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Boom XB-1 First Supersonic Flight [video]

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Re: Boom XB-1 First Supersonic Flight [video]

#61

Post by Ajedi32 »

mppm wrote: post #55
Ajedi32 wrote: post #38

Earlier quoted context omitted.

Once you get out of the atmosphere, drag (and fuel consumption) is ~0. So theoretically possible, but I'm not sure if that's what he was talking about. Certainly Overture won't be capable of that.

Once you get out of the atmosphere, lift is ~0 too.

If you're going fast enough, you don't need lift.

But judging by "in four hours" I'm guessing he's imagining something somewhere in between those two extremes. High enough to substantially reduce drag, low enough that you don't need to approach orbital velocity to maintain altitude.

Re: Boom XB-1 First Supersonic Flight [video]

#62

Post by credit_guy »

hnuser123456 wrote: post #31
kindatrue wrote: post #9

Earlier quoted context omitted.

Previously Boom's CEO said this: “That’s not travel, that’s like a thing you might hope to do once in a lifetime,” says Scholl, before adding, “Versus where we want to get, which is anywhere in the world in four hours for 100 bucks.”[1] Anywhere in the world in four hours for $100 USD really caught people's imagination and attention. I'm puzzled by how they will achieve this. [1] https://www.cnn.com/travel/article/bo…

Huh. The longest flights are around 10,000 miles. They usually cost over $1000. Fuel apparently accounts for about 25% of ticket price on long haul, so $250 in fuel normally. To do that in 4 hours is to travel 2,500 mph. Naively, traveling twice the speed requires 8x the power, so going over 4x the usual 550mph should mean over 64x more fuel burn, or $16,000 in fuel alone. Maybe a bit less since drag doesn't grow qui…

The air density decreases exponentially with the altitude, while the drag only increases quadratically with speed. It is entirely possible that there is an altitude, maybe 70km, where it is much more economical to fly (at supersonic speeds) than the current subsonic planes. Most likely the CEO of Boom ran the numbers, and the $100 ticket price is doable, at least if you exclude things like profit, capital depreciation, insurance, etc.

Re: Boom XB-1 First Supersonic Flight [video]

#63

Post by 16bytes »

dylan604 wrote: post #6

I know nothing about Boom. Why is this impressive? We've achieved supersonic for passengers before. Are we meant to be interested just because someone is taking up the mantle again, or is there some new design that makes it impressive?

They're betting that they can make supersonic travel sustainable and profitable with a new aircraft and engine design. The Concord wasn't either of those.

The business case is apparently solid enough that several airlines are partnering with them during development.

This is the first actual demonstration that they can achieve supersonic flight in their demonstrator aircraft, so it is a significant milestone but they are years away from their full-scale aircraft.

Re: Boom XB-1 First Supersonic Flight [video]

#64

Post by ortusdux »

giarc wrote: post #59
anothertroll456 wrote: post #39

Earlier quoted context omitted.

[flagged]

Not really, that's like saying "they relied on closing the doors to the aircraft to achieve supersonic flight". Both happened, but aren't related if I'm reading the comments correctly.

"The Concorde used its afterburners during take off and to get through the transonic region,"

https://en.m.wikipedia.org/wiki/Transonic

Re: Boom XB-1 First Supersonic Flight [video]

#65

Post by mppm »

Ajedi32 wrote: post #61
mppm wrote: post #55

Earlier quoted context omitted.

Once you get out of the atmosphere, lift is ~0 too.

If you're going fast enough, you don't need lift. But judging by "in four hours" I'm guessing he's imagining something somewhere in between those two extremes. High enough to substantially reduce drag, low enough that you don't need to approach orbital velocity to maintain altitude.

"Fast enough" is very nearly orbital speed, though. Suborbital range is very short on the lower end, and increases rapidly and nonlinearly later. E.g. if you can boost to 2km/s (~ Mach 7), this gives you, I kid you not, around 200km of ballistic range. It's either atmospheric flight or orbital flight, and there's nothing really useful in between.

Re: Boom XB-1 First Supersonic Flight [video]

#66

Post by mshook »

jdblair wrote: post #29
hangonhn wrote: post #22

Earlier quoted context omitted.

No. I don't think that's correct. The Concorde used its afterburners during take off and to get through the transonic region, where the drag is very heavy. Once you've gone past that the drag drops. At that point the Concorde can turn off the after burners. Source: https://www.heritageconcorde.com/concorde-engine-re-heats

That's right, the Concorde had engines capable of supercruise - long distance supersonic flight without afterburners. https://en.wikipedia.org/wiki/Supercruise#Aircraft_with_supe...

This is correct, reheat / afterburner was used from Mach 0.9 something to 1.7, after which they'd were off. So yes, Concorde could supercruise.

Re: Boom XB-1 First Supersonic Flight [video]

#67

Post by vpribish »

giarc wrote: post #59
anothertroll456 wrote: post #39

Earlier quoted context omitted.

[flagged]

Not really, that's like saying "they relied on closing the doors to the aircraft to achieve supersonic flight". Both happened, but aren't related if I'm reading the comments correctly.

haha, good analogy - but his name has "Troll" right in it.

Re: Boom XB-1 First Supersonic Flight [video]

#69

Post by mshook »

dmitrygr wrote: post #10
bangaroo wrote: post #8

Earlier quoted context omitted.

there hasn't been supersonic civil aviation, as far as i am aware, since the concorde was grounded. there are no active commercial aircraft capable of going supersonic. this is significant because it's the first civil aircraft to reach that milestone since the ending of the concorde program.

> there hasn't been supersonic civil aviation There still isn’t, and this is not a very interesting stepping stone. We already knew that we could fly a plane quickly. This company has no engines for their allegedly full scale plane. The last manufacturer dropped them a few years ago, and there has been no movement in that direction. This demonstrates the easiest part of what they’re trying to do, not the hardest. Thi…

I'm not sure why you're being downvoted because you're right: they have the technology, they don't have an engine, and this just looks like a civilian version of a fighter jet pretty much (except it has 3 turbojets).

And what people always fail to mention when it comes to supersonic flights is one of the main issue is neither a technological nor an economical one nor a supersonic boom one.

Traveling west bound is great: you leave in the morning and you arrive, local time, before the local time of your origin point. But traveling east bound isn't that great: you still have to leave in the morning and you land in the evening, so the only thing you gained is a shorter flight time but not a full day of work or shopping or what not.

So on regular flights (because Concorde was profitable, at least on the French side, thanks to charter flights), people would fly Concorde to go to NYC and fly back on a red eye...

As someone who worked for and flew on Concorde, I think what they're doing is amazingly cool though and I hope they succeed. But I'm still unsure what the long term plan is...

Re: Boom XB-1 First Supersonic Flight [video]

#70

Post by mshook »

EA-3167 wrote: post #32
dylan604 wrote: post #6

I know nothing about Boom. Why is this impressive? We've achieved supersonic for passengers before. Are we meant to be interested just because someone is taking up the mantle again, or is there some new design that makes it impressive?

There are some interesting technological developments around fuel efficiency and minimizing the "sonic boom" that's felt on the ground. Neither of those killed Concorde though, because the entire idea of Concorde turned out to be incredibly faulty. MOST people weren't in such a hurry to get from point A to point B that they'd pay 5x-10x a normal business/first class ticket to cut a trip down by 50% or so. The intende…

My take is it's not even an economic problem. Unless you fly really fast (like Mach 3++), flying east sucks.

Let's assume we have a plane capable of Mach 3+: the SR-71 holds a record for flying from NYC to London in 1h54 and it could do well over Mach 3. Let's assume our plane can do the same in 2 hours.

If you take off from NYC at 10am, you will land at 5pm local time in London. Sure it's a lot faster than a regular flight but you didn't gain as much as flying west bound.

With the same 2 hour flight (because when you fly that high, wind doesn't make such a big difference), you could leave London at 10am and land in NYC at 7am local time, that's so much better.

But that's for a plane doing Mach 3+. Boom is planning to fly slower than Concorde (Mach 1.7 vs Mach 2.02).

Concorde did that in 3 hours FYI.

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