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- Newsgroups: rec.models.rockets
- Path: sparky!uunet!spool.mu.edu!agate!ames!news.dfrf.nasa.gov!altair.dfrf.nasa.gov!maine
- From: maine@altair.dfrf.nasa.gov (Richard Maine)
- Subject: Re: Tracking
- In-Reply-To: billn@hpcvaac.cv.hp.com's message of Tue, 26 Jan 1993 01:16:03 GMT
- Message-ID: <MAINE.93Jan25195403@altair.dfrf.nasa.gov>
- Sender: news@news.dfrf.nasa.gov (Usenet news)
- Organization: NASA Dryden, Edwards, Cal.
- References: <25JAN199313112698@vx.cis.umn.edu> <1993Jan26.011603.22455@hpcvaac.cv.hp.com>
- Date: Tue, 26 Jan 1993 03:54:12 GMT
- Lines: 39
-
- On Tue, 26 Jan 1993 01:16:03 GMT, billn@hpcvaac.cv.hp.com (bill nelson) said:
-
- bill> soc1070 writes:
- bill> :
- bill> : As for decent rates, I think a basic problem would be that two
- bill> : different rockets, each exactly the same weight and with the
- bill> : same size 'chutes, would fall at different rates, because the one
- bill> : with the larger exposed area (i.e. fins, tube, etc) would be carried
- bill> : further down wind.
-
- bill> This is a little misleading. They will both fall at the same rate.
- bill> They will not fall at the same descent angle - the one with the greater
- bill> lateral area of resistance will drift further.
-
- That's still misleading. I've seen several people in the past make
- the same mistake. Presumably none of them are pilots (which I am) nor
- parachutists (which I'm not, but I presume they must have the right
- intuition even more strongly). The lateral area has essentially
- nothing to do with either descent rate or descent angle. Anything
- falling on a non-gliding parachute will move laterally with "exactly"
- (to as close as matters, excepting mainly transient gusts) the
- wind velocity, making lateral area irrelevant.
-
- The pilot in me notes that flight dynamics are always relative to the
- wind, not the ground. This is *VERY* apparent in light aircraft;
- if you have a pilot friend that doesn't appreciate this, I'd advise you
- not to go flying with him/her. The misunderstanding is a common cause
- of stall/spin accidents.
-
- I'd estimate that it probably takes on the order of one second after
- chute opening to reach the steady state condition. That one second
- or so is the only time that there is significant lateral velocity
- relative to the wind.
-
- --
- --
- Richard Maine
- maine@altair.dfrf.nasa.gov
-
-