I don't think this concept will ever beat the F9 if/when it is fully reusable, heck even partially reusable would still beat Stratolaunch price. That huge aircraft is going to cost an arm and a leg to build and maintain and it will serve a very small market in it's payload class.
SpaceX achieving viable reusability isn't a certainty yet, at all...
How often does the An-225 fly? Even a relatively low flight rate could be very helpful in amortising the cost of the mothership.
But, it isn't like this is a infrastructure-less system. You still need to integrate and prepare the vehicle. You still need to integrate the payload to the vehicle... transport the vehicle to the 'launch site' (aircraft), fuel it, etc.
Those things will cost too. If the integration facility for example is seperate from those SpaceX has at LC-40, it will have its own totally new overhead.
1. Will it cost less to produce a smaller booster like a Falcon 5?
Depends on what you mean by 'smaller'; the removal of 4 engines should help a good deal since propulsion is a major cost item (plus you still get good economies of scale combined with F9 production, etc).
I have a hunch that reducing the number of tank barrel sections won't reduce cost
that much, and you still have other things (avionics, seperation systems, etc) to deal with. They'll probably be shared with F9, which means they won't be smaller... the major price reduction factor for those components would be higher production rates.
2. If so is it enough to reduce the cost proportionately to the reduce payload mass?
That is a very good question.
Perhaps the cost/capability change of this compared to a ground-launched F5 is enough to make it work...
3. In the press conference Burt said that the air-launch concept improves performance by about 5%. Is that enough to justify the cost of building and operating one of the largest aircraft in the world?
Burt Rutan gets paid for it. What do you think he will say?
:lol:
Maybe a large portion of the business case is the terrestrial air payload market.
4. If a booster costs X, and a launch aircraft cost Y, why would it be better to
to add X+Y? Doesn't it have to be greater than X alone?
4b. Or is it the reduced costs of launching from a dedicated pad?
There are two parts to launch costs: vehicle hardware costs, and launch facility costs (hardware costs are actually dependant on the cost of the facility that produces the hardware, but for simplicity sake we can seperate the two).
The idea is that the cost of the "launch facility" with the airlaunch is lower than the cost of a traditional launch facility.
Of course, the aircraft launch facility is now seperate from the other launch facility (SLC-40/SLC-4). Which means that the other facility is used less and its costs are not shared as much.
So there is potential that this offers
less oppurtunity for SpaceX to decrease their cost per launch over all systems, including F9 and eventually FH.
There could be another rationale here: SpaceX is a contractor, not an investor. They just get money for the booster/any preperations that need to be peformed with it, and also the development work involved.
It is a way for them to make a profit. A profit that they can then use toward their numerous development projects, such as crewed Dragon, FH, and reusability/Grasshopper. The emphasis for SpaceX here might not be much about lowering their prices and attracting a bigger market, but just getting extra cash.
That said, maybe it isn't the right rationale... maybe Stratolaunch fails to attract enough customers and is a loss, maybe launching more rockets is more advantageous to SpaceX... who knows.
AT $9600 per pound to orbit this sounds like this concept is a non starter.
Why is it so shocking? Not all systems have to reduce launch costs by one to two orders of magnitude.
That said, I think it would make more sense if it were $9600 a
kilogram for a modern system. But even the EELVs don't reach this at their current flight rates.