X Prize Clean Aviation: $10 million

In summary: I seem to have with you, turns into a conversation about energy storage.In summary, an MIT collaboration with the X Prize foundation has proposed a $10 million prize for a race from California to New York in which competing planes must be powered entirely by electricity and produce no emissions. The winning plane would receive $7.5 million, with an additional $2.5 million prize for the longest distance covered on a single leg of the flight. The proposal has been met with skepticism due to the challenges of energy storage and the potential limitations of using electric motors to power ducted fans. However, the goal of spurring innovation remains a driving force behind the proposal.
  • #36
For everybody else - there is an excellent and entertaining talk by Sebastian Thrun from Stanford's team.

http://video.google.com/videoplay?docid=8594517128412883394 [Broken]
 
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  • #37
mheslep said:
Is there a standard approach for characterizing the noise?
I am not quite sure what you mean by standard approach. There is the area of aeroacoustics in which we look at the noise contributions due to aerodynamic influences. It is a relatively new area but a fair amount is known. In this case, it was mentioned that loading of the blades is a factor, as is relative mach number of each blade and blade tip. The spreding/attenuation over distances is very custom for each application in that the speeds and frequencies are always different. Plus, since this is unshrouded you don't have issues arising from waveguides, i.e. ducts. Things are different when a blade tip is sonic or supersonic. I can only assume they would be sonic, which means they will naturally attenuate/decay with increasing radius from the source.

There is a FAR (I can not remember the number off the top of my head) that governs the testing of noise signatures around airports. It is pretty detailed and measurements are required to simulate an aircraft arriving and departing and at altitudes, of I believe, 400 ft. It has been a while since I have read that FAR. I think it wouldn't be a killer for this application, but it would definitely be a concern.
 
  • #38
mgb_phys said:
For everybody else - there is an excellent and entertaining talk by Sebastian Thrun from Stanford's team.

http://video.google.com/videoplay?docid=8594517128412883394 [Broken]
Seen it many times.

Thrun's team setup next to ours in the semi-final, so I had the opportunity to talk him and his team over several days. He's a fantastic engineer, great sense of humor.
 
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  • #39
FredGarvin said:
I am not quite sure what you mean by standard approach.
I was asking for indulgence in explaining how characterization of prop acoustics - fundamentals. Googling wasn't providing any useful fundamentals. This is a start:

There is the area of aeroacoustics in which we look at the noise contributions due to aerodynamic influences. It is a relatively new area but a fair amount is known. In this case, it was mentioned that loading of the blades is a factor, as is relative mach number of each blade and blade tip. The spreding/attenuation over distances is very custom for each application in that the speeds and frequencies are always different. Plus, since this is unshrouded you don't have issues arising from waveguides, i.e. ducts. Things are different when a blade tip is sonic or supersonic. I can only assume they would be sonic, which means they will naturally attenuate/decay with increasing radius from the source.

Well eventually I wanted to estimate dBl / distance given some prop assumptions. E.g. vehicle developing ~1000 lbs thrust at take off, RPM x, tip speed sonic, etc, add in latest
prop noise reduction techniques, then compare with known noise of 200HP turbine or piston engine.
 
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  • #40
mheslep said:
Thrun's team setup next to ours in the semi-final, ... He's a fantastic engineer, great sense of humor.
Rather letting the side down, as a German engineering prof though - stereotype-wise ;-)
 
  • #41
mgb_phys said:
Rather letting the side down, as a German engineering prof though - stereotype-wise ;-)
Well he's been in the US for a long time. Then, Einstein apparently had a silly streak.
 
  • #42
mheslep said:
Sorry I don't follow. What source of power are you suggesting, if not an electric motor? Edit: Perhaps you are asking: why use an electric motor instead of a traditional gas turbine? Electric motor can be >95% efficient, is quiet, as you mentioned above, and can run on electric charge that may have been generated on the ground and stored in the aircraft.

Post #2, for purposes of this prize. 11 metric tons of battery per 850 mile leg.

I would suggest obtaining a formal education in the subject before making such outlandish claims. That 95% efficiency won't do you much good if it comes with a huge weight penalty. Gas turbine engines are really unparalleled when it comes to thrust/weight ratio and energy density.
 
  • #43
Brian_C said:
I would suggest obtaining a formal education in the subject before making such outlandish claims.
Thanks, I think I have a pretty good one, and a license to use it, though it is limited on the subject of aerodynamics. To be constructive, could you show how those numbers (11 metric tons / 850 miles) are outlandish? I think I've crunched and shown the basic numbers if you backtrack the post.
That 95% efficiency won't do you much good if it comes with a huge weight penalty. Gas turbine engines are really unparalleled when it comes to thrust/weight ratio and energy density.
Gas turbines are not an option for the prize, hence the thread topic "CLEAN AVIATION". Please see the https://www.physicsforums.com/showpost.php?p=2535479&postcount=1":
UK Drives and Controls said:
Superconducting motors operating with almost no losses could achieve power densities of 10–20kW/kg (and perhaps even higher) and torque densities of more than 35Nm/kg (compared to 10Nm/kg for the best conventional motors), the US researchers say.
Edit: maybe gas turbines hold the trophy for thrust/weight; the above challenges power/weight.

Maybe also see another thread for existing HTS propulsion research.
https://www.physicsforums.com/showpost.php?p=2292842&postcount=14
 
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  • #44
I took issue with a statement made by many of these articles: namely, that you don't need air intakes because it's electric. This is hog-wash because anyone that has flown an electric airplane knows they get very hot (battery, motor, and electronics). Cooling them is absolutely an issue. I do not buy that they don't need 'air intakes' for this vehicle. There will be significant power losses in the form of [tex]i^2R[/tex].

Also, how is this thing 'stealth' with big spinning rotors?
 
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  • #45
Cyrus said:
I took issue with a statement made by many of these articles: namely, that you don't need air intakes because it's electric. This is hog-wash because anyone that has flown an electric airplane knows they get very hot (battery, motor, and electronics).
You mean RC airplanes? That's the 'because'?

Cooling them is absolutely an issue. I absolutely do not buy that they don't need 'air intakes' for this vehicle. There will be significant power losses in the form of [tex]iR^2[/tex].
I think the point here is that the air required for combustion, on the order of liters per second per HP*, completely dwarfs any air flow required for dissipating the couple hundred watts from this one man aircraft. Given the stated battery load (45kg) for Moore's VTOL, the [STRIKE]maximum[/STRIKE] continuous power is probably ~11kW (15HP). Though a small intake would suffice, no air intake at all is required dissipate 5% of that power as heat, just air flow over sufficient dissipative surface. I've built enclosed electronics boxes that conduct/convect away 500W from a two cubic foot box.

*quick math for gasoline combustion at 30HP requires 1 liter O2/sec, 5 liters air/sec, STP

Also, how is this thing 'stealth' with big spinning rotors?
How does one calculate the dBls / distance from these rotors?
 
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  • #46
How does the fact that a UAV is RC scale, or large scale, change the fact that there *will* be power losses by the engines that pose a thermal problem?

Please explain why you think this is not the case.

Also, what calculation did you do to get this 15HP number from? I don't believe this for one second.

Also, I did not say 'quiet' I said 'stealth': as in, radar cross signature.
 
  • #47
Let's do a simple calculation using the momentum theory equation of an *ideal* rotor. A real rotor will inevitably require more power:

[tex] P = \frac{T^{3/2}}{\sqrt{2 \rho A}} [/tex]

Assuming:

[tex] \rho = 0.002378[/tex] slug ft^-3
[tex] A = 28.27[/tex] Assuming a generous 6' rotor diameter
[tex] T = 300lbs [/tex] (Assume 600lb GTOW)

That gives a power of about 25.7HP, very close to the claim on SIAM article of 60HP total (30HP each)!
 
  • #48
Cyrus said:
How does the fact that a UAV is RC scale, or large scale, change the fact that there *will* be power losses by the engines that pose a thermal problem?

Please explain why you think this is not the case.
Because the efficiency of electric motors and battery packs varies considerably. Larger motors can hit 95-98% efficient, but it is difficult to do that at small scale. Also I wouldn't imagine there is much room or effort made for thermal dissipation made on an RC, at least not the couple small ones I've toyed with. Small motor/battery mounted on poor heat conductors - plastic/composite - so yeah they'll get hot.

Also, what calculation did you do to get this 15HP number from? I don't believe this for one second.
SIAM said Moore's using a 45 kg battery load. Li Ion puts out http://en.wikipedia.org/wiki/Lithium-ion_battery" [Broken] continuous (above I said maximum and corrected that to continuous) Edit: maximum battery discharge rate is typically be 10x (250W) for very short periods, i.e. peak up to 150HP. The motor would undoubtedly be the limiting factor - SIAM suggests it is 60HP.

Also, I did not say 'quiet' I said 'stealth': as in, radar cross signature.
Wasn't the 'stealth' reference in SIAM was on thermal signature? Obviously electric will be low compared to combustion.

Yes:
SIAM said:
n addition, since electric motors are so efficient, they also generate far less heat. This not only gives them a lower thermal signature for military stealth, but means they don't need anywhere near the same amount of cooling air flowing over them that internal combustion engines do,...
 
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  • #49
Cyrus said:
Let's do a simple calculation using the momentum theory equation of an *ideal* rotor. A real rotor will inevitably require more power:

[tex] P = \frac{T^{3/2}}{\sqrt{2 \rho A}} [/tex]

Assuming:

[tex] \rho = 0.002378[/tex] slug ft^-3
[tex] A = 28.27[/tex] Assuming a generous 6' rotor diameter
[tex] T = 300lbs [/tex] (Assume 600lb GTOW)

That gives a power of about 25.7HP, very close to the claim on SIAM article of 60HP total (30HP each)!
Thanks. How does one estimate the acoustic output of such a prop?
 
  • #50
mheslep said:
Thanks. How does one estimate the acoustic output of such a prop?

Want a PhD? Hehehe, honestly, I think its all empirical. The equations look like the NS equations: no closed form solutions.
 
  • #51
  • #52
Cyrus said:
Want a PhD? Hehehe, honestly, I think its all empirical. The equations look like the NS equations: no closed form solutions.
Yes silly question but I thought some rough bounds could be put on the maximum noise. For instance, if 60HP is converted completely to audible sound (of course its not) how loud is that, assuming no resonance or amplification.
 
  • #53
mheslep said:
Yes silly question but I thought some rough bounds could be put on the maximum noise. For instance, if 60HP is converted completely to audible sound (of course its not) how loud is that, assuming no resonance or amplification.

I'll ask someone I know about a relationship to noise. I think its something like the log of the disk loading.
 
  • #54
mheslep said:
For illustration:

NEMA electric motor efficiency requirements
Power
(hp) Minimum Nominal Efficiency
1 - 4 78.8
5 - 9 84.0
10 - 19 85.5
20 - 49 88.5
50 - 99 90.2
100 - 124 91.7
> 125 92.4

I suspect the typical RC motor is 0.1 to 0.01 HP. You get the idea.
http://www.engineeringtoolbox.com/electrical-motor-efficiency-d_655.html

On takeoff, my motor would draw almost ~750W. The speed controller was rated at 100A max.
 
  • #55
Cyrus said:
On takeoff, my motor would draw almost ~750W. The speed controller was rated at 100A max.
What's rated power of the motor? That's a nice thing about electrics - they can peak well above rated (5x at least).
 
  • #56
http://www.allerc.com/z40all.htm [Broken]

~1100W
 
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  • #57
Cyrus said:
http://www.allerc.com/z40all.htm [Broken]

~1100W

I don't see efficiency or output power, only input, but its still impressive. 3kW/kg (input) continuous in 1.9" OD case. That compares to, say, 4kW/kg (output) in the much larger Tesla AC induction motor.
 
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  • #58
You asked for it. I scanned this in from one of my references. The mB notation refers to the mth harmonic/mode and B is the number of blades. The rest should be somewhat decipherable.
 

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  • #59
mheslep said:
I don't see efficiency or output power, only input, but its still impressive. 3kW/kg (input) continuous in 1.9" OD case. That compares to, say, 4kW/kg (output) in the much larger Tesla AC induction motor.

Boy let me tell you, those guys get HOT.
 
  • #60
So do the lithium batteries most of them use for power.
 
  • #61
FredGarvin said:
You asked for it. I scanned this in from one of my references. The mB notation refers to the mth harmonic/mode and B is the number of blades. The rest should be somewhat decipherable.
Thanks Fred!
 
  • #62
BTW...This all stems from the basic wave equation. I sat through many a proofs showing this stuff and it is amazing to see just how much can be pulled from such a seemingly unimposing equation. You may want to look up Ffowcs Williams for a reference.
 
  • #63
Bessel function, wave equations? Eeeeuccccwkkkk! :smile:

Quick, something more pleasing to the ear: Laplace transforms, Bode Diagrams, Nyquist plots, PSD, Autocorrelations...ahhhhhhhhhhh. I can breathe again, whew.
 
  • #64
I'll tell you what, if you guys want to formulate a list of questions, I can email them to Dr. Moore and report back his answer. I'd prefer to keep the list short, so think of good ones.
 
  • #65
Cyrus said:
Quick, something more pleasing to the ear: Laplace transforms, Bode Diagrams, Nyquist plots, PSD, Autocorrelations...
:zzz: :zzz::zzz: huh...wha?...hmmm...:zzz: :zzz::zzz:
 
  • #66
FredGarvin said:
So do the lithium batteries most of them use for power.
A good Li Ion is ~95% efficient on discharge at room temperature (unlike lead acid), so Cyrus's RC battery would shed 55W of heat on take off, probably 5W cruise. In a small package w/ no thermal path, yes I imagine that gets very hot. If so, RC'ers might consider measures to cool them, as running a Li Ion hot will degrade its lifetime.
 
  • #67
All of the ones I have used and seen have no external means for cooling other than some form of exposure to the outside air.
 
  • #68
FredGarvin said:
You asked for it. I scanned this in from one of my references. The mB notation refers to the mth harmonic/mode and B is the number of blades. The rest should be somewhat decipherable.
Think I have it all except for theta, the 'retarded radiation angle'? I would expect the SPL is not isotropic, so maybe this is addresses the acoustic pattern?
 
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  • #69
Cyrus said:
I'll tell you what, if you guys want to formulate a list of questions, I can email them to Dr. Moore and report back his answer. I'd prefer to keep the list short, so think of good ones.
On the subject of prop/fan noise, I expect that his answer would concur w/ the article which he probably informed:

SIAM said:
At up to 95 percent efficiency, electric motors are far more efficient than internal combustion engines, which only rate some 18 to 23 percent. This means electric aircraft are much quieter than regular planes—at some 150 meters, it is as loud as 50 decibels, or roughly the volume of a conversation, making it roughly 10 times quieter than current low-noise helicopters.
You gents suggested otherwise upthread, so first I want to run the numbers from Fred's Propeller and Fan Noise reference; then we can ask a more informed question.
 
  • #70
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.
 
<h2>1. What is the purpose of the X Prize Clean Aviation?</h2><p>The X Prize Clean Aviation is a competition that aims to accelerate the development of clean and sustainable aviation technologies. It offers a $10 million prize to the team that successfully demonstrates a clean aviation technology that can significantly reduce carbon emissions and other environmental impacts of the aviation industry.</p><h2>2. Who can participate in the X Prize Clean Aviation?</h2><p>The competition is open to teams from around the world, including individuals, universities, and companies. The team must have a pilot and a technical lead, and can also include other members such as engineers, scientists, and business experts.</p><h2>3. What are the criteria for winning the X Prize Clean Aviation?</h2><p>The winning team must demonstrate a clean aviation technology that meets the following criteria: it must be able to reduce carbon emissions by at least 50%, have a range of at least 100 miles, and be able to carry at least two passengers. The technology must also be affordable, scalable, and have the potential for commercialization.</p><h2>4. How will the winner of the X Prize Clean Aviation be selected?</h2><p>The winning team will be selected by a panel of judges based on the performance and feasibility of their technology, as well as their business plan and potential for commercialization. The judges will also consider the team's ability to meet the criteria of the competition and their overall impact on the aviation industry.</p><h2>5. What is the timeline for the X Prize Clean Aviation?</h2><p>The competition was launched in 2018 and the deadline for team registration is in early 2022. The final competition and winner announcement is expected to take place in late 2022. However, due to the ongoing COVID-19 pandemic, the timeline may be subject to change. Updates will be provided on the X Prize website.</p>

1. What is the purpose of the X Prize Clean Aviation?

The X Prize Clean Aviation is a competition that aims to accelerate the development of clean and sustainable aviation technologies. It offers a $10 million prize to the team that successfully demonstrates a clean aviation technology that can significantly reduce carbon emissions and other environmental impacts of the aviation industry.

2. Who can participate in the X Prize Clean Aviation?

The competition is open to teams from around the world, including individuals, universities, and companies. The team must have a pilot and a technical lead, and can also include other members such as engineers, scientists, and business experts.

3. What are the criteria for winning the X Prize Clean Aviation?

The winning team must demonstrate a clean aviation technology that meets the following criteria: it must be able to reduce carbon emissions by at least 50%, have a range of at least 100 miles, and be able to carry at least two passengers. The technology must also be affordable, scalable, and have the potential for commercialization.

4. How will the winner of the X Prize Clean Aviation be selected?

The winning team will be selected by a panel of judges based on the performance and feasibility of their technology, as well as their business plan and potential for commercialization. The judges will also consider the team's ability to meet the criteria of the competition and their overall impact on the aviation industry.

5. What is the timeline for the X Prize Clean Aviation?

The competition was launched in 2018 and the deadline for team registration is in early 2022. The final competition and winner announcement is expected to take place in late 2022. However, due to the ongoing COVID-19 pandemic, the timeline may be subject to change. Updates will be provided on the X Prize website.

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