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#251 2006-12-14 20:36:41

SpaceNut
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Re: Ares I (CLV) - status

Volvo Aero gets deal to help develop rocket engine nozzles for NASA


Volvo Aero, said Thursday it has signed a deal with Pratt and Whitney Rocketdyne to help develop rocket nozzles for NASA's new manned launcher ARES I.

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#252 2006-12-17 06:50:04

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Re: Ares I (CLV) - status

More details ...

Press release from Volvo Aero

The J-2X nozzle has two components, an upper regenerative cooled nozzle and a lower film cooled extension.

For the upper part Volvo Aero will propose a sandwich design, the same technology that was chosen by Pratt & Whitney in 2001 for the RL60 engine. In the RL60 program Volvo Aero managed to concurrently design and build a sandwich demon nozzle in the record time of 18 months. The sandwich technology, patented by Volvo Aero, has also been selected by ESA for a full scale demonstration on the Vulcain 2 engine late 2007.

The lower J-2X nozzle extension will be cooled with a supersonic film injection of turbine exhaust gases. This is a technology Volvo Aero developed with great success for the Vulcain 2 engine, and is the only flight proven super sonic film cooling technology system in the world. This experience puts Volvo Aero in a unique position and enables a straight forward development of a similar system for the J-2X engine.


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#253 2006-12-19 13:38:39

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Re: Ares I (CLV) - status

Just why is NASA Seeks Gas Gauge For Ares I Upper Stage are not the ones already in use on shuttle or the Delta medium the choices to be made from to keep developement timeline short.

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#254 2006-12-20 04:49:17

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Re: Ares I (CLV) - status

Forgotten the problems with the ECO sensors on the Shuttle? Given the timeline for the US, it's unlikely that this new sensor will be on the critical path.


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#255 2007-01-04 10:19:56

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Re: Ares I (CLV) - status

I am wondering how much may be true of the problem to get to orbit with the desired payload has to do with the Ares I SRB roll control need and being over weight for the upper stage. Thou we have heard that it should have no problem.

Reposting a piece of this from another thread.

Nice idea, so the SM sheds its skin on the way to orbit.

By extending the adaptor over the propellant tanks, engines and other systems in the Orion service module so that it reaches almost to the command module on top of that, the project would gain some load-carrying structure that could be jettisoned during ascent rather than taken all the way to orbit.

"It would be almost like a shroud," Hatfield said. "As you go to orbit, once you're at the point of the second stage engine lighting, when you're above most of the atmosphere, you could kick the aerodynamic panels off of the thing, and it saves somewhere between 500 and 1,000 effective mass to orbit."

While if this is jetisonned at the time the SRB falls off to allow for a lighter starting weight for the upper stages it does bring to mind what happened with SkyLab.

While if this is jetisonned at the time the SRB falls off to allow for a lighter starting weight for the upper stages it does bring to mind what happened with SkyLab.

The sequence is unclear. As the load bearing adaptor shroud extends over the SM it seems logical that the shroud would be jettisoned with the adaptor after US burnout. However Hatfield is quoted as saying the panels would be kicked off when the US is lit. A misquote perhaps.


Searching else where for information as posted by

OV-106
To help get you started, the current plan is for roll control to be accomplished with possibly up to 16, 800 lb-class thrusters (12,800 lbs). These thrusters will most likely be MMH/N2O4 and mounted on the upper stage and provide roll control for the second stage as well.

Jim
The upperstage has an RCS system for roll control and for 3 axis control before engine start and after shutdown. Just like the S-IVB.

So as I understand it these are seperate systems.

No looking back at how to solve the issue of being over weight for the orbital insertion or of having to go with less payload.

When the SRB drops off the roll control for the first stage is just dead weight.

What I would propose then would be to take the adaptor and extend the sleave a little to make this and the roll control a seperate mini stage. Drop this stage off shortly after the SRB is gone so as to make the starting mass of the upper stage less once the J2 is ready to fired. Then you are not carrying to orbit what you do not need.

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#256 2007-01-04 22:25:44

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Re: Ares I (CLV) - status

From what I can find searching around the Ares 1 payload capability to orbit
21.6 mT (47.4 klb) to -30 x 100 nm, 51.6 deg (ISS orbit)

23.6 mT (52.1 klb) to -30 x 100 nm, 28.5 deg


NASA Completes Review Milestone for Ares I Vehicle

the first such milestone for a U.S. human-rated launch vehicle system in more than 30 years. This review brings the agency one step closer to developing a new mode of space transportation for astronauts on missions to explore the moon, Mars and other destinations.

In January 2007, the Ares project will begin the second in a series of design analyses cycles leading to final design and fabrication of the launch vehicle

The Ares preliminary design review is scheduled for mid-2008.

Ares I-1, planned for launch in 2009, will be the first test flight of the integrated launch vehicle system.

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#257 2007-01-05 04:05:33

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Re: Ares I (CLV) - status

Yes the SRR is a very important milestone which validates the requirements and the architecture.

"This is a critical step for development of the Ares I crew launch vehicle," said Constellation program manager Jeff Hanley. "A great deal of engineering analysis and planning has culminated in a thorough review that gives us confidence to go forward with Ares I design work."

The system requirements review confirmed that the Ares I system requirements were complete, validated and responsive to mission requirements.

It also confirmed that the Ares I architecture and design concept can fulfill the mission objectives and that the Ares project is ready to begin engineering design activities. The Ares preliminary design review is scheduled for mid-2008.

This statement probably won't satisfy the skeptics, so expect to see even more personal attacks on Hanley and Griffin as the only way of destroying the project.


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#258 2007-01-05 04:12:03

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Re: Ares I (CLV) - status

166605main_Ares1_cutaway_tilt_516x405.jpg

A concept image of the Ares I Design Analysis Cycle 2 configuration. In the updated configuration, a common bulkhead between the Ares I upper stage liquid hydrogen and liquid oxygen tanks has been substituted for an intertank, thus shortening the vehicle. The thrust profile for the launch vehicle first stage also has been baselined. This means requirements have been established for how the solid propellant inside the five-segment reusable solid rocket booster burns during ascent. (NASA/MSFC)

Large image


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#259 2007-01-07 22:35:13

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Re: Ares I (CLV) - status

Earlier this year, ATK received a $29 million contract to work on a launch vehicle first stage SRB related to the Orion project.

The gravy train continues....

NASA Extends Ares I Development Contract

NASA has authorized a contract action having a value of $48 million with ATK Thiokol of Brigham City, Utah, to continue design and development of the first stage for the Ares I crew launch vehicle.

This Ares I first stage contract action will increase a first stage task under an existing shuttle contract by $48 million for a total work effort valued at $111 million.

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#260 2007-01-08 06:52:36

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Re: Ares I (CLV) - status

Yes the SRR is a very important milestone which validates the requirements and the architecture.

This statement probably won't satisfy the skeptics, so expect to see even more personal attacks on Hanley and Griffin as the only way of destroying the project.

Yeeep. The whole "NASA's way is doomed, I just KNOW it, they HAVE to be STOPPED!" crowd.

Expect to see other parts of the plan attacked, such as the on-orbit loiter of the EDS stage. Also, expect to see the process the VSE plan was formed attacked for a "lack of transparency" or "lack of engineer input" etc etc.


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[i]The glass is at 50% of capacity[/i]

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#261 2007-01-08 08:18:37

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Re: Ares I (CLV) - status

NASA press release on the ATK contract extension - January 5, 2007

CONTRACT RELEASE: C07-002

NASA Extends Ares I Development Contract

HUNTSVILLE, Ala. - NASA has authorized a contract action having a value of $48 million with ATK Thiokol of Brigham City, Utah, to continue design and development of the first stage for the Ares I crew launch vehicle.

Ares I will transport the Orion crew exploration vehicle and its crew of up to six astronauts, or other small cargo payloads, to low-Earth orbit. The first stage will consist of a single reusable solid rocket booster and motor similar to those used on the space shuttle, but with a fifth motor segment added. The upper stage will consist of a J-2X liquid hydrogen, liquid oxygen engine and the associated propellant tanks and fuel distribution systems.

This Ares I first stage contract action will increase a first stage task under an existing shuttle contract by $48 million for a total work effort valued at $111 million. These activities are a preparatory effort leading up to the Ares I first stage prime contract, which will be awarded in the February 2007 timeframe.

The contract action maintains the design, development, test and evaluation schedule; expedites the procurement of new nozzle metal hardware and production tooling for propellant casting and nozzle fabrication; maintains the necessary design and engineering analysis; and continues participation in pilot parachute development tests. The action also provides support for an initial test flight in the spring of 2009 known as Ares I-1 and provides support for Ares I-1 in preparation for Preliminary Design Review. The test flight will use a simulated fifth segment on the first stage and a simulated upper stage.

Why doesn't the Ares I-1 test flight use a real 5 segment RSRM?


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#262 2007-01-08 08:30:33

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Re: Ares I (CLV) - status

I also wondered if the 5th segment is full or empty with this test.

It sure reads as though they are being paid up front for the work.

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#263 2007-01-08 08:43:27

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Re: Ares I (CLV) - status

NASA press release on the ATK contract extension - January 5, 2007

CONTRACT RELEASE: C07-002

NASA Extends Ares I Development Contract

HUNTSVILLE, Ala. - NASA has authorized a contract action having a value of $48 million with ATK Thiokol of Brigham City, Utah, to continue design and development of the first stage for the Ares I crew launch vehicle.

Ares I will transport the Orion crew exploration vehicle and its crew of up to six astronauts, or other small cargo payloads, to low-Earth orbit. The first stage will consist of a single reusable solid rocket booster and motor similar to those used on the space shuttle, but with a fifth motor segment added. The upper stage will consist of a J-2X liquid hydrogen, liquid oxygen engine and the associated propellant tanks and fuel distribution systems.

This Ares I first stage contract action will increase a first stage task under an existing shuttle contract by $48 million for a total work effort valued at $111 million. These activities are a preparatory effort leading up to the Ares I first stage prime contract, which will be awarded in the February 2007 timeframe.

The contract action maintains the design, development, test and evaluation schedule; expedites the procurement of new nozzle metal hardware and production tooling for propellant casting and nozzle fabrication; maintains the necessary design and engineering analysis; and continues participation in pilot parachute development tests. The action also provides support for an initial test flight in the spring of 2009 known as Ares I-1 and provides support for Ares I-1 in preparation for Preliminary Design Review. The test flight will use a simulated fifth segment on the first stage and a simulated upper stage.

Why doesn't the Ares I-1 test flight use a real 5 segment RSRM?

The five-segment booster isn't simply a Shuttle booster with another segment tacked on, the new booster uses a different propellant cut in a different shape, and the nozzle will probably need to be reinforced.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#264 2007-01-08 12:38:28

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Re: Ares I (CLV) - status

The five-segment booster isn't simply a Shuttle booster with another segment tacked on, the new booster uses a different propellant cut in a different shape, and the nozzle will probably need to be reinforced.

At the SRR the propellant and burn profile were baselined, isn't that enough for ATK to build one in time? The test plan calls for a 5 seg static test (DM-1) in April 2009, same time as the Ares I-1 with the dummy seg. Perhaps NASA just haven't got the money ...


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#265 2007-01-08 13:20:12

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Re: Ares I (CLV) - status

I think this pins done the contract to build:

The Ares I crew launch vehicle will take the Orion crew and exploration vehicle into low orbit around the Earth. ATK Thiokol designed and developed the craft for $63 million under previous contracts.

NASA will award a prime contract in February.

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#266 2007-01-08 14:25:46

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Re: Ares I (CLV) - status

The five-segment booster isn't simply a Shuttle booster with another segment tacked on, the new booster uses a different propellant cut in a different shape, and the nozzle will probably need to be reinforced.

At the SRR the propellant and burn profile were baselined, isn't that enough for ATK to build one in time? The test plan calls for a 5 seg static test (DM-1) in April 2009, same time as the Ares I-1 with the dummy seg. Perhaps NASA just haven't got the money ...

Its not a small step to go from static test fire to flight hardware, even a prototype. Being that its supposed to be static fired the same year Ares-I 1 goes up, I am not surprised.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#267 2007-01-11 08:01:55

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Re: Ares I (CLV) - status

It occurs to me that if the 5 segment and upper stage combination are not able to get the job done of getting Orion to orbit then another method must be resolved for.
Is it possible to create a Liquid first stage with a SRB simulated stage preformance from Kerosene. peroxide rd-180 engine of 2 or 3 engines per fuel tank, in other words a Atlas derived first stage. Can a liquid stage get the weight to preformance that we need?

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#268 2007-01-11 09:14:10

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Re: Ares I (CLV) - status

There is no evidence other than rumor that Ares I is "not able to get the job done". The engineering has just started design cycle 2 and no serious problems have been reported. NASA has a very elaborate engineering review process involving many highly experienced people. Calling these engineers and managers a bunch of liars is so easy to do, but what is the evidence? It has been a real battle to get Ares I started, this constant undermining of the project is surely political and eventually it will have a political effect. What is so annoying about this situation is that NASA have been so open about the project and that openness is repaid by fabrication and distortion. See how little detail is available about Scaled Composites, SpaceX, RpK, Boeing or Lockheed launcher development projects, they know that the media's main interest is in publicizing problems regardless. Perhaps it's time for NASA to restrict all information about Ares I until the final design is complete.

The primary design concept behind Ares I is safety and reliability. A solid first stage is a sound way to achieve that.  Using more engines increases risk.


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#269 2007-01-11 09:32:53

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Re: Ares I (CLV) - status

Not trying to Call these engineers and managers a bunch of liars at all but trying to learn rocket design. The Srb selection as we know for safety is from past preformance and from the ability to do the flight inspection after use.

As far as the mound of paper sometimes hardware protyping is the only way to solve some issues as well as to identify them.

I agree that information is lacking from the atlern-X crowd.
As for Nasa the paper trail is complicate as to process from an outsider looking in. Then you have the military use barrier for getting what you need to build rockets in the first place since you would not want the technology in the wrong hands.

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#270 2007-01-11 12:16:50

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Re: Ares I (CLV) - status

Here's a good example, Cowing of the infamous NASA Watch says today:

This morning, at a breakfast sponsored by the Space Transportation Association, I asked Mike Griffin if NASA was working on any designs or plans for an alternate way to get Orion - and humans into orbit. Specifically, I asked if NASA was working on an alternative to the Ares I. Griffin said, rather emphatically, "No". Griffin's answer seems to contradict a variety of supposedly authoritative rumors suggesting that NASA is indeed seeking alternatives. Stay tuned.

So as predicted, the media have started subtly smearing Griffin as a liar. After all, who is Mike Griffin to contradict "supposedly authoritative rumors", his word is obviously not good enough. (that was sarcasm BTW)


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#271 2007-01-11 13:45:32

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Re: Ares I (CLV) - status

Yup thats what can happen when you give a one word ["no"] response to a media person that is looking for some technical and detailed explaination.

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#272 2007-01-11 13:45:35

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Re: Ares I (CLV) - status

Because, after all, unnamed sources are always right since the government execs always has an agenda, never the unnamed leaker.

NASA engineers can come up and consider all the Ares-I configurations they want on their own time, nobody is stopping them from doing that on their breaks and after work. And, technically, NASAWatch could truthfully say these alternate plans are from NASA engineers, but that doesn't mean they are being considered.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#273 2007-01-11 13:47:11

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Re: Ares I (CLV) - status

Yup thats what can happen when you give a one word ["no"] response to a media person that is looking for some technical and detailed explaination.

No, they just don't believe his answer no matter what he says, because it doesn't follow the media's desired "NASA brass are ignoring the engineers, VSE is doomed unless they do!" narrative.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#274 2007-01-12 16:27:13

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Re: Ares I (CLV) - status

Griffin was asked again about the performance of Ares I, this time at the Internal NASA update meeting. He replied saying there was not a problem, it was all "chatter" from people who were not knowledgable about the project. He said he was following the project closely and was happy with the mass margins and added that Steve Cook was on top of them.


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#275 2007-01-14 17:12:03

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Re: Ares I (CLV) - status

Doug Stanley (NASA ESAS leader) addresses the "issues"

I will also take this opportunity to address on the record some of the alleged "issues" with the ARES 1 vehicle from "anonymous sources" that have been discussed in this forum and certain NASA-Related-Personal-Axe-to-Grind-Single-Source-is-Good-Enough-Blog sites.

An entire section of the Direct proposal is devoted to alleged "Flaws With the Ares Launch Vehicle Family". Very little that was written in the section concerning "problems" with the current Ares Program is correct. The premise that the current (or original ESAS) Ares 1 approach is "broken" and needs to be "fixed" by something like what is being proposing is simply not correct! I will attempt to address some of them in this section for the record in one place. All of the data in these responses come directly from the knowledgable NASA people in the responsible engineering or program office...

DIRECT Assertion: “The original design, of 4-segment SRB with Space Shuttle Main Engine Upper Stage, would probably have lived up to expectations - if the SSME could have been air-started. It can not. NASA is left with a compromise which attempts to fulfill the same requirements, but which fails to.”

NASA Response: This is not true. NASA was confident in its plan to air-start the SSME and no showstoppers were identified at the time NASA elected to change the Ares I baseline. NASA switched to the 5 segment/J-2X approach to achieve greater commonality with the Ares V, reducing the number of developments required - resulting in significant development and recurring costs savings (billions). This included moving from 2 SRB’s (4 and 5 segment) to one (5 segment), 2 upperstage engine developments (alt start SSME and J-2X) to one (J-2X), and moving to a low cost, commercially developed core stage engine flying on the Delta IV today (RS-68 ) vs. an engine unique to NASA needs (SSME derivative).

DIRECT Assertion: “The “Stick” Crew LV's biggest selling point was its high safety figures. However, the difficulties the design is suffering from today are continually whittling those away, with each 'fix' causing ever larger penalties to the performance.

NASA Response: This is not true. NASA currently projects a loss of crew of 1 in 2,150 - a robust vehicle when compared to STS and with any other alternatives evaluated and consistent with ESAS projections.

DIRECT Assertion: “The new 5-segment SRB's and J-2X engines are both completely unproven.”

NASA Response: This is not true. A 5 segment ground test motor was fired in October, 2003. The J-2X is a derivative of the Saturn J-2 and J-2S engines, elements of which (turbopumps) were recently utilized on the X-33.

DIRECT Assertion: “Together their performance is so desperately low that other parts of the vehicle are having to be designed down to dangerously minimal weight, in order just to get the system to fly at all.” Performance of just 22mT -30x100nm 28.5deg is at best, mediocre, at worst, anæmic. This poor performance is causing detrimental domino effect throughout every phase of the development of the new vehicle.”

NASA Response: This is not true. The original ESAS baseline CLV delivered ~27mT (without performance margin) to LEO/28.5°. This was with a much lighter launch abort system and before wind tunnel data was available. Using much more detailed models, the current Ares I is projected to deliver ~26mT (without performance margin) to LEO/28.5° - equivalent to ESAS. Orion is being designed to weigh no more than 22mT (in ESAS, this was 23mT, but was a 5.5m diameter capsule). Ares I will be the largest heavy lift capability in the U.S. until Ares V is developed.

DIRECT Assertion: “A normal rocket is naturally stabilized throughout its flight by having the Center of Gravity (CofG) ahead of the Center of Pressure (CofP). Like a thrown dart, the rocket will naturally fly nose-first. But the Ares-I's CofG is behind the CofP - which causes the rocket to want to flip around in mid-air. Only with very precisely applied Thrust Vector Control, can the rocket be kept on track without applying very high stress loads to the structure. The first stage has a very slow Thrust Vectoring system, simply because it is a Solid Rocket Booster. This is causing concern during the first minute after launch, before speed builds and aerodynamics affect the ascent. It is the job of the SRB's Thrust Vectoring system to keep the very tall and ungainly rocket stable and pointing in the right direction as it lifts from the Pad. It is a problem often equated to balancing a pencil, on end, using your finger. The nozzle at the bottom of the SRB is proving to be a very slow ‘finger’ performing the balancing act. If the rocket becomes unbalanced, perhaps due to crosswinds, the nozzle may be too slow, and be forced to apply very high bending moment forces on the structure in order to try to re-stabilize.”

NASA Response: This is not true and shows a lack of understanding of large rocket design. Typically, large, orbital capable rockets have a C.G. aft of the C.P., hence you utilize a TVC system. NASA has conducted over 1,500 wind tunnel tests of the Ares I configuration, and conducted analyses on the flight control system design. While Ares is a long and slender vehicle, it is within the control dynamics experience base of previous programs, most notably the Saturn V. 6DOF simulation results indicate a ~2x margin on first stage thrust vector control (angle and rate) and an ~8x margin on the vehicle structural response to control frequency ratio.

DIRECT Assertion: “The two issues above can cause forces which, quite literally, try to bend the vehicle in half. The SRB is a very strong structure. The pressurized Upper Stage tanking is also a very strong structure. But the Interstage between them is a hollow cylinder, 18ft (5.5m) wide, and 40ft (12m) long, with walls only 1.25" (3cm) thick - and complicated further by a conical structure changing diameter from 13ft (3.9m) to 18ft (5.5m). The Interstage will be the “weak point” if the vehicle suffers instability issues during flight. It is the structure which would fail first if the rocket goes off-course and takes too much time to be forced back on course. The Ares-I test vehicles’ Interstages are being specifically over-built to combat this problem in a bid to dissuade disparaging comment from the space community, who is already well aware of this concern. But the final flight versions of Ares-I must be built down to the lowest possible weight limits in order to keep performance high enough - which means this will be the weakest structural point in the final design. The SRB first stage is currently 18,000lb overweight because the seals around all of the segments need additional, unplanned, strengthening. This is because the in-line design, with the stage and payload located above the booster instead of beside it, are experiencing different loads during flight from the SRB’s intended design - so require additional strengthening at these joints to compensate.”

NASA Response: This is not true. While the Shuttle RSRM was not originally designed to have a second stage ride atop it on the way to orbit, this is a very robust stage which carries the entire load of the Shuttle External Tank and offset load of the Shuttle Orbiter. In addition, it was sized to carry the offset load of 3 Space Shuttle Main Engines firing at ignition (“twang load”) which Ares will not have due to its single engine, in-line first stage configuration. The NASA team is using proven, validated engineering tools and loads models and conservative margin factors at this stage of the design. Analyses performed to-date indicates that the existing Shuttle RSRM cases, joints and aft skirt have sufficient design capability to support the Ares in-line configuration and are not “overweight” as characterized above. In addition, the upperstage and interstage are being designed for the loads expected on the ground and in-flight. The upcoming Ares I-1 flight test in 2009 will give NASA important data early in the development cycle.

DIRECT Assertion: “The roll-control system was not predicted to be as considerable an issue as it is proving to be. It requires an extra system which was unplanned originally, which impacts the weight of the vehicle, and increases the number of systems which can cause an expensive Loss of Mission or, worst of all, a Loss of Crew contingency.”

NASA Response: This is not true. Characterizing and controlling roll torque has been a high priority since Ares’ inception. NASA has utilized what it believes are worst case roll torque predictions and then designed the control system to handle 1.7 times that torque using RCS thrusters. Our goal now is to further refine the roll torque predictions through ground test firings of the motors with calibrated sensors, analyzing similar launch systems (Athena, for example) and the Ares I-1 flight test in 2009. We believe we have utilized very conservative predictions and then used a conservative design approach.

DIRECT Assertion: “The original “Stick” launcher utilized the Upper Stage to reach an initial elliptical orbit of 60x160nm, then that Upper Stage to then perform the Circularization burn to achieve the stable 160x160nm orbit. The Orion is now required to perform a 1000ft/s high-Delta-V burn to reach an initial orbit of just -30x100nm - that means the low-point is 30 nautical miles under the Earth’s surface.”

NASA Response: This is not true. In ESAS and until last Spring, the Ares I injected the Orion into a 30x160nmi transfer orbit and the Orion then circularized itself, to avoid the complexity of deorbiting the large upperstage. Working with Constellation and CEV project teams, the program elected to change to a -30x100nmi orbit to move the ocean impact of the CLV upperstage to the Indian Ocean from the South Pacific to stay away from populated islands. This also allowed the impact point for both ISS and lunar missions to be in the same general vicinity. Appropriate performance was transferred from Ares to Orion so that the spacecraft was not penalized. Performing multiple OMS types burns is commonplace on STS today and does not increase risk. Also, Orion does not have to do a burn to reach -30x100nmi - Ares places it in that orbit. Orion carries 1,000 ft/s to perform all orbital maneuvers, including transferring from -30X100 to 160 circ, and on to 220 for ISS, rendezvous, prox ops and docking, and deorbit.

DIRECT Assertion: “Together, this reduces the original “Stick” concepts Loss of Crew (LOC) figures below the stated 1 in 1918. The Ares-I’s fundamental design requires that the Upper Stage engine be ignited at altitude, only after the SRB First Stage has burned-out. There is no guarantee that any engine will start correctly, or safely, let alone at altitude. If there is a problem, the mission would become an abort, requiring the use of the escape system. NASA has yet to publish new, independent, ‘apples-to-apples’ comparison safety figures between the original CLV and the current evolution. The figures will obviously be lower today. Loss of Crew (LOC) safety figures of between 1 in 1500 to 1600 are rumored for the current risk factor as this paper was compiled - so the gap to DIRECT’s 1 in 1355 LOC risk is now very narrow indeed.

NASA Response: This is not true. The current Ares probabilistic risk assessment, which is much more comprehensive than the PRA used in ESAS is predicting a loss of loss of crew of 1 in 2,150 (mean). This is ~1.6x the DIRECT claim of 1 in 1,355 LOC (which is not supported with any analysis - the best ESAS vehicle in this “direct” class had an LOC of 1 in 1,170).


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