|Suborbital RLV's As A Method Of
Reducing Spacecraft Loss Rates
by Pat Bahn
(as published by spaceequity.com)
When I was in grade school, I used to tell my teacher "Don't I deserve an 'A' for 'Effort'" and she used to reply "No, you get an 'E' for 'Effort', you get an 'A' for doing good work". Unfortunately in the space industry, the US Government established the fundamental ideas, processes and values. The Feds have long paid for effort, not results and the resultant decayed mindset has infected much of commercial aerospace today. Spacecraft of today are built with a focus on effort, not results and as a result, spacecraft costs continue increasing and spacecraft losses are as high as 40 years ago. Currently loss rates for spacecraft are averaging almost 30% in spite of spacecraft costs of $30,000/lb and up. A practical Suborbital RLV could decrease failures while saving on costs and schedule.
Currently Spacecraft are designed around a mass optimization function.
Specifically, how do you achieve all of the in space functional requirements
(stationkeeping, lifespan, transponders, antenna pattern, power) for the
lightest possible package. Stringent mass goals, tend to vitiate test
capabilities, so design reliability is achieved through very tight design
specifications and extremely expensive external test procedures that attempt
to closely match on-orbit conditions. Spacecraft are tested on large,
mechanical shake tables that precisely match launch conditions for vibrations
and acoustic loads. Spacecraft are placed in large thermal-vacuum chambers
to simulate heating + Cooling. Later elaborate mechanical pantographs
will be used to test mechanical structures.
The existing test program is extremely expensive & time consuming. Spacecraft test & verification is estimated to run 2/3rds of the total cost of spacecraft development. This means for commercial commsats the testing costs run upwards of $6,000/Lb and that for government payloads this can run up to $30-60,000/Lb. This level of up-front costs might be acceptable if spacecraft were 100% reliable through their design life. In face, though almost 30% of all suffer a serious failure that impacts service life and 15% suffer at least one serious malfunction in the first 90 days. All of this expense is aimed at reducing infant mortality and the failure rate is over 15%.
How does a system this problematic occur? In the early 1950's the US and soviets decided to begin exploring and exploiting space for the natural high ground as a communications relay and observation point. Space was a natural base for high-energy weapons, but treaty limits closed off this endeavour. Access to space was difficult and expensive because the earliest methods were to take artillery-derived systems and improve them. This provided a method of access but it was difficult and expensive with low flight rates. With these high costs and the political visibility of space efforts, failure was "not an option". For a worker at a desk, a bad ballpoint pen out of the box is a minor inconvenience. A failed communications satellite or weather spacecraft is extremely embarrassing. For political entities, with failure rates approaching 50% in the early days any improvement was desired. Given the low flight rates, mass production was deemed infeasible and human intervention would not be available for years. Instead, simulation of all environmental conditions would be tried and initially this was an improvement. Programs such as ranger went from 6 failures in a row to successful flight.
However, other approaches to testing are possible, if one can recover the hardware and examine the systems after a brief test. Deep-water electronics are routinely immersed for 30 days retrieved and examined for anomalies. Arctic equipment is tested for weeks in Minnesota or upstate New York prior to deployment in the arctic regions. Being able to examine and recover failed systems after short trial run results in durable and economical systems. A Suborbital RLV can perform this role for orbital spacecraft hardware.
The iridium satellite phone company also pursued an alternate testing
philosophy. Iridium placed 77 spacecraft of identical design into orbit.
Irdium built a single spacecraft and tested it for performance, then without
testing they built 77 spacecraft and without additional testing, flew
them. Approximately 10% suffered a significant failure, but this was a
30% lower rate then of spacecraft tested in the conventional manner.
The economic impacts of Suborbital flight testing is hard to imagine. Fully intergrated into spacecraft design, this could reduce spacecraft development costs by over 2/3rds an extremely expensive ($6-30,000/Lb.) testing process could be reduced to a low cost Suborbital qualification flight. Schedule constraints to build spacecraft could be reduced by almost a year and insurance costs on vehicles could be reduced by a third or more.
Spacecraft testing has evolved into an expensive, slow and complicated regime. The system evolved because of the limited and expensive nature of space access launchers. This system is not serving the economic needs of customers. A space qualification regime using suborbital vehicles will easily reduce costs while shortening schedules and reducing insurance claims.