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Boom supersonic jet readies for rollout

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Re: Boom supersonic jet readies for rollout

#211

Post by gsnedders »

TylerE wrote: post #106
axaxs wrote: post #105

Earlier quoted context omitted.

I'm still hoping for rail. It's much more carbon friendly, and has the opportunity to be way less stressful. I'd do 18 hours on a NY to LA if I could walk around, eat, talk, sleep, etc over a 5 hour misery ride in an airplane any day.

A single NY-LA route alone would cost over $500 billion. High speed rail is well $100m/mile, just for the track.

> High speed rail is well $100m/mile, just for the track.

That's frankly an insane figure, and depends vastly on what you're building and where. For something that's largely running through rural landscape, you really should expect no more than half that for the total construction cost. Maybe US construction is that expensive, but… wow.

Re: Boom supersonic jet readies for rollout

#212

Post by ghaff »

JKCalhoun wrote: post #66
jazzyjackson wrote: post #63

Earlier quoted context omitted.

OTOH if flying becomes more rare, then the only demand left will be from people with deep pockets. Maybe the only way there is a market for supersonic jets is if all the other long haul routes go bankrupt.

And the people with really deep pockets already have a jet. ;-)

I know you're half-joking but it is still often missed in these discussions that private flight (whether owning a jet or something like NetJets) is an existing competitor. And I assume that many wealthier people would rather fly private (for a variety of reasons) than commercial, even if the commercial jet is faster and/or has longer range.

Re: Boom supersonic jet readies for rollout

#213

Post by shawabawa3 »

agurk wrote: post #205
throwaway_pdp09 wrote: post #198

Earlier quoted context omitted.

I'm a bit suspicious of the qualification 'thermal' in 'thermal efficiency' which sounds like it's hiding something. From the wiki article on thermal efficiency https://en.wikipedia.org/wiki/Thermal_efficiency , and I'm no wiser for reading it: "For a heat engine, thermal efficiency is the fraction of the energy added by heat (primary energy) that is converted to net work output (secondary energy)." Does thermal effi…

A heat engine is a device that converts heat into kinetic energy. The amount of heat that is converted into movement as a proportion of the total heat is the thermal efficiency. With a jet engine it's the amount of energy in the burnt fuel that's converted to both rotation in the shaft and the speed of the expanding burnt gasses exiting the back. Propulsive efficiency is how good the engine is a converting this energ…

> divide the thermal efficiency by the propulsive efficiency

Multiply surely? Otherwise reducing the propulsive efficiency would increase overall efficiency

Re: Boom supersonic jet readies for rollout

#214

Post by gsnedders »

paulie_a wrote: post #158
TylerE wrote: post #101

Earlier quoted context omitted.

High-speed rail isn't high speed enough. Even with way faster than current tech and NO stops you'd still be looking at taking 12+ hours for what a plane can do in 5. That's ignoring the trillions it would cost. The US does not have the population density to make HSR viable.

There is no need for it to be fully end to end on the country. Regionally it would make a ton of sense over absurdly short flights. Most people are not flying LA to NYC so that is a minority use case anyways.

> Most people are not flying LA to NYC so that is a minority use case anyways.

This is true, but it is however one of the busiest aviation routes in the US. Certainly you can almost certainly go after some of the busiest routes (New York/Chicago, LA/SF), but where you go after that is less clear.

Re: Boom supersonic jet readies for rollout

#215

Post by agurk »

shawabawa3 wrote: post #213
agurk wrote: post #205

Earlier quoted context omitted.

A heat engine is a device that converts heat into kinetic energy. The amount of heat that is converted into movement as a proportion of the total heat is the thermal efficiency. With a jet engine it's the amount of energy in the burnt fuel that's converted to both rotation in the shaft and the speed of the expanding burnt gasses exiting the back. Propulsive efficiency is how good the engine is a converting this energ…

> divide the thermal efficiency by the propulsive efficiency Multiply surely? Otherwise reducing the propulsive efficiency would increase overall efficiency

Yes, you're absolutely right. Edited my comment to correct it.

Re: Boom supersonic jet readies for rollout

#216

Post by iso1631 »

DomenicoMazza wrote: post #18

If I recall correctly the Concorde used about 2 tonnes of fuel rolling on the ground alone.. I wonder how this new aircraft fares for fuel consumption? I believe the Concorde is a marvel. You could travel faster than the rotation of the earth in it! However I don’t think we need more environmentally unsustainable travel.

I wonder what the fuel usage of a spacex starship doing a sub-orbital flight from say NY to Tokyo would compare with a 787 or a concorde doing the same journey.

Re: Boom supersonic jet readies for rollout

#217

Post by regularfry »

sneak wrote: post #167
nimbius wrote: post #41

Real question: have we solved the radiation problem yet? The concord's solution was to sample exposure with a cockpit Geiger counter and descend to 40kft if things got too hot.

This is an issue of altitude, not speed. If the Concorde’s solution was to fly at a lower altitude, I know of no reason that wouldn’t be possible for other supersonic craft.

You fly lower, you fly slower. When your main selling point is "damn that's quick" anything that gets in the way of that is a problem.

Re: Boom supersonic jet readies for rollout

#218

Post by bluGill »

mertd wrote: post #134
TylerE wrote: post #101

Earlier quoted context omitted.

High-speed rail isn't high speed enough. Even with way faster than current tech and NO stops you'd still be looking at taking 12+ hours for what a plane can do in 5. That's ignoring the trillions it would cost. The US does not have the population density to make HSR viable.

You say like it is a bad thing but I'll take 12 hours in a nice stable train over 7 hours spent in going in and out of airports and sitting on economy airliner seats. I would actually pay a premium. This actually is reality today. Acela on the Northeast corridor is more expensive than comparable air fares and it's not even that good.

Maybe you would. We know from other countries that in general 5 hours is about the max time people will spend on a train before they choose to fly instead.

Because of air resistance planes are more fuel efficient as well for those longer trips (don't forget about energy lost to brakes when the train needs to stop)

Re: Boom supersonic jet readies for rollout

#219

Post by C1sc0cat »

agurk wrote: post #171
DomenicoMazza wrote: post #18

If I recall correctly the Concorde used about 2 tonnes of fuel rolling on the ground alone.. I wonder how this new aircraft fares for fuel consumption? I believe the Concorde is a marvel. You could travel faster than the rotation of the earth in it! However I don’t think we need more environmentally unsustainable travel.

Looking at the Concorde's fuel usage taxing is only part of the picture. All turbine engines are very inefficient at low power outputs due to the need to use energy to create sufficient compression for them to function. On top of this the Olympus engines generated a lot of thrust at idle, so much so that only two were used for taxing and it was still apparently tricky to control. While cruising at supersonic speeds t…

That's why you have tugs to move jets around - back in ww2 the Me226 was towed up to its start point on the runway by a Kitenkrad (and in some cases horses) to save fuel and engine life.

I think the industry was thinking of having electric tugs or motors built into the plane to move passenger jets around on the ground to save the fuel used getting from the stand to the start of the runway.

Re: Boom supersonic jet readies for rollout

#220

Post by mkl »

dotancohen wrote: post #188
paulmd wrote: post #154

Earlier quoted context omitted.

Concorde itself could have been much more efficient, there were plans for a "Concorde B" with high-bypass engines that would have carried a larger payload with additional range at higher efficiency. https://www.heritageconcorde.com/concorde-b

Warning: That page contains a background animation that cannot be disabled, even when disabling page styles. I had to open it in W3M, which I'm glad I did as it was very informative.

Running this in the browser console worked for me:

  $('video').remove()
(There aren't any other video elements.)
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