Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The potentially revolutionary Celera 500L aircraft

thedrive.com

Post reply on HN
Print view View original

221–230 of 252 posts

Re: The potentially revolutionary Celera 500L aircraft

#221

Post by scarier »

Robotbeat wrote: post #204
scarier wrote: post #95

Earlier quoted context omitted.

I wouldn't be surprised by a long-range cruise altitude around FL300, but if it was FL450 I'd be extremely surprised. If the plane achieves the advertised 20mpg on a hypothetical 4500-mile flight at FL500, but only makes a small fraction of that on a more realistic 400-mile regional hop at FL210, it's not really a practical success. (Aside: the advertised range seems like drastic overkill for something designed to of…

The whole business case for this vehicle is that it enables extremely low cost granular travel between distant city pairs. The short regional hop is not its target market. It’s designed to be competitive with commercial air travel.

That's fair--400 miles is on the shorter end of the spectrum.

Still, "low cost" is relative to a chartered private jet--which, emphatically, is not a service that people purchase because it's the most economical option--rather than a commercial airliner (although, if true, the SFC per passenger of the Celera would be in the same ballpark as modern commercial airliners, which is very impressive). The average domestic flight is under 1000 statute miles (https://www.bts.gov/content/average-length-haul-domestic-fre...), so this plane needs to offer compelling efficiency gains at ~500-1500 mile ranges in order to compete with existing services, unless they're strictly planning to fill the niche of one-leg, long-range flights that existing private jets don't have the legs for.

Re: The potentially revolutionary Celera 500L aircraft

#222

Post by kube-system »

NovemberWhiskey wrote: post #211
kube-system wrote: post #150

Earlier quoted context omitted.

Most V engines can operate this way -- obviously not at full power. GM, Daimler, Honda, and FCA do this on some of their production v6, v8, and v12 engines. It is not that difficult to skip some cylinders, engines have a lot of rotating momentum. https://en.wikipedia.org/wiki/Multi-Displacement_System https://en.wikipedia.org/wiki/Active_Fuel_Management https://en.wikipedia.org/wiki/Active_Cylinder_Control https://en…

There is a huge difference between being able to operate in a managed cylinder deactivation mode vs being able to operate when one whole bank is experiencing some kind of catastrophic failure.

True, I was addressing the question at face value.

Re: The potentially revolutionary Celera 500L aircraft

#223

Post by adrianmonk »

karlkatzke wrote: post #80
_uy6i wrote: post #47

Earlier quoted context omitted.

3,300 feet in not a long runway - it means you can access ~80% of the ~5,000 runways in the US. On the the other hand A 777 needs 8,000-10,000 feet meaning it can only access https://www.cia.gov/library/publications/the-world-factbook/... https://en.wikipedia.org/wiki/Boeing_777#777-200LR

3300 feet in balanced density conditions. You’d better not bet on 3300 feet in Phoenix during the day time most of the year. Or Denver for that matter.

This is a tangent, but are runways generally longer in hotter areas? Is, for example, the median length of all runways in Arizona longer than the median in North Dakota?

It seems like ideally this is the way it should be because it's a known factor, so they ought to just build in compensate for it / normalize around it from the start. But I could imagine things standing in the way of that, like cost or land availability or maybe people focus more on meeting some minimum standard length.

Re: The potentially revolutionary Celera 500L aircraft

#224

Post by VBprogrammer »

asdfadsfgfdda wrote: post #219
VBprogrammer wrote: post #173

Earlier quoted context omitted.

I'm calling bullshit. Compare it to the TBM900 which has a 900hp turbine engine and vastly similar layout. There is no way they can go 60 knots faster on 300 less horse power. And even if they somehow pull off that trick, that short skinny wing will make the MU-2 feel like a safe family minivan.

The layout/payload may be similar to a TBM, but I'm guessing the wing loading and cruise altitude will be higher. So it's definitely feasible to go faster on less power.

Aerodynamic drag is a square relation so the difference in drag there is about 40%. With 65% of the power.

I think occam's razor applies here. Either the aerodynamics of reasonably modern aircraft designs leave a huge amount on the table or this startup is telling fibs.

There are other reasons to be suspicious, modern diesel engines rely on a large amount of turbo charging to achieve sea level rated power, it's difficult to believe they are able to maintain this rated power to 50,000ft or 60,000ft. (In the case of the TBM the engine is actually capable of about 1300hp at sea level but is "flat rated" to what it can maintain at altitude).

Finally, almost all high altitude aircraft have long wings (think the U2 as that is not far from what we are talking about here). Adding longer wings typically increases high altitude performance (there are aircraft with model variants where the wings got longer, like the twin commander). This aircraft appears to have borrowed a couple of surfboards.

Re: The potentially revolutionary Celera 500L aircraft

#225

Post by nradov »

qzw wrote: post #137
aidenn0 wrote: post #111

Earlier quoted context omitted.

TFA did not say maximum speed 450mph, it said "maximum cruising speed of at least 450mph" Still doesn't mean it gets 18-25mpg at 450. If it can realistically do half of 4500 miles at 450mph, there are a lot of interesting routes (Gets you as far as Tel-Aviv from London, Boston to Phoenix, or Los Angeles to Miami). Using that completely-pulled-out-of-my-ass number of half the range at 450, and assuming quadratic drag,…

$5k plus pilots (I’d want two for a transatlantic flight). And you’d still be stuck inside a very small space for 12 hours, with what’s likely to be a porta-potty level lavatory and minimalist galley. Oh, and a single piston engine, which is less reliable than turbines, over a lot of very cold water. Not sure that would be the best use case for this plane.

The single engine is a concern.

Something like Garmin Autonomí might eventually allow for single pilot flights while maintaining a reasonable level of safety.

https://www.garmin.com/en-US/autonomi/

Re: The potentially revolutionary Celera 500L aircraft

#227

Post by refurb »

Gravityloss wrote: post #171
refurb wrote: post #130

Earlier quoted context omitted.

You don't have to cancel flights because of weather. I don't think many flights today are cancelled because of weather on the route there, it's the weather over each airport, which would still impact this aircraft.

Small unpressurized planes do cancel a lot of flights since they fly lower and are affected by weather. Many other six seat planes are like that.

Ahhh.. of course. Good point.

Re: The potentially revolutionary Celera 500L aircraft

#228

Post by 0xffff2 »

nikitaga wrote: post #142
Stevvo wrote: post #88

Earlier quoted context omitted.

As awesome as the new Flight Simulator is, as an avgeek the Flight model is very disappointing. X-Plane can, and has, been used to design real world aircraft because you input the aircraft geometry and it simulates how it should fly based on that. MSFS extrapolates a lookup table over the input geometry, making it useless for real-world aerodynamic predictions. From the consumer perspective, both models are capable o…

Which aircraft were actually designed with X-plane, and why? I've heard this several times but that never made sense to me. I wouldn't be surprised if their blade element theory approach is superior to whatever Microsoft is doing (not familiar), but still both of those are optimized for realtime simulation, not for correctness. When I wanted to analyze performance of a hypothetical rigid wing hang glider I went with…

I don't know about production aircraft, but NASA uses X-Plane pretty extensively for all kinds of research, including modeling flight dynamics for small UAVs. It's used often enough that several years ago I developed (and released on NASA's GitHub) a tool to simplify programmatic interaction with the X-Plane simulation engine. It's not nearly popular enough to make maintaining it a full time job (thankfully), but I do get pretty regular comments from NASA researchers and members of the public.

I have never heard of anyone using MS Flight Sim in the same way, although another fairly common use case for my library is to disable the X-Plane physics completely and just use if as a visualization tool. If someone developed a library that made that equally easy for MSFS, I can see it taking over that role. It certainly looks better the X-Plane IMO.

Re: The potentially revolutionary Celera 500L aircraft

#230

Post by zentiggr »

dmix wrote: post #102
karlkatzke wrote: post #80

Earlier quoted context omitted.

3300 feet in balanced density conditions. You’d better not bet on 3300 feet in Phoenix during the day time most of the year. Or Denver for that matter.

Sorry for the amateur question, but why does it take longer to take off in hot places? Doesn’t heat generate lift, like in gliders crossing hilly terrain? Or is it the heat offsetting with the cooler ground that helps, so you’d need a greater amount in hot places?

The effect operating on gliders is from thermals - warmer ground heats the air which then rises relative to the cooler air around it. When the glider is in the thermal, it is still gliding downward through that air, but the whole column is rising faster than the glider's sink rate.

Warmer air reduces density, thus reducing lift and slightly reducing the amount of oxygen reaching the engine's combustion area, thus some power loss as well. In order to take off in the same distance, it must be operating at reduced takeoff weight.

Post reply on HN