Black Zones – Part 4

I keep meandering around on this topic and if you get confused, I’m sorry about the writing style. 

Just to review the story:  Mercury, Apollo, Soyuz, Shien-Zou, and the Orion all use launch escape towers for crew safety.  Gemini used ejection seats.  The shuttle famously does not have a crew launch safety system although it had ejection seats for early flights for problems during entry and now has a bail-out pole and parachutes for problems resulting in not being able to reach a runway.

I will discuss re-entry safety in a later post; I know a lot of folks are interested in that, too.

Of course a launch escape tower does not provide complete safety.  For example, off the pad or very early in the launch of a Saturn rocket, the launch escape system would get the astronauts away from the rocket, but the Apollo capsule would land on the beach.  Those capsules were not rated for anything other than a water landing so crew injury potential was high.  Similarly, there was a tremendous concern about running into the launch umbilical tower shortly after liftoff.  In some of those scenarios, the launch tower might not be effective in getting the capsule away. 

At a certain point in the launch sequence the escape tower is jettisoned.  Survival here depends on several factors.  First of all, that the launch vehicle failure still results in the spacecraft being pointed in the direction of travel.  As we saw in the Soyuz 18A story, the third stage firing with the second stage attached resulted in large attitude excursions and a subsequent flight direction that resulted in far higher loads than a controlled abort at that point should have.  A real spin up of a launch vehicle would probably overwhelm any of the launch escape systems ever designed.

Second, after launch escape tower jettison, for multi-engine rockets, the capability must exist for all the running engines to be shut down.  So if you have an engine out case and everything is still holding together but you cannot shut the remaining engines down perhaps due to an electrical fault, generally the capsule cannot get away.  There must be a rocket engine to separate the capsule from the failed launch vehicle, but many times these are relatively small.  For example, the Gemini Orbit Adjust Maneuvering System (OAMS) provided such slow acceleration that even with one engine out on the Titan II second stage, the capsule could not get away.  Mercury used very small separation rockets with the option to fire the solid retro rocket package, but these could not overcome the acceleration of even the Atlas sustainer engine burning alone.  So attitude control upsets which in themselves can be caused by electrical faults, coupled with the inability to shut down the upper stage engine(s) – again could be the same electrical fault – could lead to very bad outcomes.  On the other hand, Apollo with its huge Service Propulsion System (SPS) engine — designed to launch the CSM off the moon when direct flights were envisioned — had enough oomph to get the Apollo capsule out of almost any circumstance.

All that being said, a capsule with moderate rocket engines and a launch escape tower on top of a long slender rocket is much safer than any tandem design like the space shuttle. 

The space shuttle is safe if any single SSME prematurely shuts down and both of the other engines keep running AND the attitude control system is functional AND there was no debris generated in the engine shutdown that affects the orbiter’s heat shield.  That is quite a bit of difference.  One of the reasons for the difference is that the cargo – up to 30 tons – goes everywhere the crew goes. 

In the current design for Ares/Orion, the cargo goes up on a separate rocket.  This allows for improved crew safety, but at some operational cost — the crew capsule must rendezvous with the cargo on orbit before any work can commence.

Two other quick points.  One person wrote a comment that the SSMEs are so reliable that we could quit worrying about one shutting down in flight.  While the engine designers and builders are justifiably proud of the extraordinary reliability of the SSMEs, nobody that has studied them in detail rests easily.  Too many parts are rotating at too high speeds, combustion is taking place at too high temperature and pressure for anybody to not keep their fingers crossed for the entire duration of engine firing. 

Second, a number of folks have wondered why we did not put a crew escape system on the shuttle.  Various systems have been proposed, a number have been studied to a high level, and a couple of designs have been looked at in detail.  Ejection seats have been rejected for reasons I mentioned earlier.  Putting the crew in a capsule in the payload bay that could be separated has received a detailed examination.  Some of the limitations associated with this proposal can be easily imagined.  Another idea was to separate the crew module with large solid rockets away from the rest of the shuttle in a launch emergency.  And there have been others.  The problem with designing in these solutions to an already flying vehicle is that none of them are as reliable as we would like; all of them are very heavy and drive the center of gravity out of an acceptable region, and they all cost an incredible amount of money to retrofit in.  So, none of them have been implemented. 

Any winged orbital vehicle under consideration needs to have a serious capability for crew escape designed in from the beginning.  As to vehicles which are carried aloft by other aircraft for their launch; crew (and passenger) safety in that environment has its own challenges and is going to be neither a simple nor cheap capability to design into that type of vehicle.

I think this rounds out my discussion on Black Zones for launch and how they affect spacecraft design.  All you guys out there working to design a spacecraft, keep these points in mind.

16 thoughts on “Black Zones – Part 4”

  1. Just a quick thank you for an extremely interesting and informative blog.

    I may not be a rocket scientist but I’ve certainly learned something here


  2. Hi Wayne –

    First, other people have told me that for Columbia there initially was an explosive bolt system to sever the crew compartment from the rest of the vehicle. True or not?

    Second, during the second STS losss, did Columbia’s crew compartment maintain integrity during the disintegration until its hatch was opened?

    If the news of the heat shield failure had of made it up through channels, could Columbia’s crew have gotten rid of entry energy by dumping payload and firing thrusters before re-entry?

    Could Columbia’s crew have made it down to bail-out speeds?

  3. i’m very happy to listen these kind of experiments done by the scientists. i always dream of the dealing of the projects with in the team .
    i have special thoughts about our vast universe. But i dont have special guidence how to start.
    please guide me in that way, which i can build it as my future fortune come true.

  4. Dear Sir,

    Being a student of literature, thereby being an alien to any scientific or technical knowledge, I do not have any technical suggestion to offer with reference to safety of astronauts. But I write this to you on the occassion of being disposed to a state of melancholy, cantemplation and restricted happiness comforting my soul. While the STS-126 is up there in the darkness, I am happy, as well as, confused and afraid. There is no doubt in the fact that I thoroughly enjoy the realisation that the world we live in can humbly cherish its astronomical beauty. Complimenting this is the indomitable progress of mankind. This age – gifted with wonderous advancements – from cure of life threatening diseases to conversion of urine into pure drinking water – is a miracle in the history of spaceand time. I wonder what all of these would have meant to the stone-age man. But this happiness dwealling in my heart is restricted by thoughts that have disturbed me. Deep inside my mind, heart and soul, I find it painful to realise the amount of cost that mankind pays for it.

    Today while browsing through the webpage of NASA, I thought of having a look at the pictures of those men and women who were in the Columbia of 2003. And when I looked at the pictures, tears filled up my eyes.

    I may be a very ordinary boy from a very ordinary town somewhere in the interiors of India. But above all, I am a human of this planet. And I can not stand any pain that any human has to suffer for no fault of his or her own. And when I was looking at the brightly lit smiles and eyes of those innocent, hard-working and courageous men and women in saffron, I was so sad. I just kept on looking at them and asked myself, “Why? Why? Why?”

    Out of the many men and women our country is proud of, one was Kalpana Chawla. When I looked at the smile in her eyes in one of her images taken inside the cockpit, I was almost mesmerised. I could not believe that there had been an end to this. I could not understand on what account the Lord chose such action. I could not understand why there has to be limitations imposed deliberately and constantly by Nature on all the good that we try to do whereas it quite reluctantly allows the terrorists to move around and commit the mose heinous deeds.

    I have set that wonderful picture of all seven of those grand eagles clad in saffron as my desktop wallpaper. When I see those smiles I tell myself that they are still very much here on earth with us and among us. And so are those who had been on the Challenger of 1986.

    With the Endeavour up there, I am feeling uneasy, afraid, but also have faith. I believe in living. So do us all. And our friends up there, all alone in the darkness, are not alone. We are looking up at them with love, care and faith. Sometimes I wait on my roof to see the International Space Station pass cross the sky. But I have never seen it. Nor do I know whether it can be seen from my little town or not. But when I look up at the stars – which were my frst love – I am reminded of those extra-ordinary men who have helped me realise my love for these stars. Those poems, those astronomers, those astronauts, and all those who have worked to reach out to the stars, have made the existence of these space birds valuable. Being poor in maths and science, and for having not-so-good lungs, I had to forget my childhood dream of becoming an astronaut. Sometimes i look up at the moon and remember how I used to tell my mother lovingly in my younger years, “Mom, look at the moon. Oneday I’ll be there looking at you.” The Lord, however, had other plans for me. But when I see those musketeers of 2003 and 1986,I ask God, “Why was I not in one of those ill-fated shuttles in place of all of them?”

    Yours Sincerey,

    Subhanjan Sengupta
    Durgapur, India.

  5. Wayne, you play the hand you’re dealt, and the fact that the STS was designed by the same generation that brought American drivers the Pinto tells you instantly how dated it is. Yeah, so you’re relying on pumps spinning at 40,000 rpm to deliver cryogens at a rate sufficient to hold a flame front against hypersonic combustion. Old tech. It doesn’t get any easier; controlling the flow of hydrogen atoms and positrons in a magnetic vacuum constriction “bottle” is far more difficult, and the results of failure equally catastrophic.
    Think of it another way…who in their right mind would pay to ride inside an aluminum tube that carries thousands of gallons of highly flammable fuel that could explode at any minute from 30,000 feet?

    Yet millions of people do it every year, without thinking about it.

    I will tell you a story about a terrified girl I sat next to on a flight from Minneapolis to Pittsburgh. She had been visiting her father, who was stationed in the Phillipines. On her way home, the Number Three engine on her 747 detonated somewhere in the blackness over the Aleutians. They were fortunate, setting down in Anchorage.
    She asked if I minded if she held my arm, and I said no. Somewhere above Toledo, my hand became numb, but she was still terrified and I didn’t say a word.

    It’s all about risk tolerance. Life isn’t safe. You do the best you can with what you have and live with the risks.

  6. Hello Wayne

    Can the OMS engines be used to extend the glide distance of a Shuttle during a RTLS, TAL or AOA abort or is that OMS fuel dumped as part of the abort sequence?

    Also it seems now procedure to burn the 2 OMS engines for a couple of minutes just after SRB sep. What extra payload does that allow the Shuttle to carry or is there another reason for this burn?

    Could you also explain exactly how the tiles and RCC work. I read so many varied articles on how they work I’m still confused. Do the tiles absorb the heat and then re-radiate that back out to space at a different wave length? How do the RCC panels reject heat?


    Peter Davio

  7. Thanks for your blog, Mr. Hale…so way back to the mention of the reduction of payload capacity in designing escape pods into spacecraft – let’s say that our first design focus is an “escape pod” (we’ll call it that for the time being although it’s more than that…) and our second focus is an LEO service/science vehicle. In other words, if a space shuttle orbiter is a “truck”, this orbiter is a “car”, it just needs a trunk not a truck bed for carrying service packs for things like space stations and space telescopes, etc. What would you estimate the payload capacity to be if the ship is designed around the escape pod? I realize this question is more complicated than I’m making it out to be given you know nothing of the rest of the parameters of the vehicle, but if it were a space shuttle orbiter, how much would the escape pod deduct from the payload capacity?

  8. Wayne, E.P. Grodine asks some good questions, and I thought that perhaps I might be able to help answer them. Feel free to correct me if I’m wrong.

    First, other people have told me that for Columbia there initially was an explosive bolt system to sever the crew compartment from the rest of the vehicle. True or not?
    (Unfortunately, no. This option was studied in much detail after Challenger’s investigation revealed that the crew compartment was fairly intact when it impacted the ocean at somewhere around 200 mph. It was determined at that time to be too heavy and too complex, and would affect the structural integrity of the orbiter.)

    Second, during the second STS losss, did Columbia’s crew compartment maintain integrity during the disintegration until its hatch was opened?
    (Computer simulations based upon data transmitted from Columbia indicated that its final maneuver was a counter-clockwise overhead spin-roll, caused by the drag from the deteriorating left wing being strong enough to overwhelm the aero surfaces and the RCS thrusters. Another theory states that an explosion of the port side landing gear tires from plasma intrusion into the wheel well caused the port wing to disintegrate. Either way, they were traveling at 12,500 mph when the ship broke up, and friction had heated the atmosphere to around 3,000 degrees F.)

    If the news of the heat shield failure had of made it up through channels, could Columbia’s crew have gotten rid of entry energy by dumping payload and firing thrusters before re-entry?
    (Nearly all of the energy imparted into the orbiter during liftoff is returned to the atmosphere in the form of heat during re-entry. The process is not unlike driving a car; you accelerate to a given speed, and when you have to stop you use the brakes. This simple version ignores earthly friction, but think of the atmosphere as the brake rotor and the bottom of the orbiter as the brake pads.)

    Could Columbia’s crew have made it down to bail-out speeds?
    (Even if you use a high subsonic speed as a basis, the answer is still no. The plasma generated by re-entry entered the port side, or left side wing through a break in the reinforced carbon-carbon heat shield, where it was able to burn through the aluminum spar that is behind the RCC. Once through, the plasma followed the path(s) of least resistance, creating a large hole that exerted more and more drag on the port side until the ship’s controls could no longer compensate. They began re-entry at 17,500 mph, and were at 12,500 mph when the ship came apart.)

    I hope that this helps to answer your questions. They were good ones.

  9. Just to clarify, I had been told the Columbia was equipped with an explosive bolt crew cabin separation system for its first flight, and that that system was later removed.

    I understand the answer below, but how much inertia could have been dumped,had the debris observation, the analysis systems,the reporting systems, and examination systems actually been working?

    Could another crew have gotten rid of the spacelab before entry?

    Could the entry profile been changed to reduce the thermal load on the left wing? Could Columbia have come in with its right wing forward, and with no S curves? Could the initial entry have been a skip, or a more gradual entry with periods of cooling, or with intermediate heating allowing for dissipation of the heat load?

    Were the remains ground distribution fall points ever mapped back to the crew cabin breakup sequence?

    I’d love to read an summary analysis of this one by Gene Kranz.

    E.P. Grondine

  10. Hi Wayne,

    Is there any emergency procedures in case of SRB or ET failure during launch? For example, for Challenger type scenario. Is SRB emergency separation possible and what could be done in such case to save the crew?


  11. Yes indeed the launch tower doesn't seems to be safe enough but then this is how science works.


  12. i’m not sure who i can share this concern w/, but after the landing of endeavor, it was learned that Astronaut Greg Chamitoff apparently had some trouble re-adapting to gravity. now when Astronaut Garrett E. Reisman, flight engineer returned from ISS he was able 2 adapt well 2 gravity. this concerned me, because this is why it’s strongly encouraged to exercise in 0 G. if there was a problem w/ re-adapting to gravity, what will we face when we return to the moon & even go to Mars??? a trip through space to either place will last a while, & when we get to Mars, we’ll probably have to again; re-adapt to gravity; but this time on Mars.

  13. On the anniversaries of landing on the moon why haven’t we turned our telescopes and shown our landing zones and the equipment we have left there? When performing re-entry back to earth why can’t our shuttle just slow down? Instead of going very fast and causing substantial heat to the shuttles tiles, Slower speeds creates less friction. These are questions i’ve wondered my whole life. Thankyou.

  14. Was it my imagnination or was the landing of STS-126 a bit different? It seems to me that after main gear touch the landing attitude was maintained considerably longer than normal (longer being relative at these speeds). The drag chute was fully deployed just as the vehicle began to derotate and a nice gentle derotation it was, in my view. If I am correct, the only reason I could think of was that the vehicle was on the heavy side and the available runway length was a bit less than normal. Keeping the nose up if I am correct with my observation would allow for more aerodynamic drag to aid in slow down?

    It’s always been interesting to observe you at the press conferences educating the media.

    Ron Magnus-Portland, OR

  15. Fred, you asked:

    “On the anniversaries of landing on the moon why haven’t we turned our telescopes and shown our landing zones and the equipment we have left there? When performing re-entry back to earth why can’t our shuttle just slow down?”

    The first is that our telescopes actually aren’t powerful enough to see them. All the galaxies we see show up clear because galaxies are absolutely _tremendous_, even from very far away. Compare to Hubble photos of Pluto or even Mars; not so nice.

    For the second question.

    Orbits are elliptical. There’s a low point and a high point. For example the Shuttle might have a low and high point around 350 km altitude, traveling at around 7 km per second.

    If you suddenly slow down, it will change the shape of your orbit; your altitude on the _other_ side of the orbit will drop. (If you speed up, the opposite happens.)

    So the Shuttle returns to Earth but slowing down just a tiny bit, lowering the other side of it’s orbit so that it dips into the atmosphere.

    The Shuttle is limited in how much it can change it’s speed. It’s capacity for velocity change is called delta-v. The Shuttle typically has around 300 meters/second of delta-v. So if it’s travelling at 7000km/second, it could slow to around 6700km/second before running out of gas. (Obviously this number varies depending on payload and mission.)

    Some of that delta-v is spent up at launch because it’s expensive to reach the Space Station’s orbit from the Shuttle’s launch site. Some of it is spent maneuvering to the Space Station. Some of it is spent raising the station’s altitude. After all that, you have just enough to deorbit.

    Now here’s a pretty counterintuitive part. The more it slows down, the _faster_ it will hit air. This is because slowing down more makes the orbit more elliptical, and the more elliptical your orbit is, the more speed you _gain_ on your way to the low point.

    To make it worse, the atmosphere gradually becomes denser as you approach the ground. If the Shuttle takes a steeper path down, it will hit thicker air at higher speeds than it otherwise would.

    I suggest you read up on Kepler’s laws of motion, the basics of orbital maneuvering, and play this game (in that order):

  16. That new launch escape system video was the coolest video, of the coolest vehicle, NASA has ever made! It was amazing the way it worked so perfectly the first time. I loved the vehicle’s 1950’s retro look with the huge fins, and the way they had the whole thing sitting on wooden blocks! Better yet, the fins were made out of carbon fiber, making it look like the vehicle got caught in some sort of time warp. That low-budget office with the unpainted drywall looked like, ‘The Accountants Strike Back’. You would not believe how long it took me to figure out why they used Roman numerals to number the fins, instead of Arabic ones. At first, I thought that there must be some hidden meaning to it all, or that they wanted to add to the incongruous look of their cool creation. You know, Gen X scientists finally get to show their stuff, but then I thought about painting a 2. The comments of the spectators during the flight were classic. They were like, ‘WOW, it actually worked!’ Whoever put the video together should get an award, as should the team that built the system.

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