Night Flying

I just finished reading ‘Origins of 21st Century Space Travel’ SP-2019-4415 from the NASA history office.  A fascinating book recounting the development of the Vision for Space Exploration in the Bush administration leading up to 2004.  Most of the action takes place in Washington, DC.  After all, this is about national space policy direction, not execution.  Those of us out in the field centers who were doing the detailed work to make the shuttle fly and build the ISS were not involved in the policy development.

My name appears in the book only on one of the last pages where the authors correctly observe that being able to launch the shuttle at night was critical to the ISS assembly.

This post is about how the night launch decision was made down at the program technical level.

Shortly after the loss of Columbia – while I was still assigned as the Shuttle Program Launch Integration Manager at KSC – the Eastern Range folks sent me a CD ROM with the radar tracking information from January 16, 2003.  Purportedly the radar tracking scans would show any debris falling away from the shuttle stack.  This was something that could be of great importance in the ongoing accident investigation.

I studied that data long and hard.

It was incomprehensible.

I consulted the experts who were experienced interpreting the squiggles and dots on the radar tracking data.  They confirmed there was a lot of things apparently coming off; none of it correlated to the time of interest that when the long-range tracking cameras saw foam coming off the ET.  No way to tell the nature of the material in those radar indications: foam, ice, metal; it was unknowable from the radar, just something that reflects radar waves came off.

A few things are known to came off during shuttle launches: ice from the extremely cold hydrogen channels on the main engines, engine covers from the booster separation motors.  And foam of course, but that is not very reflective.  And that was the extent of the list.  Nothing on the radar traces correlated.

Conclusion:  while the radar data was interesting and probably telling us something, it was not very useful given current state of understanding.

Fast forward two years to the hard work of getting ready to fly the shuttle after that accident.  One key element in our safety of flight rational was that detection of debris liberation during launch phase was mandatory.  Impact detection sensors we installed inside the leading edge of the obiter’s wings to detect anything that might impact those critical areas.   A bevy of new ground cameras with high magnification telescopes and super accurate tracking mounts were deployed around the launch area.  There were new in-flight cameras installed onboard both the SRBs and the ET.  A tremendous amount of money was spent to develop and install tracking cameras on NASA’s WB-57 aircraft to see the shuttle stack from a different viewpoint.

Trying out the new ground camera trackers

Two compact X-band radars were deployed on offshore ships to monitor for debris.  A powerful C-band radar became available from a Navy installation that was closing so we bought that and installed it well north of the launch pads to plug a hole in our radar coverage.  All these efforts were made at great taxpayer expense just to detect any debris that might come off the shuttle stack during launch.

Inspecting the X-band radar installation on one of the SRB recovery ships

Navy Surplus C-band radar installed north of Haulover Canal










Also developed was a special inspection boom that attached to the end of the shuttle robot arm.  The ISS crew was trained to use long lens cameras to photograph the underside of the orbiter as it did a backflip during near approach.

For the first two flights after Columbia, we required daylight launches to ensure that all those cameras would see anything that came off during ascent.  And we saw lots of stuff, mostly foam that missed the orbiter.  I wrote about that in How We Nearly Lost Discovery


During those first two flights we found out how well all the new detection/inspection systems worked.  The onboard cameras were fantastic; the new ground-based cameras were superb; the wing leading edge impact detectors gave a lot of false indications; the airborne cameras on the WB-57s just didn’t have the resolution to be helpful; and the radar was . . . incomprehensible.  Never could correlate any of the visually detected debris events to the squiggles and dots in the radar tracking data.  Seemed like we had wasted our effort and a lot of taxpayer money.  However, the real proof of health of the orbiter turned out to be in the in-space inspections; that saved the day.

To maintain our safety rationale in its entirety, many in the human spaceflight community really did not want to fly without that real time ascent monitoring of debris events, and the cameras were useless at night.  Orbital mechanics dictates the launch window to rendezvous with the ISS and without the capability to launch at night it might be months between available launch days.

What to do?  Rely on the radar, of course.  Not exactly an untruth but certainly a stretch.  Knowing that the real proof of safety was the in-space inspections, we continued to gather radar data and try to understand it.  Some experts even came to believe they could make use of the data.

I was never convinced.

Nonetheless, I publicly said that we could launch at night and would depend on the radars to detect any significant debris events during launch.

A fib?  A white lie?  An outright falsehood?  Never!  We poured over the radar plots every launch.

For what they were worth.

About waynehale

Wayne Hale is retired from NASA after 32 years. In his career he was the Space Shuttle Program Manager or Deputy for 5 years, a Space Shuttle Flight Director for 40 missions, and is currently a consultant and full time grandpa. He is available for speaking engagements through Special Aerospace Services.
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10 Responses to Night Flying

  1. Lappan says:

    Did a persuasive theory emerge for why the radar data was so noisy? Is it something that only occurred with the SST launches, or is it common to other launches but nobody previously examined the traces in that detail?

  2. Steve Pemberton says:

    I remember that the on-orbit inspections were even done again after undocking from ISS, which I thought was really an amazing amount of thoroughness considering how unlikely it would be for damage to occur to the thermal protection system while on orbit. And with a certain amount of risk just doing an inspection as they carefully maneuvered the robotic arm over virtually every square inch of the underside of the orbiter.

    I also remember that the on-orbit inspections took several hours, essentially most of an entire astronaut work period. And using lasers which provided mountains of precise data for the analysis teams on the ground to pore over. I remember one flight where they found a gouge in one of the tiles on the underside of the orbiter, and they used the 3D laser data to create an exact duplicate of the tile on the ground including the gouge, which they then placed into an arc jet to see how the gouge would affect heating during reentry. I can certainly see why data from the on-orbit inspections was considered far more valuable than trying to mull over fuzzy film footage taken from a long distance away.

  3. kevin rusch says:

    I saw a Scott Manley video about ballistic vs. “flown” re-entry, and it got me to thinking about the Columbia disaster, and you said you guys looked into trying a different re-entry to keep the heating loads down. Can you point me towards anything that’s been written about that. As a total amateur, my thought was that wings that big could be used (in some to-be-determined manner) to keep it up over 400k feet for a long time until its speed was burned down to a not-forming-plasma level. Is this stuff written up anywhere?

    • waynehale says:

      Good idea but unfortunately the shuttle wings did not create enough lift at high altitude to stay there for any significant time.

      • Kevin Rusch says:

        Fascinating. The more I think about the compromises made in designing the shuttle, the more it all feels like a very expensive lost opportunity.

  4. Charles F. Boiden Jr. says:

    The never truly solved problem, Wayne, was what do we do if/when we find damage to the tiles. As you will remember, prior to STS-1, we worked tirelessly with the “Tile Repair Tiger Team” under the late Bill Lenior only to conclude that the technology to provide for reliable on orbit repair to the TPS just wasn’t within our capability. It was here that we failed to evaluate the risk from impact to the RCC that brought down Columbia. I frequently had the feeling that we were taking a lot of very prudent actions to determine damage without the ability to effect repair once we were launched. All the imagery and imaging you cover in your blog i feel falls into that very broad category. As a flyer, I knew deep down inside that there were risks i would have to accept.

    Charlie B.

    • waynehale says:

      With advances in materials over 30 years we were able to come up with good on-orbit tile repair options in 2005. Risks were never completely eliminated and that was recognized.

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