Question: how did they slow down in space?

[Glom]

The only way that I can come up with them slowing down in space is to reverse the module to the EXACT opposite of their flight path and fire the main thruster and travel through their exhaust.

If the spacecraft is moving at 2000 m/s relative to some frame and performs a retrograde burn (firing against its motion as you say), the exhaust will leave the spacecraft at a speed of maybe 300 m/s say, them the exhaust will have speed of 2300 m/s relative to our frame. In other words, the exhaust is travelling faster than the spacecraft and so the spacecradt does not travel through it.

[Allan F]

Actually, the exhaust runs away at about 3000 m/s relative to the spacecraft.

[Glom]

Actually, the exhaust runs away at about 3000 m/s relative to the spacecraft.

I may have gotten the figures for specific impulse confused with exhaust velocity.

[nomuse]

Either way, the exhaust moves away from the spacecraft. It would be pretty funny exhaust if it just sat there inside the engine bell.

Putting aside frames and compound vectors aside for the moment, how exactly would one run into the exhaust? For it to make it back to the spacecraft after being blasted out of the engine, it would have to, ITSELF, slow down in space.

(More, it would have to slow to a complete stop relative to the spacecraft then accelerate back towards it. Now unless the J-2 was somehow capable of throwing a gaseous curveball, I simply don't see how this could happen).

[Bryanpoprobson]

I think, you are overthinking this problem. If you were on a moving spacecraft outside the hull with a ball in your hand and you threw the ball in the direction of travel. It would move away from you, despite the velocity of the spacecraft. The same is true of the exhaust, even if it were possible for the spacecraft to be moving faster than the velocity of exhaust.
In a denser medium such as air or water there would be a problem because of back pressure, but not in a vacuum.

[nomuse]

What's funny is it even works if, for some reason, the exhaust does it's work but then hangs around moving at near-enough-the-same velocity of the spacecraft. Because if there is a velocity change on the spacecraft, then it is one that moves it away from the spent fuel. Once again, there's no way to fly through the stuff.

[ka9q]

Actually, the exhaust runs away at about 3000 m/s relative to the spacecraft.

I may have gotten the figures for specific impulse confused with exhaust velocity.

Specific impulse is exhaust velocity. The only difference is that in the US, "specific impulse" is arbitrarily expressed as the exhaust velocity divided by earth's nominal surface gravity (~9.8 m/sec²). In Europe and elsewhere, the two terms are generally equivalent.

[Peter B]

I'm really confused about all this.
I will take time to check out the links you provided.
Thank you very much.
When a person can't admit they're ever wrong, they are rendered unteachable and can't learn any more. I can admit I'm wrong but I do have to do some learning apparently.
Oh, someone just said a reverse rocket landing has been done, I would really like to see that if someone could post a link.
Thank you

Supercut of multiple Falcon 9 landings, both on land and at sea. 

As others have pointed out, the CSM would not have been flying through its own exhaust; there's no air or other medium to impede the exhaust flow.  It flies away from the spacecraft at X m/s regardless of the direction the spacecraft is facing.

Thanks for the link jfb. I hadn't previously seen the footage of the stage (around 0:43 in the video) descending from space. It's amazing to think that it's still less than a year since SpaceX managed their first successful first stage landing, and that they managed five such successful landings in seven months.

And, by the way, welcome to Apollohoax!

[Glom]

Actually, the exhaust runs away at about 3000 m/s relative to the spacecraft.

I may have gotten the figures for specific impulse confused with exhaust velocity.

Specific impulse is exhaust velocity. The only difference is that in the US, "specific impulse" is arbitrarily expressed as the exhaust velocity divided by earth's nominal surface gravity (~9.8 m/sec²). In Europe and elsewhere, the two terms are generally equivalent.

I know. Hence why the value of the figures are different.

[Dalhousie]

Don't forget the LLRV/LLTV...

Don't forget the original flying bedstead

- 25 years before Apollo 11

[bknight]

...

Don't forget the original flying bedstead

- 25 years before Apollo 11

I had never seen this one before.  Kind of makes those who believe that vertical landings were next to impossible look even more foolish(JW)

[Dalhousie]

...

Don't forget the original flying bedstead

- 25 years before Apollo 11

I had never seen this one before.  Kind of makes those who believe that vertical landings were next to impossible look even more foolish(JW)

You can see the original at the Science Museum in London

https://en.wikipedia.org/wiki/Rolls-Royce_Thrust_Measuring_Rig

[Zakalwe]

Don't forget the LLRV/LLTV...

Don't forget the original flying bedstead

- 25 years before Apollo 11

Or the Bell X-14

https://en.wikipedia.org/wiki/Bell_X-14

Or the Bell Model 65 (1954!)

[raven]

And the French SNECMA Atar Volant, as well as many others.

[Willoughby]

Thinking that the LM would pass through its own exhaust is the same thing as thinking you can shoot yourself simply by firing a bullet in the same direction as you are traveling.