So, who wants to win 1 million Euro?

[peter eldergill]

Count Zero .... Puny God....

HA!

[gillianren]

Seems about right to me, yeah.

[ka9q]

Or dedicated small rockets to settle the propellants before ignition..."ullage motors".

Right, as on the S-IVB stage. I think ullage motors were used on both versions for the first starts, with the APS (auxiliary propulsion system, essentially an RCS) used for the restart on the Saturn V version.

Another interesting approach to the problem is to use special baffles or meshes to hold the propellant in place via surface tension.

Yeah. The dynamics of liquid propellants in weightlessness were complex and mysterious enough in the 1960s that a major objective of a Saturn IB test flight, SA-203, was to study them. It was launched with no payload and less than nominal LOX so the S-IVB had plenty of LH₂ left, and then TV cameras inside the tanks watched how it behaved in weightlessness.

[JayUtah]

Right, as on the S-IVB stage. I think ullage motors were used on both versions for the first starts, with the APS (auxiliary propulsion system, essentially an RCS) used for the restart on the Saturn V version.

All the Saturn V ullage motors were made just a few miles from my house, at Thiokol.

[Noldi400]

Right. I can't think of a pressure-fed hypergolic rocket that isn't restartable, and can be fired an arbitrary number of times until its propellants are depleted. The only complication would be ensuring ullage, i.e., getting the propellants in partly filled tanks to the bottom where they can be piped off.

Or, in the case of the LM motors, until the liquid He used to pressurize the propellant gets too warm and pops the burst disk.

And speaking of neighbors, according to the local paper, the fabric for Curiosity's parachute was made just a few miles from my house.

Re: Heiwa; overall I found the three-drunken-sailors story more credible.

[ka9q]

Or, in the case of the LM motors, until the liquid He used to pressurize the propellant gets too warm and pops the burst disk.

The descent stage used it, and it was supercritical helium, that is, helium stored above its critical temperature (5.19K) and pressure (227 kPa) so that it exists in a single fluid phase that's both liquid and gas and neither. The same technique was used to store H₂ and O₂ in the Apollo Service Module.

The burst disk would pop if the engine wasn't fired by a certain time, as heat slowly soaked into the tank and raised its pressure. I am not sure, but I think that if the engine were to fire at least a certain fraction of its propellants the SHe tank would no longer necessarily pop its burst disk because of the extra tank volume into which the warming helium could expand.

[Noldi400]

Or, in the case of the LM motors, until the liquid He used to pressurize the propellant gets too warm and pops the burst disk.

The descent stage used it, and it was supercritical helium, that is, helium stored above its critical temperature (5.19K) and pressure (227 kPa) so that it exists in a single fluid phase that's both liquid and gas and neither. The same technique was used to store H₂ and O₂ in the Apollo Service Module.

The burst disk would pop if the engine wasn't fired by a certain time, as heat slowly soaked into the tank and raised its pressure. I am not sure, but I think that if the engine were to fire at least a certain fraction of its propellants the SHe tank would no longer necessarily pop its burst disk because of the extra tank volume into which the warming helium could expand.

The ascent stage, too; at least there are helium tanks in the ascent stage in the NASA LM diagrams and opening the He valves is a checklist item for LM lift-off. I can't put my finger on the reference right this second, but I'm pretty sure I remember reading that the valves were pyro operated - once open, they stayed open.

According to Jim Lovell's account in Lost Moon, AS-13 had an HE disk to rupture during the coast home, after the descent engine had been fired multiple times. Of course their circumstance was about as far from normal ops as you can get.

[Bob B.]

The spaceship kinetic energy before braking was 43574*2400²/2 = 125.4 GJ and after braking 32676*1500²/2 = 36.76 GJ, i.e. change in kinetic energy due braking was 88.64 GJ, i.e. fuel consumption was 8.13 MJ/kg.

No, Heiwa, your calculations are wrong.  You have to consider the kinetic energy of the total system, which includes both the inert mass of the spacecraft and the propellant.

I'm going to use your mass and velocity figures, but that is in no way an admission that I agree with them because I haven't looked up the figures to verified whether they are correct or not.  Furthermore, the calculation I'm about to perform is just a "back of the envelope" calculation to get us close.

I concede that the kinetic energy before the burn is 43574*2400²/2 = 125.4 GJ.  I'll also concede that the kinetic energy of the spacecraft and remaining propellant after the burn is 32676*1500²/2 = 36.76 GJ.  But you must recognize that the expelled mass also has kinetic energy, thus the total kinetic energy after the burn is that of the spacecraft plus that of the mass expelled during the burn in the form of exhaust gas.

The exhaust gas velocity relative to the spacecraft is equal to the engine specific impulse times g_o, or 314 s * 9.807 m/s² = 3079 m/s.  The exhaust is expelled in the direction of travel, therefore the true velocity of the exhaust is the velocity of the spacecraft + 3079 m/s.  Let's make it simple and assume the spacecraft velocity is the average of the initial and final velocities, i.e. (2400+1500)/2 = 1950 m/s.  We then have an exhaust velocity of 1950 + 3079 = 5029 m/s.  Therefore, the kinetic energy of the expelled mass is 10898*5029²/2 = 137.8 GJ.

We now see that the kinetic energy of the total system at the end of the burn is 36.76 + 137.8 = 174.6 GJ.  Kinetic energy was added to the system in the amount of 174.6 - 125.4 = 49.2 GJ.  This energy came from the chemical energy of the propellant that was released during combustion, first as thermal energy and then as kinetic energy as the gas was expanded in the engine nozzle.  The energy released from the propellant on a mass basis is 49.2 GJ / 10898 = 4.5 MJ/kg.  This number is in the ballpark of what should be expected from the type of propellant used.  (I've calculated that the actual change in enthalpy of the propellant is about 5.16 MJ/kg.)

Everything works out just fine.  No problems here.

[Tedward]

Well, at Oslo you have to pay with Norwegian crowns, NOK, at Stockholm with Swedish, SEK, and at Copenhagen, Danish, DKK. They do not use Euro in Scandinavia, you see. Same in China or Japan. Or North Korea! But enjoy your flight anyway. My Euros? In the bank, of course.

Which bank?  Where is the actual evidence that you have so much as a buck seventy-five?  (That's in American dollars; I leave you to do your own conversion.  Doubtless you will be just as "competent" at it as you are at everything else.)  You keep telling us to trust you, but why should we?  We know nothing more about you than what you present here, and nothing you have presented thus far is trustworthy.

. . . I am 100% certain of that, and can hardly read.

Finally!  A statement of fact from you!  You can hardly read, or else you would start acknowledging the most egregious and obvious of your errors.

If I may, not sure someone else has mentioned this (33 pages now?) but would there not be a protocol when someone offers up a reward? At least serious ones anyway. For some reason I would expect an independent authority to verify and adjudicate in such a matter? I don't expect armed guards around a pile of notes on the floor, rather a simple system whereby it can be verified.

Either way I do not think the loot is available and never will be. He does mention a cheque, wonder what material it is made from?


Edit. The replys are interesting, as always my knowledge increases.

[nomuse]

...
Either way I do not think the loot is available and never will be. He does mention a cheque, wonder what material it is made from?
...

Any one of a variety of polymerized monomers -- probably styrene and butadiene.

[ka9q]

The ascent stage, too; at least there are helium tanks in the ascent stage in the NASA LM diagrams and opening the He valves is a checklist item for LM lift-off.]

Yes,  both stages used helium to pressurize their propellant tanks. Only the descent stage used supercritical He, though it also had a gaseous He tank (not sure why). The ascent stage used gaseous He only.

The pressure supplied to the propellant tanks had to be above the combustion chamber pressure while the engines were firing, or else they'd stop. It's something like the fuel injector pump in a Diesel engine overcoming the combustion chamber pressure during the power stroke.

Small pressure-fed rockets are extremely common, but they don't scale to launcher size because of the heavy tanks required to withstand that much pressure.

I can't put my finger on the reference right this second, but I'm pretty sure I remember reading that the valves were pyro operated - once open, they stayed open.

Yes, pyro valves isolated the helium until they were fired open, once. But the helium then had to flow through pressure regulators, and these could be switched off. The pyro valves were there to minimize leakage for the first part of the mission, as helium has a nasty habit of leaking through the tiniest cracks.

[Glom]

The spaceship kinetic energy before braking was 43574*2400²/2 = 125.4 GJ and after braking 32676*1500²/2 = 36.76 GJ, i.e. change in kinetic energy due braking was 88.64 GJ, i.e. fuel consumption was 8.13 MJ/kg.

No, Heiwa, your calculations are wrong.  You have to consider the kinetic energy of the total system, which includes both the inert mass of the spacecraft and the propellant.

I'm going to use your mass and velocity figures, but that is in no way an admission that I agree with them because I haven't looked up the figures to verified whether they are correct or not.  Furthermore, the calculation I'm about to perform is just a "back of the envelope" calculation to get us close.

I concede that the kinetic energy before the burn is 43574*2400²/2 = 125.4 GJ.  I'll also concede that the kinetic energy of the spacecraft and remaining propellant after the burn is 32676*1500²/2 = 36.76 GJ.  But you must recognize that the expelled mass also has kinetic energy, thus the total kinetic energy after the burn is that of the spacecraft plus that of the mass expelled during the burn in the form of exhaust gas.

The exhaust gas velocity relative to the spacecraft is equal to the engine specific impulse times g_o, or 314 s * 9.807 m/s² = 3079 m/s.  The exhaust is expelled in the direction of travel, therefore the true velocity of the exhaust is the velocity of the spacecraft + 3079 m/s.  Let's make it simple and assume the spacecraft velocity is the average of the initial and final velocities, i.e. (2400+1500)/2 = 1950 m/s.  We then have an exhaust velocity of 1950 + 3079 = 5029 m/s.  Therefore, the kinetic energy of the expelled mass is 10898*5029²/2 = 137.8 GJ.

We now see that the kinetic energy of the total system at the end of the burn is 36.76 + 137.8 = 174.6 GJ.  Kinetic energy was added to the system in the amount of 174.6 - 125.4 = 49.2 GJ.  This energy came from the chemical energy of the propellant that was released during combustion, first as thermal energy and then as kinetic energy as the gas was expanded in the engine nozzle.  The energy released from the propellant on a mass basis is 49.2 GJ / 10898 = 4.5 MJ/kg.  This number is in the ballpark of what should be expected from the type of propellant used.  (I've calculated that the actual change in enthalpy of the propellant is about 5.16 MJ/kg.)

Everything works out just fine.  No problems here.

That was pretty much what I got.

The problem for Heiwa, aside from the fact that he has a really bad case of Dunning-Kruger, is:
1) he wants to keep things simple, so thinks it's fine to miss out energy terms in an energy balance equation, much like the Haber process works just fine without nitrogen.
2) he's comparing energy density to the wrong propellant system

[gwiz]

but the ascent stage rocket was a fire once only type, correct?

I seem to recall that on some missions the APS was fired in lunar orbit to perform part of the rendezvous maneuvers.  Of course the rendezvous procedures changed, so thus also did the maneuvers.  Many of the maneuvers where performed with the RCS, so it's possible the APS was never used, but for some reason I seem to remember that it was.  I can't keep track of all of the different engine firings without looking them up for each mission.

As fas as I can find out, the APS was fired twice on seven missions, these being Apollos 5, 9, 10, 14, 15, 16 and 17.  It was used just the once on Apollo 11 and 12 and on Apollo 13 it wasn't used at all.

[Heiwa]

I concede that the kinetic energy before the burn is 43574*2400²/2 = 125.4 GJ.  I'll also concede that the kinetic energy of the spacecraft and remaining propellant after the burn is 32676*1500²/2 = 36.76 GJ.  But you must recognize that the expelled mass also has kinetic energy, thus the total kinetic energy after the burn is that of the spacecraft plus that of the mass expelled during the burn in the form of exhaust gas.

Thanks for agreeing to the kinetic energy values of the space craft before/after the braking maneuver due to burning fuel in the rocket engine producing a brake force.
The difference in kinetic energy of the space craft before/after the braking maneuver is solely due to burning fuel aboard and causing the brake force to be applied to the space craft during the braking time.
The energy (fuel mass) used up to brake the space craft (the mass of the fuel 'burnt') is evidently not part of the space craft after braking but has been transmitted to the surrounding space through the rocket exhaust and cannot be used by the space craft. It is gone. For ever. Unless you can produce a method to recycle energy in space.

Pls return to topic So, who wants to win 1 million Euro? In order to win you have to understand basic space travel physics, e.g. that a mass of fuel transformed into a force to brake the space ship in the voyage is gone. Same applies to fuel used during travel at sea? Compare a car running out of fuel, etc, etc. 

[Andromeda]

We do understand it - better than you do, because you are still getting it wrong even in your last post.

You do not because you refuse to acknowledge the information given, let alone attempt to read or understand it yourself.  Either that or, as I said earlier, you are pretending to get it all wrong for trolling purposes (or some other reason known only to yourself).

Simple as.