Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

Lilium vertical take off "jet"

Rotorheads A haven for helicopter professionals to discuss the things that affect them

Lilium vertical take off "jet"

Old 14th May 2016, 23:45
  #1 (permalink)  
Thread Starter
 
Join Date: Nov 2003
Location: UK/OZ
Posts: 1,686
Lilium vertical take off "jet"

Lilium Aviation
Another people carrying drone.
This simpler than others as it isn't trying to be a car.

Verticle takeoff and land using 36 electric fans.
2018 rollout.
The Lilium Jet, cruise 500km (310mi) max 400kph (248mph), and reach an altitude of 3km (9,900ft). Recharges overnight from a standard household outlet. Max range at 180mph. Autonomous landing.
Sports liscence.
360kw battery, over 400hp.
200kg payload.


I wonder what the endurance is in the hover...
The wing appendage that look like a flap is the array of motors that swivels down to hover.


Price of a Tesla maybe?

Mickjoebill

Last edited by mickjoebill; 21st Jun 2016 at 02:53.
mickjoebill is offline  
Old 15th May 2016, 04:31
  #2 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 2,481
The cg is WAY in front of the wing, with no canard to supply lift at the front, so that cylinder at the front will be permanently pointing down to provide upward thrust to counter the cg moment. Instant death if the battery goes flat or the motor quits.

Another dream of some dude playing with a 3-d drawing program and no understanding of physics. Where is the fan motor with its huge intake? Where do the wheels go? Will they add a "Verticle" fin for some stability? And just a little bit of sunburn from that big canopy.
Ascend Charlie is offline  
Old 15th May 2016, 04:40
  #3 (permalink)  
 
Join Date: Jul 2002
Location: Downwind
Posts: 347
Originally Posted by Ascend Charlie View Post
The cg is WAY in front of the wing, with no canard to supply lift at the front, so that cylinder at the front will be permanently pointing down to provide upward thrust to counter the cg moment. Instant death if the battery goes flat or the motor quits.

Yeah, but you'll get a great view!
Freewheel is offline  
Old 15th May 2016, 06:38
  #4 (permalink)  
 
Join Date: Jul 2012
Location: Scotland
Posts: 158
That looks daft.

I prefer this one,

and the CGI is better too.
DeltaV is offline  
Old 16th May 2016, 03:19
  #5 (permalink)  
Thread Starter
 
Join Date: Nov 2003
Location: UK/OZ
Posts: 1,686
The 36 motors are distributed to create some redundancy.

Not sure about CG as the battery could be rearward and won't alter during flight


For reference
A boffin has torn down a Tesla battery. It is a good reference for the weight and specs of a state of the art battery
https://teslamotorsclub.com/tmc/thre...ry-pack.34934/
Tesla battery (LiCoO2):
Total 85kwh battery cell weight is 900lbs plus uber strong housing of 300lbs.
The pack contains modules. Each module weights 56 lbs and delivers 5.31kWh with a mass of 1001 in^2 -

Or 10.55 lbs per kWh
188.4 in^2 per kWh

Edit: The above are specs of a tesla car battery for reference. No specs released yet for the Lilium battery.

M

Last edited by mickjoebill; 16th May 2016 at 15:56.
mickjoebill is offline  
Old 16th May 2016, 04:56
  #6 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 2,481
Total 85kwh battery cell weight is 900lbs plus uber strong housing of 300lbs.
That makes 1200 lb or about 500kg, the total takeoff wt is 600kg, which minus the 200kg payload leaves an airframe of 400kg, 100kg short of the battery weight by itself - doesn't add up.

Go to the website, look for the photo looking up at the machine and see that everything is forward of the wing - it will not fly.

See also the pop-out cylinders for hovering - when they pop back in, the occupants' feet are crushed.

Looks very pretty, but somebody is playing with himself.

Last edited by Ascend Charlie; 16th May 2016 at 04:58. Reason: additional stuff
Ascend Charlie is offline  
Old 16th May 2016, 08:03
  #7 (permalink)  
 
Join Date: Nov 2015
Location: Farnham, Surrey
Posts: 1,204
No vertical surfaces? Is the directional stability synthetic as well?

Also canard is at the same height as the mainplane, so the inner 25% iof each semispan won't do anything useful.

From that picture it looks like the man propulsion uses ducted fans embedded in the flaps, which would have intakes above the mainplane in forward flight. This could provide some "blown" surface enhancement in the cruise (when you shouldn't need it) which will suddenly disappear as soon as the flap/thrusters are dropped for transition to the hover (when you WOULD need it).

The originator should be given some crayons and left to amuse himself while grown-ups are talking. Oh, he was...

PDR
PDR1 is offline  
Old 16th May 2016, 16:24
  #8 (permalink)  
Thread Starter
 
Join Date: Nov 2003
Location: UK/OZ
Posts: 1,686
That makes 1200 lb or about 500kg, the total takeoff wt is 600kg, which minus the 200kg payload leaves an airframe of 400kg, 100kg short of the battery weight by itself - doesn't add up.
It doesn't add up because the figures you quote include the weight of the massive battery frame needed to form the superstructure of the Teslar Model S car.
Base your power v weight calculations on the individual battery modules, these weight 5 kilos and deliver 1kWh.

No specs available on the batteries planned for the Lilium, so using the tesla battery modules as a guide.

In respect to what look like flaps, perhaps they are not required to reduce stall speed.

Wouldn't lifting the nose, let's say, 45 degrees and simultaneously gradually tilting the canard and wing fans downwards, produce a smooth transition from the wing providing lift to the fans taking over?

The Lilium is mentored by ESA, so hard to imagine that they are crackpots.

Mickjoebill
mickjoebill is offline  
Old 16th May 2016, 17:22
  #9 (permalink)  
 
Join Date: Nov 2015
Location: Farnham, Surrey
Posts: 1,204
As far as I can see the concept is trying to use the fuselage as a canard, but even assuming this works I struggle to see how a canard surface with a sub-unity aspect ratio could ever be even vaguely efficient. It should be hideously draggy.

But it might be trying to do something clever with the heavily blown foreplane (more evident in this view):



Concepts like this have been done before. There was a Cessna 150(?) which was fitted with a tiny wing all within the propwash and on its sole flight appeared to fly very well - right up to the point where the engine stopped, revealing the essential weakness of the concept. When I get home I'll loook out the references for that one.

The thing is that other images on the site appear to imply that the "foreplane" and its thrusters would be retracted in the cruise:




So it would then be dependant on the fuselage as a foreplane which (as I mentioned) should be hideously inefficient.

With that number of fans active (synthetic) yaw stabilisation should certainly be possible, but certifying it as an alternative to a fin could be a challenge. It's not at all clear how this machine would survive a complete power failure. for this and many other reasons.

PDR
PDR1 is offline  
Old 16th May 2016, 18:04
  #10 (permalink)  
 
Join Date: Oct 2002
Location: 1 Dunghill Mansions, Putney
Posts: 1,797
The wing layout is reminiscent of the RQ-3A DarkStar, though the forward CG is far more extreme.

The propulsion approach is similar to the recently announced Aurora LightningStrike concept, which may have prompted the ESA 'business incubation' funding.

Given that the Lilium project was only "founded in February 2015 by four engineers and doctoral students," I'd say we have a better chance of seeing the sky blackened with Mollers, Hoverbikes or Terrafugias by 2018 than we do of seeing the Lilium reach the marketplace.

I/C
Ian Corrigible is offline  
Old 17th May 2016, 00:54
  #11 (permalink)  
Thread Starter
 
Join Date: Nov 2003
Location: UK/OZ
Posts: 1,686
I don't disagree with comments about the aerodynamic puzzle.
Hard to see how it can be controlled with the forward canards retracted.
The things that looks like wings may not need to produce much lift if motors are tilted down?

They claim 325kw/435 horsepower and endurance at cruise of approx 1hr 25min. Empty weight of 400kg.
Is this achievable if applying the specs of Tesla batteries of 5kilos per 1kWh? The Tesla modules themselves in an 85 kWh Model S are about 900 lbs. The other ~300 lbs is everything else for the pack.


Mickjoebill

Last edited by mickjoebill; 17th May 2016 at 01:09.
mickjoebill is offline  
Old 17th May 2016, 02:37
  #12 (permalink)  
 
Join Date: Sep 2007
Location: USA
Posts: 601
The vertical lift efficiency of all those small diameter/high speed rotors will be miserable. And it's VTOL operation that drives the size of the electric motors/power electronics. An electric propulsion system sized for VTOL operation that accounts for less than 5% of total flight time usually means the motors/PEs will be over-sized for the other 95% of flight time in conventional (wing-borne) operation. This weight penalty can be significant.

Compare this to a battery-electric 2 seat rotorcraft that was actually built and flown. It was a modified S-300C helicopter which already had a well developed rotor system and lightweight airframe. The electric motor was rated at 141 kW which was the same power produced by the original Lycoming piston engine. The lithium ion battery pack weighed 1100 pounds which was limited by the S-300C max GW capability . This allowed around 15 minutes of flight with a single pilot on board.

I'm sure the engineers that designed the Firefly were competent, and the motor/controls/battery were all based on current technology. So it would be fair to use the Firefly's demonstrated performance as a baseline to evaluate concepts like Lilium.
riff_raff is offline  
Old 17th May 2016, 10:12
  #13 (permalink)  
 
Join Date: Jul 2004
Location: Europe
Posts: 288
Apart from the things already pointed out - it doesn't even look as it should fly in an environment commonly know as air - , they should have studied the regs a bit more.
They want it to be a light sport aircaft.
A few points:
Max speed 180mp/h - Oh no. Max speed of an LSA can't be more than 138 mph.
No rotorcraft in the LSA category. Since it has lots of rotors, it disqualifies even multiple times.
One engine/motor only in a LSA.

... and a 600kg it would be just 1.2 kg too heavy for an LSA. But that's nitpicking.

Looks like somebody didn't even do the most basic research or they are just in the business to get crowd funding and then disappear to somewhere sunny ... to get in the mood for the project, I am sure.
Rotorbee is offline  
Old 17th May 2016, 22:45
  #14 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 2,481
No pix of it on the ground or with wheels showing - where in the nose could you put a retractable nosewheel that doesn't get in the way of the retractable cylinders? Where would the main gear go and still leave room for a battery?

And just imaging the NOISE from 36 screeching little fans doing 15,000rpm to push some air downwards. Pure pud-pulling.
Ascend Charlie is offline  
Old 18th May 2016, 10:19
  #15 (permalink)  
 
Join Date: May 2011
Location: uk
Posts: 580
Come on, cut them a bit of slack, it's no more than silly verbiage applied to a series of pretty pictures drawn by someone with no knowledge whatsoever of aerodynamics.

It clearly isn't a serious proposal or anywhere close to one.

If anything it's a good troll judging by all the serious technical replies.
Wageslave is offline  
Old 18th May 2016, 10:36
  #16 (permalink)  
 
Join Date: Jul 2003
Location: Brum
Posts: 641
drawn by someone with no knowledge whatsoever of aerodynamics
Really...??
Well either the armchair designers here are wrong, or this lot are...

We are a team of visionary aerospace engineers and product designers from the Technical University of Munich, Germany.
Our academic and professional backgrounds span from aeronautics and aerodynamics to robotics and ultra-lightweight structures. Initially funded by the European Union and supported by the European Space Agency and its Business Incubation Centre Bavaria we are developing the most advanced personal aircraft the world has ever seen.
Nige321 is offline  
Old 18th May 2016, 10:53
  #17 (permalink)  
 
Join Date: Nov 2005
Location: Zulu Time Zone
Posts: 653
This is the Lilium Jet, the world's first electric vertical take-off and landing jet
...just one problem with that: HELLO, it's only a pretend photo!
oggers is offline  
Old 19th May 2016, 06:20
  #18 (permalink)  
Thread Starter
 
Join Date: Nov 2003
Location: UK/OZ
Posts: 1,686
And just imaging the NOISE from 36 screeching little fans doing 15,000rpm to push some air downwards. Pure pud-pulling.]
But its German visionaries say it will be much quieter than a helicopter!??

Some reasonable criticism of most of its specs on PPRuNe, are we losing something in the translation or are they onto something new?

Mickjoebill
mickjoebill is offline  
Old 19th May 2016, 08:22
  #19 (permalink)  
 
Join Date: Sep 2007
Location: USA
Posts: 601
"We are a team of visionary aerospace engineers and product designers from the Technical University of Munich, Germany. Our academic and professional backgrounds span from aeronautics and aerodynamics to robotics and ultra-lightweight structures. Initially funded by the European Union and supported by the European Space Agency and its Business Incubation Centre Bavaria we are developing the most advanced personal aircraft the world has ever seen."

Based on what this team is proposing, I would question their claims of expertise as "visionary aerospace engineers" or the ability to develop "the most advanced personal aircraft the world has ever seen". Unfortunately, this group of young inexperienced engineers will learn the cold, hard lesson of the difference between conceptual and real world designs. Those 36 tiny electric rotors will produce far less lift than they predict, the complete system will be far heavier than they predict, and it will be much more difficult to control this system than they predict.
riff_raff is offline  
Old 19th May 2016, 10:48
  #20 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 2,481
Then these "Experts" should know that it is far more efficient to accelerate a large amount of air to a low speed, then a small amount of air to a high speed, as well as the noise. Compare the noise and downwash disturbance from a 5-ton helicopter (S-76) in the hover to a Harrier jet.

And their claim to hold degrees from a particular university is far outweighed by my degrees and doctorates from Snotgobbler University, Noo Joisey, they cost me $50 each.
Ascend Charlie is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.