Ares I-X TVC retesting taking place – Range Safety Waiver overview

by Chris Bergin

Engineers have replaced the faulty GN2 accumulator on Ares I-X’s Thrust Vector Control (TVC), ahead of rollout to Pad 39B, currently set to take place on Tuesday or Wednesday morning – pending successful retests on the replaced hardware over the weekend. Meanwhile, documentation has outlined the extensive – and ongoing – work that has been undertaken to earn a Range Safety waiver to allow the vehicle to launch.

Ares I-X Processing Latest:

Most of the processing work has been completed on the test flight vehicle, with final power connections and closeouts taking place throughout the previous few days.

“Flight batteries installed. Open circuit voltage checks, main vehicle battery connections and pyro battery connections are complete,” noted Ares I-X processing information on L2. “The Flight Test Vehicle (FTV) was powered up for approx five hours to support additional Developmental Flight Instrumentation (DFI) software load and testing.

“DFI software load and testing was completed with sufficient data gathered to perform system analysis. The Upper Stage Simulator (USS) access door has been installed for flight. Final closeouts for the First Stage Avionics Module (FSAM) are in work.”

However, during testing late on Wednesday, engineers detected a gaseous nitrogen leak in the TVC accumulator. The pressurized nitrogen was found to be leaking past a seal and into the area of the accumulator containing hydraulic fluid.

The accumulator is used to absorb hydraulic pressure spikes as the system – which is used to steer the vehicle – operates. The accumulator is being removed and replaced on Friday, with retesting taking place through to the weekend.

A2“During routine surveillance, the team found the First Stage Tilt Thrust Vector Control Actuator hydraulic reservoir sight glass indicating 100 percent when it should be reading 78 percent,” outlined processing information at the time the issue was found.

“Further investigation indicates that the GN2 accumulator may have failed. A replacement accumulator is being built-up as a potential replacement while the team hooks up GSE (Ground Support Equipment) to confirm the GN2 accumulator has failed.”

Once the suspect hardware was confirmed as failed, engineers carried out its replacement.

“The Thrust Vector Control (TVC) GN2 Accumulator replacement is complete. The new hardware passed leak checks. TVC actuator has been de-pinned to allow actuator cycling for the hydraulic system re-test over the weekend. The project continues to assess the rollout and launch date for the mission pending successful retest of the TVC system.”

The delay to rollout is classed as at least 24 hours to Tuesday morning, although the complexity of the system requires the bleeding of the entire TVC hydraulic system for retests, which can sometimes take much longer than expected.

Recent Ares I-X Articles on can be found on this link:

Ares I-X Range Evalautions and Waiver:

One of the main challenges in the run up to the launch of Ares I-X has been the requirement to acquire the approval from the Range.

Given the Eastern Range is hosting the launch of what is a new type of vehicle, the US Air Force 45th Space Wing need to be satisfied that it won’t become a safety threat during its two minute flight to either the public or assets along the Florida coastline.

A3A key element to safety is the Flight Termination System (FTS), which would allow for the vehicle to be destroyed by pyrotechnic charges embedded into the first stage, in the event it veered from its planned trajectory.

Vibration-loads issues were raised during the stacking of Ares I-X, which have the potential to disrupt the avionics box – associated with the FTS – on the vehicle, and subsequently disable the ability for controllers to destroy the vehicle during an off-nominal event.

Engineers verified the vehicle’s integrity during several stages of stacking to ensure this concern did not hold any potential to become a real risk during flight, while a waiver was called for as part of NASA’s presentation to the Range.

A large section of one of the several Ares I-X: Launch Readiness Review presentations (all available on L2) overviews the Range requirements and waiver.

“Range Safety data deliveries to Air Force 45th Space Wing – NASA/Langley Research Center (LaRC) is prime (while) Flight Design is providing technical support, including some verification and validation (V&V). Activities are being coordinated through Launch Constellation Range Safety Panel (LCRSP),” noted information in the Ares I-X Flight Design and Dynamics presentation.

“LaRC is responsible for the Ares I-X test flight and is the primary organization responsible for completing the analysis and products in the Ares I-X Final Flight Data Package (FFDP) for the Air Force. Other NASA centers are assigned to perform V&V of each analysis or product.”

A5It does appear that Ares I-X – via simulations at least – already passed several Range requirements back in the summer, via a set of complex assessment processes.

“Flight Design supported data generation for meeting Range requirements detailed in Air Force Space Command Manual (AFSCPMAN) 91-710, volume 2, for Ares I-X FFDP delivery package,” added the presentation. “Ares I-X FFDP Malfunction Turn and Probabilistic Risk Assessment (PRA) products delivered to the 45th Space Wing on May 21, 2000.

“Flight Design has provided technical support and V&V for the malfunction turn trajectories. Performed V&V and integration of the delivery for the malfunction turn products. Completed reformatting of Malfunction Turn Trajectories in the Range RSTAPE format (LaRC performed V&V).

“Ares I-X FFDP nominal ascent trajectory and flight envelopes (valid for July – Nov launch) generated by LaRC were delivered to the 45th Space Wing on July 30, 2009.

“Provided technical support for the flight envelope methodology. Completed reformatting of the trajectory data in the Range RSTAPE format (LaRC performed V&V). Ares I-X FFDP First Stage and Upper re-entry trajectory and footprints (valid for July – Nov launch) generated by LaRC were delivered August 31, 2009. Completed reformatting of the re-entry trajectories in the Range RSTAPE format (LaRC performed V&V).”

Further notes confirm that all elements of Range Safety information were provided to the US Air Force 45th Space Wing by August 31, although LaRC were still providing refined debris footprints right up to L-30 days.

It is also noted in another of the Ares I-X Launch Readiness Review presentations that the actual waiver for the Range was still in draft form and unsigned as of September 30.

“Range Safety waiver for the Flight Termination System passive components (antennas and couplers) (RS). Draft waiver for AF and NASA range safety review – Waiver in review,” confirmed one of the presentations.

A4The preparation of the final version for signature was scheduled for the “Steering Panel” early this month, though this schedule was classed as “ambitious, but doable.” It is likely that confirmation the waiver has been signed will be forthcoming at the Agency level Launch Readiness Review around a week prior to launch.

“The range has reps at the testing, so they will know as soon as we do,” added the presentation. “Range Safety deliverables (FFDP): Malfunction Turn Trajectories – Analysis is complete and data delivered on 9/25. Formal paper signed out on 9/29. Updated debris footprints (US and FS) are complete and delivered on 9/28. Formal paper still in work.”

However, it does appear the Range waiver is not going to be a problem for Ares I-X, providing it launches prior to November 30 – after which time, further analysis will be required.

“Launch slip past November 30th would require regeneration and redelivery of some Range Safety products,” was the only note relating to the Range on the risk assessments and concerns page.

L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.

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