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Boom (YC W16) – Supersonic Passenger Airplanes

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Re: Boom (YC W16) – Supersonic Passenger Airplanes

#241

Post by Scramblejams »

alex_duf wrote: post #94
ohitsdom wrote: post #75

Earlier quoted context omitted.

Definitely worth mentioning in the article, but not a big concern. Even if this plane actually comes to market and is successful according to their wildest hopes, it'll only be a very tiny fraction of the aviation market. This is due to many factors: small cabin, limited capacity, limited routes (only over water)...

> it'll only be a very tiny fraction of the aviation market. So is everyone driving in the morning: a tiny fraction of the transport pollution. Add every tiny fraction and you get a significant fraction. To add to staceymakano's point: in the transport industry, I feel very uncomfortable when a a new alternative doesn't perform better on the environmental side.

Add every tiny fraction and you get a significant fraction.

Not even remotely true in this case. Aviation accounts for about 2% of carbon emissions, by my cursory Google search. Boom aircraft will, in the absolute best of outcomes, never account for more than a very small fraction of that number. And a small fraction of 2% is still, no matter how one tries to spin it, a very small fraction.

In any event, power (P) required to increase velocity (V) is a cubic relationship (P=FV, where F is the drag force, which has as one of its components V^2), so doubling speed requires 8 times the power. There are ways to mitigate that increase -- fly higher to reduce air density, reduce drag by using specialized airfoils and reducing excrescence, take advantage of increasing engine efficiencies, etc. -- but I think it's safe to say that a supersonic aircraft will always require gobs more fuel than its subsonic cousins. By your logic then, one should probably never be manufactured.

Full disclosure: I once worked as an aerospace engineer.

Re: Boom (YC W16) – Supersonic Passenger Airplanes

#242

Post by neurotech1 »

bscholl wrote: post #192

Hi - I'm Blake, Founder/CEO at Boom. After watching no tangible progress in supersonics since Concorde was shut down, I started Boom because I want supersonic flight in our lifetime. Not just as a private jet, but something most anyone can afford to fly. Will try to answer as many questions here as I can.

What type of intake design are you using? Comparable to the F-22A fixed square intakes?

Are you using current turbofan engines (GE F110?) or something exotic?

Re: Boom (YC W16) – Supersonic Passenger Airplanes

#243

Post by aidenn0 »

david-given wrote: post #207
BinaryIdiot wrote: post #167

Earlier quoted context omitted.

I could have sworn the Concorde was still glass-breaking loud at 40,000. Reardless, NASA is working on getting rid of the sonic boom http://www.sciencealert.com/nasa-is-building-a-jet-that-brea...

I used to live under the Concorde flight path near Heathrow. Twice a day there'd be this crackling rumble and all the windows would shake; and this was flying subsonic. Concorde was really, really loud --- a lot of that was due to being a really old plane with old engines (aircraft have gotten way quieter since the 1970s), but even back then it was considered loud: http://news.bbc.co.uk/2/hi/uk_news/3581192.stm It wa…

I lived under the Concorde flight path near Dulles. I couldn't hear it, but we'd go out side to watch it fly over every now and then.

Re: Boom (YC W16) – Supersonic Passenger Airplanes

#244

Post by jandrese »

jessaustin wrote: post #71
aidenn0 wrote: post #51

Earlier quoted context omitted.

If they could make it quiet enough to go over land, transcontinental US flights would be great; LA/NY in 2.5 hours would likely have a pretty high demand. [edit] As someone who flies LA/DC fairly regularly I do have to mention my favorite record of the SR-71 doing that flight in under 65 minutes.

I wonder if the "no booms over land" rule will always remain in force. When I was a child, the planes from Whiteman AFB broke that rule quite often. It was interesting to hear the boom over the phone when speaking with a school friend who lived say eight miles away, and then immediately hear the whole house shaking when the plane got to my end of the circuit. It would have been annoying at night, I suppose, but durin…

The no commercial sonic booms legislation might go away if it were an American company asking for it. I have no doubt that the Concorde being foreign owned helped speed that legislation through Congress.

Of course being a little no-name company won't help matters much here, but I expect that actual production of this would involve a partnership (or probably buyout) with one of the big name companies that have a lot of congressmen on their payroll.

There has also been a lot of research into minimizing Sonic Booms since the 70s. Military jets typically don't care, but passenger jets could definitely benefit.

Re: Boom (YC W16) – Supersonic Passenger Airplanes

#245

Post by schwarrrtz »

btilly wrote: post #240
bscholl wrote: post #192

Hi - I'm Blake, Founder/CEO at Boom. After watching no tangible progress in supersonics since Concorde was shut down, I started Boom because I want supersonic flight in our lifetime. Not just as a private jet, but something most anyone can afford to fly. Will try to answer as many questions here as I can.

Elon Musk says that eventually we will move to VTOL supersonic electric jets, but he is too busy with other projects to implement it. Have you thought about this idea, and in what time frame do you think someone might try to implement it? Elon's basic idea is that air-breathing jets are limited to altitudes at which oxygen tops out, and then are mostly fighting drag from nitrogen. Electric ones can go to higher altit…

The specific energy of kerosene is ~40 MJ/kg [0] while the specific energy of lithium ion batteries is ~1 MJ/kg [1].

Unsure how much energy you'd save from the difference in drag, but I'd guess that significant improvements in electric energy storage would be required to make an electric plane doable.

[0] https://en.wikipedia.org/wiki/Kerosene#Properties [1] https://en.wikipedia.org/wiki/Lithium-ion_battery

Re: Boom (YC W16) – Supersonic Passenger Airplanes

#246

Post by nether »

bscholl wrote: post #192

Hi - I'm Blake, Founder/CEO at Boom. After watching no tangible progress in supersonics since Concorde was shut down, I started Boom because I want supersonic flight in our lifetime. Not just as a private jet, but something most anyone can afford to fly. Will try to answer as many questions here as I can.

How are you reducing the boom? Are you widening part of the forebody to increase the local air temp & mach no to weaken the shock? What about redirecting the shock?

Re: Boom (YC W16) – Supersonic Passenger Airplanes

#247

Post by jandrese »

david-given wrote: post #207
BinaryIdiot wrote: post #167

Earlier quoted context omitted.

I could have sworn the Concorde was still glass-breaking loud at 40,000. Reardless, NASA is working on getting rid of the sonic boom http://www.sciencealert.com/nasa-is-building-a-jet-that-brea...

I used to live under the Concorde flight path near Heathrow. Twice a day there'd be this crackling rumble and all the windows would shake; and this was flying subsonic. Concorde was really, really loud --- a lot of that was due to being a really old plane with old engines (aircraft have gotten way quieter since the 1970s), but even back then it was considered loud: http://news.bbc.co.uk/2/hi/uk_news/3581192.stm It wa…

It's really hard to quiet down Turbojets. Turbofans are much easier, but they don't work well at supersonic speeds.

Re: Boom (YC W16) – Supersonic Passenger Airplanes

#248

Post by oh_sigh »

ido wrote: post #79
rdl wrote: post #9

Pretty amazing that materials science (lighter, carbon-fiber aircraft; hotter, more efficient/powerful turbines) has made this economic. Concorde never was. NYC-LON seems like the one market where this enables something fundamentally new (well, Concorde did); single-day business trips between two major business centers which were otherwise a full day apart. Transpacific flights would be nice, too, but cutting an alre…

The top speed of a 747 is 0.85 Mach, so it should cut the duration by more than 2x.

Amdahls law

Re: Boom (YC W16) – Supersonic Passenger Airplanes

#250

Post by bertil »

bscholl wrote: post #204
ADRIANFR wrote: post #198

Earlier quoted context omitted.

Is SFO-NYC a feasible route for Boom?

Unfortunately, there's a ban on supersonic travel over land in the US since the 1970s. When this is reversed, we can fly SFO-JFK in about 2:20.

Would it make sense for you to fly West from SFO, turn around, go super-sonic over the ocean and fly towards NY — then again, decelerate over the Atlantic, and turn back?

i.e. what is the distance from the shore you can boom?

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