3
$\begingroup$

Ludwig Wittgenstein designed (and received a patent for, at the remarkable age of 22) an aeronautical propeller.

Wikipedia describes it:

Wittgenstein’s design required air and gas to be forced along the propeller arms to combustion chambers on the end of each blade, where it was then compressed by the centrifugal force exerted by the revolving arms and ignited.

and adds:

Propellers of the time were typically wood, whereas modern blades are made from pressed steel laminates as separate halves, which are then welded together. This gives the blade a hollow interior, and therefore creates an ideal pathway for the air and gas.

I've found some plans for this design, and some discussion of it, but it's not clear to me whether a working model was ever built, or attempted. I'd love to know whether it actually offered any advantage, or even whether it could be made to work with a reasonable degree of success.

$\endgroup$
4
$\begingroup$

Ian Lemco of the Royal Society published a note on this in 2007. He described the invention more as a jet engine than anything, as it featured a central compressor feeding tip-jet nozzles. Burner position varied during development of the design, from central to blade tip. A patent dating from 1910 shows jet combustion at the tip. One central compressor was of the centrifugal type. Thus, it is seen in some ways as foreshadowing the Whittle jet engine.

Lemco found sources to be scarce, mostly anecdotal, and unreliable. Certainly Wittgenstein constructed various experimental devices and tested them, both in the lab and on a railway track. Some may have been rockets. One source remarks in passing on the engine that he constructed, but the reliability and context are far from clear. There is no confirmation that he ever built a complete jet engine.

It seems to have been fundamentally workable, as compressor-driven tipjet rotors were indeed later flown, but it was probably beyond the technology of Wittgenstein's day.

Ian Lemco; "Wittgenstein's Aeronautical Investigation", Notes and Records of the Royal Society of London, Vol. 61, No. 1 (Jan. 22, 2007), pp. 39-51. Stable URL: http://www.jstor.org/stable/20462605

$\endgroup$
2
$\begingroup$

In a way, yes.

The Doblhoff WNF 342 was a helicopter with tip jets, flown first in 1943, with rotor propulsion not unlike Wittgenstein's idea. Wikipedia describes it:

The conventional piston engine drove both a small propeller (to provide airflow across a rudder) and an air compressor to provide air (subsequently mixed with fuel) through the rotor head and hollow rotor blades to combustion chambers at the rotor tips.

The compressor helped to get the blades moving. This, however, was not used on the propeller, but on the rotor. Another design which used a rotor with tip jets is the Fairey Rotodyne which flew first in 1957. Again Wikipedia:

the Rotodyne featured a tip-jet-powered rotor that burned a mixture of fuel and compressed air bled from two wing-mounted Napier Eland turboprops.

The noise from the tip jets proved to be its undoing, however, since it could not attract orders because of concerns over the noise.

In the US, tip-ramjet powered micro helicopters were successfully developed in the late Forties and Fifties (see XH-20, XH-26 and YH-32) but all suffered from high noise and low fuel efficiency, so the concept never went beyond the prototype stage. They were different from Wittgenstein's concept, however, because they did not use centrifugal acceleration to compress their working medium but relied solely on ram pressure which is low at the subsonic speed of helicopter blades. This low pressure resulted in low efficiency of the ramjets and in their high fuel consumption.

$\endgroup$
2
  • $\begingroup$ Avimech Helicopters (dragonfly df1) comes close to wittgenstein's concept, even if it uses hydrogen peroxide, it seems to at least use centrifugal acceleration to feed the rocket engines. (And it is quiet) $\endgroup$ – qq jkztd Mar 25 '20 at 13:09
  • $\begingroup$ @qqjkztd: Thank you for the hint; I've not known about the DF1 so far. Using the rocket fuel of the Me-163 makes it – how should I say – interesting. Availability of the fuel is probably also an issue. $\endgroup$ – Peter Kämpf Mar 25 '20 at 14:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.