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Constellation Lunar Launch
tuvas
post Jun 28 2008, 07:30 PM
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Just saw this video, thought I'd hear what you all had to say about it.

http://www.space.com/php/video/player.php?...stellation-rock

It looks to be quite interesting. I must say, the computer animation is amazing too!
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ugordan
post Jun 28 2008, 07:41 PM
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Some related stuff on YouTube (be sure to click "Watch in high quality" where available):

Ares 1x-V2.1 Test Flight
Ares 1-Y_R1
Ares V launched 8 Meter Telescope Mission Concept

Excellent CGI animation, I'm especially impressed by the billowing smoke effect on the launch pad, that's pretty hard to pull off realistically.


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Airbag
post Jun 28 2008, 07:46 PM
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Fantastic video; great details such as the ulage rockets firing post-staging and the "eyeballs out" G force on TLI.

Airbag
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ugordan
post Jun 28 2008, 07:52 PM
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QUOTE (Airbag @ Jun 28 2008, 09:46 PM) *
the "eyeballs out" G force on TLI.

It's most likely not going to happen that way. The J-2X engine is efficient, but it's not going to put serious G forces onto the stack, especially right at the beginning of the TLI burn. It's an upper stage engine and having large thrust is not really crucial once you hit orbit. They'll feel it ignite, though, that's for sure.


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dvandorn
post Jun 28 2008, 08:12 PM
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Well, let's do a little back-of-the-envelope calculating, here, then.

In Carrying the Fire, Mike Collins notes the formula for acceleration G forces -- his SPS engine on Apollo 11 developed about 20,500 lbs of thrust (sorry for the Imperial units, they're what I learned all this stuff in) and when it was used to slow Columbia and Eagle into lunar orbit, it generated roughly one-fifth of a G. Collins set it up thus: 20,500 lbs of thrust is about one-fifth of the total mass of the spacecraft at ignition (something over 100,000 lbs), and so the G force of the acceleration will be about one-fifth.

So, the uprated J-2X engine generates what, about 240,000 lbs of thrust? The heaviest Apollo TLI stage massed, at ignition, something on the order of 317,000 lbs. I have no idea what the current concept is for the mass of the Constellation TLI stage at ignition, but I'd have to guess it in the range of 500,000 lbs or less.

So, at ignition, with a J-2X and a roughly 500,000 lb TLI stage, acceleration at ignition would be roughly a half a G. That would increase to something like two-thirds of a G to nearing a full G by the end of the burn, I would imagine.

It might not be quite as much of a shock as depicted in this excellent CGI animation, but still -- it's not trifling. The best analog anyone has experienced would be the Gemini flights in which the Agena main engines were ignited while docked. Those crews hung on through one-G eyeballs-out burns, plastered to their straps. And no one ever complained.

-the other Doug


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Juramike
post Jun 28 2008, 08:27 PM
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QUOTE (tuvas @ Jun 28 2008, 03:30 PM) *
Just saw this video, thought I'd hear what you all had to say about it.


Way cool!

Apollo on steroids AND a Guitar Hero soundtrack.




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David
post Jun 28 2008, 10:42 PM
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QUOTE (ugordan @ Jun 28 2008, 08:41 PM) *
Some related stuff on YouTube (be sure to click "Watch in high quality" where available):

Ares 1-Y_R1


I'm surprised that this one depicts a splashdown. I thought the intention was to land the capsule on land?
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ugordan
post Jun 28 2008, 10:51 PM
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It might be this is an outdated video or (more likely) a capsule landing isn't doable with a suborbital flight due to range safety issues. The Cape launches head east and it's nothing but sea there. More so since the SRB is meant to splash down.


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jmjawors
post Jun 29 2008, 04:06 AM
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The current revised plan is for splash-downs.

[Source]


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nprev
post Jun 29 2008, 04:44 AM
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Jeez...deja vu all over again, eh? Now I'm waiting for the stick to be deleted while they re-invent the Saturn V... rolleyes.gif


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tuvas
post Jun 29 2008, 01:49 PM
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I've heard they weren't sure which way to land it yet, on land or on water, but I could be wrong. I too was very impressed with the dust flying away from the rocket blast.
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David
post Jun 29 2008, 04:11 PM
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QUOTE (tuvas @ Jun 29 2008, 02:49 PM) *
I've heard they weren't sure which way to land it yet, on land or on water, but I could be wrong.


It looks like the designers have been flopping back and forth on this issue for a year. Here's a relatively recent article:


May 7, 2008
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ugordan
post Jun 29 2008, 11:43 PM
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I came across this article while browsing the BA forums. Apparently, the Ares I is not the only one having performance issues. Ares V original spec seems to fall short of that required to launch a heavier (than expected ?) EDS stack. There's talk of stretching the SRBs even more, to 5.5 segments and also adding an additional RS-68 engine to the core stage. Even this falls a bit short of the 75 mT payload-to-TLI requirement. When one remembers the Saturn V had a 47 mT TLI payload, one sees this is supposed to be a big booster. And no doubt an expensive (and loud!) one. Let's hope it doesn't end up being too big to handle in the end. Seems to me the SDLV architecture (or any chemical propulsion concept for that matter) is being stretched to its limits here.


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nprev
post Jun 29 2008, 11:55 PM
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Hmm. Wonder if they're starting to lean towards a clustered architecture like the Delta IV heavy...might make more sense.


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peter59
post Aug 23 2008, 12:32 PM
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Long and rough way before Ares V, literally and metaphorically.
Ares V Rocket Could Crush Kennedy's Crawlerway: No Funding to Upgrade.


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