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GregLocock (Automotive)
1 Aug 09 0:00
The rules are tremendously biased in favour of electric aircraft, but here you are
http://cafefoundation.org/v2/pdf_AGP/2009/AGP.TA.04.22.09.pdf
Personally I think 1.5 million is nowhere near enough.
Quick calc suggests that 50:1 L/D aircraft with a conventional very efficient gasoline engine, weighing just 4 times as much as its passengers, just squeaks in. But you won't get 50:1 with the defined wingspan. Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
MikeHalloran (Mechanical)
1 Aug 09 0:28
It would be a challenge just to do the paperwork for less than 1.5million.
Mike Halloran
Pembroke Pines, FL, USA
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tbuelna (Aerospace)
1 Aug 09 1:13
The first paragraph says it all: community acceptance, efficiency, door-to-door speed, utility, environmental-friendliness, affordability and safety of future
air vehicles.
It reminds me of the old joke: "Low-cost, reliable, efficient, lightweight......pick any two."
This contest is typical of the clueless, academic, pie-in-the-sky mindset of taxpayer-funded federal bureaucracies like NASA. If there was a practical, economical, aircraft propulsion system (like battery electric), it would be worth billions, not a paltry $1.5 million.
Think about it. NASA claims that their annual multi-billion dollar budget is justified by all of the scientific discoveries that result from the manned space program. A lightweight, efficient, economical battery-electric propulsion system would literally change the world, and be worth $trillions. Each single space shuttle launch costs over 300 times what they're offering for this prize, yet can any of you name one single significant technology that came out of the last $400 million space shuttle mission. Nope? Didn't think so. 字串6
To illustrate just how ridiculous this contest is, Toyota has spent over $2 billion on the technology for their Prius electric hybrid. And in the end, its real efficiency is no better than a small VW diesel costing thousands less. And GE spent over $2.5 billion to develop their (very impressive) GeNx turbofan engine.
Physics and free-market economics dictate what types of propulsion systems we use for transportation. That's why our commercial airliners use turbofans, our cars and trucks use 4-cycle piston engines, and big ships use giant slow-revving two-strokes.
The inside joke about NASA is that the organization is simply "Space-Based Socialism".
SAITAETGrad (Aeronautics)
1 Aug 09 13:05
I have to disagree with some of the sentiments expressed.
The experimental/homebuilt sector has produced plenty of designs that cost no more than the efforts of one or two men. 字串3
Someone will step up with the skill to make this a reality.
Also, note that the rules allow for folding wings down to the required 44' span. Also, I don't see anything that disallows a tandem design. An engine 4x weight of pax is heavy. An EJ22 weighs what, 240lb all dressed and oiled?
In the end, it won't be about the engine so much as it will be about efficient layout, detail design, and construction.
SAITAETGrad (Aeronautics)
1 Aug 09 13:09
Oh, now I see Greg is talking total aircraft weight of 4x pax. Well, it does sound like a tall order.
GregLocock (Automotive)
1 Aug 09 22:46
I've just rerun the model with LiPo batteries, and retract my comment about it being tremendously biased towards electric.
Roughly speaking you'd need about 200 kg of batteries, that'd cost about 65000 dollars, and an efficient 11 hp electric motor, that would cost about $20000 as a one-off (I know someone who would be very happy to design a very efficient motor for this), and a rather expensive motor controller 字串8
http://en.wikipedia.org/wiki/Schleicher_ASG_29
looks like a good starting point, it achieves the 4:1 weight, and I imagine would still do so with folding wings.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
SAITAETGrad (Aeronautics)
2 Aug 09 16:27
An aside, check out Windward Performance sailplane capabilities:
http://machinedesign.com/article/windward-performance-designs-and-manufactures-sailplanes-and-gliders-the-perlan-to-set-altit
Given some of their other ambitious projects, I would not be surprised to see these guys take their shot at it.
flyboy52 (Aeronautics)
11 Aug 09 18:40
An aircraft with a gross weight 4X the passenger payload isn't remarkable, it's average.
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flyboy52 (Aeronautics)
12 Aug 09 19:10
Space-based socialism. I worked for NASA for ten years and I never heard that joke. What precisely is socialistic about NASA? And what does that rant have to do with aircraft efficiency?
GregLocock (Automotive)
12 Aug 09 19:35
"From each according to his abilities, to each according to his needs" for a start? Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
berkshire (Aeronautics)
12 Aug 09 22:17
An excerpt from the rules
"On the ground or in-air re-fueling (or re-charging) during the 2011 CGFC 200 mile
competition flight attempts will not be allowed, with the exception of in-the-air 字串2
recharging of vehicles that fly with their own photo-voltaic solar cell panels, which is
allowed, and the solar energy so obtained is not included in that vehicle's energy
consumption for scoring purposes. In the case of hybrid-electric and Hydrogen powered
vehicles, please see the examples given in Appendix E."
This would give a very clear advantage to aircraft like the ones Eric Raymond designs.
B.E.
GregLocock (Automotive)
12 Aug 09 23:09
Yes, but with 8 sq m of panels you could spend a small fortune (easily $250000) to get 1-2 kW, that wouldn't give 500W if it is raining hard.
However the idea is good. Incidentally I saw Sunseeker at an airshow, amazing to think how long ago he flew across the USA. Very sensible design. Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
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SparWeb (Aerospace)
14 Aug 09 18:03
As a reality check, it would be informative to take a known airplane and work out how it would score on the test.
A Cessna 172 can meet many of the requirements. With about 30 gallons fuel and 4 passengers, you've got a machine that weighs about 1/3 the contest limit, yet still has the 400 sm range, with reserve, using 55% power and speed 113 mph.
Flying 200sm in the 172 would use about 15 gallons of fuel, so 13 mpg. Carrying 4 passengers would give 52 Passenger-MPGe. Doesn't make the 100 pax-mph cut.
That's the trick, then. You need to improve the fuel consumption by 2x just to qualify for the minimum 100 pax-MPGe limit. You'd need less than 4 gallons per hour fuel consumption with 4 passengers. The Rutan voyager used about 5 gph during its flight around the world. It had two Continental engines, but it used only one for most of the flight. 字串6
Tough nut to crack. If using a gasoline engine, you can't use much more than 100 horsepower. That wouldn't slug a 6000 pound airplane around, but a 2200 pound homebuilt might have a chance. I'd be worried about rate of climb, too.
I won't comment on the alternative fuel possibilities.
Steven Fahey, CET
GregLocock (Automotive)
18 Aug 09 8:32
It's 200 mpg per passenger. Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
plasgears (Mechanical)
19 Sep 09 13:33
Look to Burt Rutan to meet the specs, and designed elegantly, too.
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