The Triumph of the Flexible Path

These days I frequently travel to the Denver area for personal and work reasons.  Driving in from the south, just at the edge of town, I always think when I pass the big Marriott at the I-25 Lincoln street exit:  “That’s where the space program changed.”  Let me explain.

Just as my year of ‘education’ was ending in 2009; poof! – a new administration came in.  Everything changed, subtly at first but nevertheless significantly.  While we were waiting for a new Administrator to be nominated, the OMB and OSTP commissioned a blue ribbon study group: “The Review of Human Spaceflight Plans Committee” more popularly known by its chairman’s name as The Augustine Commission.

Several of us NASA HQ types were assigned to provide assistance to the commission:  Phil McAlister was chosen to be the ‘Secretary’, Tricia Mack was his assistant.  Tom Cremins and I were assigned to provide support along with a few others.  We soon found out that the committee members did not want the opinions of this support staff, we were responsible to ensure only that the experts they wanted to hear were provided to them.

Many of the meetings were public, but the pivotal meeting that I recall most clearly was not.  The west coast members started complaining that all the meetings were held on the east coast causing the westerners to bear the biggest travel burden.  An arrangement was made for a meeting in late July in Denver, near the Lockheed-Martin facility building the Orion spacecraft.

As the meeting evolved, no side trip to visit to the LM plant happened. Various experts were called to the Marriott to be interrogated by the committee.  It was at this closed meeting in late July that I recall hearing Dr. Ed Crawly first mention ‘the flexible path’ as a possible plan for human space flight.

It was clear that there was just not enough money in the out-year budget plan to fly the shuttle, fly the space station, build the big rocket that everybody felt was required for deep space missions, and develop the landing vehicles as well.  Even with the shuttle retired, the committee felt that at least $3B a year would be required to continue the existing plan.  As Norm Augustine put it in one of the public sessions later on ‘It appears you can’t have a very interesting space program without an additional $3B per year.”

Since OMB was implacably opposed to additional money for NASA’s budget, ‘The Flexible Path\ plan evolved as a way to allow development of the early parts of any human deep space plan until more money would be available under a future administration.

After the report was published, the ‘Flexible Path’ option quickly became nicknamed ‘The Path to Nowhere’.  Not really accurate, but right up there with the assertion that NASA had spent the last 30 years ‘going around in circles.’  Various factions have always been ready to apply disparaging labels to any plan they oppose.

The new administration liked a hodgepodge of the ideas in the Augustine commission.  Particularly they seemed to like a policy which would return NASA to its predecessor agency NACA’s status as a research and development organization while providing financial encouragement to private industry to develop new, more affordable space vehicles.  This would be a complete break with the previous goals and policies that NASA had been instructed to accomplish.

After the administration announced the cancellation of Constellation on February 1, 2010, there was a huge disconnect between the administration and the congress.  After months of contentious wrangling, a compromise (there is that magic word!) or more accurately a tense détente resulted.  The money which was proposed to go to R&D was largely moved to build a big rocket – no longer called Ares V but SLS.  There was continuation of development of a deep space capsule – Orion – and increased support to commercial space development for transportation to LEO.  And there we stand to this day.

Bill Gerstenmaier has masterfully orchestrated the political and financial resources available for human space flight.  He has sought to maximize progress toward both commercial crew and cargo to LEO but also develop the big rocket and deep space capsule.  But in the near future, the wherewithal to build a landing vehicle (think of it like the descendant of the Apollo LM) must come.  Lander design depends on where we would land:  a design that would work on the Moon would not work at Mars and vice versa.

And where is the money to come from?  When the shuttle retired, one might have expected NASA to keep all that money to apply to future projects; sadly that was not the case, funds have eroded.

So everybody is anxious to see what the incoming administration will direct.  The crystal ball is cloudy.  Will it be the Moon?  Will it be Mars?  Probably not the Asteroid Retrieval Mission.  Or will it be stasis:  giving NASA just enough budget to continue development of the vehicles and systems in work today and waiting for some future time when the money will become more readily available?   The clock starts ticking at noon on January 20.

Meanwhile, of all the options that the Augustine commission offered, the Flexible Path is the one we have chosen, whether we wanted it or not.

And when I see that Marriott in Denver again, I will still think:  that is where America’s space program changed.

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The Road Not Taken

I always knew what I wanted to do:  anything in the space program.  Getting a job offer to come to work at NASA Mission Control in Houston was beyond my wildest dream.  To tell the truth, I would have paid them to let me come and sweep out the floors.  But it worked out much better than that.

The very best job I ever had was that of Flight Director.  Each flight was different, but we put together the teams, decided how we would approach the challenges, and trained like the devil.  Every shuttle flight was an exercise in pure adrenaline rush.  Whether it was two days or three weeks, nothing else in life mattered while the shuttle was in flight – every waking moment spent reviewing, planning, preparing, and then executing the most difficult and riskiest work I know.  After the flight was over, well, sometimes I needed to sleep for a week.

One short illustration; as the Entry Flight director (26 times!) I had to go over to the press room after the landing and sit with the Program Manager for the press conference.  Generally, there were only a handful of reporters present, but there were many more watching the video and tied in by phone to ask questions.  I was always exhausted; running on fumes as they say by that point.  I learned that the Entry Flight Director got to make a little opening statement, how great the landing was, how challenging the weather was, so forth.  Then the Program Manager made a statement about the flight just over and the challenges upcoming.  Then the media questions started.  I quickly learned that there were never any questions for the Entry Flight Director.  After all, the landing went fine; it was over, what more could I have been asked?  All the questions went to the Program Manager.  And the Program Manager could drone on with long and involved answers as to what might or might not be next.  There were two cameras in the media room, a wide shot that captured both the PM and me, and a narrow shot that was focused on whichever of us was speaking.  The red light indicated which camera was active.  When the narrow shot was on the PM, I could nod off – for just a short while – close my eyes, rest my brain.  But I had to be awake enough to know when the PM was winding up his long answer and the wide shot was going to be selected.  Time to look alive!  I practiced this trick many times.

Getting to be Deputy Program Manager, and later PM, I got to practice the other end of the media role – a lot less fun, I must say.  In fact, I never enjoyed the Shuttle PM job as much as being a Flight Director.  To this day if the Chief of the Flight Director Office were to call me up and ask for my help, I would be there in an instant.  Unfortunately, being a Flight Director is a young person’s job – quick reflexes, quick study of the issues, and indefatigable alertness even in the wee hours of the morning when all is going boringly well because the next moment may not be boring at all.

After five years in the Shuttle Program Office as deputy and chief, Mike Griffin asked me to take a role that would let me learn about ‘the whole agency’ as he put it.  It was really time for me to have a change, so I went on HQ staff – but they allowed me to work and live in Houston.  It was an eye opening year as I learned a lot about Washington, and about the various parts of NASA beyond human space flight.  Sitting with the Administrator in the Heads of Agencies meeting in Paris gave me a glimpse at how hard it is to hold together the fragile international coalition that keeps the ISS going.  Sitting in on Congressional hearings gave me the strong sense that, in spite of the theater involved, the real work at HQ was earning the respect and support of the legislators who ultimate decided what resources the agency would get.

Just as my year of ‘education’ was ending, poof – a new administration came in.  Everything changed, subtly but nevertheless significantly.  I was pleased to help support the Augustine Commission during the summer months; another intensively educational experience.  Following that, Bill Gerstenmaier assigned Frank Bauer and I to develop plans for the proposed Commercial Crew program since that was clearly one of the common themes from Augustine Commission likely to be approved by the new administration.  Meanwhile, Charlie and Lori were nominated and confirmed as the new heads of NASA.

I made it known that I would be happy to have to more substantive role, feeling that my ‘sabbatical’ was over.  But, despite repeated inquiries at NASA HQ, JSC, KSC, and MSFC, there appeared to be nothing for me other than to continue in my support role.  As the shuttle program wound down, most of the other senior leaders in that program found themselves in the same situation; no place to put that talent to good use inside the agency.  With the cancellation of the Constellation program, NASA was awash in senior leaders without jobs.

Being well past the age and years of service to take my retirement, I turned in my paperwork and thought about what would be next.  Bill Gerstenmaier offered to bring me to Washington to be of closer assistance to him, more about that later, but by the time of that offer I had made my decision.

I found a small, family owned specialty engineering firm run by ex-NASA folks which was a good fit for me.  It was a place where I could bring my experience and lessons learned to the aid of the new companies building the new vehicles on a commercial basis.  This continues to be very exciting work and I like to think that I have provided critical help to several organizations.  It has been a new component to my education to closely observe how private industry makes decisions.  Certainly different from the government.  And it has been extremely interesting to deal with some of my old colleagues and organizations from the vantage point of the outside.  Makes it much more clear how the government could be more effective.  Finally, I have been asked to volunteer my time (that’s right – unpaid volunteer) to advise both NASA and the FAA Office of Commercial Space.  Additionally we are working with Johns Hopkins University Energetics Department to document lessons learned from reusable space vehicles.  Hopefully this will help future programs be more successful, especially in the financial sense.

Still, my heart is with NASA, and I wake up about once a week wishing that I were back in the agency, back in the trenches fighting the good fight to advance human space flight.  Maybe back in mission control making sure that we get the most research possible accomplished.  Maybe back in Washington haggling with the OMB about funding levels.  I don’t know, back there somewhere substantive.

I wonder about that last minute job that Bill G offered me, to come to DC and help him directly.  Would I have made a difference?  Would plans and goals have evolved differently?  Could I have made a difference in the budget wars?   Or would an old Flight Director just have mucked things up? But one thing is for certain, that was the road not taken.  And you can’t change the past.

I believe I am making a contribution in a different way right now.  And, oh-my-goodness, I don’t miss the sheer bureaucratic nonsense that my still-working colleagues remind me about on a regular basis.  Changing an Agency is very hard.  I think that there may be a number of folks in the new administration who will try to change various agencies in their goals and internal culture.  I wonder how likely that is to succeed.

When I was having a particularly hard time with some of the bureaucrats at NASA HQ, I encountered a group of retired senior JSC leaders one day and asked them how they dealt with HQ in their day.  They just laughed at me.  And then one of them said: “Just remember, they won’t be there very long.”

You can take that several ways.  And for the record; I really don’t want to work in Washington.

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Auld Lang Syne

The last day of 2016 is appropriately dreary here with rain and a damp chill.  Just the thing to reinforce a melancholy mood or at least induce a good nap.  All around it seems every media outlet has complied their list of notables that we have lost in 2016.  This is as it should be.  These shared lists run to actors and singers and other entertainers.  Too seldom do they list the heroes whose names are not written on stars in the sidewalk but who made a real difference in someone’s life.  Pity, that.  We need to be reminded of heroes more.

Many of us take a cup of kindness yet to remember those who have departed that will never show up a list of ‘notables’ except in our hearts.  Family and friends no longer with us who shared themselves in uncountable ways.  Faces no longer to be seen except in old photographs or their digital cousins.  Voices ditto no longer shared fresh daily but sometimes played back from a recording.  Quiet stillness everywhere but always alive in our hearts.

It is now commonplace to remind one another that no one ever ‘gets over’ a loss, but that time can fade the pain somewhat.  For those who have lost a loved one this year, that anesthetic has scarce effect.

So at the end of the year, in melancholy fashion, it is right and proper to remember those departed so dear to us.  Tomorrow will dawn a new and bright new year full of promise and fears; how that will turn out depends on us.  Tomorrow resolve to hug those dear to you a little tighter; to make on new occasions memories that will remain fragrant through the years no matter what else may come.

“Will the circle be unbroken,

by and by Lord, by and by?

One by one their seats were emptied.

One by one they went away.

Now the family is parted.

Will it be complete one day?”

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Accident Investigations

This week’s crash of a commuter train in New Jersey plus other recent events got me thinking about the lessons I have learned the hard way through several accident investigations.

One of the toughest parts of investigating an accident is that everyone wants to know the answer, the cause, right away.  Folks, it simply does not happen quickly.  Accidents involving complex high energy systems are tough to figure out.  Even little incidents can be hard:  as we used to say in the shuttle program:  “The first story is always wrong”.  It takes time to get an accurate picture and compile the evidence.  It will be long after the news cycle has moved on to other things before the true cause becomes apparent in these complex systems failures.  The boss and the media want answers right away and sometimes will make something up – or at least grasp on the first theory – to get a quick answer.  Real accident investigators know it takes time.  Typically the NTSB takes a year to finalize their reports; I’d have to say that is about right in most cases.

So I’d offer this explanation about why it takes so long.  And I would offer a few tips and rules from my experience.  This is not what they teach in accident investigation school where the emphasis is typically on preserving the data, making sure the evidence is uncontaminated, gathering witness statements, collecting the maintenance records, examining training records, and the other mechanics of the process – which are important.  These rules are in addition to those good practices which should be followed at all times.  Sort of ‘Gibbs Rules’ here:

Rule #1 for accident investigators:  keep an open mind.  Do not start making theories too early. Stay away from quick conclusions and let the facts lead to the conclusion, not the other way around.  This is very hard to do, not to start spinning theories right away.  Don’t speculate and don’t let others lead you into conversations that speculate on the cause. It is amazing how biased thinking becomes and how easy it is to overlook evidence once your mind (consciously or subconsciously) believes it has a conclusion.  Keep an open mind as long as you can.  When we had shuttle ‘anomalies’ the first analysis was almost invariably wrong and sometimes it would take months before we got to the correct conclusion.  Fixing the wrong thing is never helpful.

Rule #2 for accident investigators:  make a good, comprehensive timeline of all the information around the time of the accident.  This is not as easy as it sounds.  In the rocket business we always have a stream of telemetry of pressures, temperatures, valve positions, operating speeds, etc., recorded in a central place.  But sometimes the telemetry is built up from different sources on the rocket or on the ground.  It is important to dig into the time sources and make sure every event is put on a master time line with the correct and cross correlated time.  When milliseconds count, as they often do in these investigations, make sure that time lags and adjustments in the system are fully understood and accounted for.  For other evidence, video from external cameras for instance, be certain about the timing source, make sure the frame rate of the video is accounted for.  It is vitally important that video or still photos give their evidence in the right time frame.  Knowing what happened when, in the right order is the most powerful tool in the investigator’s toolbox.  Getting all the evidence and timing right can take weeks.  Be patient and adjust the timeline as the evidence comes in.  Continue to keep an open mind at this stage.

Rule #3 for accident investigators:  make sure the physical evidence is examined by a dis-interested third party that is well qualified to evaluate it.  To avoid the appearance of impropriety that may cloud a final report, using a well-qualified lab that is not associated with the manufacturer or operator of the equipment is vital.  Well qualified labs and experts are hard to find and often expensive, but it is worth the time and cost to come to a final conclusion that is as free of controversy as possible.

Rule #4 for accident investigators:  make a fault tree.  This helps the accident investigator build up knowledge about the system and makes sure that all possible causes are investigated.  Fault trees typically are of less use than the outside world may think.  The most important result from building the fault tree is that it makes the accident investigators aware of all the items that need to be examined.

Rule #5 for accident investigators:  ask ‘why’ seven times.  It is much too easy to come to a first level conclusion and leave the investigation.  That is guaranteed to result in future accidents.

I have no idea why the train crash occurred, but let’s take an imaginary trip through the kind of questions that an accident investigator should ask later in the investigation when a proximate cause is identified.  Here is that strictly hypothetical example: Q1: Why did the train not stop? A1:  The brakes failed to apply when commanded by the operator.  Q2: Why did the brakes fail?  A2:  part X in the braking system failed.  Q3: Why did part X in the braking system fail?  A3 It was installed improperly at the last maintenance period. Q4:  Why was part X installed improperly? A4:  The maintenance installation procedure was incorrect.  Q5:  Why was the maintenance procedure incorrect? A5:  The procedure was not updated when a new part manufacturer was selected to build part X.  Q6: Why was the procedure not updated?  A6:  The process for updating maintenance procedures did not allow for a change in part manufacturer.  Q7:  Why did the process not allow for a new manufacturer:  A7:  It was not foreseen that a new part manufacturer would make a part that needed new installation procedures.  Following this hypothetical case – and just note that I know nothing about the train crash, I am just making this up as a teaching tool – an accident investigator would find that the proximate cause of the accident was a braking failure, but the root cause was an inadequate process to account for new part manufacturers and the corrective action is to update the maintenance procedure change process to ensure that when a new part is introduced, the maintenance procedures are updated properly.

It is easy to see that if one quit with the part failure, a band aid fix would probably ensure that that particular part never failed again, but other failures could occur.  Similarly if at step 3, the investigation were to blame the maintenance person who installed the part, not only would an injustice occur, but the way for other failures in the system would be left open.  It is important to get to root cause – which is almost always a process problem – and address that as well as the more simple corrective action for proximate cause.

All of this takes time and discipline.  Months may pass before the real cause of the accident can be established.  That is true for rocket ships and airplanes and I’m sure it’s true for trains.

Don’t expect the media to get this right, or even care about it when the final report comes out.  Short attention span there.  The important thing is that the source of future accidents has been cut off.

Rule #6 for accident investigators:  there will always be conflicting and confusing information.  It is very rare in these failures of complex systems to come to a one and final guaranteed 100% conclusion.  There are always counter indications and other possibilities.  A good accident report will always give the most likely cause and list other causes which are less likely but cannot be completely ruled out.  Absolute certainty is not something that engineers or accident investigators deal in.

So be patient and let the investigators do their job.

Oh, and follow Gibbs rule #13.  Look it up.

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Running for President

The NASA JSC chapter of the NASA Alumni League (the retiree’s association) has been trying to get me to be the president of the chapter for years.  I enjoy the organization but did not want to put in the time and effort that it takes to be president.  This year, they finally caught me in a moment of weakness and I agreed to run.  All the other potential nominees breathed a sigh of relief.  I’m running unopposed and the ballots are in, we should hear the results in a few days.

It probably comes as no surprise that in middle school and high school, I was one of the nerdy kids.  Smart with good grades, but lacking in social awareness and completely lost in sports.  That did not prevent me from running for student office; encouraged by my mother I undertook a campaign every year for class officer of some sort.  And of course, I always lost.

That carried over into college; I continued to run for various student government offices and was repeatedly unsuccessful.  One year, my residential college awarded me the Whittington trophy – named for a student who once ran for a student office unopposed but came in third place behind two write in candidates.  My record, while unblemished by success, was never that bad.

Nowadays, I get the occasional encouragement to run in the real political world:  “You should run for Congressman!”  This heartens me but I know that it is a non-starter.  All any opponent of mine would have to do is point out that I spent 32 years as a government bureaucrat and the campaign would be over.

Nor would I want that job anyway.  No political ambition here.

Back in college, I had much better luck getting appointed to positions which did not require an election.  I served on several committees, was appointed to be chairman of the committee that brought speakers to campus, served as an ombudsman to the honor council, parliamentarian to the Student Senate, things like that.  (I still have my rabbit eared copy of Roberts Rules of Order – I guess that confirms my geek status).

I watched with a lot of amusement when one of my classmates ran for student body president on an absurdist ticket.  He really could make us all laugh and made it clear that his campaign was a joke.  I wish I could remember all the funny things that he promised, but it was too long ago and my sense of humor might be different now than what my 19 year old self thought was funny.  Anyway this friend of mine became the class clown, the court jester; everybody liked him and nobody took him seriously.

My junior year, the outgoing president of the student body and some of the other officers encouraged me to run for student body president.  Thought my service on various boards and panels made me a good candidate.  I had some modest name recognition from bringing entertaining speakers to campus (see my post on ‘The Great Bird of the Galaxy; about bringing Gene Roddenberry, the creator of Star Trek, to speak).

So of course I filled out the paperwork to run.  My only opponent was the class clown.  This year he was running a serious campaign.  He acted serious, he made serious proposals, and said nothing, nothing, nothing to laugh about.  I figured that we would beat me.  Surprise, when the votes were counted I was the overwhelming winner. Unbelievable.

I certainly learned a lot that year.  I got into a verbal tussle with the editor of the student newspaper and learned the truth in that old Mark Twain quotation:  “Never get in an argument with someone who buys ink by the barrel.”  There were factions on the student senate that had to be recognized, soothed, and compromised to get anything done.  There were student protests that resulted in detention by campus security which became a crisis for the student government.  Dealing with the administration was a challenge, but not nearly as bad as it could have been.

But as I look back on it, the number one lesson that I learned is that it is very difficult to transform yourself from class clown into serious candidate.  Apply that as you will.

Anyway, I am waiting for the NAL election results.  Wonder if I will finally earn that Whittington trophy the hard way.

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When I was a boy, world was better spot
What was so was so, what was not was not
Now, I am a man, world have changed a lot
Some things nearly so, others nearly not

There are times I almost think
I am not sure of what I absolutely know
Very often find confusion
In conclusion, I concluded long ago

In my head are many facts
That, as a student, I have studied to procure
In my head are many facts
Of which I wish I was more certain, I was sure

  • Rogers & Hammerstein: “The King and I”


As a young student, my science teacher made sure that we knew there were nine planets in our solar system.  Nowadays science says that there are only eight plus a host of ‘dwarf planets’.  Lately there has been some evidence, causing some scientists to debate the possibility, that way way way out there is a new ninth planet in our solar system.  But this is uncertain.  ‘Some things nearly so, others nearly not’ as the song says.

Don’t even get me started on the nutritional sciences.  What a few years ago was absolutely bad for your body to consume is now not so bad, maybe even good.  Every week there is a ‘discovery’ of a new wonder food that is guaranteed to help you live longer and healthier.  And in a few years we will be told that it probably doesn’t work that well.  Me, I still take extra vitamin C when I get a cold even though now the doctors tell us that really doesn’t do any good.  Some things you learn early in life are hard to get over.

Just about a century ago, a group of crackpot, radical geologists proposed that the very continents we stand on – made of solid rock! – float on an ocean of magma underneath.  And the continents actually drift – apart, together.  Roundly ridiculed by the establishment in the geological sciences, it took six or seven decades of gathering evidence and furious debate to win over the majority of their brethren.  Literally a tectonic change in our understanding of our planet.  From this we have a better understanding of volcanism, earthquakes, and the distribution of minerals and plant and animal life around the globe.

About four centuries ago, Isaac Newton discovered and mathematically described the laws of universal gravitation.  An unseen force, acting at a distance, caused an attraction between everything in the universe.  Newton proposed that this force acted proportionally to the product of the mass of the bodies and inversely proportionally to the square of the distance between them.  This theory was hailed as a great achievement; Newton was knighted and at his death buried with honors in Westminster Abbey.  To this day our children are taught about the gravitational force, the way it works, and how to predict and analyze movement with Newton’s mathematics.  As physics progressed, other forces have been discovered and added to the list:  the strong nuclear force, the electromagnetic force, the weak nuclear force; all stronger than the gravitational force.

Along comes Albert Einstein in the last century and, like so much else that we were absolutely sure of, completely blows up the subject.  According to Einstein, there is no such thing as the gravitational force.  Mass distorts or warps the space time continuum.  As object travel along their world lines in the space time continuum of our universe, the world lines themselves are curved by the warping effects of mass in the space time continuum.  So gravity, as a force, does not really exist.  Newton’s laws are useful for describing how bodies move – at less than relativistic speeds – but gravity, per se, has been removed as a physical force and is now just a general term that describes the warpage of space time.

This is not a subject that is frequently taught in high school science classes.

And let’s not even get started talking about the nature of time.  My head is already hurting. “ In my head are many facts/That, as a student, I have studied to procure/In my head are many facts/Of which I wish I was more certain”

Science, it seems to me, is an ever evolving body of knowledge and our attempt to organize and understand it.  Science is not static and unchanging.  We know more today than we did yesterday, and thank goodness for that.  Our understanding of the nature of the universe is more profound than that of scientists in former days.  Science, it seems to me, is full of discussion and debate as we try to revise our thinking to accommodate the new information constantly streaming in.

Science, it seems, is never ‘settled’.  I certainly wouldn’t believe anyone that says it is.

To finish our song:

There are times I almost think
Nobody sure of what he absolutely know
Everybody find confusion
In conclusion, he concluded long ago

And it puzzle me to learn
That tho’ a man may be in doubt of what he know
Very quickly he will fight
He’ll fight to prove that what he does not know is so

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Test Like You Fly



Convair 990 used for Space Shuttle Tire Testing

The retired aircraft that is serving as a sign for the Mojave airport deserves some notice. It was absolutely critical to the safe landing of the space shuttle. Here is why.

No other aircraft put as much stress on the tires, brakes, and landing gear as the space shuttle did. Only the Concorde came close, touching down at about the same speed and weight. But the Concorde had four tires on each main gear truck as opposed to the space shuttle’s two so the load on each tire was much less.

In the early design of the space shuttle, the landing weight was calculated to be about 150,000 lbs. and the landing gear designed accordingly. In actual practice, due to weight growth and other factors, the shuttle rarely weighed in at less than 200,000 lbs. at landing. When returning with a payload – say a SpaceHab or SpaceLab – the weight could be considerably more. Maximum normal landing weight could be up to 230,000 lbs. In an abort landing, we were prepared to touch down at 258,000 lbs. All this on the same gear that was designed for 150,000 lbs.

Just to make it more fun, the ‘derotation’ of lowering the nose to touch down on the nose wheel tires caused even more loading. Rolling on all tires on the runway, the shuttle is 5 degrees or so nose down. At the instant of nose gear touchdown, the downward pressure on the main tires is increased by the aerodynamic forces pushing down on the top of the wing.

Speed is critical to tire performance; at speeds over 225 kts, a kind of reverse curvature in the rubber tire sets in that can quickly heat the tire to failure. Normal landing speed for the shuttle was targeted at 195 kts but for some heavyweight flights, the big glider had to touch down at 205 kts. With piloting variations, some landings approached the critical 225 kts touchdown speed.

Runway surface can make a difference; desert runways like Edwards are smooth but runways in wetter climates are grooved to shed rainwater quickly. The shuttle landing facility at KSC had groves and we found that landing there chewed up the tires.

And sideways forces from a crosswind at landing could cause even more damage to the tires.

In fact, for all the early landings, the post landing inspection of the tires showed more damage that we expected. More damage than we were comfortable with. Consternation over the tire and brake situation resulting in tests, redesigns, improvements to the tires, the brakes, and the runway surfaces.

We used several main tools in testing the shuttle tires to these extreme conditions they would experience during landing. First, the big tire dynamometers at Wright-Pat AFB in Dayton Ohio. Tires and wheels were pressed hard onto bug drums of steel spinning to simulate touchdown speeds. These dynamometers gave great data. But they didn’t do side forces and since the drums are curved, the effects were not quite like real flight.

DSC_0028 Cmp

SSP Management inspects tire test equipment at Wright-Patterson AFB

Second, we used the test track at Langley Research Facility. A big carriage with the main gear tire was propelled to high speed and ‘touched down’ on a section of track a quarter mile long that had the surface – grooved or smooth – that was of interest. A great improvement; but it lacked the full rollout length and was limited again in side forces.

Analysis and these partial mode tests revealed a lot but the real landings were still incurring more damage than we predicted. So finally it was decided to actually fly the tires.

A Convair 990 transport was converted with an armored bay that could carry a shuttle main gear truck and one or two tires. We could land at high speed, hydraulically force the tire onto the runway with as much force as required, sideslip or take crosswind to well documented levels, and see what happened. Many many runs reviled the data was needed. Final adjustments were made to the tire manufacturing; improvements to the brakes; changes to the runway surface; and most importantly, limits on speed, crosswind, and weight were all confirmed using real flight data.


Armored bay in Convair 990 where shuttle landing gear was tested

In space flight, it is almost impossible to test ‘combined environments’. We get one or two dimensions. Analysis has made great strides and computer models can inform engineering decisions greatly. But when complete accuracy is really important, the only real test is a flight test. No matter how much it costs.

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