Part III-Last Hubble Mission Approaching
Personally distributing Hubble documents to Congressional staffers and circulating them throughout Capitol Hill has been the responsibility of a supposedly author William S. Smith, according to Keith Cowing of Space.com. For those not in the loop, the Space Telescope Science Institute is staffed by AURA, the Association of Universities for Research in Astronomy, and AURA’s president is William S. Smith. Denying his role in the articles, he also states the articles state a position that should be taken into consideration before making a final decision. The following are some of the key points in the two documents which are making such a splash.
The final planned HST Servicing Mission, SM4, will be at least as safe as shuttle flights to the International Space Station (ISS). If shuttle return-to-flight occurs prior to the full implementation of an autonomous inspection and repair capability, the overall risks during a flight to Hubble would be comparable to those associated with an ISS flight in which the shuttle failed to reach ISS.
Ultimately, when an autonomous inspection and repair capability is implemented, a mission to Hubble will then be as safe as any mission to ISS. Thus, an HST flight requires few, if any, unique capabilities to ensure safe flight beyond those developed for flights to the ISS. NASA plans to provide a Shuttle rescue capability for all flights. The flexibility to schedule SM4 immediately prior to one of the ISS flights provides a ready capability to mount a rescue mission if needed. Risks of micrometeoroid and orbital debris damage to shuttle on ISS flights exceeds that on flights to HST, given the flexibility in the latter to place the shuttle in a protective orientation.
The NASA Administrator has publicly stated “that a Hubble mission would require new and unique procedures that, taken individually, were surmountable but that in the aggregate were risks significantly higher than a shuttle mission to the space station.” The aforementioned data and references from NASA RTF plans demonstrate that this statement cannot be supported. Given that NASA’s plan is to be fully compliant with the CAIB recommendation to develop an autonomous inspection and repair capability, the aggregate risks are higher for ISS flights than for a flight to HST.
When looked at from a TPS survivability perspective, there is a good basis for concluding that HST missions are as safe as or perhaps safer than ISS missions conducted in the same timeframe. HST missions will have:
• A reduction in the risk of debris damage during ascent after the ET and SRB are modified; equivalent to ISS missions.
• Impact sensors to identify impact locations and to focus early and time efficient inspections; in common with ISS missions.
• Inspection sensors that will allow for accurate and time efficient inspections; in common with ISS missions.
• A tile repair capability; in common with ISS missions.
• A rescue capability as readily implemented for an HST mission as for ISS, since the HST mission can be timed to be launched immediately before an ISS mission.
• A better MMOD environment than an ISS mission and more flexibility than ISS flights to fly a protected on-orbit attitude
The existence of or lack of a RCC repair capability will be a problem that is common to HST and ISS missions. While an HST mission will not have a safe haven capability, the risk associated with the absence of a safe haven is the same as ISS missions that fail to dock with the ISS.
SUMMARY
When looked at from a thermal protection system (TPS) survivability perspective, HST missions have a good basis for claiming that they are as safe as or perhaps safer than ISS missions conducted in the same timeframe. HST missions will have:
• A reduction in the risk of debris damage during ascent after the external tank (ET) and solid rocket boosters (SRBs) are modified; equivalent to ISS missions.
• Impact sensors to identify impact locations and to focus early and time efficient inspections; in common with ISS missions.
• Inspection sensors that will allow for accurate and time efficient inspections; in common with ISS missions.
• A tile repair capability; in common with ISS missions.
• A rescue capability as readily implemented for an HST mission as for ISS, since the HST mission can be timed to be launched immediately before an ISS mission.
• A better micrometeoroid and orbital debris (MMOD) environment than an ISS mission and more flexibility than ISS flights to fly a protected on-orbit attitude.
HST missions may not have a practical or comprehensive reinforced carbon-carbon (RCC) repair capability, but this will be a problem shared with ISS missions. A HST mission will also not have a safe haven capability, but this could be offset by the ability to launch with an ISS mission fully ready to launch (which would become the rescue mission).
One could argue, on the aforementioned logic, that the final planned HST Servicing Mission, SM4, will be at least as safe as flights to the ISS. Finally, one can also conclude that no additional work needs to be performed over and above what must already be performed for ISS missions launched in the same timeframe.
This entry was posted on Friday, July 18th, 2008 at 8:07 am and is filed under Public Relations, Space Agency News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
