>>[...] >No, because a similar sized LAP can only carry 1/4 the payload; so you >only launch as much payload per unit time. > >In fact I found an expendable LAP can only carry 1/4 the payload of an >expendable TSTO of the same size/GLOW/dry mass.) A reusable LAP would be >even worse.
You're not looking at the things that make LAPs useful. Mass is not the figure of merit; cost is. Cost is driven by R&D cost (which is in turn driven by complexity and performance requirements) and marginal cost (which is driven by propellant choices, mass, and maintenance). A true TSTO has two large vehicles, which take a lot of design effort, are complex and high performance, and will likely be high maintenance. A LAP platform plus stage to orbit has one complex vehicle and one simpler one, one low maintenance and low performance one, etc. The LAP will be cheaper to design (by far), cheaper to operate from an operational perspective due to simpler recovery, lower performance requirements so lower stress and more robust, etc. Traded off against that is the larger GLOW for the combined vehicle, and correspondingly higher propellant masses and costs. If propellant and dry GLOW mass cost more than the savings in design, operations and recovery, maintenance etc. then obviously, that design space is better served by a balanced TSTO than a LAP/nearlySSTO combination. There are probably some vehicle concepts where that is true. There are also strong suspicions that there are LAP/nearlySSTO solutions where it is in fact a lot cheaper, despite the GLOW and propellant costs... The devil is in the details. You have to make common assumptions about design parameters and then compare apples and apples. -george william herbert [EMAIL PROTECTED] _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
