X Prize Clean Aviation: $10 million

[mheslep]

That is not a proper statement. It should read that the ENGINE noise is lower, not the overall aircraft noise. You can not change the acoustic performance of a prop by changing the thing that drives it. The prop noise will still be there.

Right, the implication of the SIAM statement is that engine noise dominates in a helicopter w/ combustion engine. That's why I'm running down the prop noise alone. SIAM says its 50dbL at 150 M, a number that can be calculated (if I can define the terms :uhh:)

Assumptions per prop:
B (blades) = 4
y = sideline distance = 450 ft
D = 6 ft
T = thrust = 300 lbs takeoff
W = shaft power = 30 HP
c0 = 1000 ft/s
zeff = 0.8

I want worse case, so I'm bypassing all the modal analysis and setting the sincx and Bessel functions to one.

Edit:Still need help on defining theta? It can't be zero or the SPL is zero.

 

[Cyrus]

That is not a proper statement. It should read that the ENGINE noise is lower, not the overall aircraft noise. You can not change the acoustic performance of a prop by changing the thing that drives it. The prop noise will still be there.

According to the article, they made rotors with lower tip speeds to reduce noise as well.

 

[Cyrus]

Oh man, I just read that the battery power will only allow it to hover for 6 mins before they are drained.

 

[mheslep]

Oh man, I just read that the battery power will only allow it to hover for 6 mins before they are drained.

For comparison, the total flight time of those novelty http://en.wikipedia.org/wiki/Jet_pack" is about 9 minutes. Total flight time (not hover) of this VTOL appears to be about 20 minutes (80 km / 240 km/h), with today's batteries. I expect a good idea would be to equip the VTOL with a small but very high density primary battery as a one-time emergency backup, maybe 2 minutes worth of flight time. The military might go with an all-primary, throw away battery set which would triple the flight and hover times immediately.

 

[Cyrus]

Why would add a backup battery (more weight) that adds 1/10th more flight time, when you could just make the original batter a 1/10th bigger?

I would hold of on any extrapolations as to what the military may or may not due until this thing is actually built.

As I said in my blog though, all of this still comes off as pie in the sky concepts with little to no calculations or experiments to validate the technology. That's leaving out the fact that NASA hasn't been supporting this idea either.

The electric airplane will come into fruition once a battery with sufficient energy density has been developed. Now is not that time.

 

[mheslep]

Why would add a backup battery (more weight) that adds 1/10th more flight time, when you could just make the original batter a 1/10th bigger?

Because as I indicated above the best primary (non-rechargeable) batteries have 3-4X the energy density of the best rechargeable ones. So to add 10% emergency flight time, add only 2.5% more battery by weight.

I would hold of on any extrapolations as to what the military may or may not due until this thing is actually built.

More generally I was pointing out that if the VTOL user had the resources to throw the battery away after every flight, the hover and flight time is much more reasonable using today's technology, i.e. 1 hour, 250 km range.

The electric airplane will come into fruition once a battery with sufficient energy density has been developed. Now is not that time.

Maybe, but this thread at its root is about the feasibility of one particular event: a coast to coast aviation speed contest using electric aircraft, the outcome of which will help demonstrate just what is actually possible.

 

[Cyrus]

Because as I indicated above the best primary (non-rechargeable) batteries have 3-4X the energy density of the best rechargeable ones. So to add 10% emergency flight time, add only 2.5% more battery by weight.

Since this battery is one time use, I have to ask: what is the shelf life and cost of this thing going to be? If I have to replace a several thousand dollar battery every few months because it goes bad from not being used, that's not a very attractive backup option.

More generally I was pointing out that if the VTOL user had the resources to throw the battery away after every flight, the hover and flight time is much more reasonable using today's technology, i.e. 1 hour, 250 km range.

That's not very practical, from an operational or budgetary standpoint, you'd agree?

Maybe, but this thread at its root is about the feasibility of one particular event: a coast to coast aviation speed contest using electric aircraft, the outcome of which will help demonstrate just what is actually possible.

How will it demonstrate what is actually possible if it uses one shot, expensive batteries though? I'm still not seeing why this is a good challenge. Why not just make a 'long life' battery challenge?

 

[mheslep]

Since this battery is one time use, I have to ask: what is the shelf life and cost of this thing going to be? If I have to replace a several thousand dollar battery every few months because it goes bad from not being used, that's not a very attractive backup option.

http://www.all-battery.com/alarmsecurityandmeter.aspx" appears to be the current top performer, 10 years. Used in alarm systems, remote metering systems, etc.

That's not very practical, from an operational or budgetary standpoint, you'd agree?

Again I'm not talking about the common 'flying car' zaniness. For the military, it depends on the alternatives. Might be a very reasonable cost to transport a couple of Special Operations folks quietly in, and then out again, of a tight spot.

How will it demonstrate what is actually possible if it uses one shot, expensive batteries though? I'm still not seeing why this is a good challenge. Why not just make a 'long life' battery challenge?

Because the effectiveness or the economics of the aircraft is not simply f(battery energy density), though I grant that's a big part. There are many other important factors:

• efficiency of the electric drive system
• electric propulsion means the power source (battery) and the propulsion (e-motor/prop) can be separated and distributed over the aircraft, unlike a standard turbo prop or turbo fan engine which are (far as I know) mechanically coupled along an axis. This may open up some possibilities for aircraft design.
• noise (yes that's still an open issue). Quiet aircraft will be allowed in many places louder ones are not.
• pollution
• 're-energize', take-off, land time. That is, if the aircraft could land, re-energize, and take off again in very, very short time perhaps maybe short range is not an issue in some scenarios
• cost of electricity + amortized battery cost versus the cost of fuel for the same distance traveled.
  and so on

 

[Cyrus]

http://www.all-battery.com/alarmsecurityandmeter.aspx" appears to be the current top performer, 10 years. Used in alarm systems, remote metering systems, etc.

Does this battery technology also work in the high power regime for VTOL flight?

Again I'm not talking about the common 'flying car' zaniness. For the military, it depends on the alternatives. Might be a very reasonable cost to transport a couple of Special Operations folks quietly in, and then out again, of a tight spot.

Are you referring to the X-prize, or the NASA puffin here?


Going back, let's assume your numbers of 95-98% efficiency. Then the puffin is looking between 1.2-3HP of losses that will be converted into heat (yes, I've been sloppy using HP here, but we can think of it as the rate of energy per hour). That's a good deal of energy to dissipate. Without an air scoop, the only means of heat transfer is conduction to the skin of the nacelle, and then convection of the aircraft skin to the boundary layer. Thats not a good way of dissipating heat. If you have an air scoop, you have nice turbulent air going over the motor and batteries (turbulent air is an order of magnitude better for convective heat transfer than laminar). You could probably even get away with a low drag http://en.wikipedia.org/wiki/NACA_duct" .

 

[FredGarvin]

There is nothing wrong with using HP for energy losses. We use it all the time.

 

[RonL]

You guys seem to be having a hard time getting out of the box :)
An idea or two if you will allow.

First, consider your batteries built into a ring around the props (5 or more blades?) acting as a flywheel, with lots of air flow to keep them cool.

Props would consist of tractor and pusher design giving counter rotation, which gives options of dual power application to the two motor parts (housing and armature).

Current technology (PWM) feeds motors in pulses, so a generating action, (also in pulses) and maybe 4 or more times the motor voltage, might offset a lot of battery weight.

Ground power to the point of being airborne, battery power to altitude and top speed, then at top speed wind energy allows power applied and generated to be cycled as needed. This can happen because of speed of the plane and flywheel action of the props.

The almost instant reaction times between power used and power generated is much like the chicken and egg question,( Which one needs to be first ?).
If a speed of 300 knots is assumed, in one instant your plowing through the air and in the next instant your sitting in a windmill with a 300 knot wind blowing past it.

The main question in all this is, can the duration of batteries be extended by any worthwhile amount ??
I just hope everyone interested, will not dismiss these thoughts too quickly.

Ron

 

[OmCheeto]

You guys seem to be having a hard time getting out of the box :)
An idea or two if you will allow.

um. Ron. There's thinking outside of the box, and then there's jumping out of the box at an altitude of 30,000 feet without a parachute.

First, consider your batteries built into a ring around the props (5 or more blades?) acting as a flywheel, with lots of air flow to keep them cool.

I believe mheslep mentioned that they'd weigh 11 tons. I don't think it would be desirable to have 11 tons of anything spinning.

Props would consist of tractor and pusher design giving counter rotation, which gives options of dual power application to the two motor parts (housing and armature).

Current technology (PWM) feeds motors in pulses, so a generating action, (also in pulses) and maybe 4 or more times the motor voltage, might offset a lot of battery weight.

Increased voltage <> increased energy density.

Ground power to the point of being airborne, battery power to altitude and top speed, then at top speed wind energy allows power applied and generated to be cycled as needed. This can happen because of speed of the plane and flywheel action of the props.

There are locations on the trip where there will be excess lift due to thermals, but I doubt your flywheels will be practical to store this energy.

The almost instant reaction times between power used and power generated is much like the chicken and egg question,( Which one needs to be first ?).
If a speed of 300 knots is assumed, in one instant your plowing through the air and in the next instant your sitting in a windmill with a 300 knot wind blowing past it.

I think the trip is 2600 miles, which in 24 hours, yields an average speed of about 110mph. I'd say that should be the target speed. Unless of course we can reach a high enough altitude where the wind resistance is less.

The main question in all this is, can the duration of batteries be extended by any worthwhile amount ??
I just hope everyone interested, will not dismiss these thoughts too quickly.

Ron

Your ideas are either:

a. completely unthought out mind spinning(which I can totally relate to)

or

b. so far advanced as to be technologically unfeasible in this or the next century.

Though your flywheel battery pack did remind me of Cort Nozzles, which makes me wonder how much more efficient we could make props with such a device. I mean, when was the last time anyone saw an open framed turbine?

Ah ha! http://en.wikipedia.org/wiki/Ducted_fan" . Just what we were looking for.

Uh. Oh.

Turbofan engines are used on nearly all airliners, fighters, and bombers.

Did I mention that I know almost nothing about airplanes?

 

[mheslep]

Does this battery technology also work in the high power regime for VTOL flight?

No, not that particular chemistry I happened to grab off the shelf - it doesn't have great power density, not as much as its rechargeable cousin Li Ion. I'd have to look some more.

Are you referring to the X-prize, or the NASA puffin here?

Puffin.

Going back, let's assume your numbers of 95-98% efficiency. Then the puffin is looking between 1.2-3HP of losses that will be converted into heat (yes, I've been sloppy using HP here, but we can think of it as the rate of energy per hour). That's a good deal of energy to dissipate. Without an air scoop, the only means of heat transfer is conduction to the skin of the nacelle, and then convection of the aircraft skin to the boundary layer. Thats not a good way of dissipating heat. ...

A good way is whatever is good enough. For comparison, a big tower case home computer dissipates a HP of heat, which it seems to do without an air scoop.

 

[mheslep]

I believe mheslep mentioned that they'd weigh 11 tons. I don't think it would be desirable to have 11 tons of anything spinning.

This is my fault - bringing both the X prize and the small Puffin into this thread. 11 tons of battery was of course for the 850 mi leg of the X prize in semi-large aircraft. The two (Puffin/prize) really should be separated into different threads. Ron was talking about the Puffin I believe.

 

[RonL]

um. Ron. There's thinking outside of the box, and then there's jumping out of the box at an altitude of 30,000 feet without a parachute.

I believe mheslep mentioned that they'd weigh 11 tons. I don't think it would be desirable to have 11 tons of anything spinning.

Increased voltage <> increased energy density.

There are locations on the trip where there will be excess lift due to thermals, but I doubt your flywheels will be practical to store this energy.

I think the trip is 2600 miles, which in 24 hours, yields an average speed of about 110mph. I'd say that should be the target speed. Unless of course we can reach a high enough altitude where the wind resistance is less.


Your ideas are either:

a. completely unthought out mind spinning(which I can totally relate to)

or

b. so far advanced as to be technologically unfeasible in this or the next century.

Though your flywheel battery pack did remind me of Cort Nozzles, which makes me wonder how much more efficient we could make props with such a device. I mean, when was the last time anyone saw an open framed turbine?

Ah ha! http://en.wikipedia.org/wiki/Ducted_fan" . Just what we were looking for.

Uh. Oh.

Did I mention that I know almost nothing about airplanes?

Hi Om,
Nothing really advanced, It's just a matter of putting things in motion that are normally bolted down and in a static condition.
Manage air flow, it can be more than just a barrier to push through.

I started to try and explain things, but there is just too much interaction that must be blended together.

Speed and air flow are key to making use of a generator that can replace a large amount of battery weight.

My thoughts are geared more to a conventional airplane design.

Ron

 

[RonL]

This is my fault - bringing both the X prize and the small Puffin into this thread. 11 tons of battery was of course for the 850 mi leg of the X prize in semi-large aircraft. The two (Puffin/prize) really should be separated into different threads. Ron was talking about the Puffin I believe.

mheslep,
While the Puffin is pretty neat, I was thinking of a more conventional plane, not too big and most likely a twin motor design.

Ron

 

[OmCheeto]

My thoughts are geared more to a conventional airplane design.

Ron

My opinion is that this is going to be a non-conventional design.

The first airplane was made by a couple of bicycle mechanics with a very rudimentary ICE at best.

Now that we have laptops that exceed the capabilities of supercomputers from just 30 years ago, superconductors that did not exist 40 years ago, composite materials that are improving daily, I'd say we are in for something very..., um, I'm going to go for cheating.

 

[RonL]

My opinion is that this is going to be a non-conventional design.

The first airplane was made by a couple of bicycle mechanics with a very rudimentary ICE at best.

Now that we have laptops that exceed the capabilities of supercomputers from just 30 years ago, superconductors that did not exist 40 years ago, composite materials that are improving daily, I'd say we are in for something very..., um, I'm going to go for cheating.

The dream weaver always makes it sound easy and simple, a fact I'm aware of.

Consider a cesna 310, just as an example, remove the big bulky ICE's and replace with the two electric power tubes.
These power tubes might be placed over or under the wing, and based on motor size will likely be less than 12" in dia. and long enough to hold a tractor prop in front and a pusher prop behind the wing, one on each side of the fuselage. The motors/generators in series inside the tubes.

The props (say six blades) have a composit ring of proper thickness and width, secured to each of the six tips, with batteries secured inside or, on the outside of the ring.

As I said before, it seems to me that thrust load and RPM of the props can be much greater, but this may in fact be false, being as I am not an engineer, finding the answers will be very hard for me if at all I can.

Ideas have to start somewhere, right? Lots of ring products in the market, I have not seen one on a real airplane.

Ron

 

[OmCheeto]

The dream weaver always makes it sound easy and simple, a fact I'm aware of.

Consider a cesna 310

A Cessna? Talk about thinking inside the box...

I was thinking more on the line of meshing and morphing the technologies of the desired attributes of existing electric vehicles:

Speed:

105 mph. Batteries not included.

Altitude:

96,863 feet

Range: Lots of range on most vehicles. Though there are none that have both range and speed.

, just as an example, remove the big bulky ICE's and replace with the two electric power tubes.
These power tubes might be placed over or under the wing, and based on motor size will likely be less than 12" in dia. and long enough to hold a tractor prop in front and a pusher prop behind the wing, one on each side of the fuselage. The motors/generators in series inside the tubes.

The props (say six blades) have a composit ring of proper thickness and width, secured to each of the six tips, with batteries secured inside or, on the outside of the ring.

As I said before, it seems to me that thrust load and RPM of the props can be much greater, but this may in fact be false, being as I am not an engineer, finding the answers will be very hard for me if at all I can.

Ideas have to start somewhere, right? Lots of ring products in the market, I have not seen one on a real airplane.

Ron

Rings? This one has lots of rings:

But seriously, I would imagine, based on the the Nuna and Helios examples above, that the most efficient and likely candidate to win the race would be some sort of flying wing.

Kind of like this little fella:

Only not quite so thick. I don't think we need to be carrying around 40,000 lbs of bombs.

 

[mheslep]

...

But seriously, I would imagine, based on the the Nuna and Helios examples above, that the most efficient and likely candidate to win the race would be some sort of flying wing...

I doubt it. This is a speed contest, not a stay-aloft-a-long-time contest. Adding a bunch of wing adds a bunch of drag.

On any kind of aircraft at all I doubt if solar panels help for this one time, one trip contest. Panels might provide 8 kWh (10 M^2 x 200W/M^2 x 4 hours ), which is provided by 53 kg of rechargeable Li Ion batteries (150 Wh/kg), or 16kg of non rechargeable batteries. Dump the panels, go with extra batteries.

 

[RonL]

A Cessna? Talk about thinking inside the box...

I was thinking more on the line of meshing and morphing the technologies of the desired attributes of existing electric vehicles:

Speed:

105 mph. Batteries not included.

Altitude:

96,863 feet

Range: Lots of range on most vehicles. Though there are none that have both range and speed.



Rings? This one has lots of rings:

But seriously, I would imagine, based on the the Nuna and Helios examples above, that the most efficient and likely candidate to win the race would be some sort of flying wing.

Kind of like this little fella:

Only not quite so thick. I don't think we need to be carrying around 40,000 lbs of bombs.

All fine examples, and I love flying wings.

When I talk about outside the box, I'm generally thinking about things that can be done at my time and financial level, which is pretty small.

About the picture of the ring ducts, that is quite like what I was trying to describe only what I picture is smaller and not as bulky looking. Now if you can see in the minds eye those rings as part of the prop and in spin motion, they will store energy like a flywheel and I might dare say the drag of air flowing around and through them will be less than if motionless (?)

What I think to be most outside the box, is what happens at the motor/generator section.
If the housing and armature are allowed to spin in opposite directions twice the voltage (or more) can be applied, and if cooling based on air velocity will allow, the amp load might be doubled, you then have 4 times the power being applied between the two props.
The power being supplied is from batteries and is in modified wave form (or pulses).
The instant of change from power being supplied to power being generated, the load against the motor action being minus, becomes positive to the generator action and goes to the batteries in a continuous flow.
This might be just a very small difference, but something to look at.
Only electrical control can take advantage of those thermals you mentioned

The power switches happen in microseconds and changes in speed and rotating mass will have almost no change.
This is completely different than something bolted to a shop table.

Ron

 

[RonL]

Well Om,
Looks like you were right about me being out at 30,000 feet without a parachute

Everyone left to go win the prize before they got the "rest of the story".

Energy always has to be obtained and paid for, before being used. Because energy can be stored it can be compared to money in a bank account which generally earns interest, these accounts most often allow for deposits and withdrawals as long as a certain balance is maintained. A flywheel (a single or any group of rotating parts) is like the bank account. Electrical energy can be controlled with such precision that 95% or better efficiency is claimed for many motors on the market today. Motors and generators are generally one and the same for all practical purposes and as I understand, more speed always equates to more efficiency. (just a rule of thumb)

Thermal energy from air that flows through and around the aircraft, is the source of replacment for the losses in the electrical system.

A simplified description (of one) of several more parts that make up the whole.

Most are now aware of three phase brushless motors, they come in two versions, inrunners and outrunners, you have two options for each in what part mounts to the firewall or frame. The armature can be stationary and the housing rotates or the housing mounts and the armature rotates (not sure which offers the best advantages)
The design I'm putting in words here, is to use the armature mounted and the housing to be the rotating part, a body is machined and is made to hold two sets of neo. magnets, one set inside to work as an outrunner motor, and the second set of magnets (on the outside of the housing) work as the rotor inside a common alternator.
There are many ways to put this in motion with power input from other sources, a key factor is the outrunner motor action, spinning the rotor of the alternator at speeds of 15,000 rpm or more is independent of some slow moving power source.

It might be that everybody and their pets have been doing this for the last year or two, but I think it is a new idea.

Can electrical energy be levered through mechanical motion? I think yes. Along with heat being converted to work (air flow) it seems to me that battery quantity might not be as important as everyone is being led to believe

Guess my 30,000 feet is about used up

Ron

 

[OmCheeto]

All fine examples, and I love flying wings.

When I talk about outside the box, I'm generally thinking about things that can be done at my time and financial level, which is pretty small.

Well, I don't think anyone at the forum could afford to build our hypothetical plane.
But I can envision incorporating scaled down ideas into my electric boat design.
Or vice versa.

About the picture of the ring ducts, that is quite like what I was trying to describe only what I picture is smaller and not as bulky looking. Now if you can see in the minds eye those rings as part of the prop and in spin motion, they will store energy like a flywheel and I might dare say the drag of air flowing around and through them will be less than if motionless (?)

What I think to be most outside the box, is what happens at the motor/generator section.
If the housing and armature are allowed to spin in opposite directions...

I'll stop you right there and say, what?

How are you going to generate any meaningful torque on the prop if your housing is spinning? In my minds eye, your airplane is going to be an expensive tarmac ornament.

I doubt it. This is a speed contest, not a stay-aloft-a-long-time contest. Adding a bunch of wing adds a bunch of drag.

On any kind of aircraft at all I doubt if solar panels help for this one time, one trip contest. Panels might provide 8 kWh (10 M^2 x 200W/M^2 x 4 hours ), which is provided by 53 kg of rechargeable Li Ion batteries (150 Wh/kg), or 16kg of non rechargeable batteries. Dump the panels, go with extra batteries.

I don't know about that. I can imagine cubing the size of the Nuna and obtaining a doubling of speed to 200 mph. Add a few hundred kg of batteries, and we've got a race.

Though as I've said before, I know nothing about airplanes. I'll do a bit more number crunching this weekend to see what it takes to get a brick to fly.

 

[RonL]

I'll stop you right there and say, what?

How are you going to generate any meaningful torque on the prop if your housing is spinning? In my minds eye, your airplane is going to be an expensive tarmac ornament.

If a motor is mounted in such manor as to allow the housing to turn as well as the armature, and each has a prop of proper rotation mounted, any amount of power supplied to the motor will be split between the two parts based upon the thrust resistance of each prop.

P.S. Should work on your boat as well...Twin screw counter rotating props...


Ron

 

[minger]

If a motor is mounted in such manor as to allow the housing to turn as well as the armature, and each has a prop of proper rotation mounted, any amount of power supplied to the motor will be split between the two parts based upon the thrust resistance of each prop.

P.S. Should work on your boat as well...Twin screw counter rotating props...


Ron

I won't pretend to have been involved in this thread, but from quickly reading I'd point out that windage losses from spinning such a housing could be significant.

 

[OmCheeto]

If a motor is mounted in such manor as to allow the housing to turn as well as the armature, and each has a prop of proper rotation mounted, any amount of power supplied to the motor will be split between the two parts based upon the thrust resistance of each prop.

P.S. Should work on your boat as well...Twin screw counter rotating props...


Ron

Tell you what, let's build miniature models of our engines. We can compare thrust vs energy numbers on Monday.

Actually, the full size engines would probably be very small to begin with. Let's go with 12 inch diameter fans, as you mentioned the other day.

 

[RonL]

Tell you what, let's build miniature models of our engines. We can compare thrust vs energy numbers on Monday.

Actually, the full size engines would probably be very small to begin with. Let's go with 12 inch diameter fans, as you mentioned the other day.

I can see how the words didn't make for a clear picture.
The power tube size is based on motor/generator diameter, and is much like a super size canister vacuum.

High RPM motor/generator units transfer power to much larger props, 48" or more.

More than a weekend project for me
I'll be lucky to work on anything before late spring, if your interested in something to play around with on your boat ?, I'll send you a PM.

Ron

 

[mheslep]

Aviation Week did a piece on the VTOL Puffin
http://www.aviationweek.com/aw/blogs/business_aviation/index.jsp?plckController=Blog&plckScript=blogScript&plckElementId=blogDest&plckBlogPage=BlogViewPost&plckPostId=Blog%3A2f16318d-d960-4e49-bc9f-86f1805f2c7fPost%3Ad341a5a0-b4d4-4ae1-a99b-9488d0b1d281

A key design breakthrough is the redundancy in the electric propulsion system, says Moore. Detailed reliability analyses and powertrain build-up by M-dot Aerospace “showed that for each nacelle, we could achieve an FAA equivalency to a multi-engine rating. This is what allowed us to avoid having a cross-shaft, as each engine can fail any two components and still operate at the full 30-hp. rating [per nacelle].”
[...]
The rotors’ speed can be controlled through a wide range by varying the electric motor without the need for complex and heavy gear systems. Moore says that “electric motors have no lapse rate at high/hot conditions, nor with altitude, so that full power can be produced as you go to higher cruise altitudes.”
[...]
“Everything about electric propulsion is better than reciprocating or turbine engines for these small vertical-takeoff-and-landing platforms—except for battery energy storage,” says Moore. “And with billions of dollars going toward that problem, and exciting near-term technologies being developed by MIT, Stanford [University] and industry—how can we afford to not be looking at the incredible design freedom that electric propulsion offers to aircraft designers?”

 

[mgb_phys]

Everything about electric propulsion is better than reciprocating or turbine engines for these small vertical-takeoff-and-landing platforms

Except for the extension cord.

—except for battery energy storage

Yep like the only thing between me and an olympic gold is energy storage.

 

[Cyrus]

Aviation Week did a piece on the VTOL Puffin
http://www.aviationweek.com/aw/blogs/business_aviation/index.jsp?plckController=Blog&plckScript=blogScript&plckElementId=blogDest&plckBlogPage=BlogViewPost&plckPostId=Blog%3A2f16318d-d960-4e49-bc9f-86f1805f2c7fPost%3Ad341a5a0-b4d4-4ae1-a99b-9488d0b1d281

First of all, I'm glad they finally accurately quoted the electric system as not having a lapse rate, and not the entire system. That being said, the ability to not have a cross drive system is really great. This is classically a problem in terms of empty weight fraction in the XV-15 (precursor to the V-22), and its bigger brother, the V-22. If they can avoid having articulated rotor systems (think a helicopter mechanical controls) on each blade, that is also great because it reduces the complexity, cost and weight.

Their main problem; however, is that the FAA requires at least 30 mins reserve fuel. The Puffin flies for 5 minutes - total. This is really a fundamental problem.

 

[mheslep]

Their main problem; however, is that the FAA requires at least 30 mins reserve fuel. The Puffin flies for 5 minutes - total. This is really a fundamental problem.

5 minutes is the longest prototype test flight so far. The final design spec is ~20 mins, or http://www.scientificamerican.com/article.cfm?id=nasa-one-man-stealth-plane" (c. Reserve Fuel), and may apply only in air traffic control situations, i.e. in and out of FAA controlled airports.

 

[Cyrus]

5 minutes is the longest prototype test flight so far. The final design spec is ~20 mins, or http://www.scientificamerican.com/article.cfm?id=nasa-one-man-stealth-plane" (c. Reserve Fuel), and may apply only in air traffic control situations, i.e. in and out of FAA controlled airports.

To my knowledge, there have been no test flights of this prototype. The fuel issue still stands. I am looking outside my window right now, and it is IFR weather. If this is a 'flying car' in the most general sense, it is fundamentally not going to work because it is not robust to the environment.

When I get home, I will look through my FAR/AIM and give you the exact rules on fuel reserves required by law, and how it applies (I never really fly far enough to know this off the top of my head).

 

[mheslep]

To my knowledge, there have been no test flights of this prototype.

So then where did you get 5 minutes?

The Puffin, named because it resembles the bird, has not yet flown publicly, but Moore said its longest flight lasted five minutes.

The fuel issue still stands. I am looking outside my window right now, and it is IFR weather. If this is a 'flying car' in the most general sense, it is fundamentally not going to work because it is not robust to the environment.

<shrug>

"We're not trying to replace the car or the airplane," Moore said. "Cars are great at what they do, which is go a couple of miles at relatively slow speeds. Commercial air carriers are great at going long distances at faster speeds. But what happens when we want to go 100 or 200 or 300 miles? We have to take this very long drive

http://news.discovery.com/tech/nasa-aircraft-puffin-transportation.html

When I get home, I will look through my FAR/AIM and give you the exact rules on fuel reserves required by law, and how it applies (I never really fly far enough to know this off the top of my head).

Look forward to it, though AFAICT the source I supplied above are the current FAA regs.

 

[Cyrus]

The 5 mins are based on lab tests they have done, to my knowledge. (Edit: after reading your link, it does appear they have actually flow it. I wonder, why no pictures of the actual vehicle).

<shrug> ... really? You're answer to a 'flying car' that has to work in IFR conditions (and hence have fuel reserves for 30 mins, longer than the vehicle can even fly is ...<shrug>? This is called a fundamental problem, not ...<shrug>!

Clarification: now the article says it's not a flying car..however, one has to ask. What do you use a 5 minute, 50 mile range vehicle for? Let's be real here, at best this is a flying car (but worse than a car in performance!).

Obviously, the car is meant for use of 100 -300 mile trips, and the article states that the only way to do this (currently) is by car. But, what's wrong with taking the train?

 

[mheslep]

Clarification: now the article says it's not a flying car..however, one has to ask. What do you use a 5 minute, 50 mile range vehicle for?

https://www.physicsforums.com/showpost.php?p=2682088&postcount=101"