|
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Horizontal take off/landing
|
#2
|
|||
|
|||
Horizontal take off/landing
On 10/24/15 6:37 AM, Fred J. McCall wrote :
JF Mezei wrote: But on mars, what if you did re-entry over say 5 days with a vehicle that loses orbital speed but maintains altitude due to wings generating lift ? Couldn't you arrange it so that before each drop in altitude, you wait to lose enough speed/energy so plane can glide safely at the lower altitude/air density ? (aka, not burn up, and not break up) No, you can't. Physics - get some. Nothing in physics says it can't be done. Getting the vehicle to be sufficiently aerodynamic for that would be hum!, let's say a challenge. But that is an engineering challenge, not physics. So basically, you are right it can't be done. Alain Fournier |
#3
|
|||
|
|||
Horizontal take off/landing
On 10/24/15 8:47 AM, Fred J. McCall wrote :
Alain Fournier wrote: On 10/24/15 6:37 AM, Fred J. McCall wrote : JF Mezei wrote: But on mars, what if you did re-entry over say 5 days with a vehicle that loses orbital speed but maintains altitude due to wings generating lift ? Couldn't you arrange it so that before each drop in altitude, you wait to lose enough speed/energy so plane can glide safely at the lower altitude/air density ? (aka, not burn up, and not break up) No, you can't. Physics - get some. Nothing in physics says it can't be done. Wrong. If you disagree, run the numbers and show your work. Your the one making a claim, your the one who should run the numbers if you wish so. If you don't want to do it but still want to convince that physics says it can't be done, you should at least say which law of physics you think would be violated. As I already said. I don't think it can be done. Alain Fournier |
#4
|
|||
|
|||
Horizontal take off/landing
On 10/24/15 9:03 PM, Fred J. McCall wrote :
Alain Fournier wrote: On 10/24/15 8:47 AM, Fred J. McCall wrote : Alain Fournier wrote: On 10/24/15 6:37 AM, Fred J. McCall wrote : JF Mezei wrote: But on mars, what if you did re-entry over say 5 days with a vehicle that loses orbital speed but maintains altitude due to wings generating lift ? Couldn't you arrange it so that before each drop in altitude, you wait to lose enough speed/energy so plane can glide safely at the lower altitude/air density ? (aka, not burn up, and not break up) No, you can't. Physics - get some. Nothing in physics says it can't be done. Wrong. If you disagree, run the numbers and show your work. Your the one making a claim, your the one who should run the numbers if you wish so. "You're". Thank you. I appreciate when someone helps me improve my English. Prove God doesn't exist. That's what you're asking me to do. No. You seem to say that doing so violates some law of physics. If so, you could say which one. It is possible to prove that something is impossible to do because of laws of physics. I don't think this is the case here. I can come up with any number of configurations that DON'T work. The trick is to come up with one that does. No one has been able to do that. So if you disagree that any configuration that purports to work must violate one or more laws of physics (built of unobtainium, powered by handwavium), you need to show a configuration that works that doesn't violate any of those laws. If you don't want to do it but still want to convince that physics says it can't be done, you should at least say which law of physics you think would be violated. As I already said. I don't think it can be done. Why don't you think it can be done? Too complicated. But it doesn't violate any laws of physics. Alain Fournier |
#5
|
|||
|
|||
Horizontal take off/landing
On 10/25/15 4:12 AM, JF Mezei wrote :
On 2015-10-25 02:58, Fred J. McCall wrote: Handwavium is not a convincing argument. Run the numbers... That is something NASA or JPL have expertise to do. Not me. however, what i am saying is that the "no, can't be done" comes from current experience with re-entry which has always been ballistic. One big de-orbit burn causes vehicle to drop into elliptical orbit with perigee low enough for vehicle to hit dense atmosphere at still orbital speed. Entry into atmosphere is as a ballistic object with aerodynamics playing a small part to slow descent rate. And in the case of Apollo, just come in extra fast and aim for the right atmosphere density to capture you and slow you down, but not destroy you/burn you. Obviously, in those scenarios, a "flying" vehicle cannot survive this quick descent at orbital speed into dense atmosphere. It would break up before it has a chance to burn up. But what if you had no significant de-orbit burn, remain circular orbit, and simply let drag in thin atmosphere slow you down, and use the wings to maintain altitude until you are close to stalling at that altitude and then drop at lower altitude where wings once again maintain altitude until you bleed enough speed to drop again ? The goal here is to never drop to an altitude at a speed that you can't survive. And you can use the wings to stay at survivable altitude until ready to drop. Do you agree that a B787 can fly at mach 0.84 at 30k feet ? Yes. Do you agree that a B787 would survive at 25,000km/h at 400km altitude (ISS orbit) ? There would be insufficient drag to cause the plane to break up. Yes. As soon as the 787 would drop low enough to start to feel a bit of drag, do you agree that such drag at very thin atmosphere but high speed could exert forces well within the plane's structural capabilities ? Do you agree that the wings would generate some lift at that point ? (not much, but just enough to keep altitude which would otherwise decay slowly due to orbital speed going down bit by bit). Would you not agree that for such a plane, one could devise a table of maximum speed for each altitude where the plane would neither break up nor burn up ? Certainly not for a 787. I don't think you understand the difficulty of generating lift at very high speeds and in very thin atmosphere. You will generate more heat than lift, so you will burn through your wings. You will also likely generate enough drag to bring you down into denser parts of the atmosphere too quickly. When you are going 90% of speed needed to maintain orbit at altitude x, the wings only need to generate a small amount of lift to keep plane at that altitude since the orbital speed does most of that work. For normal scenarios, that small amount of lift needs to be generated in an ionised gas because the very high speeds generate so much heat. Not generating too much drag when you are ionizing the gas around you is, to put it mildly, challenging. Alain Fournier |
#6
|
|||
|
|||
Horizontal take off/landing
|
#7
|
|||
|
|||
Horizontal take off/landing
|
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
cause taps in favour of the horizontal snake | [email protected] | Amateur Astronomy | 0 | August 22nd 07 09:32 AM |
horizontal jet into superintendent | Ratana[_2_] | Amateur Astronomy | 0 | August 15th 07 12:34 AM |
Horizontal and Vertical Scratches on Enceladus | PaulCsouls | Amateur Astronomy | 8 | March 25th 05 03:58 PM |
Vertical-horizontal landing on Mars.... | dave schneider | History | 5 | July 2nd 04 07:57 PM |
Horizontal and Vertical Translation of Functions | Venona Wickstrom | Misc | 1 | April 1st 04 12:48 PM |