Path: utzoo!mnetor!uunet!husc6!bbn!uwmcsd1!dogie!uwvax!umn-d-ub!umn-cs!dayton!joe From: joe@dayton.UUCP (Joseph P. Larson) Newsgroups: comp.sys.amiga Subject: Re: JET | Supra 2400 | Multi-Tasking Hard Drives Message-ID: <4110@dayton.UUCP> Date: 15 Mar 88 16:31:26 GMT References: <4578@garfield.UUCP> <9280@sunybcs.UUCP> Reply-To: joe@dayton.UUCP (Joseph P. Larson) Organization: Dayton-Hudson Dept. Store Co. Lines: 88 Keywords: All of the above! In article <9280@sunybcs.UUCP> ugmiker@sunybcs.UUCP (Michael Reilly) writes: >sorry, I don't think ANY airplane can go "straight up" for ever, there are just >too many stress factors to control, not to mention the fact that for a pilot >to handle/survive going straight up at mach 2+ for an extended amount of time >he would have to be able to withstand a very high G count..... Sorry, but this is inaccurate. The speed at which you are traveling has absolutely nothing to do with G factors as long as you are moving in a straight line. Nothing at all. In any case, the F16 has a thrust-to-weight ratio greater than 1. This means it can accellerate pointed straight up. (This assumes you're already at flying speed before you try it....) Of course, they can't do it forever. The F16 is not an orbital vehicle. It has a definite ceiling of operation (somewhere around 80000 feet, I believe). So at 400 MPH (a reasonable speed to climb straight up), this means they could only do it for about 2 minutes. (80000 / 5280 is around 16 miles. 400 / 60 is around 7 Miles per minute. These are approximate numbers....) There are probably other limits such as difficulty in continuing to fly at only 400 MPH at 80000 feet (the air is too thin) and things like this. ======= To those who want to know, I'll discuss G's for a second. If you already know about them, type "N" at the next available break ("Which means NOW" -Toots Mutant, "Ruby"). G's are a measure of the amount of force an object is under. 1 G is equivalent to standing on the ground at sea level on Earth. When you accellerate, you are experiencing a force in some direction causing your velocity vector to change direction. Note that accelleration doesn't mean you have to increase speed -- just change the vector either by changing the direction you are moving or by changing the speed or both. If you jump off your roof, for instance, you accellerate towards the center of the earth (center of mass, that is) at 32 feet per second per second (or just under 10 meters....). You are experiencing 1 G of accelleration, but because your entire body is being pulled equally, you are actually feeling 0 Gs of force. (Some science fiction writers play with gravity as a means of accomplishing high-G manuevers without physical damage....) If you are in a plane that is climbing straight up without accellerating, you will feel 1 G of force due to gravity. You will not feel anything more than that. If the plane has enough thrust that the thrust-to-weight ratio is 2 (plane weighs 2 tons but has 4 tons of thrust), it can climb straight up, accellerating a 1 G, so you'll feel 2 Gs of force. However, most times that one feels high-Gs, is because of a turn. You're still changing your velocity vector even though you are probably actually slowing down a little (unless you add a little more thrust that you had before) due to a variety of things I won't go into (like the fact that you're disturbing the air more to help you turn). If you're moving at 700 MPH (just under Mach 1, which is where a lot of air combat is going to happen) and you pull a 180 inside, say, 20 seconds, this means that you have changed your velocity vector by 1400 MPH in 20 seconds. This works out to 103 feet per second per second on the average. This is about 3 Gs. Pretty mild. To see how that works out, look at it this way: 1400 MPH times 5280 feet/mile is 7,392,000 feet/hour. (Change in velocity) Or divided by 3600 seconds/hour is 2060 feet/second. (Change in velocity) In 20 seconds, this averages to 103 feet/second/second. (Average accell.) Most pilots talk about 1-minute or 2-minute turns. Very mild. However, if a fighter took 20 seconds to turn around to face an opponent, he's going to be in trouble. At the very least, his opponent isn't 20 seconds behind him, so the opponent is *still* going to be behind him once he's turned around. The numbers get pretty wild. Imagine a 20-second 180 at Mach 3. We're talking 9 Gs. 7 Gs sustained (more than a couple of seconds) are likely to black you out. 9 Gs for 20 seconds won't leave you awake. They don't pull 20-second 180s at Mach 3. You'll also notice that air-show manuevers are NOT at sound-barrier speeds.... Whatever. Enough of Elementary Physics -- Motion. -J -- UUCP: rutgers!dayton!joe Dayton Hudson Department Store Company ATT : (612) 375-3537 Joe Larson/MIS 1060 (standard disclaimer...) 700 on the Mall Mpls, Mn. 55402