A Case Study in NASA-DoD - The Black Vault

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to increase to 13. That was found to be true across a wide number of
excursions.
It should be noted here that assuming a maximum number of payloads
per spacecraft of 13 results in an average number of payloads per spacecraft
of only 5 to 8, depending on the procurement option. The largest
benefit is from orbits 1 and 2 where the majority of Space Test Program
payloads are scheduled to be flown. To illustrate that, Fig. 8 presents
a detailed breakdown of the distribution of the actual maximum number of
payloads per spacecraft by orbit for the all-STPSS procurement option.
For orbit l-S, for example, if the assumed maximum number of payloads
per spacecraft is allowed to increase from 6 to 13, the actual maximum
number of payloads assigned to a spacecraft increases from 5 to 10.
The difference between the actual number of payloads assigned to a
spacecraft and the upper limit occurs in all orbits because of the
limited number of payloads in each orbit.
In orbit 1-S, for example,
the mission model includes only 20 payloads, which were distributed
evenly between two spacecraft when the assumed maximum number of payloads
per spacecraft was increased to 10.
Consequently, the average
number of payloads per spacecraft for a given procurement option does
not increase substantially as a result of allowing the assumed maximum
number of payloads per spacecraft to increase from 6 to 13.
The main difficulty associated with increasing the number of payloads
per spacecraft lies in the payload-integration area. Although
the specific performance limits of each spacecraft were imposed while
allocating payloads, payload-integration problems and costs were not
explicitly examined. Based on the saving in program costs identified
as a result of increasing the maximum number of payloads per spacecraft,
it appears that a systematic study of the payload integration problems
and costs would be useful.
Figure 9 illustrates the variation in program cost as a function
of Space Test Program size.
Here program size was doubled to a total
of 228 payloads to see if economies of scale might preferentially benefit
the MKS and thereby alter the ordering of the procurement options.
*
While 13 payloads are never allocated to a spacecraft in the
example shown in Fig. 8, this is not the case for other procurement
options, especially those including the MMS.