Constellation engineers are continuing work on an extension to the Ares I First Stage nozzle, which will provide an extra kick for the vehicle’s assist of Orion’s Lunar mission profiles.
Meanwhile, ATK have successfully carried out a test firing of an old Reusable Solid Rocket Motor (RSRM) – which enabled the gathering of additional data for the Ares I program, in tandem with additional margin on the “Age Life” certification of boosters.
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Lunar Ares I Nozzle Extension Latest:
The change to the nozzle on the Ares I First Stage RSRM is documented as increasing the performance of the vehicle for Lunar missions. It will no longer be implemented into the Ares I vehicle that will carry Orion on missions to the International Space Station (ISS).
‘Extended Nozzle – Ares First Stage: Increase Ares I nozzle expansion ratio from 7.2 to 9.3,’ noted a Constellation presentation acquired by L2. ‘Justification: Provide 1200-1300 lb increase in overall vehicle payload capability.’
According to the presentation, a larger 10.25 expansion ratio was preferred as ‘optimum’ – though impacts to shipping, manufacturing, the TVC (Thrust Vector Control) hardware and the Mobile Launcher had to be considered in the approved ratio change.
‘9.3 expansion ratio provides optimum performance with TVC attach constraints and manufacturing limitations,’ cited the document.
However, the Ares I Mobile Launcher may still require a re-work, as noted im the Ground System Impacts, referencing a one year modification period between the ISS and lunar Ares I variants.
‘Mobile Launcher impacts: Current ML cannot accommodate extended nozzle,’ added the presentation. ‘Only one ML in baseline – would need to take ML out of flow for around one year to modify.
‘Proposed launch mount provides scar for protecting phased implementation of Nozzle extension for Lunar Ares I.’
Originally, the nozzle extension was intended for both ISS and Lunar Ares I, and even the Ares V vehicle – as noted by Marshall Space Flight Center’s Ares I First Stage Element Manager Alex Priskos in a November, 07 interview with this site.
‘We are evaluating a trade study to increase performance margin of the Ares I and V systems by using a slightly longer nozzle which uses the same aft skirt and related subsystems,’ noted Priskos.
‘The trade study has been completed and is being reviewed by the Constellation Program. We will not release any information about the results until these briefings have been completed.’
Now, via the new presentation, that modification has moved forward, with the decision to change the extension’s implementation to a latter stage of Ares I’s development, but in time for the opening missions to the moon at the end of the next decade.
‘Integrated Stack Technical Interchange Meeting (ISTIM) outcome: Defer the Ares I modification to Lunar (start of Ares I block upgrade strategy).’
This decision helps the short-term development timeline of Ares I, allowing Ares I-Y – the second test flight for Ares I in around 2011 – to be developed as planned, as opposed to taking a five month hit with the new nozzle.
‘Post ISTIM: Ares I-Y schedule threat mitigated. Conduct trade study for the processing and interface/hold down configurations to support implementation for Lunar mission to allow for a better definition of configuration and cost impacts.
‘Replanning of DAC (Design Analysis Cycles) for separate ISS and Lunar missions.’
ATK Test Fire:
Thursday saw the manufacturer of the RSRMs – ATK – carry out another test firing of a four segment booster at their Utah test range, as part of ‘continuous testing to improve performance and ensure safety of the space shuttle and to aid development of the first stage of Ares I.’
The main element of the test firing for Ares I related to the gathering of data to aid in the development of the new Ares I vehicle and its launch pad, specifically acoustic environment measurements.
‘By collecting acoustic environment measurements, engineers can make better predictions of how the sound will affect the surrounding area,’ noted ATK.
‘The shuttle program uses massive sprayers, called the water deluge system, to reduce the acoustic effects of the space shuttle propulsion systems as it lifts off.
‘A similar system is being developed for the Ares I and data collected from this test will play an important role in the final design.’
A crucial milestone will be achieved by ATK when they test fire a ‘full up” five segment booster next April, which will be the first real test of the larger motor. ATK have fired a five segment booster before, back in 2003, though it did not use the configuration that is being implemented for Ares I.
Booster “Age Life” Test Element
The second element of the test related to the “Age Life” certification of the boosters, a process which first came into focus ahead of STS-117 due to the requirement to extend the previous certified lifetime of five years, in order to allow Atlantis’ boosters to fly with her on what was later launch date than originally planned.
To that end, ATK presented extensive rationale on extending the lifespan from five years, to five and half years, avoiding what would have been a change of boosters for that mission.
Following PRCB (Program Requirements Control Board) approval, the decision relaxed the tight timeline on four sets of motors in total, namely RSRM-96, 97, 98 and 99, which were used on STS-117, 118, 120 and 122 respectively.
The booster fired today was more than seven years old – the oldest RSRM ever fired, which will add further confidence on the margins of using booster hardware that is heading into the age range of five to five and a half years, and any subsequent extension – though no specific reference has been made with regards to this test – of the shuttle program past 2010.
“This test is an example of the aggressive testing program NASA pursues to assure flight safety,” said David Beaman, manager of the Reusable Solid Rocket Booster Project office at NASA’s Marshall Space Flight Center. “It also allows us to gather information on how motors with different ages perform.”
“Ground test firings provide valuable data to ensure the reliability and safety of space shuttle motors,” added Ron Dittemore, president ATK Launch Systems.
Interestingly, ATK had already been looking into the age life certification of their motors for some time, with several expansive presentations (available on L2) outlining their findings with technical overviews of the motors, along with test history.
That test history proved their confidence in being able to extend their lifetime certification of the motors, with evidence such as a 1993 firing of a 7.5 year old test motor, and history successful tests on “chemically similar” solids, such as a motor from a Minuteman missile, which was 39 years old.
The results showed the subject materials did not age or interact significantly/adversely for the five and a half year period to be approved. Thursday’s test is likely to prove a healthy margin exists even past the recently changed certification period.