TheSonntag From Germany, joined Jun 2005, 2377 posts, RR: 17 Posted (1 month 4 days 18 hours ago) and read 1962 times:
It seems this did not come up here so far, in any case the Ares V design was changed to become more powerful and larger. The plans suggest now that it is to have even larger SRBs and 6 instead of 5 RS-68 engines, and the Size is to become 115 metres. The reasons lie in shortcomings of the Ares I.
I know this does not really make the Ares V more likely to be built, but merely shows what a mess the Ares I is, but, hey, I WANT to see this rocket, its lauch would be perfect.
TheSonntag From Germany, joined Jun 2005, 2377 posts, RR: 17 Reply 2, posted (1 month 4 days 14 hours ago) and read 1918 times:
Quoting N328KF (Reply 1): Ares I is a joke. What fool decided that solid rockets were a good idea for manned boosters? That thing's a damn firecracker...
It certainly is the most ugly looking manned rocket ever made. Nothing wrong with that, as form follows function, but it even looks delicate from my untrained view.
Analog From United States, joined Jul 2006, 1900 posts, RR: 0 Reply 3, posted (1 month 4 days 14 hours ago) and read 1906 times:
Quoting N328KF (Reply 1): Ares I is a joke. What fool decided that solid rockets were a good idea for manned boosters? That thing's a damn firecracker...
Well the Space Shuttle uses two firecrackers. 1 failure in 242 uses (121 launches, 2 solid rockets each, 1 failure). That's not bad for a rocket system.
DfwRevolution From United States, joined Mar 2004, 7511 posts, RR: 53 Reply 4, posted (1 month 4 days 11 hours ago) and read 1859 times:
Quoting N328KF (Reply 1): Ares I is a joke. What fool decided that solid rockets were a good idea for manned boosters? That thing's a damn firecracker...
There is no more fundamental risk between launching a manned vehicle on a solid rocket versus a liquid rocket. There's just a whole lot of problems with this particular solid rocket (Ares I) that might be better solved using a liquid first stage or a solid/liquid combination.
Thorny From United States, joined Jul 2005, 1339 posts, RR: 10 Reply 5, posted (1 month 4 days 10 hours ago) and read 1828 times:
Quoting N328KF (Reply 1): Ares I is a joke. What fool decided that solid rockets were a good idea for manned boosters? That thing's a damn firecracker...
That may be true, but Ares I's performance problems are essentially tied to the decision to abandon the Space Shuttle Main Engine as the upper stage powerplant. That cost the vehicle 200,000+ lbs. of thrust and a few dozen seconds of ISp where it needed it the most. Since the decision to go with J-2S (and then J-2X) the SRB grew from four segments to five, and now might inherit Ares V's 5 1/2 segment design. It will be so long, they might as well name it the Javelin.
NASA needs to pull the plug on Ares I as soon as possible. Sure, all launch vehicles have gone through teething problems (Saturn V's second stage was a real bear) but there are alternatives essentially available off the shelf now, or at most requiring 1/2 the development time and costs to field. Why is NASA wasting so much effort on this dog of a rocket? To save Ares V, which itself is turning into an unaffordable behemoth?
Pull the plug, NASA. Change the architecture from 1 1/2 launches to a full-fledged 2 (which it really is anyway) and use Delta or Atlas as the basis of Ares I (call it Ares II to save face) at least for the first stage, perhaps a smaller version of the Ares I Upper Stage on top, using the earlier/easier J-2S engine instead of the costly and unproven J-2X.
Or go the DIRECT/Jupiter direction, NASA. Call them Ares III and Ares IV if you want to... they started out as NASA NLS proposals anyway, and it won't be the first time rockets skipped numbers in their designation series (no Saturns II, III, and IV, or Atlas IV was ever built, remember.) The public won't really notice, and all Congress is worried about is jobs, and all the alternatives still employ a lot of Shuttle people.
TheSonntag From Germany, joined Jun 2005, 2377 posts, RR: 17 Reply 8, posted (1 month 4 days 8 hours ago) and read 1800 times:
Quoting Moo (Reply 6): Solid rockets can't be shut off, liquid rockets can be - the degree of control is much greater.
And while the same was true for shuttle, its SRBs at least could have been jettisoned, although I am not sure which consequences this would have had for Shuttle in early stages.
I mean, if we look at the current situation, the Orion capsule and its safety system can also be put on another rocket system. So this is no wasted use of money. Scrapping Ares I now would still be relatively cheap.
I must admit I lack the insightful knowledge on further details of the Ares system, but to me it seems that the concept of Ares I itself is pretty flawed from the beginning. If problems occur at a later stage, those can regularly be overcome, but if the concept itself is flawed, it is a very bad start.
In the end, I do not care how we get back on the moon, but this newly proposed Ares V will be extremely expensive, everybody can see that at once. Therefore its use beyond its moon role is pretty limited, even if Nasa indicates its use for "beyond" is already taken into consideration. Somehow I think we would be better off with some medium scale rockets with more applications.
Thorny From United States, joined Jul 2005, 1339 posts, RR: 10 Reply 9, posted (1 month 4 days 7 hours ago) and read 1787 times:
Quoting N328KF (Reply 7): This is exactly my point. SRBs are great for ICBMs or satellites,
They're not good for satellites, either. Vibration levels are much worse, although its mitigated somewhat on Shuttle and Ariane V by the big liquid tank between the boosters. This would be true with a DIRECT type launcher, too.
Quoting N328KF (Reply 7): but Ares I is a recipe for death.
No, it isn't. The Thiokol/ATK Solid Rocket Booster actually has a better safety record than most liquids. (1 failure in 246 firings, and that 1 was in extreme conditions against the advice of the SRB engineering team.)
Quoting TheSonntag (Reply 8): And while the same was true for shuttle, its SRBs at least could have been jettisoned,
Not while they were firing... they'll race ahead and incinerate the Orbiter/ET if the stack somehow survives the seperation (which will be violent). Shutting down the SRBs in flight is theoretically possible (blowing off the nose cap to reduce chamber pressure to zero) but the stack wouldn't survive that, either, so the option was dropped early in development (you can still find some pictures of Titan IIIs with thrust-termination covers on the tops of the solids)
Quoting TheSonntag (Reply 8): I mean, if we look at the current situation, the Orion capsule and its safety system can also be put on another rocket system. So this is no wasted use of money. Scrapping Ares I now would still be relatively cheap.
And the J-2X engine can still be used for upper stage of Ares V or whatever replaces it if we change the architecture. We'll still need an Earth Departure Stage of some sort.
DfwRevolution From United States, joined Mar 2004, 7511 posts, RR: 53 Reply 10, posted (1 month 4 days 7 hours ago) and read 1774 times:
Quoting Moo (Reply 6): Solid rockets can't be shut off, liquid rockets can be - the degree of control is much greater.
Quoting N328KF (Reply 7): This is exactly my point. SRBs are great for ICBMs or satellites, but Ares I is a recipe for death.
Solid rocket motors can be "shut off" using range safety systems in which shaped explosives rip the casings open, effectively reducing thrust to zero. Any new manned vehicles are going to require a launch escape system and the design requirements to escape a solid vehicle are no more challenging than escaping the blast wave of a failed liquid stage.
Ares I is not a recipe for death. It's just a terrible value to the taxpayers.
Connies4ever From Canada, joined Feb 2006, 1107 posts, RR: 1 Reply 11, posted (1 month 4 days 5 hours ago) and read 1743 times:
Quoting Thorny (Reply 5): That may be true, but Ares I's performance problems are essentially tied to the decision to abandon the Space Shuttle Main Engine as the upper stage powerplant. That cost the vehicle 200,000+ lbs. of thrust and a few dozen seconds of ISp where it needed it the most. Since the decision to go with J-2S (and then J-2X) the SRB grew from four segments to five, and now might inherit Ares V's 5 1/2 segment design. It will be so long, they might as well name it the Javelin.
NASA needs to pull the plug on Ares I as soon as possible. Sure, all launch vehicles have gone through teething problems (Saturn V's second stage was a real bear) but there are alternatives essentially available off the shelf now, or at most requiring 1/2 the development time and costs to field. Why is NASA wasting so much effort on this dog of a rocket? To save Ares V, which itself is turning into an unaffordable behemoth?
Pull the plug, NASA. Change the architecture from 1 1/2 launches to a full-fledged 2 (which it really is anyway) and use Delta or Atlas as the basis of Ares I (call it Ares II to save face) at least for the first stage, perhaps a smaller version of the Ares I Upper Stage on top, using the earlier/easier J-2S engine instead of the costly and unproven J-2X.
Or go the DIRECT/Jupiter direction, NASA. Call them Ares III and Ares IV if you want to... they started out as NASA NLS proposals anyway, and it won't be the first time rockets skipped numbers in their designation series (no Saturns II, III, and IV, or Atlas IV was ever built, remember.) The public won't really notice, and all Congress is worried about is jobs, and all the alternatives still employ a lot of Shuttle people.
Could not agree more. With such a high aspect ratio on the solid booster, is there any risk that flex in the structure will cause gaps in the solid fuel ? That could/would be catastrophic, I think.
The decision to back away from the SSME to me is unfathomable. So now Ares I is a seriously underperforming booster. Woo-hoo.
Quoting Thorny (Reply 9): Not while they were firing... they'll race ahead and incinerate the Orbiter/ET if the stack somehow survives the seperation (which will be violent). Shutting down the SRBs in flight is theoretically possible (blowing off the nose cap to reduce chamber pressure to zero) but the stack wouldn't survive that, either, so the option was dropped early in development (you can still find some pictures of Titan IIIs with thrust-termination covers on the tops of the solids)
Seem to recall reading (sorry, I have no link) that if the crew tried to bail on the SRBs while they were firing, the orbiter would pivot back on the aft attach points, wings would come off, and then what's left (if not incinerated as indicated by Thorny) would do essentially what the crew cabin did on -51L. Same conclusion.
DfwRevolution From United States, joined Mar 2004, 7511 posts, RR: 53 Reply 12, posted (1 month 4 days 5 hours ago) and read 1740 times:
Quoting Connies4ever (Reply 11): The decision to back away from the SSME to me is unfathomable.
The SSME delivers amazing performance but it is on hell of a complicated engine. The start-up sequence in particular was a major PITA to master. Building a variant that could be air-started and be manufactured cheap enough to throw away each flight was apparently too much to ask.
What is unfathomable IMO is that they couldn't see that coming sooner, and that they stuck with the Ares I configuration when so much of the performance depended on the SSME.
Nomadd22 From United States, joined Feb 2008, 263 posts, RR: 0 Reply 13, posted (1 month 4 days 3 hours ago) and read 1714 times:
I'm pretty sure that the one booster failure everybody refers to wouldn't have been that serious on the Ares I, although it caused the destruction of Challenger.
I'm also pretty sure that a solid rocket booster isn't likely to blow up like a bomb, and the abort rocket on Ares will be powerful enough to separate the capsule at any stage of the flight if something goes wrong. Liquid fuel rockets are a lot more complex with a lot more things to go wrong. Saying that they're safer because you can shut them down is simplistic and ignores the many catastrophic failures that could occur where the ability to shut down the engine wouldn't be of any benefit.
TheSonntag From Germany, joined Jun 2005, 2377 posts, RR: 17 Reply 14, posted (1 month 4 days 2 hours ago) and read 1709 times:
Since the Space Shuttle was the first man-rated rocket with solid boosters, I think it is fair to say that enough experience could be gathered in those Shuttle flights that they can be considered safe enough. The SRB failure in the Challenger launch would not have caused any problem in an Ares-I style rocket.
This is not my problem with the Ares-I, my problem is that it is ugly (irrelevant for its purpose), it looks unstable from the outside already (irrelevant if engineers know how to do it), and that it obviously falls short of what it is intended to do, so that an already overpowered Ares V behemoth needs to be made even stronger.
How much weaker is a J-2x compared to a SSME? Maybe this is a very stupid question, but why don't they just try to man-rate the RS-68 and put it on the Ares I? As far as I know, isn't that in the same class as the SSME?
Thorny From United States, joined Jul 2005, 1339 posts, RR: 10 Reply 15, posted (1 month 4 days ago) and read 1681 times:
Quoting Connies4ever (Reply 11):
Seem to recall reading (sorry, I have no link) that if the crew tried to bail on the SRBs while they were firing, the orbiter would pivot back on the aft attach points, wings would come off, and then what's left (if not incinerated as indicated by Thorny) would do essentially what the crew cabin did on -51L. Same conclusion.
Not quite the same thing. That would happen in "Fast Sep" (which is still an option, I think) where the Orbiter separates from the External Tank while the SRBs are still attached and firing. Its not 100% unsurvivable, but its close enough that its only a "well, they're dead anyway if they don't try" option.
Quoting Nomadd22 (Reply 13): I'm pretty sure that the one booster failure everybody refers to wouldn't have been that serious on the Ares I, although it caused the destruction of Challenger.
It would almost certainly have a forced a launch abort due to reduced performance of the SRB. But the crew would likely have survived.
The problem with solids is that the Challenger accident was a non-typical failure. The slow leak is rare, usually solids just plain let go in a firecracker-like explosion. See the 1986 Titan 34D failure (which wiped out the pad at Vandenberg) or the 1997 Delta II failure. The warning time in most solid motor failures is dangerously low. The Shuttle SRB design is very robust (made more so after Challenger) and their recovery for inspection helps greatly to improve their safety, but with the Ares I performance problems, the larger size of the SRB, and the switch to a new propellant, we're moving too far away from the Shuttle experience to be useful. Its time to pull the plug and go with a better known comodity, like RD-180, RS-68, or even F-1 for the boosters. Tell ATK that we gave it the old college try, but it just wasn't working.
Quoting TheSonntag (Reply 14):
How much weaker is a J-2x compared to a SSME?
They've gotten the J-2X's Isp up a lot more than I thought from the J-2's 418 seconds and J-2S's 436 seconds.
RS-68 (which grew out of the Space Transportation Main Engine effort of the late '80s, early '90s) is less fuel efficient and has much worse thrust-to-weight numbers than J-2 or SSME, both of which were sacrificed to make the engine cheaper. Its too big, heavy, and powerful for an upper stage engine. Isp should go up a little if the regenerative cooling nozzle and other improvements are made for Ares V (Delta IV will like them too, but it isn't economical for P&W to pay for them unless a lot more engines are bought for Ares.)
DfwRevolution From United States, joined Mar 2004, 7511 posts, RR: 53 Reply 17, posted (3 weeks 4 days 11 hours 57 minutes ago) and read 1345 times:
Quote: New engine configuration under evaluation for Ares V
By Chris Bergin/David Harris, 8/1/2008 12:21:54 PM
The Ares V core stage team is currently evaluating a configuration change to the location of the six RS-68 main engines on the ever-growing Ares V. External engine fairings - similar to the Saturn V first stage - are being considered, in order to configure the six RS-68 engines away from the Solid Rocket Booster exhaust. (snip)
Thorny From United States, joined Jul 2005, 1339 posts, RR: 10 Reply 18, posted (2 weeks 5 days 4 hours 46 minutes ago) and read 1147 times:
Rumors are now flying that the Astronaut Corps has said "enough is enough, we're not getting on that thing" about Ares I and its many technical shortcomings, and that NASA is now scrambling to find alternatives. A "Big DIRECT" seems to be in favor.
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