Orbital Minotaur I - Manual (Page 39)

Minotaur I User’s Guide Section 4.0 – Payload Environment
The fairing peak vent rate is typically less than 0.6
psi/sec. Fairing deployment will be initiated at a
time in flight that the maximum dynamic pressure
is less than 0.01 psf or the maximum free
molecular heating rate is less than 1135 W/m
2 (0.1
BTU/ft 2 /sec), as required by the payload.
4.6.3. Nitrogen Purge (non-standard service)
If required for spot cooling of a payload
component, Orbital will provide GN
2 flow to
localized regions in the fairing as a non-standard
service. This option is discussed in more detail in
Section 8.3.
4.7. Payload Contamination Control
All payload integration procedures, and Orbital’s
contamination control program have been
designed to minimize the payload’s exposure to contamination from the time the payload arrives at the
payload processing facility through orbit insertion and separation. The payload is fully encapsulated within
the fairing at the payload processing facility, assuring the payload environment stays clean in a Class
100,000 environment. Launch vehicle assemblies that affect cleanliness within the encapsulated payload
volume include the fairing, avionics assembly, Stage 4 assembly, and 3/4 Interstage. These assemblies
are cleaned such that there is no particulate or non-particulate matter visible to the normal unaided eye
when inspected from 2 to 4 feet under 50 ft-candle incident light (Visibly Clean Level II). After
encapsulation, the fairing envelope is either sealed or maintained with a positive pressure, Class 100,000
(ISO 8) continuous purge of conditioned air.
If required, the payload can be provided with enhanced contamination control as an option, providing a
Class 10,000 (ISO 7) environment, low outgassing, and Visibly Clean Plus Ultraviolet cleanliness. With
the enhanced contamination control option, the Orbital-supplied elements will be cleaned and controlled
to support a Class 10,000 clean room environment, as defined in ISO 14644-1 clean room standards
(ISO 7). This includes limiting volatile hydrocarbons to maintain hydrocarbon content at less than 15 ppm.
Also with the enhanced contamination control option, the ECU continuously purges the fairing volume
with clean filtered air and maintains humidity between 30 to 60 percent. Orbital’s ECU incorporates a
HEPA filter unit to provide ISO 7 (Class 10,000) air. Orbital monitors the supply air for particulate matter
via a probe installed upstream of the fairing inlet duct prior to connecting the air source to the payload
fairing.
4.8. Payload Electromagnetic Environment
The payload Electromagnetic Environment (EME) results from two categories of emitters: Minotaur I
onboard antennas and Range radar. All power, control and signal lines inside the payload fairing are
shielded and properly terminated to minimize the potential for Electromagnetic Interference (EMI). The
Minotaur I payload fairing is Radio Frequency (RF) opaque, which shields the payload from most external
RF signals while the payload is encapsulated. Details of the analysis can be provided upon request.
Figure 4.6.2-1. Typical Minotaur I Fairing
Pressure Profile
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