Samizdata

While I was at tea (or more accurately, pizza) after my earlier flurry of keystrokes, I received a call from Jim Bennett. Some of you know him from “Anglosphere”. I known him from his AMROC and Starstruck launch company ventures. The pizza got cold but the ideas flowing back and forth over the phone line should have been enough to reheat it.

First of all, Jim came up with one more question which needs to be dealt with.

If the engineers saw the insulation hitting the wing, couldn’t they have called for an RTLS (Return To Landing Site) or TAL (Trans Atlantic) abort? No. The material was not easily seen. It was later that it was noticed and at least two days before it was analyzed. An abort would have had to occur almost instantly. Even if we assume someone could have monitored, realized implications and reported it as it happened, we are left with a stark choice. We don’t know if it is a Category 1 problem and the shuttle has never flown an RTLS or TAL outside of a computer simulator. I won’t go into great detail on the maneuvers required. Lets just say they are “interesting”.

As we talked, it struck me there was a possible scenario if a shuttle could be gotten up quickly. Those old rescue balls must surely be in storage somewhere. A second shuttle with a skeleton rescue crew could send one man across to stuff the plastic balls in the outer airlock. Then they could cycle the crew through one at a time and have them carted across. I still had strong doubts a shuttle could be programmed for the weight and balance and particulars of the rendezvous in less than 6 weeks unless NASA took serious risks. (If there is anyone at KSC or HMSFC out there willing to put a hand up, please correct me). Then Jim came up with the idea. Some of the new commercial ELV’s are more easily programmable. All you really need to get up there is probably O2 for breathing and CO2 scrubber cartridges. You could perhaps get some food and water as well, but I don’t believe they are as limiting.

I can only see one problem here. The Canadarm was not installed and there is not (to my knowledge) any sort of portable maneuvering unit on board a flight that only has an EVA suit for the contingency of payload bay doors not closing properly. So the one astronaut in the one EVA suit is going to have to bet his life on a jumping for it. If he hasn’t enough tether, he’ll have to free jump. That’s an all or nothing, life or death bet.

Then they have to survive.

The shuttle is in a low orbit, it would probably re-enter in much less than 6 weeks unless measures were taken to reboost. They could do a small OMS burn since their goal is not re-entry. They might even have enough margin to do it without cutting into the fuel for re-entry.

Then they power every thing down; sit as quietly as they can; talk to friends and relatives on the ground and try to stay alive for 6 weeks or more. It would be simply awful, and I imagine the – how to put this delicately – “scent” would be somewhat like a sewage treatment plant in the summer sun. But they might be able to last.

Then bring the crew across in a combination of rescue balls and EVA suits. If a repair kit can be put together, the damage could be assessed and perhaps repaired. If it cannot, the shuttle can be set on autopilot to do a controlled self destruct re-entry; if repair is possible, a two person crew of pilot and commander could take the risk of bringing it back.

If all of this seems to be moving in the direction of large numbers of dice rolls falling your way… you are absolutely right. There are so many potential problems with the re-supply and rescue I’ve not even bothered listing them. But if there were no other way and we were sure of the consequences of the re-entry, I’m sure drastic measures would have seemed more reasonable than watching seven people die.

NOTE: Many thanks to Jim Bennett for the brainstorm upon which this post is based.

By the way: Here is Jim’s column about the shuttle and its’ replacements in National Review.

I have seen numerous questions which come down to “If NASA had taken the wing impacts on launch seriously, the astronauts could have been saved”.

Unfortunately this is not true. I’ll work through the scenarios. Some have been covered reasonably well in the media; some not so well due to a lack of real understanding of orbital mechanics.

• Why didn’t they have a docking collar?

The Columbia is the heaviest of the shuttles because it is the oldest. For that reason it performs many of the non-space-station missions. This one in particular had a Spacehab in the bay. The spacehab couples to the main airlock of the crew cabin. It also supplies an EVA lock if I remember correctly. What it does not do is allow for an International Docking Collar. There simply will not be room (or more accurately enough payload weight capacity or “payload mass budget”) for one on any flight doing really major non-station hauling.

• Couldn’t they have gone to the space station if they’d known?

No. The space station is in an “orbital plane” tilted around 50 degrees to the Equator. Since KSC is at around 25 degrees latitude, a spaceship going into orbit there will be best off going into an orbit that is tilted 25 degrees to the equator. If you have a globe handy, look at the location of KSC in Florida. An orbit is a circle around the earth with the centre of the earth as its’ centre.

The Earth is about 24,000 miles in circumference. If you are standing on the equator, you must do a full rotation in 24 hours; thus you are travelling at about 1000 miles per hours. If you were to launch from there, in the direction the Earth is turning, you get your first 1000 mph for free. As you move further north or south, the “length” of your line of latitude gets smaller and smaller. You travel a shorter distance in 24 hours, so the velocity is lower. When you reach the pole, you just turn in a circle once a day but don’t actually go anywhere. Your velocity is 0 mph.

When a rocket takes off, it must go into an orbit; it cannot follow a line of latitude except if it is at the equator. So it not only gets a lower free boost the further it is from the equator; it can’t even use all of it. I’d really like to get into the velocity vectors but that would require diagrams and an assumption you have all had geometry. Instead, just think of the extreme case: if you wanted to launch due North, a “free velocity” in the due East direction is something which not only doesn’t help; it must be cancelled out.

So we now have an idea about why a particular orbital plane (actually a pair of them) is the “cheapest” for a given point on the Earth’s surface. If you are at KSC, it is about 25 degrees; if you are at a Russian launch site, it is more like 55 degrees or higher.

When a shuttle is going to the ISS, it must do a “plane change”. This is most efficiently done during the boost phase. The shuttle rolls onto an azimuth for that orbit and boosts up along the East coast of America. But this is costly; it is not getting the full use of the “free velocity” it would have gotten if it instead rolled onto a 25 degree azimuth. It has to replace that lost factor by burning more fuel. A longer burn means more fuel; more fuel means more fuel to lift that fuel and so forth… this is what is known as the rocket equation.

Carrying more fuel means less of the total mass budget is available for payload.

Once you get into orbit, a “plane change” maneuver is just about the costliest (in terms of fuel) thing you can do. You are travelling at 18000 mph in a very heavy vehicle in a “straight line”. Remember “things in motion tend to stay in motion”. There is a lot of momentum. If you want to go from 25 degrees to 50 degrees inclination, you have to fire your engines at right angles to your direction of motion. You have “turn” your entire orbit. It is almost “cheaper” to land and re-launch than to make that change. It is certainly beyond the abilities of any of the shuttles.

But that is only the first maneuver! The ISS is in a higher orbit. So you also have to do a burn that raises the apogee or high point of your orbit. This is a “Transfer Orbit”. When you next reach perigee, you have to do another burn to raise the perigee. This is a “Circularization burn”.

Oh, yeah… you will have to then be in an orbit slightly above that of ISS so you’ll rendezvous with it within a few days. Then you do minor orbital changes and carry out the rendezvous and docking.

If this all sounds like a nonstarter… you are correct.

• Well, couldn’t they just sit tight and be rescued?

No. They have limited food and water, but most critically, they have limited Oxygen. Whether the margin left after that 16 day mission was in days or a couple weeks I don’t known. I guarantee you it was very finite.

Shuttles are not “launch on demand” reusable vehicles. They are more “re-buildable” vehicles that are extensively refurbished after each flight. There might have been one already stacked (I haven’t checked the status) but even so, it would take days to get it out to the pad; days more to do a rush checkout job… and they still wouldn’t have the computers set up for the mission. I do not know how hard they can push that. Maybe weeks if they took lots of risks. Shuttle flight software used to be scheduled and tested over a period of many months in advance. They have in recent years done some “rapid” re-profiling of missions, but at the best I think we are talking 4-6 weeks.

Not soon enough I’m afraid.

• Couldn’t we have asked the Russians to rescue them?

The Russians had an unmanned, full cargo ship on the pad. But the Progress vehicle is discarded. It has no re-entry system. The Russians currently build 2 Soyez per year. None were on the pad to my knowledge. Even if they were, a Soyuz holds 3 persons. You are going to need at least one inside to deal with on the spot issues. So best case, you can draw lots and save two… but ooops… There is only one EVA suit. So I guess you save one guy and wave to the rest.

• Couldn’t one of the Astronauts have gone EVA and fixed it?

No. It’s conceivable the EVA could have been carried out; however one astronaut spokesman has pointed out the risk of the inspector causing damage. And if he finds “a situation”… there is no means of in-orbit repair.

• Couldn’t they have just been really gentle on re-entry?

Doubtful. The re-entry glide path is tightly constrained. Too shallow and you skip a number of times and then when you dig in you dig deep; too deep and you burn up. Like the three bears, you have to get the one that is just right. Perhaps they could have avoided the S turns, started re-entry further out and stayed wings level… but my level of hope for that is rather low. It’s probably the option they would have tried.

It comes down to this. If they had known from immediately after launch, those seven people would have spent their last 20 days of life facing certain death. Instead they enjoyed themselves immensely and died instantly doing exactly what they wanted to do.

Who could ask for a better way to go?

Since Doug Jones uttered the name Henry Spencer in a recent comment, I decided to ring Henry and compare notes. A very interesting 15 minutes pooling our various bits of hearsay and rumour…

Henry thinks a heat induced tireburst in the wing is one possible scenario. As we know (think Concorde) such events can be extremely violent and cause air frame damage.

For my part, I note the best place to run the hydraulic loops from the APU’s is right through a section of rear fuselage and wing root where the news have been pointing to as places where the temperature rises were seen shortly before loss of communication. Neither of us knows exactly how the hydraulic lines run and how far apart their independant paths are. However the lines all have to come together at the actuators for the ailerons (or elevons since they can provide both functions I believe).

Loss of the hydraulic loops would cause instant and violent loss of control, but I would expect at least a small amount of data showing the lines popping before the control loss occurs. I am not privy to any such data.

Henry’s suggestion on the tire gives us a very sudden air frame damaging event, but unless it causes immediate catastrophic structural failure, I can’t see it happening without the crew knowing a few seconds in advance something was terribly wrong.

I would expect clear signatures of either in telemetry. I guess we all have to say “we don’t know”, and we are at a disadvantage without access to the actual telemetry and time sequence.

Which is of course what teams of engineers at NASA are most likely doing right now.

Also, Henry reports from his sources that there is uncertainty that remains of all 7 have been found yet. They announced one way and then back tracked apparently.

No one has found the significant heavy structures of the shuttle: the SSME’s or major portions of the crew pressure vessel. Something the size of a compact car is said to have gone down into a reservoir but it has not been found and no one knows what it was. The fact that remains have been found tells us the pressure vessel must have been split open.

It is likely these items travelled the farthest. They could be deep into Louisiana or perhaps into the Gulf of Mexico. If the latter, there is the risk they will not be found for a very long time.

Hopefully Henry will drop by and add his tuppence (Canadian) to these random jotting about our brief brainstorm.

MORE: A 6-7ft long piece of the cabin has been found. Added to the evidence that astronaut remains have been found, I think it is safe to say the pressure vessel and contents were shredded pretty thoroughly. The good news is, more of it is likely to be found around Nacogdoches rather than further down range. There is still no word of the three SSME’s.

STILL MORE The Indendant claims bits will still be turning up in ten years. Ten years hell: centuries more like. Not to mention the few odd bits that will make it into fossil layers to be dug up a hundred million years hence. We are talking about hundreds of thousands of shuttle bits spread over half of East Texas and potentially spread from California to Louisiana and the Gulf of Mexico. They’ll be lucky to even find all the big parts this side of 2100!

AND MORE They have now found the nosecone

Fox News today reported information given out by Shuttle program manager Ron Dittemore I find quite useful:

“He [Dittemore] added that engineering data shows a rise of 20 to 30 degrees in the left wheel well about seven minutes before the spacecraft’s last radio transmission. There followed a rise of about 60 degrees over five minutes in the left hand side of the fuselage above the wing, he said.

The shuttle temperature rose the normal 15 degrees on the right side over the same period, he said. All the readings came from sensors underneath the thermal tiles, on the aluminum hull of the craft.

The temperature spikes were accompanied by an increased drag, or wind resistance, that forced Columbia’s automated flight control system to make rapid adjustments maintain stability. Dittemore said the corrections were the largest ever for a shuttle re-entry, but still within the craft’s capability.”

If you put this together with other information, the picture starts falling together. An amateur astronomer in California saw an orange trail before the shuttle crossed the US Pacific coast. This roughly matches up in time with the sensor data and I believe what this man saw was the ionization trail of material being burned off the port wing. I am unable to state what material it was, but perhaps someone who did more than barely pass Qualitative can suggest. I can only think of Potassium (K) and Sodium (Na) of course those would be likely constituents of the tiles (I think – I have not dug into literature to refresh my memory on the tile ceramic). I out right do not remember the colour of ionized Aluminum; there are many other possibilities as well, such as hydrazine or hydraulic leaks.

But his description of “an L shape” makes me think of a tile or tiles unbonding and disintegrating into powder as they smash against the pitched up wing, and then being ionized into a burst of glowing plasma… followed by a steady erosion of surrounding tiles in the 3000F+ slipstream. A spectrogram would have been wonderful for the investigation team.

His photos may well show the beginning of the end, the initiation of an unzipping of tiles.

NOTE: The DOD sometimes uses the re-entering shuttle as a sensor test target for space defense systems. It is possible NASA is already getting such information. I have seen unclassified photos of a shuttle re-entry taken by experimental DOD optical systems. Such might exist this time as well.

I have absolutely no way of knowing. This is pure (but “educated”) speculation on my part.

STILL MORE: Doug Jones from XCOR may also have seen tiles disintegrating if I am right. He posted a comment here on Saturday:

“I watched the reentry from Mojave, CA at about 0553 this morning. Although there was some light haze (clearly visible when viewing Venus and Jupiter with 10×50 binoculars while waiting for the event), I was able to see an orange dot leaving a glowing trail behind it. At about the time of closest approach (about 220 miles, I believe) the brightness flared for an instant and a small speck came away from the main body, drifting backwards relative to it. Over about ten seconds, it dimmed and went out, then perhaps thirty seconds later the shuttle flared again but no debris was visible.”