I was wondering when this was going to happen...

[kgbsquirrel]

No rocket assist for the MOP, gravity only.  Rocket during impact wouldn't buy you much, any conceivable rocket is far too low of thrust to really do much during the 30-50ms of the penetration event.  ...

I was thinking more of a very fast burn rocket motor that kicks in during the last 10,000 feet of descent once the ordnance is more or less "on-target".

[birdman]

I was thinking more of a very fast burn rocket motor that kicks in during the last 10,000 feet of descent once the ordnance is more or less "on-target".

It's possible, but it turns out once you are at this size, the rocket motor mass is better used to simply add bomb mass.  Also, the MOP is at the size limit already, so it would be hard to package.  Knowing the guys at Eglin, if a rocket would have helped, it would have a rocket :)

[kgbsquirrel]

Hmmmm.... think we could strap on a pair of SRB's to the sides, between the fins, ala space shuttle?  After all, we wont know if it'll help until we test... for science!

[cordex]

Thanks KGB.  I'd heard of the MOP just not the claim that it could punch 200ft of reinforced concrete.

Given the size of the MOP, and its average density, even Newtonian penetration gives a depth of over 100ft in concrete.

That doesn't sound right.
Given a cylinder 20.5 feet long and 31.5 inches in diameter weighing 30,000lbs, that gives us a density of something like 4332 kg/m^3 for the MOP, ~2400 kg/m^3 for good concrete ...
D ≈ L * (A/B) where L is length, A is the projectile density and B is target density, right?
D ≈ 20.5 feet * (4332 kg/m^3 / 2400 kg/m^3 )
D ≈ 37 feet
Right?

For the record, this is the source for Wikipedia's claim of 200 feet penetration:
http://web.archive.org/web/20110629060725/http://www.af.mil/news/story.asp?id=123080622

It is designed to penetrate up to 200 feet underground before exploding.

Okay, so if loose dry dirt is 1,220 kg/m^3 ...
D ≈ 20.5 feet * (4332 kg/m^3 / 1220 kg/m^3 )
D ≈ 72.79 feet.

That's not even close to 200 feet, and seems like a best-case scenario as anything buried that deep is almost certainly going to be under something denser than loose, dry dirt.

Hmm ... so how dense would it have to be given the length?
200 feet ≈ 20.5 feet * (X kg/m^3 / 1220 kg/m^3 )
X = 23,415 kg/m^3
That's considerably denser than tungsten or uranium.

I know that the MOP isn't a cylinder and the nosecone is probably extremely hard and helps with penetration, but that still seems like a significant difference.

[birdman]

Hrm.  I did the calc in my head and used the density of steel (7.5) and concrete (2.4) but I assumed a length of 30ft, got 90+, and rounded to "100"
My bad.

Don't know how to model penetration effects for inhomogeneous bodies, but I know for a fact that a BLU-109 will go well over 30ft into dirt.

My mistakes:
Wrong inputs
Assuming Newtonian penetration, when in this case, it yields flawed results, and I don't know off the top of my head what the correction factor is, but I assume it has to do with a blunt vs aerodynamic penetrator.

I was wrong, your math is right :)

[birdman]

Okay, using a more accurate way to estimate
(Young's equations, see: http://www.globalsecurity.org/military/library/report/1997/penetration_equations.pdf )

And the following:
D=2.625ft / 0.8m
Subsonic Cd =0.3, transonic 0.9, supersonic 0.5 (conservative)
Mass = 30,000lb / 13600kg

Terminal velocity should be supersonic ( sqrt(2Mg/(CdA) yields >1000m/s for a supersonic Cd of 0.5, however, falling from 50,000ft, it is likely the bomb would only reach (I'm estimating, here, I don't feel like doing the integrals) about 500m/s (8m/s2 average, ~60seconds).

So V = 500m/s (1640fps)

Looking at the bomb, it looks like a tangent Ogive with Ln/D of about 1.5-2, so lets assume 1.5.

Penetrating 5000psi 1% reinforced concrete (F=20), and assuming the roof is 10 penetrator calibers across (30ft) (W1=10), cure time tc >1yr, and thickness >>>Dbomb (Tc=50)

That gives the following parameters:
Ke=(F/W1)^0.3 = 1.23
S= 0.085 Ke(11-P)(tcTc)^-0.06 * (FC/5000)^0.3 = 0.827
Nose factor N =0.18(Ln/D)+0.56 = 0.83

Penetration is:
D = D = 0.000018 S N (m/A)^0.7 (V - 30.5)
Where m/A is 27850kg/m2
So D =7.5m , which doesn't make a lot of sense, we know it goes further than that.
Applying the hard target correction of Kh=0.46(m)^0.15 = ~2
Now we have D=15m, or about 50ft. Which is almost exactly what I would expect.

So more than Newtonian, but less than what I said before, but still, 50ft is a metric ass load of concrete.

[Brad Johnson]

Okay, using a more accurate way to estimate
(Young's equations, see: http://www.globalsecurity.org/military/library/report/1997/penetration_equations.pdf )

And the following:
D=2.625ft / 0.8m
Subsonic Cd =0.3, transonic 0.9, supersonic 0.5 (conservative)
Mass = 30,000lb / 13600kg

Terminal velocity should be supersonic ( sqrt(2Mg/(CdA) yields >1000m/s for a supersonic Cd of 0.5, however, falling from 50,000ft, it is likely the bomb would only reach (I'm estimating, here, I don't feel like doing the integrals) about 500m/s (8m/s2 average, ~60seconds).

So V = 500m/s (1640fps)

Looking at the bomb, it looks like a tangent Ogive with Ln/D of about 1.5-2, so lets assume 1.5.

Penetrating 5000psi 1% reinforced concrete (F=20), and assuming the roof is 10 penetrator calibers across (30ft) (W1=10), cure time tc >1yr, and thickness >>>Dbomb (Tc=50)

That gives the following parameters:
Ke=(F/W1)^0.3 = 1.23
S= 0.085 Ke(11-P)(tcTc)^-0.06 * (FC/5000)^0.3 = 0.827
Nose factor N =0.18(Ln/D)+0.56 = 0.83

Penetration is:
D = D = 0.000018 S N (m/A)^0.7 (V - 30.5)
Where m/A is 27850kg/m2
So D =7.5m , which doesn't make a lot of sense, we know it goes further than that.
Applying the hard target correction of Kh=0.46(m)^0.15 = ~2
Now we have D=15m, or about 50ft. Which is almost exactly what I would expect.

So more than Newtonian, but less than what I said before, but still, 50ft is a metric ass load of concrete.

Dude, there are these things called "girls"...

Brad

[birdman]

Dude, there are these things called "girls"...

Brad

I'm married, and she is at belly dance class, so its "Marc time".  Anyway, I was taking a break from actual work :)

[De Selby]

I'm married, and she is at belly dance class, so its "Marc time".  Anyway, I was taking a break from actual work :)

Evaluating weapons, many of which you build, while the wife is at belly dancing class!?

Yeah, I'm going to say that's living the dream!

[Fitz]

Birdman is a failure.

He designs cool *expletive deleted*it. And yet

- No hoverboards
- No plasma rifles in the 40 watt range
- no fully functional cybernetic recreations of seven of nine

[cordex]

Birdman is a failure.

He designs cool *expletive deleted*. And yet

- No hoverboards
- No plasma rifles in the 40 watt range
- no fully functional cybernetic recreations of seven of nine

Just because he hasn't told you about them doesn't mean they don't exist.

Birdman, 50 feet is a huge amount of concrete, and would be an accomplishment in and of itself.

[birdman]

Birdman is a failure.

He designs cool *expletive deleted*. And yet

- No hoverboards
- No plasma rifles in the 40 watt range
- no fully functional cybernetic recreations of seven of nine

HoverBIKE is higher priority
My plasma weapon was closer to 20MW (Gatling plasmoid launcher with a laser induced breakdown channel)
7 of 9?  No way, I won't build a cyborg that won't take its clothes off.

[De Selby]

HoverBIKE is higher priority
My plasma weapon was closer to 20MW (Gatling plasmoid launcher with a laser induced breakdown channel)
7 of 9?  No way, I won't build a cyborg that won't take its clothes off.

How long until plasma weapons are something the world builds countermeausures against?

[Brad Johnson]

I'm married, and she is at belly dance class, so its "Marc time".

Ah, yes... we come to "mythical spouse" syndrome.  The sad, pathetic, inexorable fate of Basement Nerds everywhere.  Lemme guess, you're also six-two, look like Fabio, drive a Rolls-Royce, and do consulting work for heads of state world-wide, right? 

Brad

[birdman]

Ah, yes... we come to "mythical spouse" syndrome.  The sad, pathetic, inexorable fate of Basement Nerds everywhere.  Lemme guess, you're also six-two, look like Fabio, drive a Rolls-Royce, and do consulting work for heads of state world-wide, right? 

Brad

5'11", don't look like fabio, drive a GTR, and do consulting for heads of very large companies? :)

[kgbsquirrel]

5'11", don't look like fabio, drive a GTR, and do consulting for heads of very large companies? :)

Need an occasionally narcoleptic, slightly-amnesiac personal assistant? 

[Fitz]

5'11", don't look like fabio, drive a GTR, make my friends jelly with my gun collection and my moorsickles, and do consulting for heads of very large companies? :)

fix't

[dogmush]

fix't

And trucks.  I'm jelly of the Raptor.

[roo_ster]

I'm married, and she is at belly dance class, so its "Marc time".  Anyway, I was taking a break from actual work :)

My wife likes Zoomba and free weights.  Trying to talk her into the Tae Kwan Do class.