31–40 of 47 posts
Earlier quoted context omitted.
I'm having trouble recreating the poster's numbers. I'm sure it's my own ignorance, so I'd appreciate some correction. radius is 3500m velocity is 82m/s 82^2/3500 ~ 1.92 atan(1.92/9.81) ~ 0.19 or 10 degrees of bank. Where have I gone wrong?
It looks like you used 3500m as the radius when 3500m is the diameter.
Yeah. Not so much. http://www.airliners.net/forum/viewtopic.php?t=1357935#p1941...
Well that's interesting. They seem to be arguing that the bank angle is super high, causing the planes to pull massive Gs just to land or take off, and that's terrible. Even if it's true all that means is, (a) planes achieving takeoff instantly have better than stall speed in the open air and can safely get up and away from the city, (b) planes landing can come in at any angle, have infinite space to negotiate a dece…
Regarding b, wind direction is still important. Your airspeed would be constantly in flux when negotiating a landing at a bank since your angle to the wind is constantly changing. This is especially perilous at low speed near the ground due to the risk of spinning.
There may absolutely be benefits to a circular runway, but I see a lot of increased risk around inducing low altitude spins.
1. It doesn't actually solve the problem it sets out to solve (crosswind landings). To the contrary, a circular runway guarantees that if you have any wind at all then you will have a crosswind at some point in the landing. Not only that, but the apparent wind direction will be constantly shifting during the landing, making the landing even more difficult than a normal crosswind landing.
2. Flying in a circle at a low airspeed and at low altitude is absolutely the single most dangerous thing you can do in an airplane. When you are flying in a circle, the outboard wing is moving faster than the inboard wing, and so if you are flying close to stall speed the inboard wing will stall first, resulting in a spin. It is possible to recover from a spin but you have to descend in order to do it. If the spin starts at low altitude there is nowhere to descend to, so you will crash. Spins on approach to landing are one of the leading causes of fatal crashes in small general aviation aircraft.
3. Airport approach and departure procedures are designed around the fact that runways are aligned in particular directions.
How the heck can you camber the runway at the right angle to work for both a Boeing 747 landing at 160mph and a Cessna Skyhawk landing at 60mph?
My intuition tells me that a straight runway would be less burdensome on the flight crew. You set up for your approach then you can go back to dealing with the issues at hand.
Earlier quoted context omitted.
Air resistance hurts you for sure. but the prospect of not bringing your fuel with you (see the rocket equation) really saves the most. In my design I have the ship tethered by a cable and a pipe that's delivering the fuel.
Orbital velocity is about Mach 25. You would need to be going much faster than that, if your only power is applied in the atmosphere (you'd need enough additional speed to get above the atmosphere, and enough to overcome air resistance. And after the cable lets go, the the orbit will be elliptical, which means that at the end of one orbit you come right back to the launch site. So you need to bring enough fuel with y…
Earlier quoted context omitted.
Air resistance hurts you for sure. but the prospect of not bringing your fuel with you (see the rocket equation) really saves the most. In my design I have the ship tethered by a cable and a pipe that's delivering the fuel.
Orbital velocity is about Mach 25. You would need to be going much faster than that, if your only power is applied in the atmosphere (you'd need enough additional speed to get above the atmosphere, and enough to overcome air resistance. And after the cable lets go, the the orbit will be elliptical, which means that at the end of one orbit you come right back to the launch site. So you need to bring enough fuel with y…
Earlier quoted context omitted.
Air resistance hurts you for sure. but the prospect of not bringing your fuel with you (see the rocket equation) really saves the most. In my design I have the ship tethered by a cable and a pipe that's delivering the fuel.
Orbital velocity is about Mach 25. You would need to be going much faster than that, if your only power is applied in the atmosphere (you'd need enough additional speed to get above the atmosphere, and enough to overcome air resistance. And after the cable lets go, the the orbit will be elliptical, which means that at the end of one orbit you come right back to the launch site. So you need to bring enough fuel with y…
Okay only slightly related, I had an idea a long while ago for putting satellites into orbit where you just fling them? I didn't think it good for humans because of the G but for stuff. The win being that the power required is all on earth and you don't have to carry fuel with the payload. You could spin them up on a centrifuge and then let go at just the right time (and angle). I was going to mention it to Elon one…
that works well on the moon because there isn't an atmosphere to speak of but on the earth trying to accellerate to 26km/hr at sea level is both very energy intensive, and the vehicle experiences intense heating due to the atmosphere. Atmospheric drag makes this idea impractical for pretty much anything.
Earlier quoted context omitted.
Orbital velocity is about Mach 25. You would need to be going much faster than that, if your only power is applied in the atmosphere (you'd need enough additional speed to get above the atmosphere, and enough to overcome air resistance. And after the cable lets go, the the orbit will be elliptical, which means that at the end of one orbit you come right back to the launch site. So you need to bring enough fuel with y…
I don't think you could build a cable that has the tensile strength to hold a payload spinning at 27+ km/s. Even if it was made of carbon fiber I think it would have to be crazy thick and massive. Probably orders of magnitude heavier then the payload itself.