Orbital Minotaur I - Manual (Page 56)

Minotaur I User’s Guide Section 5.0 – Payload Interfaces
5.4. Payload Design Constraints
The following sections provide design constraints to ensure payload compatibility with the Minotaur I
launch vehicle.
5.4.1. Payload Center of Mass Constraints
Along the Y and Z axes, the payload CG must be within 2.54 cm (1.0 in.) of the vehicle centerline and no
more than 30 in. (76.2 cm) forward of the payload interface for the standard configuration. Payloads
whose CG extend beyond the 2.54 cm (1.0 in.) lateral offset limit will require Orbital to verify the specific
offsets that can be accommodated.
5.4.2. Final Mass Properties Accuracy
In general, the final mass properties statement
must specify payload weight to an accuracy of at
least 0.5%, the CG to an accuracy of at least 6.4
mm (0.25 in.) in each axis, and the products of
inertia to an accuracy of at least 2.7 kg-m
2 (2.0
slug-ft 2 ) as shown in Table 5.4.2-1. However,
these accuracies may vary on a mission specific
basis. In addition, if the payload uses liquid
propellant, the slosh frequency must be provided
to an accuracy of 0.2 Hz, along with a summary of
the method used to determine slosh frequency.
5.4.3. Pre-Launch Electrical Constraints
Prior to launch, all payload electrical interface circuits are constrained to ensure there is no current flow
greater than 10 mA across the payload electrical interface plane. The primary support structure of the
spacecraft shall be electrically conductive to establish a single point electrical ground.
5.4.4. Payload EMI/EMC Constraints
The Minotaur I avionics share the payload area inside the fairing such that radiated emissions
compatibility is paramount. Orbital places no firm radiated emissions limits on the payload other than the
prohibition against RF transmissions within the payload fairing. Prior to launch, Orbital requires review of
the payload radiated emission levels (MIL-STD-461, RE02) to verify overall launch vehicle
Electromagnetic Interference (EMI) safety margin (emission) in accordance with MIL-E-6051. Payload RF
transmissions are not permitted after fairing mate and prior to an ICD specified time after separation of
the payload. An EMI/EMC analysis may be required to ensure RF compatibility.
Payload RF transmission frequencies must be coordinated with Orbital and range officials to ensure non-
interference with Minotaur I and range transmissions. Additionally, the customer must schedule all RF
tests at the integration site with Orbital in order to obtain proper range clearances and protection.
5.4.5. Payload Dynamic Frequencies
Typically, in order to avoid dynamic coupling of the payload modes with the natural frequency of the
vehicle, the spacecraft should be designed with a structural stiffness to ensure that the lateral
fundamental frequency of the spacecraft, fixed at the spacecraft interface, is greater than 12 Hz.
However, this value is affected significantly by other factors such as the coupled dynamics of the
Table 5.4.2-1. Payload Mass Properties
Measurement Tolerance
Measurement Accuracy
Mass ±0.5%
Principal Moments of
Inertia
±5%
Cross Products of Inertia
±2.7 kg – m 2
(±2.0 sl – ft 2 )
Center of Gravity X, Y,
and Z Axes
±6.4 mm
(±0.25 in.)
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