Hypersonic Jet Ready for Launch

[Capt Chambo]

Follow this link from the BBC's website:-


http://news.bbc.co.uk/2/hi/science/nature/4832254.stm

[Nov71]

That's one hell of a 'vomit comet' ride
Did Australia ban Concorde?

[Daysleeper]

Perhaps someone could help with my rather poor maths.
In order to fly UK-OZ in 2 hours what G would the pax be exposed to?

I've chosen 10,000 miles as the distance (aprox london to sydney)
thats (16,093,440 Meters.)

In order to do it in 2 hours we need to average 5000 MPH, so assuming an even accel and decel the PEAK speed is 10,000 mph (4,470 meters/second) and we have 1 hour (3600 seconds) to reach this speed.

Right now gravity is 9.8m / s2.


er so now that I'm lost what is the next step. I'm thinking divide peak speed by time.

4470/3600= 1.24 m/s2 which doesn't seem that impressive, or am i wrong somewhere?

[chornedsnorkack]

Perhaps someone could help with my rather poor maths.
In order to fly UK-OZ in 2 hours what G would the pax be exposed to?

I've chosen 10,000 miles as the distance (aprox london to sydney)
thats (16,093,440 Meters.)

In order to do it in 2 hours we need to average 5000 MPH, so assuming an even accel and decel the PEAK speed is 10,000 mph (4,470 meters/second) and we have 1 hour (3600 seconds) to reach this speed.

Right now gravity is 9.8m / s2.


er so now that I'm lost what is the next step. I'm thinking divide peak speed by time.

4470/3600= 1.24 m/s2 which doesn't seem that impressive, or am i wrong somewhere?

I do not see anything amiss about the calculation... but let´s rather not assume even acceleration and deceleration.

Concorde engines, I think, were something like 17 tons thrust each, 68 tons between the 4 of them. The MTOW was about 185 tons, so I get something like 0,36 g acceleration on takeoff run. 3,6 m/s2.

The subsonic airliners normally have slightly lower thrust loading than Concorde, but not much lower. Above 0,2 g on takeoff run sounds normal.

And the planes on climb after takeoff are accelerating as well as steeply pitched up.

When the Concorde decided they could attack the sound barrier, how long did it take to accelerate from M 0,9 subsonic overland cruise to Mach 2,0 supercruise?

If you have a plane which can accelerate at 0,3 g along runway and then after lifting off sustain the same 0,3 g all the way to Mach 8 cruising speed, then Mach 8 is something like 2300 m/s... which mean that sustaining takeoff thrust 3 m/s2 gets you to Mach 8 in, well, around 13 minutes.

And then cruising at Mach 8, it takes slightly less than 2 hours to reach Sydney. The quarter an hour acceleration in both end adds only half an hour, and you do cover some of the distance in that time... Mach 2 or Mach 6...

[The Nr Fairy]

Those sort of speeds will make for some interesting descent planning !

[Gertie Vow]

But you need to get to Mach 5 before it works!

[Agaricus bisporus]

Aren't we getting a bit ahead of ourselves here with talk of hypersonic services from London to Sydney?

This thing is only an engine, and a very experimental one too. The last time they tried to get it going I seem to remember it all ended in tears (probably tears of molten metal)

We are about as far from anticipating 2 hr flights to Oz as Herr Otto was from predicting a Super Constellation on the day he first tried to start his gas engine in 1880-whenever-it-was.

Still, hope it goes OK this time.

[AlexB]

Does this remind anyone else of those cheesy "views of the future" you see from the 50's, of rocketmen and jetcars by the year 2000?

Innovation is good, but its better to concentrate on realistic advances before releasing outlandish claims. If we had a currently operating supersonic passenger aircraft it could seem more viable, however with the recent demise of Concorde, it just seems too far away unfortunately.