Wednesday, 7 October 2009

Doing More With Less.

I was delighted to see that Burt Rutan won the Robert Heinlein Memorial award for 2008. Other recipients have been Neil Armstrong, Chuck Yeager, Carl Sagen. So who the hell is Burt Rutan?

Burt Rutan first appeared on the radar back in 1980, his CV was a lot shorter then. Then known as an innovative designer of aircraft intended for home building. He’d designed a plane called the VariEze. (pronounced very easy) This plane was developed at a time when most commercially built aircraft were made from aluminium. VariEze was made from composite, foam plastics and glass fibre. Composite aircraft were not completely unknown, but these were largely European built gliders. These were factory made machines which required expensive tooling. Glass fibre was laid up in these fixtures and components were moulded, much like the parts for a model kit.

The VariEze and its successors, featured two Rutan design characteristics, an unusual configuration and a novel construction system.

The configuration features a canard. The canard serves the same function as the horizontal tail surface. It provides stability in pitch, but without the need to produce a lift reducing down force like traditional, aft mounted tails. The Eze also has swept wings, most unusual in slow flying, piston engined aircraft. They offer no aerodynamic advantages at lower speeds and make a conventional structure more complicated, but they do offer the more subtle advantage of inherent stability in roll.

Rutan’s second major innovation, was the mouldless composite construction method. This allows a relatively simple implementation of swept wings, and much else. Borrowing ideas from surfboard and model aircraft construction, this entails cutting foam plastic cores to shape using an electrically heated wire. The foam blocks are carved and sanded to the required shape for the component, perhaps a wing or tail surface. Cardboard templates are used to devlop the shape to the required section and then the foam is covered in glass fibre and resin. The foam itself provides very little strength, most strength is in the glass fibre skin.

Other innovations are the ‘pusher’ engine and the twin, wingtip fins. Both these features offer aerodynamic advantages. With the VeriEzi Burt Rutan took the traditional aircraft configuration, as used on numerous aircraft from the Spitfire to the A380, completely changed it around and in the course of doing so, made it much better. The whole thing is a wonderful, organic creation. Balanced, logical and beautiful, a brilliant early effort from a man who has never stopped innovating.

Since the VariEze was prodced big aerospace manufacturing has adopted winglets as add ons to conventionally constructed wings. But this is just a 'bolt on' feature, in the VariEze the winglets also support the rudders and, because the rudders and other control surfaces are outside of the higher speed airflow developed by the propeller the aircraft is less directly subjected to changing its handling characteristics with different power settings. Rutan's winglets serve a dual purpose.

The image below shows SpaceShip One being carried aloft by its mothership. Tucked in close behind is the Beech Starship, another of Rutan's designs.

SS1, Space Ship One is Rutan’s greatest achievement thus far, (but he’s still only 66) and would have been sufficient to make him one of Heinlein’s people. Back in the day when Heinlein was writing his first stories, engineering was done very differently. In some respects it was all done the Burt Rutan way. Men such as Willy Messerschmitt and DeHavilland had their names on the aeroplanes they made, and their style all over them. As we moved into the 1960s aircraft design became institutionalised, immensely expensive and the work of huge teams. Aircraft were no longer designed by, or even especially associated with single individuals.

With the very high cost  came conservative configurations, design refinement, not revolution. Improvements, none the less, but expensive solutions to well understood problems. Rutan always been on the cutting edge.  “Any fool can find a difficult, complicated and expensive solution to a problem, but it takes somebody really smart to find a very simple solution.” For Burt Rutan. simplicate, and add lightness are mandatory.

Another Rutan hallmark is to design inherent stability into the aircraft's configuration, as with the swept wings of the VeriEze. On SS1 Rutan came up with a huge innovation for re-entry, the Shuttle is pedestrian by comparison.  He came up with a revolutionary way of turning a super streamlined hypersonic rocket plane into a high drag, stable, re-entry vehicle.

This image shows SS1 at apogee, adopting ‘Feather mode’. This mode is taken up after it has achieved its maximum altitude, and is outside most of the atmosphere. Re-entry, from similair speeds that SS1 achieves, was done the conventional way in the government funded X15. It used ablative heat resistant materials and precision guidance by an automatic flight control system. By contrast, SS1, in feather mode, is inherently stable, neither the pilot, or an automatic guidance system has anything to do while the aircraft re-enters the atmosphere. It decelerates from over 2,300 miles per hour, at 367,000ft, to a few hundred miles an hour by around 50,000ft. It is then 're-moded', out of feather, back to its standard configuration then glides down for a conventional, runway landng.

At a stroke Rutan knocked billions off the development budget. Developing automatic control systems is immensely expensive. It’s hard to overstate the value of this kind of innovative thinking.

Mike Melville, one of Rutan’s long time colleagues, someone who has worked with him since the VariEze days, became, the first SS1 astronaut. In the video below a system failure led to the loss of the primary attitude indicator, and this was during the boost phase. Melville maintained the craft in the correct attitude by monitoring the real world horizon in his peripheral vision. Now that's pretty hot stuff, even by the standards of one of Heinlein’s fictional heroes, it's seems that Rutan, as well as being a great innovator, can pick his pilots pretty well too.

Mike Melville

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