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Author Topic: VTOL On Demand Mobility  (Read 10874 times)

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #75 on: November 07, 2018, 02:37:28 am »
In my humble opinion, pure battery electric vehicles are a blind alley.  Developed on the back of a knee jerk reaction mostly by politicians and dreamers.  Hydrogen and fuel cell tech would reduce the weight of battery components and provide a real solution for car, planes, anything.  Why we continue to faff with pure battery tech I do not know.  Question, how are we going to deal with recycling the number of batteries required for this failure to think in a joined up manner?  Will we have to deal with environmental disasters like we potentially could with nuclear waste?

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #76 on: November 07, 2018, 08:40:36 am »
Rhetoric question - How long have hydrogen fuel cells existed for, and how many successful airplanes are flying them?
 
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Machdiamond

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Re: VTOL On Demand Mobility
« Reply #77 on: November 07, 2018, 02:40:19 pm »
In my humble opinion, pure battery electric vehicles are a blind alley.  Developed on the back of a knee jerk reaction mostly by politicians and dreamers.  Hydrogen and fuel cell tech would reduce the weight of battery components and provide a real solution for car, planes, anything.  Why we continue to faff with pure battery tech I do not know.  Question, how are we going to deal with recycling the number of batteries required for this failure to think in a joined up manner?  Will we have to deal with environmental disasters like we potentially could with nuclear waste?

(aero engineer working on battery powered airplanes here)

As far as cars are concerned, hydrogen is not a viable alternative to battery powered vehicles from practical, economical and environmental standpoints. I recommend you check this excellent documentary:

Hydrogen cars are already dead (or as Trump would put it, they are a total disaster). You still see a few around because of politics and lobbies. Some groups of people really don't like the idea that you could refuel your car almost (comparatively) for free at home each night.

For airplanes, battery technology is not quite there yet except in some special cases - like VTOL on demand mobility (hey we are staying on topic!) and short range small aircraft such as trainers. While it is only a matter of a few more years before it gets to short haul regionals and freighters - it will be a very long time before it gets to medium to long haul carriers.

As aircraft fuel, Hydrogen has been promising and beaten to death for 30-40+ years and all engine and aircraft manufacturers have given up.

As far as recycling is concerned, you are misinformed. Well designed batteries such as those manufactured by Tesla are 100% recyclable and economically self sustaining due to the high cost of raw materials and due to the original design intent for recycling (unlike many recycling industries). They are also designed to last many years, unlike cellphone batteries.

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #78 on: November 08, 2018, 03:06:48 am »
Thanks for that, always willing to find out what I am missing.  Not an entirely balanced view but much food for thought.  It is interesting to note that the orator suggests hydrogen may make sense for aircraft.

Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #79 on: November 08, 2018, 02:23:04 pm »
Thereís a widely held belief that the automotive sector will push battery technology to the point that a high energy/power density becomes available.

But this belief is flawed.

The U.K. ATI battery technology road map (as presented at Warwick Uni in May) highlights the flaw. It shows a near term push for a lithium battery technology which will enable a 450-500 mile charge range for a  car (base on the max expected while awake) and a six hour recharge time. Once achieved, the target becomes reduceing cost and the imperative will be moving away from lithium because thereís simply not enough of it. Presently the favourite for a lithium replacement is sodium which is inherently at a lower energy density, but greatly improved availablity and much lower cost.

Of course there maybe be a breakthrough but equally the high energy/power density battery but it could become the next cold fusion.

I too was recently involved in a full size electric twin seat TMG, and itís very different doing the real thing compared to CGI and model aeroplanes;- just where did all that extra weight come from? the drag is much more than the vsaero predict, even ďsafeĒ battery chemistry suddenly have ADís for random  fires, just how do I protect the occupants from all that lithium in the event of a drama?

As to current batteries being ok for e-vtol? Wingless proposals, not a snowball in ....chance. Winged proposals;-well itís strange I can only make the claimed performance match the best case weight/optimistic drag is to use a 2d range flight profile;- even a modest assumption for delta altitude during the profile  burns the claimed performance to ash.

E-vtol jet with wings = highly loaded fans =megawatt motors/PE/battery power density in an exceptionally lightweight airframe = fraud.

And finally when I look at Uberís specified day to day useage profile, with current battery C rating, the  thing will need a brand new 100k$ battery every month...... like thatís going to be practical.

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #80 on: November 09, 2018, 02:41:28 am »
What I miss most is a joined up logic when it comes to clean energy.  Those who promote pure electric do not account properly for the production and shipping of gas for power stations for example.  Add to that the huge pollution from marine diesels in for example, supertankers.  For some time aviation has promoted clean aviation fuel but that has gone on the back burner for all the news there has NOT been.  Apparently Virgin are pushing/investing in clean aviation fuels but also very quiet now.  Apparently a source of pollution more impactful than the vehicles, animal farming.  All that fart gas has to go somewhere.

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #81 on: November 09, 2018, 03:43:40 am »
For some time aviation has promoted clean aviation fuel but that has gone on the back burner for all the news there has NOT been.  Apparently Virgin are pushing/investing in clean aviation fuels but also very quiet now.  Apparently a source of pollution more impactful than the vehicles, animal farming.  All that fart gas has to go somewhere.

Methane and fuel cells are your friends.  Gentlemen... fart your engine.*

And most importantly it take away gases that would damage the bio-sphere before they can be harmful; and that on a cost-efficient way (states with clever ecological policies use to subsidize the removal of methane gas; hence removing it and using the harvested quantities to clean power a vehicle has a double effect on the level of harmful emissions... a double treat also for the taxpayer). 


*the level of discussion was too good - thank you to the above posters - for someone not reasonably attempting to ruin it
« Last Edit: November 09, 2018, 07:35:10 am by TomcatViP »

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #82 on: November 11, 2018, 04:04:00 am »
How about a high flying drone/satellite powered by recycling the atmosphere?  A possible method of cleaning the air AND cheaper communications etc.

Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #83 on: November 12, 2018, 12:40:02 am »
...
E-vtol jet with wings = highly loaded fans =megawatt motors/PE/battery power density in an exceptionally lightweight airframe = fraud.
...

Lilium?  ::) https://lilium.com/technology/

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #84 on: November 12, 2018, 04:41:12 am »
A very pretty presentation but, where is the discussion on range and recharge?

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #85 on: November 12, 2018, 06:08:24 am »
Startup for dummies, rule One:
   - Take a problem
   - Simplify it
   - resolve the simplified case
   - Use marketing to claim you solved the problem
....
 
Rule 1bis:
 In case of failure:
   - restart
   - reload
   - repackage

....

Rules 1 (i_th iteration):
    - Insist!
« Last Edit: November 12, 2018, 07:02:21 am by TomcatViP »

Offline elmayerle

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Re: VTOL On Demand Mobility
« Reply #86 on: November 12, 2018, 10:55:16 am »
Indeed, many things that are "demonstrated" at the RC level do not scale up.
Even full scale vehicles can fly when carrying smaller amounts of batteries, and have very little range.
Ejector lift for vtol comes to mind.  Neither the XV-4A nor the XFV-12A ever managed to make the full-scale article work, despite successful sub-scale deomstrations.

Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #87 on: November 12, 2018, 11:32:02 am »
Also no discussion on battery power density, C rating, L/D at 300kph cruise, weight of megawatt rated power electronics, weight of 300kph bird strike protection on airframe, weight of ice/rain/hail protection,  weight of crashworthness, crosswind limit, lightening strike protection, wing bending stiffness mismatch between wingborne & vertical flight.....to mention a few.

Fundamentally an e-vtol Jet has only a tiny fraction of the fan area of a helo or quad cop so has to compensate by giving the air much more acceleration, hence it needs very high rotational speed on the fans = megawatt power draw. And they claim this is really quiet;- Try overdriving the biggest electric garden leaf blower by a significant factor and then power up another eleven! yeah itís going to be real quiet.

Offline Archibald

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Re: VTOL On Demand Mobility
« Reply #88 on: November 12, 2018, 09:38:12 pm »
Lithium sucks, indeed, since the Chinese have most of it and hold the rest of the world at ransom. But sodium, really ? that thing is a bastard, just ask the nuclear industry (hello, Superphoenix, Monju and Clinch River). Corrosive, flammable, reactive, explosive... what's not to like ?  :o
No need for fuel cells, folks. What we need is ammonia IC cars. Ammonia has zero carbon, the fertilizer network already in place, and, most importantly, any plain old IC engine can be modified from gasoline to ammonia pretty easily. All of this also applies to methanol, minus the carbon-free aspect.
Even if it has half the energy of gasoline, an ammonia car range would remain far, far better than any electric car. Or the technology used to make ultra light and ultra efficient electric cars... could be used for an ammonia IC car, beating lithium batteries into a pulp.
Unfortunately, ammonia for cars is like hydrogen peroxide for rockets: its (supposed) safety  issues are completely overblown (toxicity, my ass: isn't gasoline dangerous if you smoke a cigarette, breath the exhaust, or try to drink it ? common...)

Heck in the 60's they made studies of ammonia and methanol fuel aircrafts and helicopters. The US Army had a grandiose project: portable, mobile nuclear reactors to split nitrogen from air and hydrogen from water and recombine that into ammonia to replace gasoline. And then... screw you, Saudi Arabia.
The usual jet or turbine could be converted to ammonia but the aircraft performance would take a big hit. Still far more realistic than any E-VTOL or electric aircraft.

As for hydrogen cars, being a space nerd since the craddle, I can tell you, they are a folly. Handling of liquid hydrogen is a complete and giant PITA, something that really can't be folded into your daily gas station. Unless you turn it into a miniature Cape Kennedy Launch complex, as far as drastic safety rules go. Plus the silly thing has 2.5 times the tank volume of gasoline, methanol or ammonia.
« Last Edit: November 12, 2018, 09:52:42 pm by Archibald »
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Offline Archibald

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Re: VTOL On Demand Mobility
« Reply #89 on: November 12, 2018, 10:01:02 pm »
another interesting eVTOL Aircraft with fixed wing economics:

https://www.pterodynamics.com/transwing/



As an aviation nerd, I'm horrified by this thing. Just look at it this way: an electric powered, V-22 Osprey with many more failure modes, all over the design... and mass produced, and flying all over our heads in an urban environnement.
Ah, and asymetric with that !  :(

Repeat that, twice. Then check the V-22 Osprey flaws and abysmal safety records. Can't fly through dust, the washdown big issue, those things. Yeah. What could possibly go wrong ? ah, and Uber want to eliminate the pilot later. WTF ?  ::)
« Last Edit: November 12, 2018, 10:04:31 pm by Archibald »
Conservatoire de l'Air et de l'Espace d'Aquitaine
http://www.caea.info/en/plan.php

Profanity: weaker mind trying to speak forcefully

Political correctness: just bury your head in the sand for the sake of appeasement and "peace for our time"
- https://fr.wikipedia.org/wiki/Serge_Dassault#Affaires_