The airship provides little benefit. launch velocity is more important than launch altitude
SAAOPL is designed to replace expandable launch system mostly using existing technologies. While SpaceX is taking VTVL approach, SAAOPL is based on HTHL but combined with stratospheric launch.
Aye, the only meaningful advantage of launching from altitude is the ability to use near-vacuum-optimized engines from the start
Quote from: sevenperforce on 04/04/2017 05:29 PMAye, the only meaningful advantage of launching from altitude is the ability to use near-vacuum-optimized engines from the startAre there any advantages to having a much more benign aerodynamic environment (e.g., far lower max Q)? Would that allow a lighter structure for the actual vehicle, and thus better performance? If one doesn't have to worry about dense atmosphere, and thus streamlining, does that allow different form factors for the vehicle rather than a slender tube?
Short launch cycle: the next mission can be ready in 8 hours from the starting point of current mission, if using the same system.
The airship round trip flight is going take more than that
Best quote I've heard lately is "Fall in love with your customer's problems, not your own solutions."
whether you launch the rocket from an altitude of 0km, or of 30km, it still has to go from 0km/s to 8km/s in velocity.
e.g. all the equipment you need to keep the liquid oxygen liquid is heavy
"…it seems like...you're high up there and so surely that's good and you're going at...0.7 or 0.8 Mach and you've got some speed and altitude, you can use a higher expansion ratio on the nozzle, doesn't all that add up to a meaningful improvement in payload to orbit?"The answer is no, it does not, unfortunately. It's quite a small improvement. It's maybe a 5% improvement in payload to orbit...and then you've got this humungous plane airship to deal with. Which is just like having a stage. From SpaceX's standpoint, would it make more sense to have a gigantic plane airship or to increase the size of the first stage by five percent? Uhh, I'll take option two."
There was a Q&A at Aviation week some while back and this https://en.wikipedia.org/wiki/Air_launch_to_orbit was Elon Musk's response to another air launch concept involving a plane, but it could equally well apply to your platform:
Maybe replace the airship with this:https://www.nasa.gov/centers/armstrong/Features/TGALS_first_flight.html
Quote from: mikelepage on 04/06/2017 05:39 AMThere was a Q&A at Aviation week some while back and this https://en.wikipedia.org/wiki/Air_launch_to_orbit was Elon Musk's response to another air launch concept involving a plane, but it could equally well apply to your platform:I actually shared Musk's view towards conventional air-launch approaches. In the AQ section of the following page, brief comments on two conventional air launch by plane and by balloon approaches have already been included.http://saaopl.net/index.php/features/One major reason that two conventional air launch are not promising, and yet to be mentioned by Musk, is that none of them are reusable, or neither of them can be an ideal candidate to develop a reusable launch system.