TOO MUCH EDUCATION

[BertL]

It's reasoning like this that make people believe things like the Earth is still flat. I have never been to Canada; who's to say it exists? (Note: the last article is written to demonstrate the flawed logic with this kind of reasoning based solely on "common sense". The website of the first link, sadly, is entirely serious.)

[dwight]

I think it is good that people like DAKDAK post their garbage. It makes it all the more easier for the fence-sitters to make their minds up about who is right.

[Jason Thompson]

Here's another thing for DAKDAK (should he ever bother reading this again) and others to consider:

YOU DON’T KNOW FOR SURE IF THE COMMAND MODULE WAS BIG ENOUGH OR IF THE ROCKETS, LIFE SUPPORT COMPUTER   SYSYTEM COMMUNICATIONS TECHNOLOGY SPACESUITS AND OTHER TOOLS NEEDED FOR A MANNED MISSION TO THE MOON WAS SUFFICIENT IN THE 1960’S ANY MORE THAN I DO!!

The 1960s were not that long ago, and on several boards such as this one are people who were actually around at the time, and who therefore may be expected to have first hand knowledge of what the technological state of the art was in that period. In other words, people who definitely do know more than DAKDAK, me, or any number of other people who weren't there about the capabilities of those things.

[Inanimate Carbon Rod]

There's something about DAKDAK that puts me in mind of Karl Pilkington.

[Bob B.]

7.   YOU HAVE NEVER FIGURED OUT THE PROPER TRAJECTORY FOR A MANNED MISSION TO THE MOON.

Uh, yeah.

Below are some examples of the work I've done in this area:

Circumlunar Free Return Trajectory
Hybrid Lunar Profile with LOI and TEI
Apollo 11's Translunar Trajectory

I'm also in the process of writing an article explaining and demonstrating the mathematics for calculating interplanetary trajectories.  It's not quite finished yet so I can't link to it, but it will probably go live on my web site sometime next week.  I also intend to include a section specifically about lunar transfer trajectories, though that will probably be added later.  The draft I'm currently working on stands alone without that section, so I'm not going to delay making it public.

[mako88sb]

I've never been to Australia either, but I don't automatically assume anyone who claims to have been there is lying.

Good, because I've been to Australia.  It's real.  Not like Canada.

As a Canadian, I object. Ontario is real. And Quebec and the Maritime provinces. I've never been to Western Canada though. That region is totally made up.

Oh I see. I suppose all those transfer payments we send your way are made up to! Grrr!

[gillianren]

I think it is good that people like DAKDAK post their garbage. It makes it all the more easier for the fence-sitters to make their minds up about who is right.

Well, there's that, certainly.  I've often felt that being polite and informative are your best weapons in a battle of education.  Dakdak, apparently, can be neither.

[scooter]

It's pretty obvious that Dak won't be listening to anything posted here. What a perfect display of willful ignorance.
I think he personifies many others we've seen here and elsewhere, but I've just never seen the delusion so clearly stated.

[Not Myself]

Circumlunar Free Return Trajectory

How did you work that out?  The earth is fixed and the moon is easy under the assumptions made.  For the spacecraft, I take it it was numeric integration?  Was the amount/direction of the initial burn determined by trial and error, or is there a better way to do it?

[Not Myself]

I have never been to Canada; who's to say it exists?

Already covered.  It doesn't.  Do you believe in Bielefeld too?

Circumlunar Free Return Trajectory

How did you work that out?  The earth is fixed and the moon is easy under the assumptions made.  For the spacecraft, I take it it was numeric integration?  Was the amount/direction of the initial burn determined by trial and error, or is there a better way to do it?

Just to follow up, the idea has occurred to me to write a computer program which plots out these sorts of trajectories (under simplified assumptions), for my own amusement.  So what I am wondering is, a) am I going to discover quickly that it is more blood sweat and tears than amusement, and b) with the computers we have today, is it important to take the right approach, or will any reasonable numeric integration technique do the trick with sufficient accuracy?

[Glom]

I have never been to Canada; who's to say it exists?

Already covered.  It doesn't.  Do you believe in Bielefeld too?

Circumlunar Free Return Trajectory

How did you work that out?  The earth is fixed and the moon is easy under the assumptions made.  For the spacecraft, I take it it was numeric integration?  Was the amount/direction of the initial burn determined by trial and error, or is there a better way to do it?

Just to follow up, the idea has occurred to me to write a computer program which plots out these sorts of trajectories (under simplified assumptions), for my own amusement.  So what I am wondering is, a) am I going to discover quickly that it is more blood sweat and tears than amusement, and b) with the computers we have today, is it important to take the right approach, or will any reasonable numeric integration technique do the trick with sufficient accuracy?

I'll race you! Since interplanetary trajectories were done with the patched conic back in the old days, I wonder if using a patched comic would be good for getting a starting r and v and then maybe an iteration until we arrive at the right one? The problem I see with this is that orbits are funny things and an automated solution might be difficult as small changes cause unpredictable changes to the result.

[Rob260259]

I think it is good that people like DAKDAK post their garbage. It makes it all the more easier for the fence-sitters to make their minds up about who is right.

Couldn't agree more. Besides, reading all comments here was a true joy. It was very instructive as well.
 

[Not Myself]

I'll race you! Since interplanetary trajectories were done with the patched conic back in the old days, I wonder if using a patched comic would be good for getting a starting r and v and then maybe an iteration until we arrive at the right one? The problem I see with this is that orbits are funny things and an automated solution might be difficult as small changes cause unpredictable changes to the result.

(Emphasis mine.)  If it goes like most software projects, I would expect the first few versions would produce "patched comic" results, before all the bugs are found and we start to get "patched conic" results 

Thing is, I think it wouldn't be too difficult to write an algorithm that is "correct", i.e., which converges to the truth when the discrete steps get smaller and smaller.  But the simplest, most intuitive algorithms may not be the most efficient.  So I am wondering whether the difficulty of the problem and the state of computing technology are such that it is OK to just write (almost) any correct algorithm, and the awesome power of whatever level of Pentium we're at these days will save you, or if it is still important to take the effort to make the algorithm as efficient as possible.

[Glom]

I think making a first principles simulation of the three body problem will be incredibly trivial in today's terms. You could do time steps by the millisecond and it won't take too long to run.

I've done hydrocarbon reservoir simulation do full fluid physics on 10000 block reservoir models and it took about 7 minutes per run. The three body problem is slide rule territory by comparison.

[JayUtah]

Patched conics give you reasonable starting values.  If you have accurate models of Sun, Earth, and Moon motion in your solution, integrating the state vector at 0.1 second intervals will work very nicely.  My celestial body models are harmonic equations with about 200 terms each, but that's because I use the same models for interplanetary orbits.