So, who wants to win 1 million Euro?

[raven]

BTW everyone - I joined up because of this thread. I work in building structures, and I don't like things moving. So seeing the maths play out has been quite enlightening.

PLEASE don't tell me you're planning to hire Heiwa/Anders as a consultant!

Maybe in a Bloody Stupid Johnson fashion. If he says do it, don't.
Edit: Crikey, Ninja's! And on this forum!

[LunarOrbit]

lol I got that one in just in the nick of time.

[raven]

lol I got that one in just in the nick of time.

By Jove, you did, a matter of mere seconds!

[LunarOrbit]

BTW everyone - I joined up because of this thread. I work in building structures, and I don't like things moving. So seeing the maths play out has been quite enlightening.

Welcome aboard, Sharpeneer. I have learned a lot from these discussions too, so it makes dealing with a few hoax theorists worth while.

[Daggerstab]

Did Apollo 11 push a cushion or shockwave of air in front of it while trying to keep the trim angle right while flying up/down in the atmosphere? And only this cushion of air heats up and turns into ionized gas/plasma. Have this strange phenomenom been tested in a laboratory or air tunnel test installation? Pls provide some evidence. I have a feeling you are just making it up SF style.

Geez. This blunt body wind tunnel photograph is in every book about the history of space exploration:



The only way you could not have seen it is if you had never opened a book about space exploration.

Here's a larger version of one of those pictures:
http://www.fluids.eng.vt.edu/msc/gallery/shocks/a2375b.jpg

And here's a more modern one in color, with a really blunt projectile:
http://www.fluids.eng.vt.edu/msc/gallery/shocks/crkn.jpg

The whole gallery is really interesting: http://www.fluids.eng.vt.edu/msc/gallery/gall.htm

Anyway, we know that detached shock waves can form. We also know that air heats up adiabatically when compressed. And atmospheric re-entry has been extensively tested with rockets* and ballistic missiles before repeatedly confirmed by "proper" spacecraft.

* For example, go here and search for "entry". (Edited by LunarOrbit to fix the broken link)

[Sharpeneer]

PLEASE don't tell me you're planning to hire Heiwa/Anders as a consultant!

Err, no. There's only room for one idiot in my office, and I intend to keep that job for life.

Thanks for the welcome folks.

[ChrLz]

I agree that Bob (and Jay, and.. well, you know who you are!) deserve the lion's share of the 'prize' (which would seem to simply be the kudos of being the major sources of correct information..).

I think the current moderation is perfect, but I also think that he should be made to start answering the key unanswered questions - if any post doesn't contain at least one answer, then it should be disallowed.  Heiwa should not be banned, lest he claims that we were trying to suppress him - although that is now less likely to be an issue as:
- clearly no-one believes he has or ever had the money (unless by inheritance..)
- clearly no-one believes he is an engineer
- he has been given plenty of opportunity to post an almost uncountable number of errors
- the challenge is an obvious farce as it is not being judged by an unbiased, competent, credentialed person

On that last one, I am still waiting for Heiwa to nominate someone of his choosing, so we can see how he goes about choosing that person..

So I'll ask again - Hiewa / Anders Bjorkman, please tell us who you would accept as an adjudicator on this challenge, and why.

Also, could you supply the following information:
- the details of your MSc. please, such that it can be verified?
- the names of at least two of your 'company's current clients - strangely.. that isn't on your website.

Thanks in advance for that.

[Inanimate Carbon Rod]

[DataCable]

Since everyone else is busy pummeling Björkman with properly-crunched numbers, I'll just jump on this little nugget which (understandably, given the sheer volume of wrongness he is able to excrete) has gone unchallenged:

To get into Moon orbit you must, apart from slowing down, change course from a straight one into an elliptical/circular one around the Moon

Straight?  Straight?  You think the trip from the earth to the moon was straight?  There is no "straight" in space travel, at least not inside anything as gravitationally lumpy as a solar system.  Hey Bob, you still have that animation of a translunar flight you compiled from orbital data?

[Donnie B.]

Well, any object in an inertial frame is following a straight path -- in curved spacetime.  Oddly enough, the only time the Apollo spacecraft were NOT going straight (in that sense) were when the engines were operating.

But I'd be willing to venture a guess that Heiwa/Anders doesn't think any more highly of Einstein than he does of Newton.

[gillianren]

So now, we all see here what happens when you take one day off for a family get-together!  You miss everything.  But I have a question.  Isn't the answer to "how much fuel would it take?" "it depends on what kind of fuel"?  And isn't the kind of fuel one of the things he's gotten wrong?

[Bob B.]

... I therefore suspect that Heiwa believes the spacecraft had to gradually change attitude during the burn to keep the engine pointed in the direction of travel.

Well, it didn't. The spacecraft was aimed in a particular direction for the burn, and remained pointed in that direction for the duration of the burn.

In post #786 the question was about how much fuel was used (to produce a force) in order to just slow down a space ship to get into Moon orbit or to the speed up the space ship to get out of Moon orbit. Nobody seems to know the answer as no replies have turned up.

Another question is evidently in what direction this force is applied during the speed change maneuver. And for how long.

To get into Moon orbit you must, apart from slowing down, change course from a straight one into an elliptical/circular one around the Moon and Moon gravity will assist. Peter B suggests that during a 6 (or eight) minutes burn (30 kg/s fuel burnt) applying 97 400 N force in one particular direction suffices.

It is a complicated maneuver in 3-D. The inertia force of the space ship is applied in one direction, Moon gravity pulls in another direction (I assume the trajectorey is already curved due to Moon gravity) and then you apply a third force - the brake force - in a third, particular direction while losing 10 800 kg mass in the SM ... that you keep steady all the time? If the brake force is not in the direction of travel, it will evidently also change the direction.

There is then quite a number of factors to keep an eye on. Just how to keep the space ship stable in one - the right - direction during 6 minutes braking/turning, while you loose 10 800 kg mass (30 kg/s) is complicated. Imagine if the space ship tips over and goes away in the wrong direction ... and you have no fuel left or means to correct it.

So I am happy, Peter B, that you have pointed out that the brake force cannot be applied in the direction of travel but in another particular direction where it is held steady when the space ship changes direction and looses mass and slows down. You are a genious.

Now tell me how much fuel you need to slow down!

Sorry to burst your bubble, Heiwa, but Peter B. is correct – there is no need to keep the thrust vector constantly aligned with the velocity vector.  (I addressed this way back in post #434 but you ignored it.)  The spacecraft can be aligned with one fixed point in space and then maintained in that attitude throughout the burn.  That doesn’t mean it’s always done that way, but it usually is.

For example, suppose the spacecraft travels through an arc of 20 degrees during the course of the burn.  The thrust vector can be aligned in a direction that causes the angle between it and the velocity vector to change between –10 degrees and +10 degrees from the time of ignition to the time of cutoff.  If we break the thrust down into its components, we find that the component that’s aligned with the velocity vector is equal to the thrust times the cosine of the angle between the vectors.  In the worst case, COS(10) = 0.985.  If we integrate over the entire burn we find that 99.5% of the thrust goes into the direction we want it to.  A loss that small is tradeoff that is generally acceptable.

Of course, this also means that there is a thrust component that is perpendicular to the velocity vector, which is equal to the thrust times the sine of the angle between the vectors.  My response to this is, who cares?  It is a known quantity and can be accounted for when designing the maneuver.  Furthermore, if the angle between the vectors changes from negative to positive (such as in the example I’ve given), the sideways thrust also changes from negative to positive, thus canceling out much of its effect.

[ka9q]

But I have a question.  Isn't the answer to "how much fuel would it take?" "it depends on what kind of fuel"?

Indirectly, yes. The kind of fuel is incorporated into the effective exhaust velocity, V_e, which is equal to the specific impulse, I_sp, times the acceleration of earth gravity. (The reason for this strange use of earth gravity even by a rocket operating in deep space has to do with pitfalls in the English system of units, don't get me started).

Every propellant combination (fuel + oxidizer) has a theoretical exhaust velocity. Real engines always do a little worse  because of various losses. One of the biggest losses comes when you have to operate in the atmosphere, but that's not an issue for the Apollo spacecraft.

[Bob B.]

Isn't the answer to "how much fuel would it take?" "it depends on what kind of fuel"?  And isn't the kind of fuel one of the things he's gotten wrong?

Yes.  I believe he said the fuel was hydrazine.  In addition to hydrazine, N₂H₄, there are two derivatives of hydrazine that are also frequently used as a rocket fuel - unsymmetrical dimethyl hydrazine (UDMH) and monomethyl hydrazine (MMH).  The Apollo SPS used a fuel called Aerozine 50, which is a 50/50 mixture by mass of hydrazine and UDMH.  Straight hydrazine is actually be a better performing fuel than Aerozine 50, but it has other properties that makes it undesirable for this particular application.  If straight hydrazine were used, less of it would be required becuase of its higher specific impulse.  Specific impulse is really just thrust per unit mass of propellant.

[Bob B.]

Hey Bob, you still have that animation of a translunar flight you compiled from orbital data?

I sure do.  This one is the free return trajectory (click on it to see full size):



And in this one I show a hybrid trajectory with an orbit insertion lasting five orbits (click on it to see full size):