Russian Paratroopers to Land on Drifting Arctic Ice

[KenV]

FWIW, the Russians used an interesting parachute system like nothing we (USA) use. It's a combination static line system and free fall deploy system. The static line deploys/extracts a small drogue chute, the troops drop to a preset altitude at a reduced velocity free fall because of the drogue, and then the main chute is extracted by the drogue by some kind of automated system. Don't know if the auto system is timer based or altitude based or both. And it has a steerable ram air airfoil type canopy. Fascinating.

LINK

And it's hard to be certain but in the video it looked like one jumper's drogue collapsed/burst during his drop. They have a manual reserve, but the video did not show that.

[Tourist]

Originally Posted by O-P

Ken,

I beg to differ. Two objects with identical Cd and frontal area, but with differing mass, will fall at exactly the same rate.

Methinks you misunderstood your teacher during that lesson....

[O-P]

Tourist,

Do explain how mass affects gravity in a freefall acceleration.

[Basil]

Do explain how mass affects gravity in a freefall acceleration.

Ah, but it isn't acceleration they're discussing; it's TV and I'd tend to agree with KenV that WEIGHT*=THRUST
DRAG= Cd 1/2 p V^2 S
Assuming that the parachutist falls in the face-down attitude then Cd will be largely constant.
Therefore since thrust is increased, say doubled with a military load, then TV will be higher but, due to the V variable being squared, nothing like doubled.

*ie mass in a gravitational field.

Re the 'dent in the ice' wrong subscale setting seems to me the most likely explanation.

[BEagle]

O-P, what you assert is correct in a vacuum - but not otherwise.

Take a piece of A4 paper and drop it out of the window. Now take an A4 piece of steel and repeat the experiment - I think that you'll find that the time taken to reach the ground is rather less for the latter case.

Two forces are acting on the object, weight (mg) and drag (Cd½ρV²S); the resultant force which accelerates the body is (weight-drag) and only weight has a mass term. As the body accelerates, drag increases until it is equal to weight, at which point there is no further acceleration and the body is descending at terminal velocity.

[O-P]

Basil/Beagle,

Thanks for your polite responses. Rather than pure mass, it's a mix of surface area and Cd that affect the drag rate.

Ken, I apologize. Tourist go **** your self.

Ken, I guess a 300kg human will hit the same TV as 100kg human if the drag characteristics are right...like weapons.

Sorry Ken, I was wrong.

[BEagle]

I've edited my post to correct the formula for Drag - it should have been Drag = Cd½ρV²S.

[Tourist]

Originally Posted by O-P

Ken, I apologize. Tourist go **** your self.

Methinks you misunderstood your parents when they tried to teach you manners too.....

[Backinblack]

What interests me more are the arrangements to exfil the paratroopers after they land. Any information? - FODPlod

This is their first jump:
https://www.youtube.com/watch?v=w32kaOYb7lo

[Dougie M]

Free fall or not FF

The VDV seem to prefer their reefed drogue dispatch system which may be due to the drop speed of an IL76. I can't see it throttling back to 115kts. The drop itself from the helmet cam was about 50secs, half of it in "attenuated free fall" (about the same speed as in a tandem fun jump) That would equate to about 4000ft. The phase under the main canopy was about the same which equates to about 500ft so the release height would have been around 5000ft mark or 1500m. The troops weren't on oxygen so the mid level scenario fits.
UK Freefall qualifying height is 12000ft. Oxygen is used by the jumpers at or above this height. The terminal velocity of a para in the standard posture shown is around 120kts.

[Top Bunk Tester]

For a comprehensive analysis of the Antartic accident see the following link:

Tragedy in Antarctica | Parachutist Online

[beardy]

Icetrek - BARNEO ICE CAMP

There was a very interesting documentary about this.

http://www.channel5.com/show/north-pole-ice-airport

The 'civilian' parachutists prepare the runway.

Barneo is a seasonal camp, set-up in late March every year only through a highly complex and technical series of logistics incorporating Ilyushin-76, Antonov-74 and Mi-8 flights from Moscow and Siberia, parachute and skydiver drops, specialist advisers and observers and temporary camps on the Arctic Ocean. Once the ice runway has been prepared, using tractors parachuted onto the ice, technical AN-74 flights deliver the camp infrastructure and Barneo usually opens its doors to the first passenger flight around April 2.

[KenV]

For a comprehensive analysis of the Antartic accident see the following link:
Tragedy in Antarctica | Parachutist Online

So the account on post #26 was wrong on several counts:

The jump most certainly was planned to freefall to terminal velocity.
The plan was to deploy at 5000 ft AGL after a 4000 ft freefall. (Typical planning)
A 5000 ft AGL pull altitude would have given lots of margin for multiple errors. (Good planning.)
The tragedy was not a result of altimeter error due to cold.
The cause was hypoxia of the jumpers. (Very very bad planning and a major violation of the Skydiver's Information Manual.)
The three dead jumpers never used oxygen during the climb.
The three that died did not pull "too late." They never pulled at all.
None of the dead jumpers had auto deploy devices (moderately bad planning, but not a violation.)
The three surviving jumpers all used oxygen at least part time during the climb by sharing a single portable O2 bottle with the pilot. (bad planning and a violation, but just good enough to survive, if just barely.)
The lone surviving single jumper had an auto deploy device and it fired. (good planning.)
The other two survivors jumped tandem, did not suffer hypoxia and manually pulled as planned at 5000 ft AGL. (good planning)

Still a tragic event, but very different than what was originally described.
Also very very different than what the Russians did. No comparison at all between the antarctic tragedy and the Russian arctic jump.

[KenV]

Therefore since thrust is increased, say doubled with a military load, then TV will be higher but, due to the V variable being squared, nothing like doubled.

Assuming all else is equal, terminal velocity varies as the square root of the increase in mass. So mass must be four times greater to double the terminal velocity.

[KenV]

The VDV seem to prefer their reefed drogue dispatch system which may be due to the drop speed of an IL76.

The US Military jumped for decades out of the C-141 which is very similar to the IL-76 and have never (to my knowledge) used such a system. And they continue to jump out of the C-17 which has a similar jump airspeed. The C-17 is a STOL design and can fly slower than the C-141, but that requires full flaps/slats and high AOA which results in a high deck angle. The C-17 deck angle may not exceed 4 degrees during a jump which requires an airspeed similar to C-141. I doubt that IL-76 jump airspeed is significantly higher, if at all. And interestingly, they jump single stick off the Ilyushin's ramp, not double stick out of side doors. Very different in multiple ways.

[KenV]

What interests me more are the arrangements to exfil the paratroopers after they land. Any information?

They apparently jumped onto an ice flow that has an ice runway that civilian aircraft can use. Apparently, when their arctic training is done they board a jet and fly home. No Ice Station Zebra submarines.

LINK

[Skymong]

Originally Posted by KenV

The US Military jumped for decades out of the C-141 which is very similar to the IL-76 and have never (to my knowledge) used such a system. And they continue to jump out of the C-17 which has a similar jump airspeed. The C-17 is a STOL design and can fly slower than the C-141, but that requires full flaps/slats and high AOA which results in a high deck angle. The C-17 deck angle may not exceed 4 degrees during a jump which requires an airspeed similar to C-141. I doubt that IL-76 jump airspeed is significantly higher, if at all. And interestingly, they jump single stick off the Ilyushin's ramp, not double stick out of side doors. Very different in multiple ways.

They are jumping squares not rounds hence the single-stick. The parachute is deployed by either a timer or pressure device allowing it to be used across a wide range of altitudes.
I'm guessing the use of the drogue means that body position is less important on those jumps that have any significant freefall time, thus circumventing the need for the training associated with MFF ops.