New 'Worlds biggest plane'

Author
Discussion

hurstg01

Original Poster:

2,909 posts

242 months

Friday 27th February 2015
quotequote all
http://www.dailymail.co.uk/sciencetech/article-297...

Sorry for the Daily Fail link, but this sounds kinda cool smile

Simpo Two

85,147 posts

264 months

Friday 27th February 2015
quotequote all
It weighs 544 tons!

Eric Mc

121,774 posts

264 months

Friday 27th February 2015
quotequote all
Obviously Orbital Sciences are behind this in that they have used a similar concept on a smaller scale with their Pegasus launcher.

What are the advantages of air launching rockets into orbit?

Simpo Two

85,147 posts

264 months

Friday 27th February 2015
quotequote all
Eric Mc said:
What are the advantages of air launching rockets into orbit?
I guess it uses less fuel (than blasting off vertically from the ground) because it uses aerodynamic lift to gain altitude.

jmorgan

36,010 posts

283 months

Friday 27th February 2015
quotequote all
Get up high as well and less atmosphere.

wolfracesonic

6,940 posts

126 months

Friday 27th February 2015
quotequote all
Mmmmmmmmmmmm...........I bet the runway for it is lined with palm trees that flop out the way come launch time.

Mave

8,208 posts

214 months

Friday 27th February 2015
quotequote all
Simpo Two said:
It weighs 544 tons!
Less than an a380 then :-)

annodomini2

6,860 posts

250 months

Friday 27th February 2015
quotequote all
Simpo Two said:
Eric Mc said:
What are the advantages of air launching rockets into orbit?
I guess it uses less fuel (than blasting off vertically from the ground) because it uses aerodynamic lift to gain altitude.
Orbit is more about speed than altitude.

Yes there will be less drag due to the altitude, but it's minimal.

LEO is ~17500Mph, with a rough launch speed of 540Mph, you still need another 16,960Mph of delta V.

So roughly a 4.1% saving in Delta V.

Main benefit is in payload, rough fag packet calcs put them able to put an roughly extra 1.5 tonnes into LEO with the air launch vs ground launch.

Though that may be more when you account for drag and ISP changes in the engine.

Boatbuoy

1,941 posts

161 months

Friday 27th February 2015
quotequote all
It reminds me of a Lockheed Tristar that I saw as a young ATC Cadet when flying with 5 AEF out of Cambridge/Marshalls Airport. That was used to launch rockets.

See here:

http://en.wikipedia.org/wiki/Stargazer_(aircraft)

https://www.youtube.com/watch?v=lFUPkYre06E


MartG

20,620 posts

203 months

Friday 27th February 2015
quotequote all
Ground launched rockets waste a good proportion of their fuel just getting above the dense lower atmosphere

Eric Mc

121,774 posts

264 months

Friday 27th February 2015
quotequote all
The other advantage is that they can move the launch position to an area where the weather is a bit more favourable.

Ground winds can cause a launch to be scrubbed, so this is one way of getting away from that problem.

But you can see that there are size limits to the rocket you can hoist to altitude. It will take the worlds largest aeroplane to lift what is still a fairly modest rocket.

As has been said gaining 500 mph when you need 17,500 mph is not a big assist and gaining 40,000 feet when you need 106,000 feet at least is a minor help.


MartG

20,620 posts

203 months

Friday 27th February 2015
quotequote all
Eric Mc said:
As has been said gaining 500 mph when you need 17,500 mph is not a big assist and gaining 40,000 feet when you need 106,000 feet at least is a minor help.
The altitude isn't a factor, it's the air density wink

At 40,000ft 75% of the atmosphere is below you, so you don't waste fuel climbing through all that air - remember rockets only take-off vertically so they get above the dense air quickly. To get into orbit they need to be travelling at 5 miles/sec horizontally but need to be in a vacuum to reach that speed - launching them from altitude allows them to start accelerating horizontally immediately after launch thanks to the reduced air pressure

Buzz84

1,138 posts

148 months

Friday 27th February 2015
quotequote all
White Knight 2 on steroids!

Eric Mc

121,774 posts

264 months

Saturday 28th February 2015
quotequote all
MartG said:
The altitude isn't a factor, it's the air density wink

At 40,000ft 75% of the atmosphere is below you, so you don't waste fuel climbing through all that air - remember rockets only take-off vertically so they get above the dense air quickly. To get into orbit they need to be travelling at 5 miles/sec horizontally but need to be in a vacuum to reach that speed - launching them from altitude allows them to start accelerating horizontally immediately after launch thanks to the reduced air pressure
Good point.

The main drawback to the concept is the inability to lift larger spacecraft. Remember Drax and his Shuttles in "Moonraker"?