Black Zones – time out for Q&A

I have really appreciated all the questions and comments to my mini-series of blogs on Black Zones.  I am not done with the series yet, but I thought it was time to address some of the questions and comments.

First of all, not to be too grumpy, but I have to set a couple of new blog comment rules.  I have received a number of comments that are frankly undecipherable.  They are either written by non-English speakers or some type of computer program that strings together English words at random.  So my rule is if the comment is unintelligible and/or the grammar and spelling are so bad that most readers could not understand them — I won’t post them.  Clear enough?  My grammar and spelling aren’t perfect and I won’t hold you to perfection either, but it has got to make sense or it doesn’t get posted.  If your comment didn’t get posted, that is most likely why.

Second grumpy new rule:  I don’t do UFO comments.  I have no patience for these things, don’t even try to start here.  Go someplace else with your UFO comments.  I will not post them here.  This is my personal preference and should not reflect on the agency or anybody else. 

Thanks, I’m glad to get those off my chest.  On to serious comments.

No, there was no serious entry guidance anomaly on STS-1.  There was a significant lofting during ascent, but nothing to speak of during entry.  STS-2, 3, and 4 entries were flown automatically not manually with the exception of some short duration pilot test inputs to stimulate the entry flight control system to verify its robustness.  Some of these type of manual test inputs continued for a number of flights.  But there have been no manually flown entries of the space shuttle — its all been automatic until subsonic speeds.

At this date in the shuttle program, it is my belief that the bugs have been worked out of all the intact abort modes.  That is, for any single SSME premature shutdown, there is a very high confidence level that the vehicle and crew can successfully execute an RTLS, TAL, ATO.   The big assumption, though, is that nothing else goes wrong.  The shuttle requirement — which I believe it meets — is that any single premature SSME shutdown at any point in the trajectory will lead to an intact abort — safe landing by the orbiter on a runway and safety for the crew. 

I was pleased to see a post with the details of the Gemini ejection seats, but I would think that landing a mere 700 feet from an exploding Titan II rocket would not be a good thing.  Survivable if the wind was blowing the right way probably.  And I do agree that Schirra showed that he had the right stuff when he did not pull the ejection handle on Gemini 6A pad abort.

I probably should have started the series of posts with a definition of ‘black zone’ so here it is:  a portion of a manned rocket launch trajectory where the premature shutdown of any or all running booster engines will lead to loss of the re-entry vehicle and crew subsequently due to the over temperature or structural loads incurred from the resulting trajectory.  Is that too muddy?  Black zone does not mean what is going to happen in a normal case, only if an engine (or two or three) quits.  Black zone does not take into account the weather at the proposed abort landing site which is another way to kill a crew.

As to why EELVs were not chosen by the Exploration team early on — I don’t think black zones had a lot to do with it, but I really don’t know.  I should ask and I will ask and I will report to you at a later day.  However, the standard trajectory design for EELV launches would result in extensive black zones — which can be either greatly reduced or eliminated by adjusting the trajectory — which in turn leads to significant reductions in the mass which the EELV could place in orbit. 

The two early American suborbital flights — Shepard and Grissom — had carefully designed trajectories to keep the entry G level and heating relatively low.  If they had flown the type trajectory that the redstone rocket used as a weapon, that would not have been the case.  Similarly, the Soyuz T-10-1 high altitude abort had an extreme entry G level because the rocket staging went so poorly that the entry was steeper than it would have been for a clean abort — as if the 3rd stage engines had merely failed to light off. 

Well, that’s all for today folks.  The series resumes tomorrow.




10 thoughts on “Black Zones – time out for Q&A”

  1. Thank you so much for answering questions! This is a fantastic blog and I’ve read through a lot of your older posts to catch up. Great series on Black Zones. Tons of fun.

  2. hi my name is bilal and i wanna ask you all for a question .I now it’s a little bit weird but i had this idea i don’t no how to say but i was thinking off.. that i could be go in the space yes in the space i now it’s weird but if i can go then i am the first 17 year old boy it wil be realy great not only for me but for the whole world so i can let see to the people that even i a boy can do suths a big thing so that the other people nows that in the life nothing impossible is and it gains me a lot of experience and even if you all think that it cant be that i not can go to the space (is’t my lifedream) can you please send me a message if you hinks it’s not a ‘good idea’
    thanks for your time
    p.s i’am from belgium and my english is not very well as you see but i can help my self very well with it

  3. Just curious…if the STS ascent trajectory was optimized for max payload to orbit (at a cost of greatly reducing crew safety), how much more payload mass could the orbiter get to LEO?

  4. Thanks very much for this very interesting series of posts.

    Having a post-graduate degree in engineering, I’m biased, but I think NASA TV and NASA outreach in general would be much improved if the content were as sophisticated as these blog posts. Watching the pre-launch briefings (which astonishingly are not officially posted to YouTube) I am often disappointed to find that they’re really just a laundry list of things the astronauts are going to do without much discussion of the bigger picture of why something’s being done. I think the briefers would do well to make a point of discussing aspects of the mission that they think are interesting and would enjoy expounding on to one of their peers.

    I’ve found this series of posts and your “war stories” in general to be quite fascinating. Thanks again for taking the time!

  5. Wayne, Thank you very much for these postings on Black Zones. Great stuff to talk about, and including the history makes it all the more interesting to read.

    However, your point of view makes one huge, and inaccurate assumption. You point out that survivability of many possible failures is questionable at best for Shuttle, and then come to the conclusion that capsules are better. The incorrect assumption here is that these are the only 2 choices. Air-launch, multi-stage is another option. While no (known) such manned vehicle has made it to orbit yet, several air launch options have made it to much closer than your 1000x greater than an airliner example. Also, Pegasus regularly takes small payloads to orbit.

    It is also important to note that aborts of air-launch, manned suborbital vehicles has occurred. During a Space Ship One abort, there was quite a lengthy discussion about what to do during the abort itself. Despite the abort, and arguably a lack of pre-planning, the craft landed normally, and pilot and vehicle were un-damaged.

    The ability to make a decision as to whether to light off the rockets after the vehicle is already free-flying, is a tremendous advantage. Failures such as loss of pressurization, which you mention in your posts, and has sadly proven fatal in the past, become almost completely benign with air-launch. Dozens of other scenarios that are in the scary to fatal regime for capsules also become benign for air-launched vehicles. Landing back on top of an exploding stack, for example.

    Black Zones during other flight phases, such as after the rockets are lit and during entry, are likely still an issue, but I would like to see the issues discussed, not ignored.

    I fully (OK, well not fully, but somewhat) understand the limitations and costs involved with air-launch, multi-stage vehicles, but from the Black Zones point of view, it initially seems to be yet another argument for air-launch.

  6. Is there an equivalent to black zones for capsule reentry from orbit if the deorbit burn is not correct? If so, how much margin for error is there for the deorbit burn?

  7. Regarding the Gemini 6a non-launch of October 12, 1965…

    I knew a man who worked in “launch sequencing” and was in the blockhouse that day. Schirra, as you know, chose not to eject. Launch sequencing also decided that they should not eject.

    After the rocket failed to launch, the “suits” came into the blockhouse…and they were mad. They yelled at the launch sequencing people for letting the crew sit atop that dangerous Titan II.

    Then, Schirra came in. He told the suits that THEY were wrong, and that the people in launch sequencing…who agreed with him…were right.

    Schirra made some friends in the blockhouse that day.

    More about this little known incident at:

  8. Thank you Mr. Hale. Your commentary on the shuttle is of great interest to me. I’ve gotten old watching its activities over the years.

    Could you please explain why an improved shuttle was discarded in favor of the Orion capsule? There must have been a great deal of debate on which direction to go in.

    Thank you,
    H. Reagan
    Heath, Texas

  9. Thank you, Mr. Hale, for answers regarding STS “manual” landings. This was very informative. Just one more small question – you say the guidance anomaly was insignificant, however the document titled “Space Shuttle Hypersonic Aerodynamic and Aerothermodynamic Flight Research and the Comparison to Ground Test Results” by Kenneth W. Iliff and Mary F. Shafer contains the following phrase:

    “The first bank reversal on STS-1 resulted in a significantly larger response than predicted… The flight maneuver resulted in angle of sideslip peaks twice the size of those predicted and in somewhat higher roll rates than predicted. Angle-of-sideslip excursions this
    large move an area of high heating off the reinforced carbon-carbon (RCC) nosecap. The motion is also much more poorly damped than predicted. Comparing the predicted maneuver with the actual maneuver
    shows that the flight stability and control derivatives were significantly different from the predictions. These stability and control flight maneuvers were analyzed with the maximum-likelihood method. The resulting flight-determined estimates were used to significantly modify the flight simulator.

    Simulation studies resulted in modifying the control
    inputs for the bank-reversal maneuver on STS-2, as
    shown in Fig. 9.

    Was the shuttle safe nevertheless, despite the mentioned area of high heating moving off the most protected areas?

    Thank you very much for having time for the answers. Having a person of your position online answering spacebuffs questions is quite an experience.


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