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Archive for December, 2010

Wings or ‘chutes?

When you come to end of your journey, do you want to:

1) Roll to a stop on a runway, then climb down some steps and wait for a minibus to take you to the ‘terminal’.

or

2) Fall into the ocean, don a life-jacket, and wait to be rescued.

These appear to be the two modes that will be available to astronauts (professionals and ‘passengers’) in a few years. Granted, there may be some variation, but it will still be a choice of falling under parachutes, or gliding to a runway landing. Each has it’s pros and cons, but I suspect only one has a long-term future, at least for manned flights.

SpaceX's Dragon

SpaceX's Dragon

Now I’m no trained astronaut or engineer, but this is how I see it; feel free to comment.

Capsule landing:

Pros:

  • Simpler, cheaper design
  • Naturally stable re-entry, low re-entry risk
  • Less crew training required for re-entry and landing

Cons:

  • Limited cross-range, fewer re-entry opportunities
  • Possibly more expensive to refurbish for next flight (dunked in salt-water)
  • Requires more substantial recovery assets, especially for water landings
  • Additional sub-systems required for land landing (air cushion / landing rockets)

Spaceplane landing:

Pros:

  • Good cross-range, frequent return opportunities
  • May return to launch site, easier turn-around
  • Minimal recovery assets required
  • Easier to re-use (ignoring TPS for now)

Cons:

  • Re-entry control critical
  • More advanced training required for pilots (but they won’t mind!)
  • More complex and expensive
  • Probably lower payload fraction (it has to carry it’s wings into orbit)

There’s probably plenty more, but that’s how I understand it in a nutshell. But these are only the technical considerations.

SpaceDev Dreamchaser

SpaceDev Dreamchaser

Non-technical considerations for the two types of craft may be a little harder to quantify, but we’ll try it anyway:

Assume a high flight frequency. Satellites are being regularly serviced, the ISS is being resupplied, a number of Bigelow stations are continuously occupied as science stations and hotels. There are even tours to Lunar orbit (and maybe the surface?). Supporting this infrastructure are pure cargo launches, manned mini-sat deployments, and frequent tanker launches to refuel the various propellant depots. The manned spacecraft are being turned around quite quickly and re-used. Customers wishing to fly to LEO have their choice of vehicle to ride in…

Orbital's lifting body spaceplane

Orbital's lifting body spaceplane

Today, with the possible exception of the space tourists flown in the space Soyuz seats, astronauts are professionals, trained in the operation of their craft. Comfort, and other details like recovery method and convenience are relatively unimportant. When the scenario described previously arrives, however, most passengers on the spacecraft will be relatively untrained, and things like convenience and comfort will become more significant considerations.

Why would a passenger, wanting to fly to a LEO hotel and back, want to splashdown into the ocean, rather than land at an airport? Sure, there will be a few that want the ‘Apollo Experience’ but I doubt that will be a way to build a business long-term! As I see it, this is a big win for spaceplanes.

Boeing crew module

Boeing crew module

To over-use the airline analogy:

Imagine two airlines, flying say, Los Angeles to Auckland. On one, upon reaching it’s destination, the aircraft deploys parachutes and drops into Auckland harbour. Passengers fit their life-jackets, and are taken onto a boat, which then returns them to shore. They’ve arrived! Now I’m sure if this were the only option, it would indeed be popular, but would probably scare off some potential customers.

The other airline flies directly to the airport and lands in the conventional manner. It can’t carry quite as many passengers, due to the weight of the landing gear and all, but it is far more popular with passengers, and the total trip time is substantially reduced. The landing is a lot more relaxed, as the passengers don’t have to deal with emergency equipment (life-jackets), and none will become sea-sick.

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Clearly, for cargo flights, the capsule is probably going to be hard to beat for awhile, and the non-technical issues become largely irrelevant in this case.

This isn’t to say that capsules for crew launch are a bad idea. Far from it! The spaceplanes are still stuck on the drawing board, but the Dragon capsule has already flown (unmanned), and will probably be the first to carry paying passengers. That’s a good thing. But once the spaceplanes begin operating, I suspect a substantial segment of the market will shift away from the capsules for good.

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Airmanship (AWOL)

This is a bit of a negative start to the blog, but nevertheless…

The USAF is considering a ban on airshow displays of large aircraft (that is, bombers and transports) following the loss of a C-17 practicing for an airshow display on July 28 2010 at Elmendorf-Richardson in Alaska.

The remains of the tail of the C-17 after the crash

The remains of the tail of the C-17 after the crash

Banning airshow displays of large aircraft would certainly reduce the risk of losing additional aircraft and crews on airshow related flights (banning airshow displays entirely would save more…), but doing so would be treating a symptom, not the cause.

This is not the first time a large USAF aircraft has been lost practicing an airshow routine. A very similar accident occurred in 1996, this time involving a B-52 at Fairchild AFB. Both accidents were caught on video:

(Even longer version, showing entire display)

Both aircraft crashed while performing very steep, low-speed, low-altitude turns.

Both aircraft busted USAF regulations regarding airshow displays (such as safe height).

Both aircraft flew outside of the permitted flight envelope.

Both pilots were considered very highly skilled.

Both pilots knew they were exceeding aircraft limits, but considered themselves able to safely do so.

The C-17 pilot is reported to have claimed that the stall warning and stick-shaker is inaccurate (C-17 test pilots disagree), and intended to ignore the stick-shaker during the display. Despite this, he was considered an excellent pilot, requiring very little supervision.

The B-52 pilot was a known ‘cowboy’, who had been performing increasingly dangerous airshow routines for years, and had taken this sort of flying into non-airshow flights as well, prompting complaints from junior officers. On one occasion, his B-52 cleared a ridge by just 30ft, and that after the co-pilot took the controls and pulled up!

Most pilots will certainly look at these cases and shake their heads. They would never be so stupid. But I suspect most pilots have, at some point, thought after a maneuver; ‘that wasn’t such a good idea…’ and hopefully taken more care in the future. That’s an important rung on the ladder of Airmanship. But most pilots probably don’t take it any further than that, denying themselves the opportunity to develop their airmanship further.  It’s hard to criticize them for that, however, they didn’t know to do anything more!

It appears to me that there is a gaping hole in our pilot training systems. We spend hours poring over the details of the operation of gyros (presumably in case we need to design and build one in flight), and are thoroughly tested on them. Yet Airmanship gets perhaps a brief mention in Human Factors, an exam question if you are very lucky, and a few tips from your instructor (who may have completed the training your are doing himself just a few months or years ago) as opportunity and example arises.

The majority of accidents today, by far, are blamed on pilot error. Most if not all of them could be linked to an Airmanship failure of some kind. Millions of dollars and countless hours have been devoted to improving aircraft and systems, and now we are finally starting to see progress in improving the human aspect of the equation. Most widely known today is probably CRM (Crew Resource Management), which itself has a come a long way in recent years. But this is just one part of the Airmanship puzzle (though a very important one), and may not be taught to pilots until they reach higher levels in their careers.

There needs to be a dedicated and thorough education of pilots in all aspects of Airmanship. Ideally, this would include theoretical examinations, separate and far beyond what exists today as Human Factors. It should also be taught in every briefing, in the cockpit, and in de-briefings. This will require additional training for instructors, as well, even if they themselves have completed the Airmanship training suggested above.

This is true for all levels and all kinds of pilots. The examples shown here involve military crews in heavy jets, but Airmanship spans all sectors of aviation. There is no doubt some excellent Airmanship training in some places, but if we are to improve the present statistics, this training needs to become universal.

For those wishing to learn more about Airmanship, I highly recommend Redefining Airmanship, by Tony Kern.