-
#80
by
Star One
on 27 Jan, 2014 15:11
-
Either way if there is the addition of two SRBs is there any knock on as flight safety checks are concerned? I would think the less additional items on the Atlas V manned flights the better.
-
#81
by
BrightLight
on 27 Jan, 2014 15:33
-
So why does this need the 522 configuration yet DC can use the no doubt cheaper 402 configuration?
Do we know that CST-100 will use the 522? How do we know it's not the 422?
No, I don't know if the LV is a 522 - in fact, I have no clear definitions other than Atlas V what configuration the CST-100 will use?
-
#82
by
Zed_Noir
on 27 Jan, 2014 15:36
-
So why does this need the 522 configuration yet DC can use the no doubt cheaper 402 configuration?
Don't be to sure about the DC using the 402 configuration. Until we get liftoff mass of the entire DC stack. Also ULA might be unwilling to developed both the 4X2 and 5X2 versions of the AV.
-
#83
by
BrightLight
on 27 Jan, 2014 15:40
-
The web is full of pictures of the CSt-100 with and without SRB's on the Atlas V LV.
Is there a publication/article etc defining the LV?
the best I have is the FISO report in February 2013:
http://spirit.as.utexas.edu/~fiso/telecon/Reiley_2-6-13/Reiley_2-6-13.pptxthe pictures show two SRB's - but this is hardly definitive.
Just for reference, I found from another web site that the difference between a 402 and a 522 configurations was about $5 million.
-
#84
by
arachnitect
on 27 Jan, 2014 18:04
-
The capsule will launch on a version of the Atlas 5 known as the 422 model - with a two-engine Centaur and two solid rocket boosters - in the launcher's catalog of configurations tailored to the size and destination of the payload for each launch, according to a Boeing spokesperson.
I wouldn't have found that if I hadn't known what to look for, so thanks to Oli for spotting the second SRB. You win internet points Oli.
Don't know why people think this is a 500 series: the Centaur is clearly not encapsulated.
Also don't know why people think this hurts CST. They already needed at least 1 SRB, so adding another doesn't change much (a few $). If DC has mass growth they'll probably end up doing the same thing.
-
#85
by
Lars_J
on 27 Jan, 2014 18:16
-
Exactly. The image does NOT show a 500 series Atlas V. It is a non-encapsulated Centaur stage. I'm not sure what it will be called, since it has no fairing - But it is certainly closer to a 422 than a 522 model.
-
#86
by
Elmar Moelzer
on 27 Jan, 2014 18:29
-
Also don't know why people think this hurts CST. They already needed at least 1 SRB, so adding another doesn't change much (a few $). If DC has mass growth they'll probably end up doing the same thing.
DC is still supposed to use the 402, from all that is currently known. I was not aware that the CST was originally supposed to use the 412. I thought it was going to be the 402 just like the DC.
-
#87
by
BrightLight
on 27 Jan, 2014 18:35
-
Also don't know why people think this hurts CST. They already needed at least 1 SRB, so adding another doesn't change much (a few $). If DC has mass growth they'll probably end up doing the same thing.
DC is still supposed to use the 402, from all that is currently known. I was not aware that the CST was originally supposed to use the 412. I thought it was going to be the 402 just like the DC.
Right - my question still stands, does the addition of the SRB's (only about $5 million, not that much considering) change the reliability of the Atlas V.
-
#88
by
Robotbeat
on 27 Jan, 2014 18:44
-
Also don't know why people think this hurts CST. They already needed at least 1 SRB, so adding another doesn't change much (a few $). If DC has mass growth they'll probably end up doing the same thing.
DC is still supposed to use the 402, from all that is currently known. I was not aware that the CST was originally supposed to use the 412. I thought it was going to be the 402 just like the DC.
Right - my question still stands, does the addition of the SRB's (only about $5 million, not that much considering) change the reliability of the Atlas V.
Well, it doesn't /improve/ the reliability.
-
#89
by
newpylong
on 27 Jan, 2014 19:01
-
I've seen illustrations of everything from 402 to 422, so who knows what it will end up being. Too much speculation. It definitely is not a 5xx though.
-
#90
by
Lurker Steve
on 27 Jan, 2014 19:17
-
Also don't know why people think this hurts CST. They already needed at least 1 SRB, so adding another doesn't change much (a few $). If DC has mass growth they'll probably end up doing the same thing.
DC is still supposed to use the 402, from all that is currently known. I was not aware that the CST was originally supposed to use the 412. I thought it was going to be the 402 just like the DC.
Right - my question still stands, does the addition of the SRB's (only about $5 million, not that much considering) change the reliability of the Atlas V.
Well, it doesn't /improve/ the reliability.
It might improve the reliability of the overall system. since there is spare thrust in the first stage.
As long as they already had 1 solid, I don't see adding a second solid making it any less safe.
The 40x is definitely the most common / flown Atlas configuration, but from Ed Kyle's launch log it appears that the 4/521 configuration has flown 4 times while the 411 configuration has only flown twice. Of course, there are plenty of 3 and 5 SRB launches as well. The only "partial" failure Ed has ever logged with Atlas is when the Centaur shut down a few seconds early, causing the sat to need to put itself into the proper orbit.
-
#91
by
Lars_J
on 27 Jan, 2014 19:23
-
It might improve the reliability of the overall system. since there is spare thrust in the first stage.
As long as they already had 1 solid, I don't see adding a second solid making it any less safe.
Statistics. That's why. You are adding a possible failure point.
How does that spare thrust help you? There is no scenario where a first stage engine out (or booster out) is recoverable.
Atlas V doesn't launch with more SRBs than needed.
-
#92
by
arachnitect
on 27 Jan, 2014 19:33
-
It might improve the reliability of the overall system. since there is spare thrust in the first stage.
As long as they already had 1 solid, I don't see adding a second solid making it any less safe.
Statistics. That's why. You are adding a possible failure point.
How does that spare thrust help you? There is no scenario where a first stage engine out (or booster out) is recoverable.
Atlas V doesn't launch with more SRBs than needed.
Yes it adds risk to the booster, but the difference is quite manageable. Sure an SRM failure doomed a Delta II once, but how many SRMs flew without incident on Delta II alone? It's a non issue.
It improves reliability by increasing your mass margin on the spacecraft (can use heavier components, add redundancy, no need to mess around with composites). Also CST doesn't have to use its LAS to get into orbit like DC does.
-
#93
by
Robotbeat
on 27 Jan, 2014 20:05
-
...adding another SRB doesn't improve reliability compared to a similar vehicle launched without one. How is this really in question?
I agree it probably has negligible effect on reliability, though. Atlas V is one of the most reliable launch vehicles on record.
-
#94
by
edkyle99
on 27 Jan, 2014 20:22
-
...adding another SRB doesn't improve reliability compared to a similar vehicle launched without one. How is this really in question?
I agree it probably has negligible effect on reliability, though. Atlas V is one of the most reliable launch vehicles on record.
I wonder which has larger, albeit small incremental, reduction effect on reliability - one extra solid motor or one extra RL10? My bet would be RL10.
- Ed Kyle
-
#95
by
Robotbeat
on 27 Jan, 2014 20:26
-
...adding another SRB doesn't improve reliability compared to a similar vehicle launched without one. How is this really in question?
I agree it probably has negligible effect on reliability, though. Atlas V is one of the most reliable launch vehicles on record.
I wonder which has larger, albeit small incremental, reduction effect on reliability - one extra solid motor or one extra RL10? My bet would be RL10.
- Ed Kyle
...I think I agree. Especially since the RL-10 is started on-orbit (not during first-stage hold-down where it can be aborted intact in case of early problem being detected).
-
#96
by
joek
on 27 Jan, 2014 20:30
-
The wind tunnel images for both
CST-100 and
Dream Chaser (images attached) show an Atlas 4xx; no SRB shown but may be on other side. Edit: presumably that's a 4x2 as both CST-100 and DC have stated DEC is required.
-
#97
by
edkyle99
on 27 Jan, 2014 20:50
-
The wind tunnel images for both CST-100 and Dream Chaser (images attached) show an Atlas 4xx; no SRB shown but may be on other side. Edit: presumably that's a 4x2 as both CST-100 and DC have stated DEC is required.
Keep in mind that these wind tunnel tests likely run through a series of vehicle configurations to mimic the range of flight conditions. These images might just be showing the set up to test post solid separation conditions, for example.
- Ed Kyle
-
#98
by
Jim
on 27 Jan, 2014 23:31
-
It improves reliability by increasing your mass margin on the spacecraft (can use heavier components, add redundancy, no need to mess around with composites). Also CST doesn't have to use its LAS to get into orbit like DC does.
You are mixing apples and oranges.
1. The launch vehicle reliability is lowered
2. And you can't say it increases spacecraft reliability. It doesn't matter if the spacecraft doesn't make into orbit.
-
#99
by
arachnitect
on 28 Jan, 2014 00:56
-
It improves reliability by increasing your mass margin on the spacecraft (can use heavier components, add redundancy, no need to mess around with composites). Also CST doesn't have to use its LAS to get into orbit like DC does.
You are mixing apples and oranges.
1. The launch vehicle reliability is lowered
2. And you can't say it increases spacecraft reliability. It doesn't matter if the spacecraft doesn't make into orbit.
Fair enough.