|
Post by gwiz on Nov 18, 2011 13:48:18 GMT -4
...leave with out hard feelings if i am causing too much anxiety. The word is actually hilarity.
|
|
|
Post by gwiz on Nov 14, 2011 10:14:39 GMT -4
Regarding efficiency, I wouldn't expect the nozzle itself to introduce many losses. I'm thinking of losses that are inherent in that nozzle not being infinitely long. When the exhaust comes out, it still has some heat energy that wasn't converted to linear motion. Just like the rejected heat from any other heat engine, that's lost energy. True. The drop in temperature compared with the drop to absolute zero gives an idea of how much thermal rather than kinetic energy is left in the exhaust. On the other hand, the longer the nozzle, the greater the mass of the vehicle and the lower the velocity for a given kinetic energy. There is obviously going to be an optimum nozzle length. You can still compare energy input to the motor to the energy gain of the vehicle, and once again that gives very low efficiency at low vehicle speeds (energy going into exhaust speed rather than vehicle speed) and a much better result at high speed.
|
|
|
Post by gwiz on Nov 14, 2011 7:55:56 GMT -4
Can you cite your references? NACA TN 1592 These tables are for air, which is why Bob, using the actual value of gamma for the exhaust, got a different answer. The equations are in the reference and also on Bob's page. Certainly a valid topic. The efficiency of a rocket is a combination of a number of factors such as how thoroughly the propellants react, how the exhaust velocity compares with the vehicle velocity and how the pressure at the nozzle exit compares with the external air pressure, which means it can vary enormously. In general, the nozzle itself is usually not a great source of losses.
|
|
|
Post by gwiz on Nov 13, 2011 12:15:39 GMT -4
problem is no one is willing to venture a guess as to what the temperature might have been near the lm's component? Here's a good reference for you to start on: ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720018272_1972018272.pdfYou were the one who claimed the temperature was 5000 deg F. Now you say you realise that the temperature must have been lower since the gas had expanded. I suggest it is up to you to admit your initial claim was incorrect and it is also up to you to come up with the temperature. Edit to add: No use waiting for playdor. Here's the result using my air flow tables: Nozzle expansion ratio is 43, so exit Mach number is 5.70. At this Mach no. the absolute temperature ratio is 0.133, giving the exit temperature as 266 deg F. I'm aware that the exhaust gas isn't air, but I wouldn't expect a greatly different answer for another gas.
|
|
|
Post by gwiz on Nov 13, 2011 11:21:45 GMT -4
A one meter long conical descent engine skirt protruded from the bottom of the stage. Are you aware of the function of the nozzle on a rocket engine? I ask you this because you've quoted a temperature of 5000 deg F several times. That temperature is the value inside the combustion chamber. The function of the nozzle is to convert the internal energy of the gas, as indicated by high temperature and pressure, into velocity. That means that at the nozzle exit the velocity is high and the temperature and pressure are low. As others have told you, once out of the nozzle exit the exhaust expands even more so gets even cooler.
|
|
|
Post by gwiz on Nov 13, 2011 6:05:33 GMT -4
Just to make the point that engines virtually identical to the LM Ascent Stage engine were used in the upper stage of the Delta launch vehicle, and they were not test-fired before use either. www.astronautix.com/lvs/dela3000.htm
|
|
|
Post by gwiz on Nov 12, 2011 16:53:07 GMT -4
1) examine the terrain, craters are just smuges...? I don't know if you are aware, but the film has recently been compared with the best new photographic maps of that part of the moon, and shows complete agreement.
|
|
|
Post by gwiz on Nov 12, 2011 15:57:47 GMT -4
and why wrap the landing pods in mylar anyway? For much the same reason that most modern satellites have mylar wrapping: thermal control.
|
|
|
Post by gwiz on Nov 12, 2011 15:49:09 GMT -4
i would like to have a debunker debunk the real issue, and that is the times the flag moves when an astronaut moves quickly by a flag, and there is movement. And yes there is videos of this. There is only one video where the flag moves as the astronaut passes it, from Apollo 15 if I remember. It isn't clear from the video what causes the flag to move, but possible explanations other than static electricity are the astronaut actually touching the flag or the astronaut kicking up some dirt which hits the flagpole. In any case, the subsequent movement of the flag, a very slowly damped swing, is utterly unlike a flag moving in air, but much as you'd expect from a flag in a vacuum.
|
|
|
Post by gwiz on Nov 2, 2011 11:52:26 GMT -4
I think the use of L2 halo orbits for far side relays was first proposed in the late 1960s but I'm not sure. While a science satellite rather than a relay, NASA's ARTEMIS P1 became the first object to attain an L2 halo orbit on 25 August 2010.
|
|
|
Post by gwiz on Oct 31, 2011 10:54:06 GMT -4
|
|
|
Post by gwiz on Oct 16, 2011 5:41:52 GMT -4
What on earth do people do with their phones? Seeing what the traditional method for smuggling a phone into a prison involves, I'd expect the contamination level for phones inside a gaol to reach 100%.
|
|
|
Post by gwiz on Sept 17, 2011 4:52:53 GMT -4
Personally I'd like to see the Skylon fly. Is it irrationally paranoid to be nervous about any project which sounds like a portmanteau of "Skynet" and "Cylon?" Skylon predates both Skynet and Cylon.
|
|
|
Post by gwiz on Aug 29, 2011 4:57:53 GMT -4
With the upcoming GRAIL lunar mission does anyone know what kind of detail they are expecting from the cameras on board? And if they would be able to image the Apollo landers? I had a google and was unable to find any specs for them. Seeing that the camera is an educational add-on to a mission with a prime objective of mapping lunar gravity, I'd very much doubt if it was high resolution.
|
|
|
Perigee
Aug 18, 2011 6:59:55 GMT -4
Post by gwiz on Aug 18, 2011 6:59:55 GMT -4
A Google search on Chapel Bell brings up seismic experiments. I am aware of such experiments, but not that they were called Chapel Bell. What was Chapel Bell? Chapel Bell was an over-the-horizon radar system. The Saturn V was simply used as an unusual test target for the radar. It's been discussed on BAUT.
|
|