Post by Tom Goodrick on Mar 17, 2010 10:04:50 GMT -5
On TV the other day, I saw that a guy is going to try to set a new altitude record for skydiving. The old record was from a balloon at 90,000 ft done back in the '50's. This guy wants to do it from 120,000 ft, also from a balloon. Someone had estimated he would break the sound barrier.
You can do this in FS9 using my models of a Skydiver and a Parafoil (available free on my web site). Unfortunately, FS9 will let you go only as high as 100,000 ft. But that's not a big limitation. It allows considerable speed build-up and reduced stability in the upper atmosphere. this reduced stability tends to lead to a rocking motion observed in FS that can lead to trouble.
I developed the models of both the skydiver and the parfoil gliding parachute based on research I did for the US Army in these areas. You can control the skydiver just as a real skydiver would control himself. Of course these controls must utilize the aircraft controls in the sim. You start in a high-speed low lift position with legs bent and arms back. The flap control allows you to straighten the legs. The gear control allows you to move the arms forward. With legs straight and arms forward you get the max drag condition. You can look at a small instrument panel mounted on your reserve chute that tells altitude, airspeed and vertical speed (both shown in feet per second). The joystick lets you influence pitch and yaw a fair amount as a skydiver would influence these motions.
I once had the sad duty to study the problem of an out-of-control skydiver. We lost our commanding officer when he did a long freefall without proper training. He got into a tumble mode he could not get out of. He had an auto-deploy mechanism for his chute that did not work. I tried to figure out why and what we could do to prevent similar accidents. One thing I came up with was a way to make the altimeter more likely to work in a tumbling condition by splitting the static input from different source positions. That is now commonly done. A second thing I advocated that most jumpers do not use after they have had sufficient training is a drogue chute that stabilizes the person who makes mistakes and gets into a tumble mode. I incorporated this drogue chute into my FS skydiver model. It can be deployed by pressing the "/" key as you would for a spoiler.
From a freefall, I suggest using the drogue chute shortly before deploying the parafoil. But it can also be used if you get into a tumble mode.
To begin the process, choose a weather condition. I like the Fair Weather condition. You'll see a 40 knot wind down to about 20,000 ft. It will be calm below 3000 ft. Go to any airport you like and select the skydive "aircraft." Select Map mode and type in your altitude. I tried 20,000 ft, 40,000 ft and 60,000 ft before trying 100,000 ft. Start the flight. Tap S until you see the instrument display. Do nothing for a while and the body should get into a proper orientation but with a rocking motion. Experiment with the flap control and with the joystick or control wheel for roll and directional control. Control is limited as stability is marginal. Static stability barely exists. It is more of a balancing act. FS is a little more forgiving in this respect until you get rotating in one direction and want to stop.
At 10,000 ft or below (no lower than 2000 ft), you should deploy your Parafoil canopy. To do this, you must change to the Parafoil "Aircraft" in mid air. To fly the Parafoil, you use the turn flaps on the outboard sections of the wings. You might think these are ailerons but they are not. They cause banked turns by yawing the canopy and letting the sideslip push the canopy into a bank so the centripetal component of the lift can make you fly in a circle. But the turn is dynamic if you use full control. The descent rate will increase and you will go into a spin if you hold full control too long.
The center section of the wing trailing edge is deflectable as flaps just as in an airplane. This is controlled by the flap control. Zero flaps gives max glide both in speed and in glide ratio. But that speed is far too fast for a safe landing. You can see the same small instrument panel as with the skydiver so you see your altitude, airspeed and vertical speed. In still air, you have a glide ratio of about 3:1 with zero flaps. As you descend below 200 ft increase the flaps to full and you will see the jumper "flare" moderately for a nice landing. This is even better if you are heading into a slight wind.
I cannot certify the aerodynamics of the skydiver are highly accurate, but the drag area (CD S) of the diver in the different configurations is close. I do certify the parafoil aerodynamics and flight mechanics. They are accurate for the canopy design shown. For the Army I modelled that canopy on a computer 6DOF simulation that I wrote and I verified the sim with extensive flight tests I conducted with a remote-controlled instrument package.
From 40,000 ft I saw 281 fps at 32,000 ft with 279 fps vertical speed. (The glide ratio of a man is pretty low.) From 60,000 ft I saw 365 FPS falling through 42,000 ft. From 100,000 ft I saw 620 fps at about 60,000 ft (about Mach 0.64). The rocking was more pronounced. Arms out (hit G) seemed to reduce the rocking.
I was jumping over the airport at Coutland, Alabama, where airshows have been held several times. I managed to land each time right where I wanted to: on the grass between Runway 31 and the ramp near "stage center."
Note: It is highly unlikely that a human body would ever break Mach 1 in free fall because the density of the body is too low (about the same as water). A metal ball might do it but not a human body. Info I have shows the speed of sound above 65,000 ft is close to 971 fps. I doubt if anyone can get above Mach 0.7 because of the drag rise as you get near Mach 1. Remember, you start the jump from the gondola of a balloon. If you were coming in from orbit, you could easily see Mach 10 when you got down to 200,000 ft. But the G's would have crushed you and the heat rate would have burned you to a crisp. (I do have a program I worte for NASA that would simulate this.)
You can do this in FS9 using my models of a Skydiver and a Parafoil (available free on my web site). Unfortunately, FS9 will let you go only as high as 100,000 ft. But that's not a big limitation. It allows considerable speed build-up and reduced stability in the upper atmosphere. this reduced stability tends to lead to a rocking motion observed in FS that can lead to trouble.
I developed the models of both the skydiver and the parfoil gliding parachute based on research I did for the US Army in these areas. You can control the skydiver just as a real skydiver would control himself. Of course these controls must utilize the aircraft controls in the sim. You start in a high-speed low lift position with legs bent and arms back. The flap control allows you to straighten the legs. The gear control allows you to move the arms forward. With legs straight and arms forward you get the max drag condition. You can look at a small instrument panel mounted on your reserve chute that tells altitude, airspeed and vertical speed (both shown in feet per second). The joystick lets you influence pitch and yaw a fair amount as a skydiver would influence these motions.
I once had the sad duty to study the problem of an out-of-control skydiver. We lost our commanding officer when he did a long freefall without proper training. He got into a tumble mode he could not get out of. He had an auto-deploy mechanism for his chute that did not work. I tried to figure out why and what we could do to prevent similar accidents. One thing I came up with was a way to make the altimeter more likely to work in a tumbling condition by splitting the static input from different source positions. That is now commonly done. A second thing I advocated that most jumpers do not use after they have had sufficient training is a drogue chute that stabilizes the person who makes mistakes and gets into a tumble mode. I incorporated this drogue chute into my FS skydiver model. It can be deployed by pressing the "/" key as you would for a spoiler.
From a freefall, I suggest using the drogue chute shortly before deploying the parafoil. But it can also be used if you get into a tumble mode.
To begin the process, choose a weather condition. I like the Fair Weather condition. You'll see a 40 knot wind down to about 20,000 ft. It will be calm below 3000 ft. Go to any airport you like and select the skydive "aircraft." Select Map mode and type in your altitude. I tried 20,000 ft, 40,000 ft and 60,000 ft before trying 100,000 ft. Start the flight. Tap S until you see the instrument display. Do nothing for a while and the body should get into a proper orientation but with a rocking motion. Experiment with the flap control and with the joystick or control wheel for roll and directional control. Control is limited as stability is marginal. Static stability barely exists. It is more of a balancing act. FS is a little more forgiving in this respect until you get rotating in one direction and want to stop.
At 10,000 ft or below (no lower than 2000 ft), you should deploy your Parafoil canopy. To do this, you must change to the Parafoil "Aircraft" in mid air. To fly the Parafoil, you use the turn flaps on the outboard sections of the wings. You might think these are ailerons but they are not. They cause banked turns by yawing the canopy and letting the sideslip push the canopy into a bank so the centripetal component of the lift can make you fly in a circle. But the turn is dynamic if you use full control. The descent rate will increase and you will go into a spin if you hold full control too long.
The center section of the wing trailing edge is deflectable as flaps just as in an airplane. This is controlled by the flap control. Zero flaps gives max glide both in speed and in glide ratio. But that speed is far too fast for a safe landing. You can see the same small instrument panel as with the skydiver so you see your altitude, airspeed and vertical speed. In still air, you have a glide ratio of about 3:1 with zero flaps. As you descend below 200 ft increase the flaps to full and you will see the jumper "flare" moderately for a nice landing. This is even better if you are heading into a slight wind.
I cannot certify the aerodynamics of the skydiver are highly accurate, but the drag area (CD S) of the diver in the different configurations is close. I do certify the parafoil aerodynamics and flight mechanics. They are accurate for the canopy design shown. For the Army I modelled that canopy on a computer 6DOF simulation that I wrote and I verified the sim with extensive flight tests I conducted with a remote-controlled instrument package.
From 40,000 ft I saw 281 fps at 32,000 ft with 279 fps vertical speed. (The glide ratio of a man is pretty low.) From 60,000 ft I saw 365 FPS falling through 42,000 ft. From 100,000 ft I saw 620 fps at about 60,000 ft (about Mach 0.64). The rocking was more pronounced. Arms out (hit G) seemed to reduce the rocking.
I was jumping over the airport at Coutland, Alabama, where airshows have been held several times. I managed to land each time right where I wanted to: on the grass between Runway 31 and the ramp near "stage center."
Note: It is highly unlikely that a human body would ever break Mach 1 in free fall because the density of the body is too low (about the same as water). A metal ball might do it but not a human body. Info I have shows the speed of sound above 65,000 ft is close to 971 fps. I doubt if anyone can get above Mach 0.7 because of the drag rise as you get near Mach 1. Remember, you start the jump from the gondola of a balloon. If you were coming in from orbit, you could easily see Mach 10 when you got down to 200,000 ft. But the G's would have crushed you and the heat rate would have burned you to a crisp. (I do have a program I worte for NASA that would simulate this.)