Please explain the rear cargo door of the C-5 Galaxy

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I never understood the idea of dropping a tank. Its an impressive feat if you do it but if you dont control enough land to land an AC maybe you shouldnt be there.
 

The good old Sheridan. I believe 2 of the 10 dropped in Panama where destroyed on landing.
 
Once you have dropped the tank what about the crew fuel and ammunition? Surely the area becomes a magnet for the enemy, repeated drops by cargo planes must be extremely risky?
 
I stayed with my brother in the summer of 1962 outside of Ft Bragg, N.C., he was a SSgt. in the 82nd Airborne.
He said whenever they airdropped Jeeps or trucks, the ones chose for the drops were usually the motor pool sgt. rejects, sometimes they had to be towed and pushed on board.
I remember seeing a picture of a Jeep that had experienced a failed drop, it had hit flat, but was compacted to about 18-24 inches, the tires, which hadn't burst, were the tallest part of the wreckage.

A aircraft making a airdrop might be a easy target for AA, but nowhere as easy a target as it would be during landing, takeoff, and stationary on the ground unloading.
 
As a C-141 crew chief, I've been a part of any number of ERO's (Engine Running Offload) to minimize that stationary on the ground unloading. And while I only was a part of doing this on one occasion, there are many videos of Caribous and C-130's unloading in Vietnam while performing what is little more than a touch and go.
 

And the needed after evacuation wiping material, particularly if the officers map has already been used once on both sides...
 
No one has told me why it wouldn't be possible to build a 170m diameter parachute or if indeed there are fundamental physical limits.

C17's have extracting 38,000lb loads (17 tons) as part of ARES booster recovery testing. C5 Galaxy's have extracted 80,000 lbs. It's only 50% more to get to an Abrams. Elliptical guided parasail like parachutes have been built that can deliver with GPS accuracy 26000lb skids.

A crude calculation using the old T10 parachute of the US Army (11m diameter, 160kg load) suggests that the 150ft parachutes developed for ARES booster recovery could land a 25 ton load (though 12.5 tons is more realistic)

Dropping a dozen MBT would only be to protect the 80 ton Caterpillar D10. Ideally one would drop an armoured caterpillar D10, clear out a runway, put down a couple of graders and roller compaction machines. To create a runway of 5cm thick tar that is 20m wide and 1000m long one would need to drop in 25 40 tons asphalt containers. It will only take about 50 C5 missions!
 
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You don't need tar or concrete for a all weather runway. Even in WW2 they had PSP. Pierced Steel Planking.

That's all we had at NKP, Thailand, except it was PSP over a gravel base. Definitely a all weather runway. On the runway they had a different type of planking, aluminum, and much stronger than regular PSP.

Battle damaged F4s and F105s would land there, but I never saw one take off. They'd use a Skycrane to take they to Takli, or Udorn. But C141s used it often.

During the 50's before helicopters got powerful enough to lift very heavy loads, the USAF and Army needed a way to supply paratroops on the ground before they took enough ground to build a small airport, delivery by parachute, or crash landing gliders, was the only way.

I can remember the Russians had a system that used parachutes, but fairly small parachutes, so the load would come down faster and not be as subject to the winds, but used a retro-rocket to soften the landing.
 
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Considering how much a tank is worth, let alone if it is dropped loaded with minimal fuel and ammo, or fully filled, ready to go without its crew onboard for the drop, the suspension of the tank even with 2 meters of corrugated cardboard cushioning would break part of the tank at best.
At worst, the impact would crush it, cause it to blow up, roll over, bury itself in softer earths, bounce and roll over, crush someone or something else in the DZ etc, while having say a whatever the price of an M1A1 is (say $4 Mil') 65 ton sledgehammer bouncing on top of an enemy is a cool prospect, I think the crew that'd be following it down in their own chutes wouldn't want to dig it out, try to 'right it' or pick up all the spare parts that survived the impact, and that's even before thinking that such a big parachute making the tank a AAA gunners wet dream for his bonus pay.

If your going to drop 65-ish tons or $4 Mil worth of hurt on the enemy/target, I can think even the most unintelligent member of an military could think of better things to throw/drop/uses than an 'current' MBT; now if there was some sort of anti-grav arresting system with reactive attitude control thrusters used with chutes. ...but I think that might be some way off yet.
 
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Marsden Matting, a brand of PSP (perforated steal plate) seemed to weigh 24kg/square meter, so a fairly big 1000m runway 30m wide would require 720 tons of steel.

I suppose you could start small and then progressively build up to larger aircraft: a 500m x 20m runway would require only 240 tons of steel.
 
In other words, a great deal lighter than a asphalt plant.

Of course, you don't have to have PSP, and you certainly don't need asphalt for a tactical runway.
That would just be needed if you wanted a all weather, semi-permanent airfield.
 
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tyrodtom said:
In other words, a great deal lighter than a asphalt plant.

Of course, you don't have to have PSP, and you certainly don't need asphalt for a tactical runway.
That would just be needed if you wanted a all weather, semi-permanent airfield.
Click to expand...

PSP is rather heavy but it is obviously strong enough to handle a very heavy aircraft. My calculation was based around a 5cm thick asphalt runway over compacted earth. I don't known how heavy an aircraft could be used on such runway, civil engineering and soil mechanics not being my trade. I've seen runways in the Papua New Guinea highlands that used cow hides (for Ju 52 of all things).

Rapidly building a runway was obviously a critical part of WW2 aviation.
 
Somewhere, I remember reading that a C-5 could only carry one M60, because it needed a large and heavy pallet to distribute the load
 
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