Samizdata

A couple of days ago I noted it is not unusual for the USAF to use the landing shuttle as a test target for their space defense optical systems. They did so this time as well and are reported to have seen major wing damage.

I’d love to see those photos, but I would say there is a fair chance it would take a security clearance to do so unless they were taken by something non-black and not even “grey”.

ANOTHER ONE: While I was not the one to first note this, I did report it early on. Insulation hits began causing tile damage after NASA switched to an “environmentally friendly” (read that as Astronaut killing) non-CFC based material.

EXTRA! Reader GK Elliot pointed me to this Craig Covault article on the story.

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?