

Regardless, this was a very fast procurement and development project, and certainly a refreshing contrast to the process that takes a decade to develop and issue a new rucksack to the troops...

 

[BadEnoughDudeRescueRonny]

I just did it with the size of a real telephone pole.  I used 12m with a radius of 0.2m =  1.5 Sq metres ish.  With pure tungsten, that brings it in at about 18000 kg. 

This would produce 860,000,000,000 joules  or 860 gigjoules.

Wow, this is geeky.

Also, I did the penetration calculation with a 12m pole.  I couldn't find the density of cement.. er I mean concrete, so I used pure iron.

A 12m tungsten rod will pentrate 19m of pure iron.  I know 19m may not seem like a lot, but it is iron and chances are, the guys behind the iron would probably be a little unhappy.

Definitely not geeky, IMO. More like pure outstanding when an Army forum is talking about the physics of experimental weapons.


I got such a kick that a thread went from discussing the differences between two types of proven existing weapons technology to the physics of technology that doesn't even exist (yet)  ;D ;D ;D.

 

[SeaKingTacco]

Actually, I think they were surplus naval cannon barrels from 6" guns. Test articles were filled with concrete, and were able to penetrate test bunkers dug deep in the Nevada desert (including, I recall, ones which were made of reinforced concrete and surrounded by layers of gravel and earth to dissipate shock waves).

Regardless, this was a very fast procurement and development project, and certainly a refreshing contrast to the process that takes a decade to develop and issue a new rucksack to the troops...

8 Inch Barrels, left over from WW2.

 

[Nfld Sapper]

FYI, concrete has a density of about 150 lb/cuft or 2400 kg / m3.

A normal weight concrete weighs 2400 kg per cubic meter or 145 lbs per cubic foot (3915 lbs per cubic yard).

The unit weight of concrete (density) varies depending on the amount and density of the aggregate, the amount of entrained air (and entrapped air), and the water and cement content.

 

[Fishbone Jones]

THIS WAS POSTED BY RETIRED AF GUY AND MOVED HERE TO THE PROPER THREAD

From Wikipedia (yes, I know....)

http://en.wikipedia.org/wiki/Kinetic_bombardment

Project Thor

Project Thor is an idea for a weapons system that launches kinetic projectiles from Earth orbit to damage targets on the ground. Jerry Pournelle originated the concept while working in operations research at Boeing in the 1950s before becoming a science-fiction writer.[1][2]

The most described system is "an orbiting tungsten telephone pole with small fins and a computer in the back for guidance". The weapon can be down-scaled, an orbiting "crowbar" rather than a pole.[citation needed] The system described in the 2003 United States Air Force (USAF) report was that of 20-foot-long (6.1 m), 1-foot-diameter (0.30 m) tungsten rods, that are satellite controlled, and have global strike capability, with impact speeds of Mach 10, and strike 25-foot accuracy.[3][4][5]

....................................... 

(a 100kg projectile travelling at 7km/s would release about 2.5 gigajoules of kinetic energy, a tonne of TNT releases about 4.2 gigajoules)

The only comperable weapon would be hypervelocity railguns, such as the 42 Megajoule weapon being developed by the USN. Similar terminal effects can be calculated, including the idea of projectiles descending at high angles from near space trajectories...

Since the projectile is being launched from outside the earth's atmosphere wouldn't there be a problem with the projectile burning-up on re-entry?

 

[cupper]

A normal weight concrete weighs 2400 kg per cubic meter or 145 lbs per cubic foot (3915 lbs per cubic yard).

The unit weight of concrete (density) varies depending on the amount and density of the aggregate, the amount of entrained air (and entrapped air), and the water and cement content.

I was quoting the generally accepted value used when doing structural calculations. My experience in the precast concrete industry has been that a "normal" concrete mix design can vary from 145 to 165 lb/cuft, particularly depending on the method of placement. I did tests of precat pipe that used a no slump dry cast mix used in a process called vibration under pressure. We took core samples along the pipe section and found that cores taken from the top end of the pipe (was cast vertically in the machine) were around 150, but one of the samples taken we got 165 lb / cuft.

We also made ballast mats to cover under water gas pipe lines which used iron ore (hematite) and steel shot as aggregate. In order to be accepted by the purchaser, the relative density needed to be 4.8 or greater (300 lb/ cuft or 4800 kg/m3 )