NASA has 5-Seg CLV Alternatives

by Chris Bergin

NASA, world renowned for having a back up plan, has one for the Crew Launch Vehicle (CLV), with a new 2×3-segment SRB (Solid Rocket Booster) CLV design, held as a concept – in case major problems with the current 5-segment Ares I booster arise.

The new booster would employ twin three-segment SRBs and a liquid-fueled core stage, which – overall – would be significantly cheaper in terms of some ground processing and infrastructure costs, and perhaps easier to control.

Full information, hi res images and documentation and discussion relating to this concept is available on L2 (150 posts). Click right image for details.


NASA is understood to have been examining this new 2×3 SRB CLV concept, due to a number of advantages over the current 5-segment CLV, with easier ground handling and control in flight.

The new vehicle involves a core liquid-fueled stage with 2 J-2X engines, and twin 3-segment SRBs. These J-2X engines would be air started after launch along with the SRBs, and would serve as the core engines of the launcher. The core stage may be a derivative of the Shuttle External Tank.

This vehicle is about the same height of the Shuttle and resembles a much-downsized Ares V cargo launch vehicle. A number of advantages has been identified, one being the current launch pad and crawler infrastructure will require far less modification to support this CLV than the Ares I – since it uses two SRBs and is more stable on the MLP than the tall and slender Ares I.

Additionally, this CLV is more similar to both the Ares V and STS than the 5-segment CLV, offering a more direct evolution to the Ares V, along with a less complex transition from the Shuttle due to its configuration.

‘The 2X3 launcher would be much wider than the 5-seg SRB, but about half the height. It offers significant schedule, development, and ground safety improvement,’ noted a source. ‘It also makes TVC (thrust vector control) far easier than with the one SRM (Solid Rocket Motor) on the Ares I, and makes the vehicle more stable on the MLP (Mobile Launch Platform) than the extremely tall and thin Ares I.

As previously reported by this site, the Ares I vehicle will require a modified, lightweight MLP, due to the weight associated with the vehicle and its LUT (Launch Umbilical Tower). While costs can only be estimated at this stage of the development process, the 2X3 concept would at least allay such budgetary strains.

‘The 2×3 would require little in the way of launch pad modifications to fly,’ added the source. ‘The existing MLP could be used more or less as is, with the exception of having to relocate the tail service masts. The existing FSS (Fixed Service Structure) could be used, again more or less as it now is. The biggest changes would be relocation of the hydrogen vent system arm, the oxygen vent system arm, and the crew access arm.

‘The existing RSS could be used for SRB servicing, and work platform access to the entire vehicle. Modifications to the RSS would be minor, and would mostly involve removing now unused equipment. The RSS would offer the vehicle a good degree of wind and weather protection, some thing the big stick will be lacking.

‘The VAB could be used largely as is, and little would have to be modified to provide work platform access for stacking and check out operations. This is not a trivial item, as modifications to the VAB is one of the big cost factors for CLV. The stacked vehicle could be moved to and from the pad with out any bracing, the thing would be far stiffer than the shuttle stack is, while the existing transporter could be used as is, with no changes at all.’

However, such a concept would incur its own increased costs, given there are two boosters to build, service and recover for each flight, as opposed to the one with the Ares I.

At this time the 2X3-seg vehicle hasn’t advanced past the conceptual stage, as NASA proceeds as planed with the 5 segment ‘big stick’ CLV. However, it is fair to assume this could be a useful backup plan, should the stick suffer a major design problem.

According to multiple sources in industry and at NASA, the current 5-segment Ares I booster is about 10,000 pounds overweight; a number of possible fixes to the problem have been worked on with ATK, who builds the SRBs, but all are currently seen as unworkable due to time and budgetary issues.

However, this weight issue was immediately cancelled out of the overall equation, following the 6,500 lbs savings on the CEV review (DAC-2). Such savings translate into a 9:1 ration from the upper stage to the first stage, allowing for a fair amount of margin in the baseline.

While NASA continues to morph its baseline to proceed with the current concept of the Ares I, should the potential back up plan of the 2X3 concept come into play, alternative benefits could be achieved.

‘There would be no need for any RCS systems at all, except for those on the CEV. The 2X3 concept would also negate all the structural stiffness problems with the Big Stick,’ noted the source. ‘It would make required changes to the SRB TVC system a moot point.

‘There is also ‘engine out’ capability, if a J-2X fails in the last half of the powered flight stage – this reduces the chances of a trans-Atlantic abort. Also, a lot of SRB recovery problems are eliminated, as the boosters would fly trajectories much like the current boosters on the shuttle fly, which would make the SRB recovery divers work less risky.

‘The core stage could largely be made with existing ET tooling and fixturing, thus making this a truly Shuttle derived vehicle. It could be used as a cargo launcher for ISS operations, and since it is short and stubby, it could carry vehicles like the X38 to orbit.’

While this is nothing more than a concept, information acquired shows its potential, especially if there’s a major issue with the current Ares I design process. Ares I will suffer hiccups during the aforementioned process, but it would take a major problem – one that would cost a hugely unacceptable level of funding to correct, for alternatives to be considered at this stage.

However, it is encouraging that the 2X3 concept shows that NASA is not heading down a one way street.

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