Basejumper.com - archive

Ok here is a nerdy question. I have just started skydiving but BASE is starting to fascinate me.

When you are considering jumping a new object, do you do calculations of speed, distance travelled, canopy opening times etc?

I have an engineering background and out of total curiosity (as opposed to actually going to jump the thing) I was trying to figure out if you can safely jump a local bloack of flats near me with a 3 second delay (a fall of 150 feet roughly). I figured no by using Mr Newton's equations and a required deployment distance of 120 feet, doing 100 ft/sec (i got the height from the web) as the flats were about 210 feet tall.

So three questions popped up:

1) Do you decide on a delay in order to predict your fall rate and opening distance required by canopy?

2) What techniques exist in order to speed opening time? I have seen people hold the unpacked canopy and also do hand held pilot throws.

3) Do you factor in 'screw up time' - e.g. extra altitide to give an extra second of safety?

I will understand if people are reluctant to answer my questions - I appreciate they may encourage others to go out and jump without following the correct route of getting 200 skydives, finding a mentor and attending legal and safe sites first.

Ross

Sometimes slide rule figuring can get you in trouble. While you can use things like laser range finders and then do the math you want to get past that stage as fast as possible. You need to be able to "eyeball" it.

You want to get to the point where you look up at an object and imagine yourself standing on the edge. Then you can visually picture yourself doing various delays, seeing where those delays will leave you under canopy, and what your landing options are at each of those points.

I know that's hard to do without experience, but it's an ability you'll need to acquire.

Also, keep this in mind. On the medium sized objects the length of the delay, in most cases, in not decided by the height of the object, it’s decided by how long you need to be under a canopy in order to reach a safe landing area. In other words you could have a 1000-foot tall building where you can easily do a 5 or 6 second delay. But if the park you must land in four or five blocks away than your delay may be limited to 2 or 3 seconds.

My girlfriend, who works for the Jet Propulsion Laboratory (JPL) here in California, can plot the navigation of a space ship to Mars (she did the Rovers there now) using nothing but pure mathematics. But that doesn't work in BASE jumping because of all the variables. When the Rovers entered the Martian atmosphere their knees weren't knocking and their teeth weren't chattering.

So I worry sometimes when others (not you) whip out the physics formulas to explain BASE jumping. The only real physics I've ever seen in BASE is when someone admits, "Man, I just shit my pants . . ."

NickD
BASE 194

Some very simple physics applies here, and a person can have a lot of fun (if this sort of thing interests them) modeling various BASE-related phenomena.

The real question you need to be asking yourself when you stand at the exit point on (to take a recent example from the forum) a 250' antenna, though, isn't "Is it physically possible to take a 1-second delay from here," but "Do I want to take a 1-second delay from here".

... Generally, a jumper -- particularly a less-experienced one -- will start with a conservative rule of thumb, do the jump that way, then ask after the fact, "How much extra (or perhaps less) margin/canopy time/flight distance am I interested in eating up next time around?"