posted 12-20-2008 05:44 PM               

The new spacecraft, called Orion, is a capsule and service module system designed to support both the station and lunar missions.

NASA spent several years studying architectures and researching every available commercial rocket to find the design that could best accomplish those dual mission objectives in the safest, most reliable way. The conclusion we reached was that a space shuttle and Apollo derived vehicle was the best choice. Many have challenged this decision and still are advocating the use of existing commercial launch vehicles. Those have been studied extensively and fall short of our requirements for several reasons. First, existing commercial launch vehicles can lift only a fraction of the mass required for station and lunar missions in a single launch. Second, existing commercial launch vehicles have been designed and built to carry unmanned payloads; they would need to be heavily modified to meet our human rating requirements.

A core goal of the Astronaut Office is that the next launch vehicle should be an order of magnitude safer than the previous vehicle. That's a goal the Ares-Orion architecture can meet. Current commercial launch vehicles, even if they could lift the mass needed, cannot meet that goal without extensive modifications in structural strength, the addition of new launch abort systems, significant alterations of flight termination systems, addition of cockpit command and control of systems, addition of manual control, addition of redundancy and robustness in several critical systems and subsystems, and an entirely new second stage to provide adequate lift and abort performance during ascent. In our final Exploration Systems Architecture Study, the shuttle-Apollo derived launch vehicle, besides being the only design that could meet our mission requirements, was the highest-rated for crew safety. In fact, it was about twice as safe as any other option. This option also proved superior to others in terms of cost and schedule.

posted 12-20-2008 06:37 PM               

Many have challenged this decision and still are advocating the use of existing commercial launch vehicles. Those have been studied extensively and fall short of our requirements for several reasons. First, existing commercial launch vehicles can lift only a fraction of the mass required for station and lunar missions in a single launch.

How can one help but be cynical given the timing and source of this letter, particularly since actual performance data has not been collected against test flights?

posted 12-20-2008 11:30 PM               

Isn't it already over budget (possibly to as much as $7 billion) and the schedule not met?

posted 12-21-2008 09:25 AM            

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Originally posted by LCDR Scott Schneeweis:
Commercial launch vehicles have substantially greater lift capability then Ares I.

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Two questions: Which vehicles, specifically, are you referring to? And does their greater lift capability include enough margin to lift the redundant systems and reinforced support structure to LEO through the flatter trajectory manned rockets fly?

This discussion is academic until real-world data is gathered on Ares I performance, of course. I'd be curious to see if any of the wiser rocket scientists among us could put some numbers to this, rather than my amateur conjecture.

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Originally posted by Ross:
Also, what is the lift mass of Ares versus the Saturn V?

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posted 12-21-2008 11:30 PM               

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Originally posted by Mr Meek:
Ares I is projected to lift ~25,000kg to LEO. The Saturn V could lift more than 4 times that.

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Shouldn't we be comparing Ares I and Saturn 1B, and Ares V with Saturn V?

posted 12-22-2008 09:16 AM               

Saturn 1B 15300 kg to LEO
Ares 1 25000 kg to LEO

posted 12-25-2008 11:06 PM               

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Originally posted by dtemple:
The Atlas D was manned rated. I know the Atlas V in use today has little in common with the older Atlas boosters but did it lose capability in the process of its evolution?

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posted 12-30-2008 07:39 AM               

For more than three years, NASA chief Michael Griffin has maintained that the safest, most reliable and affordable way to return astronauts to the moon is on the Ares I, a rocket he helped design from parts of the space shuttle. Alternatives, he insisted, such as modified military rockets, were simply not capable of carrying humans to the moon and beyond.

But interviews, as well as documents obtained by the Orlando Sentinel, indicate that military rockets can lift astronauts safely into space -- and to the moon -- for billions less and possibly sooner than NASA's current designs.

While it's not clear how the next administration wants to proceed with NASA's lunar ambitions, one aerospace-industry official confirmed that NASA recently asked Kennedy Space Center to start examining the impacts of scrapping NASA's own Ares I rocket design and switching to modified versions of the military's Atlas V and Delta IV rockets as the agency's next-generation human spaceships.

According to documents presented to Obama's transition team three weeks ago -- including internal studies by the rockets' manufacturer, United Launch Alliance -- upgraded human-rated versions of the military EELVs would have enough power to take NASA's fully loaded Orion crew capsule into orbit. In fact, the studies say some configurations of the rockets can lift up to 6 metric tons more than NASA requires.

posted 01-08-2009 11:41 AM               

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Originally posted by LCDR Scott Schneeweis:
Both the Delta IV and Atlas V ELV derivatives have sufficient reserves to place heavy payloads in GEO; LEO is a non challenge.

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Every week, it seems, we hear that NASA should be directed to halt development of the Ares 1 crew launch vehicle, pay industry to develop a human- rated EELV to fly the Orion crew vehicle, and focus its own efforts on the Ares 5 and Altair.

Now, while a smaller Orion capsule on a human-rated EELV could cost less in the short-term to develop, it would only be capable of supporting the International Space Station. The lunar mission is more difficult; we're trying to go beyond Apollo, not merely repeat it. Our goal is to develop the option for sustained human lunar presence at the minimal level of an international crew of four rotating on six-month centers. Existing EELVs, even leaving aside the issue of human rating, cannot lift a lunar-capable Orion, without substantially compromising what is meant by "lunar capable".

If "using EELV" doesn't really mean "using an existing EELV", but instead means, "using an upgraded EELV sufficient to carry a lunar-capable Orion", then I must note that this will require much more than the few tweaks that some have suggested. We would have to modify the first stage to carry heavier loads and for human rating, among other things, and then design, develop, and build a new human-rated second stage. But that's exactly what we're doing with Ares 1: modifying an existing first stage and building a new second stage. Why is it thought that this is a good thing to do with EELV, but not for Ares?

Further, it is crucial to recall that we are designing an architecture, a family of space vehicles with synergistic commonality. We are not trying to optimize a single mission. Our analysis shows that for the complete architecture, the development costs savings for the Ares family are huge, about 25% lower than for an EELV-derived family, because of the commonality of Ares 1 systems with those on Ares 5.

In fact, given that we must develop Ares 5 for the lunar mission and, later, Mars, the additional development cost for Ares 1 is $2.7 billion. I will repeat that: if you commit to lunar exploration and beyond with Ares 5, for an additional $2.7 billion you also get the new human-rated LEO transportation system mandated by the Columbia Accident Investigation Board. Aside from the upper stage tank structure, most everything on Ares 1 - many elements of the 5-segment solid rocket booster, the J-2X upper stage engine, the upper stage main propulsion system, the guidance, navigation, and flight control systems - is common to Ares 5. Constellation is not a point design.

A spaceflight system designed for a single task - say Earth to LEO, or Earth to Moon - can clearly be optimized for that one task. In a world where NASA had substantially more money, it would certainly be desirable to build and optimize different systems for different missions. We are not in that world. I believe that, if we are lucky, we are going to get one new human space vehicle to follow Shuttle. Anyone here think that Congress is going to provide funding for more than one? Raise your hand, please. Anyone? ... I didn't think so. And if that's the case, then it would be a mistake to optimize that one vehicle for access to LEO. If we want to be a spacefaring nation, we have to be able to go to more than one place and do more than one thing, and we're going to have to sacrifice optimal performance on any single mission for versatility across an array of missions. That is why we must think "architecture" and not "point design".

Beyond the costs involved, our probabilistic risk assessment for loss of crew on Ares 1 showed it to be twice as safe - I repeat, twice as safe - as a human-rated EELV-derived vehicle. This figure of merit was a significant factor in our decision to go with the Shuttle-derived Ares 1, yet is ignored by almost everyone suggesting that we make a change. I cannot responsibly ignore it, for reasons having nothing to do with money. But if to someone else it is just about the money, then the cost of unreliability must be considered. Incurring even one additional accident through the use of a less-reliable system wipes out all of the savings of the hypothetically cheaper vehicle. Solely from a fiscal perspective, we should be willing to pay a premium for safety, if necessary.

So, while I am truly concerned about the moribund state of our U.S. commercial launch industry and about the rising costs of EELVs to NASA as a result, our task was to develop a plan for human space exploration, not to buttress the EELV industrial base. We absolutely do not have the resources to do both, and even if we did, exactly what is it that makes the EELV industrial base more important to support than the Shuttle industrial base? I remind everyone that with the Ares family, we are retiring the Shuttle orbiter, but preserving many other segments of the Shuttle industrial base. Why is it, exactly, that in this time of transition in NASA spaceflight systems, we should make decisions to augment the existing Atlas and Delta workforce, while completely decimating the Shuttle workforce?

Now, as I say, I am concerned that rising costs for expendable launch vehicles will impact our ability to carry out our robotic science missions. In accordance with the Commercial Space Launch Act and national policy, the EELV will continue to be the foundation for launching NASA's robotic missions, and we will use them to the maximum extent possible according to our mission needs, performance, cost, and schedule requirements. We are also considering emerging commercial offerings, like SpaceX's Falcon 9 and Orbital's Taurus 2. When reliably flown, they will compete on a level playing field for NASA contracts. We are supporting the commercial launch industry where we can reasonably do so.