I am amazed at the, apparently almost exclusive, use of formed composites for the entire skin of the aircraft. This was an aircraft skin design no no for a long time because of the susceptibility of graphite filled epoxy composites to failure under shock and/or point loading even though the specific strength/rigidity was better than any metal. I wonder what the composition of the composites used now are comprised of. Anyone know?
Boom supersonic jet readies for rollout
261–270 of 283 posts
Re: Boom supersonic jet readies for rollout
#262Their parallax website is pretty entertaining... https://boomsupersonic.com/xb-1/build
AFAIK this is still a no no for transonic wings at Airbus and Boeing. I am interested in knowing what they are using as well.
Re: Boom supersonic jet readies for rollout
#263Earlier quoted context omitted.
Expected fuel burn per passenger is minimum 3x a ‘normal’ business class seat on a modern plane: https://theicct.org/news/reviving-supersonic-flight-signific... Either way, it’s fairly obscene.
While fuel cost is minor part of total flight cost (most is staff + depreciation), I wonder how much will be saved by a good satellite network. Being able to work on a plane at some point starts to pay itself off.
Fuel costs accounted for 23.7% of airline operating expenses in 2019 [1], I think that's more than a minor part - especially if you triple it.
1: https://www.iata.org/contentassets/ebdba50e57194019930d72722...
Re: Boom supersonic jet readies for rollout
#264Why are they using three engines instead of just one? Looks like a maintenance nightmare.
Re: Boom supersonic jet readies for rollout
#265Can anyone here comment on the kinds of things you can and can't learn accurately from a scaled prototype? I'd guess that for something that flies, changing the surface area/volume ratio makes a big difference.
In aerodynamics we have several "similarity" quantities such as the Reynolds Number which is a dimensionless coefficient that characterizes (in a nutshell) the ratio of inertial to viscous forces in a flow. Much research has gone into the applicability of scale models to real world conditions and the validity of a model is contingent on maintaining similarity coefficients. So for example you want your model to be fly…
Their half-size model would need to be flying twice as fast for the Reynolds number to remain constant with varying length or diameter.
This changes the Mach number.
So no, in general, you can’t build and test a smaller model and transfer the results to a larger model using similarity, because your similarity model is incomplete.
You can either have similarity for the Reynolds number or the Mach number, but not both.
Re: Boom supersonic jet readies for rollout
#266Earlier quoted context omitted.
Electric Planes would make that obsolete long before its finished.
Would it make the comfort of a train absolute as well?
Nobody is willing to pay for trains that take 3-4 as long and are 3-4 more expensive. Maybe you are one of those very, very few people who would do that, but for the most part humans are willing to have 2h of less comfort to get somewhere.
Also, as European who has traveled a lot in train, they are not always so super comfortable over night.
Also, lets be honest, 90% of the discomfort of plane, has to do with boarding, and not plane rides themselves. Those things can be expressed relativity easily.
Building incredible expensive high speed trains across a territory as large as the USA is insane in scope and expense, and minimal in benefit. Specially with electronic planes, cars and autonomy happening.
There is also the reality that there are already huge amounts of airport infrastructure that could be activated with electric planes.
Building a high speed train network is a 30 year project, that in 30 years would be mostly pointless and unused.
Re: Boom supersonic jet readies for rollout
#267Earlier quoted context omitted.
NOE flying is designed to come in fast and low, to avoid radar coverage. Announcing you're coming, and your heading, by breaking everyone's windows for miles around is quite noticeable.
(Big fat disclaimer: I don’t understand anything I’m about to say) Wouldn’t the windows be broken _behind_ the plane? In my mental model, you’re flying below radar so anyone on the ground will know you’re there anyway. If you’re sub-sonic people hear/see the plane and you hope they don’t have time to do anything before you strike. If you’re supersonic they hear/see the plane, their windows break, and you hope they do…
If you are below the radar you are still visible and detectable. If they have any reason to suspect you are coming they can send people outside to look, you are low enough to be easy to see. Give that person training with a gun and you can be shot down. (speed makes it harder, but it also means the pilot does in the crash before having time to realize anything is wrong)
Re: Boom supersonic jet readies for rollout
#268Earlier quoted context omitted.
> (very very close). Eh, within 15 miles or so. 4MPH * 24h = 96 mile circumference circle, 96 miles / 2pi ~= 15 miles.
You are going to struggle to walk at 4mph in Antarctica
I think you could for a few moments at least. Of course if this is an endurance race, you're destined to lose ;)
Re: Boom supersonic jet readies for rollout
#269Earlier quoted context omitted.
The traditional solution was to only allow supersonic flights on the coasts where the jet could fly out over the ocean for the boom.
There is a common misconception that the boom happens once while accelerating through the speed of sound. In fact it happens continuously while traveling supersonic. The Concord mostly (only?) flew transatlantic mostly for that reason. The US military hasn’t always been shy about continental supersonic flight. I grew up near Beale AFB where the SR71 was stationed and hearing a sonic boom was not an uncommon occouranc…
Thanks for pointing that out. Didn't even think to look it up as I had just assumed it was that way forever.
Re: Boom supersonic jet readies for rollout
#270From my understanding a big problem with Concorde was the sonic boom which happened near takeoff and bothered urban residents. I've always wondered why they can't fly at normal airline speeds until over a rural area or an ocean before accelerating to sound barrier speeds.
a sonic boom is a phenomenon that occurs continuously when traveling over mach 1.0 so supersonic flight is usually limited to over water routes and forbidden over or near urban areas.
Many people think the sonic boom happens when one breaks the sound barrier. It happens continuously once past the speed of sound. Back to the OP's question, once could simply only fly transonic over oceans