So, who wants to win 1 million Euro?

[Tanalia]

Björkman has changed his page again. In green are the new additions.

(The spaceship velocities used here are absolute to the planets or Moon in question. The planets evidently rotate around themselves and orbit around the Sun at other velocities. Space travel experts suggest that I should add the velocity of the Earth/Moon orbiting the Sun plus the velocity of the Sun orbiting the Universe to the velocities given here but as I do not know the latter I just use the velocities given by NASA ... to calculate the kinetic energies involved. Just to get a feel of the situation ... as zero velocity or kinetic energy does not exist in space)

As far as I can remember, nobody here suggested such a thing. Heiwa, if this was written about the discussion here, point out the post where this suggestion was made, otherwise I'll just assume that you are lying.

Pretty sure he's referring to cjameshuff's post #266 but, as usual, completely missing the point that you don't need to take any of those velocities into account, any more than you do for a man walking on a plane or for calculating a change in velocity.

[Noldi400]

Maybe an illustration would be helpful.

Here is an excerpt from a thread titled "Spacecraft Design For Dummies" in the Orbiter Forum; OP was jedidia.

Thrust and ISP

Let's get back to how a rocket works: By expelling its own mass. There are two major characteristics to this process, thrust and ISP, which I'll try to explain to those who don't understand them yet.
Let's assume we have some anonymous spacecraft, and its rather brutish, old fashioned captain has found a group of clowns that escaped from the circus stowing away on board. Being the rather strict, and very well aware of the value of any of mass in space, he decides to throw them out the airlock.
So our Captain stands in the airlock with the first clown, and gives him a good shove with his boot, we won't mention where.
By Newtons law, this will have two effects. One is that our unhappy clown will float out the airlock with a certain velocity depending on the force of the shove the captain gave him. The other thing that happens is that the ship gets accelerated in the opposite direction by the same force. Heureka, we just made a rocket! We accelerated the ship using mass it carried along, and then expelled with force (no, the flames and the noise are not a strict part of the definition of the rocket engine, although they are usually included, and we'll soon see why).
Of course, this is a terribly inefficient rocket. Our meager clown weights a lot less than the vessel, so the force applied to it is, for all intents and purposes, unmeasurable. This won't do. If our captain wants to make some real use of his stowaways, he'll need to change tactics.
He can choose between two basic options, but both more or less mean that he will just have to kick harder: The first thing that may come to mind is to take a fatter clown! If he kicks that fat clown with more force than the one before, he may well give him the same velocity as the lighter clown earlier. This passes more force to the ship, obviously. We have generated more thrust, but until now we have only done so by increasing the force of the 'engine', as the captain could kick anything with that force, and the result on his ship would be the same!

But what would happen if the captain took a clown that weights even less than the first one, and kicks him with the same esprit he kicked the fat one? Well, the clown will fly off a lot faster than the fat one. We still have the same force applied to the ship, since the captain has kicked with the same force. But we have expended less mass to apply it! What we have actually done is improved efficiency! The lighter the clown, the less mass we need to expel with each kick, while the applied change of velocity to the vessel remains the same as long as our captain doesn't tire. The side effect of this is that the velocity of the spaced clown has increased. Which means that we increased the exhaust velocity, or, more technically, the ISP (specific impulse) of our engine.

Now of course this can't really be a solution. Our captain will very soon be tired. Wouldn't it be better if we had even smaller chunks of mass to expel, so the captain wouldn't have to strain himself so much and still reach a decent exhaust velocity? It sounds like a good Idea, so after doing something unspeakable to one of his poor stowaways, he continues to expel him out the airlock bit by bit. He kicks a lot less strongly now, so he can keep at it longer, giving every piece the same exhaust velocity as the light clown he kicked out before all at once. In the end this means that the same change of velocity will be passed to the vessel as before, while he could divide the effort into handy little kicks that don't tire him as much.
But oh hey, the whole procedure now takes much longer. Our Captain may now get double the DV from the same mass of clown as when we kicked out the really fat one... but it takes a lot more time! What we now did, is reduce the thrust of the rocket to optimize the exhaust velocity, and therefore its efficiency. We now get much more Delta-V per kg of clown, but we don't get it as fast. The ship, as a result, will accelerate much slower.
Now, wouldn't it be great if our captain could take the fat clown from the beginning, and kick him out at the same velocity as the small chunks of clown just now? Well, sure, it would be great, but the captain just doesn't have the strength. Even if he had, he might reach the point where he breaks his leg by the sheer force of his own kick.

And this is where I will end the morbid analogy and hope that you learned something apart from what not to do with clowns. Seriously, take politicians, it's ethically less questionable.
This is the basic struggle that any engine faces, and you will have to make a decision what you prefer: Efficiency or Thrust. It's not theoretically impossible to have both, but engineers don't care so much about the theoretically possible. The problem for whatever engine is the same as for the captain in our example: Expelling larger and larger amounts of mass at a high velocity requires more and more power. And in our spoilsport universe, great power comes with great heat. And great heat will break the engine sooner or later, as the responsible engineer will tell you.

Can't speak for anyone else, but this analogy was a big help to my poor non-engineer mind.

[Heiwa]

Heiwa, answer me this: those 10 898 kg of mass had kinetic energy before the burn, as you include them in the mass of the spacecraft. What do you think happened with that kinetic energy when the fuel was spent?

The Apollo 11 had, according Willy of NASA, total mass incl. fuel of 43 574 kg (or 96 062 lb) and speed 2 400 m/s when a retrograde firing of the service module, SM, P-22KS rocket engine with 97 400 N thrust for 357.5 seconds reduced the speed to 1 500 m/s at 2.52 m/s² deceleration and placed the spacecraft into an initial, elliptical-lunar orbit at about 115 000 m altitude.

During the 357.5 seconds braking the space ship travelled about 697 125 meter (for that you need a brake force 127 151 N that the SM engine could not provide!) or maybe 910 000 meter, with a brake force 97 400 N provided by the P-22KS rocket engine but then it took longer - 467 seconds. Who cares? It seems we all agree the Apollo 11 had to slow down.

Mass of Apollo 11 after this brake maneuver was 32 676 kg (or 72 038 lb) according WIlly. It means 10 898 kg of fuel was used to produce the 97 400 N thrust for 357.5 seconds.

The energy of the fuel burnt in the rocket engine evidently created the 97 400 N force to reduce the speed.

The spaceship + fuel 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 applying the force was 88.64 GJ.

That energy thus became part of the space environment outside the space craft and could not be recuperated. It is evidently still there! A cloud of burnt fuel exhaust at various velocities concentrations polluting space? 

I have to add that the asstrnuts really produced a clout burning so much fuel in so short time. I would have done it much slower over a longer time in my SF novel not to wake the passengers.

[Daggerstab]

Björkman has changed his page yet again. He's continuing to dig himself deeper with the determination of a "shock brigade" miner. Most of the changes are minor, again, only the larger ones:

The "absolute velocities" paragraph has been further extended:

The spaceship velocities used here are absolute to the planets or Moon in question. The planets evidently rotate around themselves and orbit around the Sun at other velocities. Space travel experts suggest that I should add the velocity of the Earth/Moon orbiting the Sun plus the velocity of the Sun orbiting the Universe to the velocities given here but as I do not know the latter I just use the velocities given by NASA ... to calculate the kinetic energies involved. Just to get a feel of the situation. It seems Moon travel is pretty easy as the Moon orbits the Earth almost circularily. If you depart from Earth orbit at exactly the right time to arrive at the Moon a few days later, you can visually see the Moon ahead of you a little to the side or up/down all the time and if you navigate correctly you will after 90% of the trip feel the Moon gravity attracting you and your space ship and your concern is then not to crash on the Moon but to get into orbit around the Moon at the right altitude/velocity. Of course the Sun radiation will heat up your space ship to 150°C during the trip, so increase the aircon inside not to get fried or boiled inside. If you miss the Moon, there is no way back because you cannot possibly turn around in space due to lack of fuel.

Apparently he has now decided that 150 degrees is the natural temperature of everything in sunlight, because he also applies it to the LM:

Armstrong stepped into the 150° C hot lunar surface dust at 02:56:15 UT on 21 July stating, "That's one small step for man, one giant leap for mankind". Somebody took a photo of the boot trace in the dust later. His boots didn't melt in the hot Moon dust. Aldrin followed 19 minutes later. The astronauts deployed the flag and instruments, took photographs, and collected very hot - 150° C - lunar rock and soil and dust. The astronauts traversed a total distance of about 250 meters. The visit ended at 5:11:13 UT when the astronauts returned to the LM and closed the hatch. Inside the LM it was now150° C hot. If the asstronuts filled the LM with cool air and get out of their space suits for a nap are not clear ... except that they slept for 10 hours. Then it was time to go back to the CSM!

The first two instances of "dust" used to be "sand".

Actually, the famous "boot trace" photo is a photo of another impression made specifically to be photographed. Armstrong's first steps got trampled by the subsequent activity.

And we can safely add "spacecraft temperature control" to the list of things Björkman is ignorant about. Hey, Heiwa, what do you think was the purpose of all that shiny foil on the lander?

[Noldi400]

And we can safely add "spacecraft temperature control" to the list of things Björkman is ignorant about. Hey, Heiwa, what do you think was the purpose of all that shiny foil on the lander?

Yeah, Heat Transfer and the second law of thermodynamics seems to be a concept most HBs have trouble grasping.

Evidently, in HB-Land, a steak is broiled through the moment you close the oven door.

[Zakalwe]

Björkman has changed his page yet again. He's continuing to dig himself deeper with the determination of a "shock brigade" miner.

Oh dear. And he is STILL keeping up the pretence of being an engineer?

It seems Moon travel is pretty easy as the Moon orbits the Earth almost circularily. If you depart from Earth orbit at exactly the right time to arrive at the Moon a few days later, you can visually see the Moon ahead of you a little to the side or up/down all the time and if you navigate correctly you will after 90% of the trip feel the Moon gravity attracting you and your space ship and your concern is then not to crash on the Moon but to get into orbit around the Moon at the right altitude/velocity. Of course the Sun radiation will heat up your space ship to 150°C during the trip, so increase the aircon inside not to get fried or boiled inside. If you miss the Moon, there is no way back because you cannot possibly turn around in space due to lack of fuel.[/color]

So getting to the Moon now seems to be "pretty easy". The €1M should be a piece of cake to pick up then.....

[gwiz]

Pretty sure he's referring to cjameshuff's post #266 but, as usual, completely missing the point that you don't need to take any of those velocities into account, any more than you do for a man walking on a plane or for calculating a change in velocity.

Quite.  He completely misses the point about what we're really telling him, which is essentially that you can't do an energy balance if you miss out part of the system.

[Andromeda]

I don't like Heiwa has linking directly to this thread on his "Is space travel possible?" page using the term "Apollo11Hoaxsters".



Heiwa

I never worked on Apollo, being born several years after the programme ended.  Nor am I anything to do with NASA - I have never even been to the US.  I am not a "hoaxster" - not only because that isn't a real word but because nothing I ever do or have done is anything to do with a hoax.  I am simply someone well-qualified in physics who knows that you are consistently in error.

It is also interesting that you describe us as "upset" and use several libellous phrases towards a poster you note by name.  One might even suggest you look at this: http://en.wikipedia.org/wiki/Psychological_projection

[Jason Thompson]

Björkman has changed his page yet again. He's continuing to dig himself deeper with the determination of a "shock brigade" miner. Most of the changes are minor, again, only the larger ones:

Pointless for Heiwa because he won't get any of what I am about to say, but I have a spare few minutes, so:

If you depart from Earth orbit at exactly the right time to arrive at the Moon a few days later, you can visually see the Moon ahead of you a little to the side or up/down all the time

So he still thinks you need to be able to see where you are going to get there properly? Physics doesn't apply if you can't see where you are going? Heiwa, I hold out little hope that you will read this, or even understand it, but a spacecraft will go wherever it is going regardless of which way it is facing. The only time it matters which way the spacecraft is actually pointing is when you burn the engine, because the direction in which you aply that force will determine the effect on its course.

Of course the Sun radiation will heat up your space ship to 150°C during the trip, so increase the aircon inside not to get fried or boiled inside.

Or cover the spacecraft in reflective material to reject most of the incoming solar heating and set it to a slow roll so it does not overheat on one side...

If you miss the Moon, there is no way back because you cannot possibly turn around in space due to lack of fuel.[/color]

Right, because gravity can't swing your spacecraft round the back of the moon and back to Earth. Free-return trajectories are something else impossible, are they? How do inert lumps of rock and ice manage to swing back around the Sun and back to the pouter reaches of the solar system without engines then?

Somebody took a photo of the boot trace in the dust later.

No they didn't. The boot print was made specifically by Aldrin to be photographed. It was not the first footprint on the Moon.

His boots didn't melt in the hot Moon dust.

Even if we assume the Moon dust is 150 degrees as you say, why would his boots melt in it? Ever seen those silicone cake moulds?

Inside the LM it was now150° C hot.

Is it? Why? I'm intrigued to hear your thoughts on how such heating would occur, taking into account things ike the material the LM was made from and how heat is transferred in the lunar environment.

[Jason Thompson]

Oh yes, why the obsession with Apollo 11 in particular, Heiwa? Surely you have grasped the fact that there were other Apollo missions by now?

[Zakalwe]

And we can safely add "spacecraft temperature control" to the list of things Björkman is ignorant about. Hey, Heiwa, what do you think was the purpose of all that shiny foil on the lander?

You can also add in the difference that atmospheric density has on the effectiveness of parachutes too.

It would evidently have been much better to use a little bigger parachute that decelerates the spaceship a little faster, so that absolute velocity had been say only 20 m/s in lieu of 80 m/s at 1 600 m altitude, so that, with final deceleration, say 0.125 m/s², you land at 0 speed 160 seconds later ... with the parachute. Or something like it. No need for rockets (!) that just complicate things. A well designed parachute should have done the job alone! But, sorry - the show must go on! Rockets add to the drama - that never took place.

In relation to the Mars Curiosity lander.

[cjameshuff]

Pretty sure he's referring to cjameshuff's post #266 but, as usual, completely missing the point that you don't need to take any of those velocities into account, any more than you do for a man walking on a plane or for calculating a change in velocity.

That seems to be it. And then he says that because he didn't know what they were, he...determined they were insignificant? No. Showed they were irrelevant (as they are)? Nope. He just ignored them. Nice attention to detail there, Heiwa.

Just another demonstration of how fundamentally his basic mindset differs from that of an actual engineer...

[Bob B.]

It thus took about 73 hours or 262 800 seconds to travel the distance 384 000 000 meters. Average velocity during Moon trip was only 1 460 m/s. If start velocity to get away from Earth was 11 200 m/s and arrival velocity was 2 400 m/s with a minimum velocity at about 9/10th of the distance travelled due to Earth gravity, you really wonder how space ship velocity varied during the trip to the Moon.

No need to “wonder” when one can figure it out.  The following is an example of a typical lunar free-return trajectory:

   Time          Distance       Distance       Velocity        Velocity
                 to Earth        to Moon    Earth relative  Moon relative
(hhh:mm:ss)         (km)           (km)          (m/s)           (m/s) 
 
000:00:00 (1)       6,563        388,677        10,943          11,629
004:00:00          63,723        322,544         3,292           2,871   
008:00:00         102,344        289,876         2,474           2,050   
012:00:00         133,629        264,655         2,074           1,680   
016:00:00         160,632        243,133         1,817           1,466   
020:00:00         184,660        223,822         1,630           1,328   
024:00:00         206,427        205,947         1,485           1,235   
028:00:00         226,380        189,041         1,367           1,170   
032:00:00         244,825        172,804         1,267           1,126   
036:00:00         261,980        157,024         1,181           1,095   
040:00:00         278,012        141,553         1,106           1,075   
044:00:00         293,052        126,276         1,039           1,063   
048:00:00         307,207        111,104           979           1,057   
052:00:00         320,567         95,963           925           1,057   
056:00:00         333,214         80,788           876           1,062   
060:00:00         345,227         65,506           832           1,073   
064:00:00         356,694         50,026           794           1,093   
068:00:00         367,738         34,191           764           1,134   
072:00:00         378,602         17,635           760           1,248   
075:32:51 (2)     387,587          3,184           998           2,021
076:00:00         387,045          4,086           933           1,845   
080:00:00         376,208         21,483           752           1,207   
084:00:00         365,388         37,818           766           1,122   
088:00:00         354,309         53,551           798           1,087   
092:00:00         342,772         68,975           838           1,069   
096:00:00         330,668         84,222           883           1,060   
100:00:00         317,911         99,379           933           1,056   
104:00:00         304,423        114,513           989           1,057   
108:00:00         290,123        129,691         1,050           1,064   
112:00:00         274,916        144,989         1,118           1,078   
116:00:00         258,691        160,499         1,196           1,100   
120:00:00         241,313        176,340         1,284           1,132   
124:00:00         222,605        192,672         1,387           1,180   
128:00:00         202,334        209,717         1,510           1,249   
132:00:00         180,173        227,802         1,662           1,349   
136:00:00         155,635        247,436         1,859           1,498   
140:00:00         127,923        269,484         2,136           1,734   
144:00:00          95,528        295,676         2,583           2,154   
148:00:00          54,631        330,780         3,594           3,183   
151:10:03 (3)       6,500        387,407        10,998          11,595
 
(1)  Translunar Injection
(2)  Pericynthion
(3)  Entry Interface

(edit)  One more thing, Apollo's starting velocity was not 11,200 m/s.  That number is the approximate escape velocity from the surface of Earth, which is not applicable.  (1) escape velocity from low earth orbit is only about 11,000 m/s, and (2) Apollo did not escape, as it only needed to get to the Moon.

[sts60]

A sea going ship, engine of which via the propeller applies a force F to the ship, proceeds at constant speed, say x knots, while the environment (water/air/friction/collisions with atoms) applies a force -F to the ship = there is balance.

Exactly.  So why would you expect a spacecraft, subject to a nearly constant gravitational force, to stop falling?  Because that is exactly what you proposed in your reply #663. 

Imagine that - you slow down from 9 000 m/s to 100 m/s just by colliding with atoms. But why don't you slow down to 0 m/s by colliding with atoms? Let me ask a stupid question or two? Why do you need a parachute at the end? What is wrong with colliding with atoms to the end?

You actually proposed that a falling object would stop falling due to air friction.  That is one reason people are asking whether you are serious or simply trolling.

If you ran out of fuel and the engine applies force F=0 to the ship, the ship slows down until the speed is 0 knots, when all forces acting on the ship including atom colliding with it add upp to 0.

Fine.  But in case you hadn't noticed, a falling object does not run out of gravity.

Now, I ask you again to address the serious problems with your claims I brought to your attention in reply #558:

1. You are offering money you don't have, for a challenge you have defined poorly and has no proper adjudication.

2. Your primary calculation is completely wrong because you don't understand energy balances.  Your errors have been explained to you in excruciating detail, yet you refuse to acknowledge them.

3. You have no idea what you are talking about, and no apparent interest or ability in relieving your own ignorance.

In light of these issues, I ask again - do you have any intention of actually learning anything at all, or are you just trolling?

I will continue to press these issues until you address them in a realistic manner.  You may ignore them, but you cannot run away from them.

[LunarOrbit]

Heiwa, answer me this: those 10 898 kg of mass had kinetic energy before the burn, as you include them in the mass of the spacecraft. What do you think happened with that kinetic energy when the fuel was spent?

The Apollo 11 had, according Willy of NASA...

I have to add that the asstrnuts...

I will not allow any more of your posts that denigrate George Low or the astronauts. They have earned some respect. I would suggest that you start acting your age instead of your shoe size.

The post you made after the one I quoted above was not allowed because in addition to calling George Low "Willy" you also told someone they were being off topic and insulted their intelligence. When are you going to realize that you're wasting your time writing posts that you know I won't allow?