Space Launch System - Orion

[Eric Mc]

Flooble said:

Neither could the shuttle or Starliner - Eric's comment was that man-rated vehicles have tighter criteria and this made it harder to launch them.

It’s not so much as being able to reach the moon as being able to place around 100 tonnes into earth orbit. Only a small number of boosters have ever had that capability and Artemis is the only one that will fly in (hopefully) near future.

[Eric Mc]

I thought that the climb rate was slow - compared to the Shuttle. But it was certainly very impressive.

All looking good so far. They've just fired the Service Module engine for the first time. The burn lasted for 30 seconds and seems to have gone well.

[Eric Mc]

It's about capability - not efficiency. We have needed a 100 ton launch capability ever since the Saturn V was retired. We can have this with Artemis. It's not perfect, but it exists and, for the moment, seems to be working.

[Eric Mc]

Dog Star said:

Anyway back to pictures - there do look to be some belters so I anticipate some excellent lunar views - hopefully real time moving 4K sort of stuff, which would be, I’m guessing, the first time since we got the low frame rate stuff from the lunar module window.

Have a look at the digital imagery that was sent back by the Japanese space probe Kagua in 2008 -

https://www.youtube.com/watch?v=H1KWtG66lEQ

NASA's LRO has been imaging the moon from orbit for 13 years - although chiefly stills rather than movies.

[Eric Mc]

I assume that the Shuttle launch structure needed a fair bit of refurbishment after each launch too.

Not sure how much damage the Saturn V did to its tower.

[Eric Mc]

Simpo Two said:

Wonder if that's because they use solid fuel boosters - do they burn hotter?


NB Artemis trivia here: https://edition.cnn.com/2022/08/15/world/artemis-i...

Edited by Simpo Two on Thursday 17th November 19:04

Don't know for sure but that was the first thing I thought of. Also, on ignition the solids go from nothing to instant full thrust, so there are multiple suopersonic shock waves generated in an around the pad. You can see them rippling through the exhaust smoke. It was the same with the Shuttle. I bet most of the damage comes from that.

[Eric Mc]

Leithen said:

Beati Dogu said:

They’re able to selectively vary the propellant grain in the solid boosters, so they effectively throttle back for max-Q. Then they throttle back up after, just like the main engines.

I don’t know if they do that for the launch too. The main engines take off at “100% power”, then throttle up to 109%, I believe it is on SLS. This is to avoid wrecking the pad. They did that with Shuttle too, but since those engines were meant to be reused, it had a lower full throttle. About 106% I think it was.

SLS throttles back the main engines a little for booster jettison. Then goes full send.

Once they are lit though, they can't be shut down?

They aren't actually "throttled" in the conventional sense. Once lit they will burn at the full thrust related to the amount of propellant that is being burned. The thrust varies due to the fact that the fuel is profiled in the tubes so that, as the burn progresses, the thrust goes up and down at predetermined points. There is no control over this process once the booster ignites. It happens automatically.

[Eric Mc]

Leithen said:

Eric Mc said:

They aren't actually "throttled" in the conventional sense. Once lit they will burn at the full thrust related to the amount of propellant that is being burned. The thrust varies due to the fact that the fuel is profiled in the tubes so that, as the burn progresses, the thrust goes up and down at predetermined points. There is no control over this process once the booster ignites. It happens automatically.

Thank you Eric.

They are just big fireworks - light the blue touch paper and run.

[Eric Mc]

That’s showing splashdown, not re-entry. Although it’s still wrong of course.
And I think you meant service module, not command module.

[Eric Mc]

By Apollo 13, that summed up the TV viewers atitude to the Apollo missions too. The live TV show broadcast from Apollo 13 to earth (just before the explosion that crippled the mission), wasn't taken up by any of the US TV networks.

At least nowadays those of us who want to folllow missions have lots of routes through which we can keep up to date.

[Eric Mc]

Watching the live progress on You Tube, it is interesting to see that Orion is currently 228,953 from earth and 59,700 miles from the moon. Its speed relative to earth has dropped down to a mere 589 mph. At some point quite soon, it will enter the moon's "sphere of influence" and the speed will start picking up again.

[Eric Mc]

I read it many, many years ago.

I actually prefer "The First Men in the Moon" by HG Wells - even though the science in that is far ropier than in Verne's book.

[Eric Mc]

We are beginning to get some cracking additional footage (and sound) from the various cameras that recorded the launch. This stuff sounds amazing if you have a sub-woofer -

https://www.youtube.com/watch?v=nUozQWAg0wE

[Eric Mc]

The chap leaping up and down was Tim Dodds - The Everyday Astronaut himself. He almost drowned out the rocket!

[Eric Mc]

Yes - nice to have a participant contributing.

Orion has finally started picking speed again and it is now up to 240 mph and accelerating towards the moon.

[Eric Mc]

Progress can be watched live here -

https://www.youtube.com/watch?v=8YMMCmLMVzI

[Eric Mc]

Braking burn in slightly more than an hour and a half.

[Eric Mc]

Really closing in now - only 2,500 miles from the moon.

[Eric Mc]

These are pretty good images - especially compared to the quality of the live TV from the Apollo era.

[Eric Mc]

And we are going to see the earth set over the lunar horizon - live.