NASA have decided to cancel the new MiniBoom, that was to replace the OBSS (Orbiter Boom Sensor System) on three future Shuttle missions, in favor of building a third IBA (Integrated Boom Assembly).
Clearance issues with the orbiter’s payload bay on flights STS-122/1E, STS-123/1J/A, and STS-124/1J, mean NASA will now work a plan to build a third boom, and leave it on the International Space Station (ISS) on one mission.
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The 50 foot long arm, which includes the OBSS (Orbiter Boom Sensor System) instrumentation package – integral for scanning the TPS (Thermal Protection System) of the orbiter – can’t be carried into orbit on those three missions due to weight restrictions, interferences and/or unacceptable clearances between the boom and the ISS cargo elements.
The decision to cancel the MiniBoom, which – as the name suggests – was a shorter version of the current OBSS system, has been confirmed, along with the approval to build the third OBSS IBA (Integrated Boom Assembly) at the cost of several million dollars.
**Click here for orginal article on MiniBoom requirement and additional images**
Further mission evaluations will be taken on situation, following a ‘decision to discontinue development of MiniBoom in favor of ‘something with OBSS’,’ according to presentations acquired by this site (and published on L2).
Those evaluations include: ‘Budget for OBSS sustaining engineering. Decision on whether to stow OBSS on ISS. Decision on which flight to stow OBSS on ISS. Budget for MiniBoom close-out costs. Budget to fix 1E (STS-122) to accommodate OBSS. Budget to fix 1J/A (STS-123) to accommodate OBSS. Budget to stow OBSS on ISS.’
NASA also evaluated that the OBSS may only be a major issue on one of the ‘IP’ flights, (STS-124), noting: ‘The number of problem flights can be reduced to just one. Solution exists to fly OBSS on STS-122 (1E), by removing Columbus PDGF pre-flight and reinstall EVA prior to Columbus deploy.
‘Solution exists to fly OBSS on STS-123 (1J/A), by modifying redundant Starboard FRGF on ELM-PS, (but) no solution exists to fly OBSS on STS-124 (1J).’
NASA appears to be in favor of ‘bringing the OBSS to ISS on STS-120/10A (or 1J/A), (stowing it on the ISS), and return it on STS-124/1J,’ thus eliminating the issue of cargo bay restrictions. However, all options appear to affect the current baselines for the affected missions, including focused inspections.
Interesting, NASA also evaluated whether to bring in another option for TPS inspection, know as AERCam (Autonomous Extravehicular Robotic Camera), which is a free flying vehicle capable of performing inspection and viewing missions. However, ‘AERCam not feasible due to schedule constraints.’
STS-124 is now what NASA will concentrate on options for inspections, with ‘at least two potentially viable 1J timeline options available: Docked inspection, which requires 2 EVAs. Inspect with OBSS prior to JPM berthing. Limited inspection of starboard wing.
‘Option two: Post undock inspection. All required EVA tasks combined into one EVA. Inspect with OBSS post undock.’
‘(However), both options carry some risk. SRMS elbow camera may need to be removed due to dynamic clearance violations. This would result in inadequate situational awareness for undocked inspections. If donâ€™t dock, will not have OBSS available to perform inspection/repairs. Full ascent debris inspection not performed until post undock. Rely on FD02 SRMS inspection and FD03 RPM.
‘May impact CSCS (Crew Shuttle Contingency Support) capability. Requires additional docked days to complete primary mission objectives.’
Interestingly, on NASA’s own conclusions over the viability of either the MiniBoom option, or the requirement to build a third IBA, they appeared to favour the MiniBoom.
‘MiniBoom: Offers very good RCC inspection. Requires crewmember for far-aft tile inspection / repair. Has medium-high project risk. No impact to ISSP IPs.
‘OBSS on ISS: Need 3rd OBSS to meet manifest. Limited RCC coverage while docked. Some impact to Flights 1E and 1J/A. Significant impact to Flight 1J. Has low project risk.’
That was also backed up by the JAXA (Japanese Space Agency) Impacts Conclusions:
‘Assuming mission duration is increased over the current 8+1+2 based on increased ascent performance, an option exists to complete the 1J primary mission objectives (install JPM and activate both avionics channels) and provide fault tolerance to the newly installed element.
‘No option provides ability to complete ascent debris assessment early in the mission. With the OBSS option, only a single inspection option is protected in all options with some capability to provide additional focused inspection if necessary.
‘From an ISSP and JAXA perspective, building and flying the MiniBoom is the best option. It minimizes the most risk, results in less weight, and has the least impact to the IPs. But we can meet the JAXA primary mission objectives without the MiniBoom if we accommodate the following impacts:
‘Incur cost to remove the starboard FRGF on the ELM-PS. Loss of post undocked late inspection capability on Flight 1 J/A. Loss of quality pre-docked inspection capability on Flight 1J. Additional docked mission requirements needed to use and return the OBSS on Flight 1J.
However, importantly, NASA conclude that ‘we believe we can find a way to make the IP flights work without funding the Mini Boom (note that JAXA has made it very clear that they require the additional mission duration to accommodate their critical tasks on Flight 1J).’
Moving on to the production of a third IBA, NASA will use some of the currently available hardware to make up the new boom.
‘A 3rd OBSS Sensor Package 1 is in development and can be completed under the OBSS sustaining engineering budget. A 3rd OBSS Sensor Package 2 has already been delivered. A 3rd IBA will need to be developed. Use spare SRMS booms. Total number of SRMS units will be reduced from four to three.’
The three ‘IP’ missions in question are set to launch in the latter part of 2007, and early 2008 – although the fluid launch target for STS-125, to service the Hubble Space Telescope for a final time, could pay a role in at least one launch date change for the three aforementioned flights.
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