Rock Drop Time Altitude
I know I've seen it before, and I've searched the forums, and couldn't find anything. Does anyone have a chart or something simmilar of the altitude from rock drops? Basejumper.com - archive
General BASE
Re: [ineed2fly] Rock Drop Time Altitude
http://www.johnnyutah.com/freefallchart1.html For those of us who are Metrically challenged.
Edited to add that this appears to be a jumper freefall chart not a rockdrop chart.
Edited again. Freefall velocity and time are very similar for a jumper vs a rock (using freefall in a vacuum as perfect rock drop data) up until about 4 seconds. At that point the jumper falls about 242' while the perfect rock falls about 257'. At 6 seconds the jumper has fallen 504' and the rock 579'. At 8 seconds the jumper falls 808' and the rock 1029'.
Personally I'd use the jumper freefall chart as it will give you more conservative data. Also consider that sound, if you're using sound for a rock drop, takes about 1 second to travel 1000' which could lead you to believe that the freefall is much greater than it really is.
Other than that I can't find a better chart than the NASA one which is unfortunately metric. I used it to make the metric/US conversions. If you make a chart for no air resistance velocity and distance in mph and feet it would be nice of you to share it.
Re: [Martini] Rock Drop Time Altitude
Thanks a bunch, been looking for that to throw in my saddle bags just to have on hand, I always forget and wind up second guessing myself. And obviously there would be a difference between tossing a pebble or a boulder off a cliff, but what size rock do you think would give the closest time to jumper impact? Baseball? Basketball? Your friend with his rig still in his stash bag perhaps? 
Re: [Martini] Rock Drop Time Altitude
Martini wrote:
Personally I'd use the jumper freefall chart as it will give you more conservative data.
Wrong end of the FF.
If you jumped from 1000ft and jumper has fallen 6 seconds he would have 496ft to impact, the rock would have 421ft to impact.
Better to think you are a rock and find yourself 75ft higher.
Laters
Re: [base283] Rock Drop Time Altitude
I always keep this in my head, it's for a perfect rock drop in a vacuum, but: Y=16*t^2
Re: [ineed2fly] Rock Drop Time Altitude
You can easily generate freefall chart yourself using a spreadsheet from here. It only depends on one parameter: terminal velocity. For terminal velocity of 120mph, the chart with 0.1s step would look like this: |
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Code |
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Time (s) Vertical speed (mph) Distance fallen (ft)
0 0 0
0.1 2.2 0.2
0.2 4.4 0.6
0.3 6.6 1.4
0.4 8.8 2.6
0.5 10.9 4.0
0.6 13.1 5.8
0.7 15.3 7.9
0.8 17.4 10.3
0.9 19.6 13.0
1.0 21.7 16.0
1.1 23.8 19.3
1.2 25.9 23.0
1.3 28.0 26.9
1.4 30.1 31.2
1.5 32.1 35.8
1.6 34.2 40.6
1.7 36.2 45.8
1.8 38.1 51.2
1.9 40.1 57.0
2.0 42.0 63.0
2.1 44.0 69.3
2.2 45.8 75.9
2.3 47.7 82.7
2.4 49.5 89.9
2.5 51.3 97.3
2.6 53.1 104.9
2.7 54.9 112.9
2.8 56.6 121.0
2.9 58.3 129.5
3.0 59.9 138.1
3.1 61.6 147.0
3.2 63.2 156.2
3.3 64.8 165.6
3.4 66.3 175.2
3.5 67.8 185.0
3.6 69.3 195.1
3.7 70.7 205.3
3.8 72.1 215.8
3.9 73.5 226.5
4.0 74.9 237.4
4.1 76.2 248.5
4.2 77.5 259.7
4.3 78.8 271.2
4.4 80.0 282.8
4.5 81.2 294.7
4.6 82.4 306.7
4.7 83.5 318.8
4.8 84.6 331.2
4.9 85.7 343.7
5.0 86.8 356.3
5.1 87.8 369.1
5.2 88.8 382.1
5.3 89.8 395.2
5.4 90.8 408.4
5.5 91.7 421.8
5.6 92.6 435.3
5.7 93.5 449.0
5.8 94.3 462.7
5.9 95.1 476.6
6.0 96.0 490.6
6.1 96.7 504.8
6.2 97.5 519.0
6.3 98.2 533.4
6.4 98.9 547.8
6.5 99.6 562.4
6.6 100.3 577.1
6.7 101.0 591.8
6.8 101.6 606.7
6.9 102.2 621.6
7.0 102.8 636.6
7.1 103.4 651.8
7.2 103.9 667.0
7.3 104.5 682.2
7.4 105.0 697.6
7.5 105.5 713.0
7.6 106.0 728.6
7.7 106.5 744.1
7.8 106.9 759.8
7.9 107.4 775.5
8.0 107.8 791.3
8.1 108.2 807.1
8.2 108.6 823.0
8.3 109.0 839.0
8.4 109.4 855.0
8.5 109.7 871.1
8.6 110.1 887.2
8.7 110.4 903.4
8.8 110.8 919.6
8.9 111.1 935.9
9.0 111.4 952.2
9.1 111.7 968.5
9.2 112.0 984.9
9.3 112.3 1001.4
9.4 112.5 1017.9
9.5 112.8 1034.4
9.6 113.0 1051.0
9.7 113.3 1067.6
9.8 113.5 1084.2
9.9 113.8 1100.9
10.0 114.0 1117.6
10.1 114.2 1134.3
10.2 114.4 1151.0
10.3 114.6 1167.8
10.4 114.8 1184.7
10.5 115.0 1201.5
10.6 115.1 1218.4
10.7 115.3 1235.3
10.8 115.5 1252.2
10.9 115.6 1269.1
11.0 115.8 1286.1
11.1 115.9 1303.1
11.2 116.1 1320.1
11.3 116.2 1337.2
11.4 116.3 1354.2
11.5 116.5 1371.3
11.6 116.6 1388.4
11.7 116.7 1405.5
11.8 116.8 1422.6
11.9 117.0 1439.8
12.0 117.1 1456.9
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Terminal velocity depends on coefficient of drag, "wing loading", and density of air (read altitude). So you can customize the chart to yourself - some people have terminal of 110mph, some 140mph.
However, in a sense, freefall chart is used to assess a "worst case scenario" - falling like a rock. If this is the case, we should construct it using the "worst" terminal velocity - that of falling headdown. So, if we plug, say, 180mph as terminal velocity, we get this "Oh shit" freefall chart:
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Code |
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Time (s) Vertical speed (mph) Distance fallen (ft)
0 0 0
0.1 2.2 0.2
0.2 4.4 0.6
0.3 6.6 1.4
0.4 8.8 2.6
0.5 11.0 4.0
0.6 13.1 5.8
0.7 15.3 7.9
0.8 17.5 10.3
0.9 19.7 13.0
1.0 21.8 16.1
1.1 24.0 19.4
1.2 26.2 23.1
1.3 28.3 27.1
1.4 30.4 31.4
1.5 32.6 36.0
1.6 34.7 40.9
1.7 36.8 46.2
1.8 38.9 51.7
1.9 41.0 57.6
2.0 43.0 63.8
2.1 45.1 70.2
2.2 47.2 77.0
2.3 49.2 84.1
2.4 51.2 91.4
2.5 53.2 99.1
2.6 55.2 107.0
2.7 57.2 115.3
2.8 59.2 123.8
2.9 61.1 132.6
3.0 63.1 141.7
3.1 65.0 151.1
3.2 66.9 160.8
3.3 68.8 170.8
3.4 70.6 181.0
3.5 72.5 191.5
3.6 74.3 202.2
3.7 76.1 213.3
3.8 77.9 224.6
3.9 79.7 236.1
4.0 81.4 247.9
4.1 83.2 260.0
4.2 84.9 272.3
4.3 86.6 284.9
4.4 88.3 297.7
4.5 89.9 310.8
4.6 91.6 324.1
4.7 93.2 337.7
4.8 94.8 351.4
4.9 96.4 365.5
5.0 97.9 379.7
5.1 99.4 394.2
5.2 101.0 408.9
5.3 102.5 423.8
5.4 103.9 438.9
5.5 105.4 454.3
5.6 106.8 469.8
5.7 108.2 485.6
5.8 109.6 501.6
5.9 111.0 517.8
6.0 112.3 534.1
6.1 113.7 550.7
6.2 115.0 567.5
6.3 116.3 584.4
6.4 117.5 601.6
6.5 118.8 618.9
6.6 120.0 636.4
6.7 121.2 654.1
6.8 122.4 672.0
6.9 123.6 690.0
7.0 124.7 708.2
7.1 125.9 726.6
7.2 127.0 745.1
7.3 128.1 763.9
7.4 129.1 782.7
7.5 130.2 801.7
7.6 131.2 820.9
7.7 132.3 840.2
7.8 133.3 859.7
7.9 134.2 879.3
8.0 135.2 899.1
8.1 136.2 919.0
8.2 137.1 939.0
8.3 138.0 959.2
8.4 138.9 979.5
8.5 139.8 999.9
8.6 140.6 1020.5
8.7 141.5 1041.2
8.8 142.3 1062.0
8.9 143.1 1082.9
9.0 143.9 1104.0
9.1 144.7 1125.1
9.2 145.5 1146.4
9.3 146.2 1167.8
9.4 147.0 1189.3
9.5 147.7 1210.9
9.6 148.4 1232.6
9.7 149.1 1254.5
9.8 149.8 1276.4
9.9 150.5 1298.4
10.0 151.1 1320.5
10.1 151.7 1342.7
10.2 152.4 1365.0
10.3 153.0 1387.4
10.4 153.6 1409.9
10.5 154.2 1432.5
10.6 154.8 1455.1
10.7 155.3 1477.9
10.8 155.9 1500.7
10.9 156.4 1523.6
11.0 157.0 1546.6
11.1 157.5 1569.6
11.2 158.0 1592.8
11.3 158.5 1616.0
11.4 159.0 1639.3
11.5 159.5 1662.6
11.6 159.9 1686.0
11.7 160.4 1709.5
11.8 160.8 1733.1
11.9 161.3 1756.7
12.0 161.7 1780.4
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It's better to stay on conservative side and think that for given height you have less time, or for given time, you'll fall more, than the opposite.
Re: [base283] Rock Drop Time Altitude
base283 wrote:
try this.take care, space
wow! Are these your own calculations? where did you get this?
Re: [rippedbx] Rock Drop Time Altitude
Andrea 689. Italy.I could do it though. Take care and a hi 5r to Andrea
Re: [jools] Rock Drop Time Altitude
Good logic, wrong application. We're using the rock to judge the cliff height. If I hear a "clunk" at 6 seconds my rockfall chart says it's a 579' cliff while my jumper chart calls it 504'. Believing that the cliff is only 504' I take a shorter delay. Using the jumper freefall chart to judge cliff height is the more conservative route.
Re: [ineed2fly] Rock Drop Time Altitude
All of the calculations are pretty moot around here anyway. Use a rock big enough so you can hear the impact. At 4 seconds the charts are all more or less equal, if the LZ isn't directly under the object you'll have to take a shorter delay anyway. If we have an 1100' E and the local custom is a 6 second delay and 8 seconds is a death wish are you going for 7 1/2 on your first jump there? I've only used the rock drop once. The LZ isn't under the exit point, you can't laser from below, you can't (without using climbing gear) look vertically from the exit. By far the easiest thing is a rock drop. BTW at this object you can see from a side angle that it is a clear drop and you aren't just tossing rocks through a gap in a ledge. Height-wise all I wanted to know is that it was freefall friendly, it's low. I threw about a dozen rocks to convince myself that it's jumpable. Making the LZ is another matter.
Re: [ineed2fly] Rock Drop Time Altitude
Don't forget that a rock 'drop' will give you different results from a rock 'toss'.