Stratolaunch

[KmH]

Scaled Composites Stratolaunch - Wikipedia

First taxi test:
Watch Stratolaunch- The World’s Biggest Plane As It Goes Through Its First Taxi Test

 

[Destin]

That’s crazy! Where will the rockets launch from?

 

[limr30 3]

Will this mean more leg room?

 

[Designer]

Will this mean more leg room?

Shirley you jest!

With two (not just the old-fashioned one) fuselages, there is a better than average chance your luggage will not deplane with you.

(passenger) Oh, you mean my luggage was in the LEFT fuselage, when I was in the RIGHT fuselage! Well how did that happen? When will I see my luggage again? Are you going to at least give me a toothbrush?

 

[KmH]

That’s crazy! Where will the rockets launch from?

Between the 2 fuselages.
The center wing can hold 500,000 lbs.
Stratolaunch

 

[compur]

What is the advantage of that huge, expensive thing with all its development, crew and maintenance costs versus simply using an additional rocket stage?

 

[KmH]

Reusability, and launching from altitude allows for more payload in the rocket because the rocket needs less fuel.

 

[compur]

But, it's not being "launched from altitude." It's being launched from the ground. They're just using jet fuel in a 300 million dollar aircraft in place of rocket fuel in a lower stage to get it up to altitude. And, then they have to maintain and house that aircraft. Is it really cheaper than just making another lower rocket stage?

 

[Destin]

But, it's not being "launched from altitude." It's being launched from the ground. They're just using jet fuel in a 300 million dollar aircraft in place of rocket fuel in a lower stage to get it up to altitude. And, then they have to maintain and house that aircraft. Is it really cheaper than just making another lower rocket stage?

I suspect that depends on the frequency at which you plan to launch rockets.

 

[KmH]

Rocket fuel is RP-1, a highly refined form of kerosene, & an oxidizer - usually liquid oxygen.
Stratolaunch doesn't need an oxidizer.
In 2011 Elon Musk said fuel for the first stage of a Falcon 9 cost about $200,000.

Stratolaunch/747s burn a somewhat different (from RP-1) type of kerosene known as Jet A, though when it's cold they burn Jet B for its enhanced cold-weather performance.
Right now at Mojave Air and Spaceport, which is where Scaled Composites is based, Jet A is $4.57 a gallon.
Falcon 9 has 9 rocket engines that burn fuel at a very much higher rate than the 6 jet engines Stratolaunch has.

According to the Wikipedia page, a Falcon 9 Full Thrust mission (allowing booster recovery) was about $62 million in 2016 - new first stage booster.
Missions using recycled first stages cost less. I don't know how much less because it's more recently Space X has used recycled first stages.

So the question boils down to - How many Stratolaunch missions does it take to cover the cost of building, operating, and storing the aircraft.
Obviously, Scaled Composites believes they'll be able to make a profit.