Figure 4-13: Illustration of Breakwire Channel Categories A minimum of one (1) PL-side breakwire is recommended to be used for each deployment from the Launch Vehicle, SpaceX will evaluate exceptions on a case by case basis. There are no restrictions from SpaceX on the number of LV- side breakwires requested by the Customer. PL-side breakwire channels must transition from a low resistance state to a high resistance state, or vice-versa. Table 4-2 defines the required properties of each state. Table 4-2: PL-side breakwire resistance requirements PL-side Breakwire State Resistance requirement Low-resistance state <200 Ω High-resistance state >8 k It is acceptable for either loopback circuits or separation switches to be used for PL-side and LV-side breakwires. The final properties of the PL-side breakwire circuits, including the expected transition during deployment, will be captured as part of the Payload-specific ICD. 4.3.4 UMBILICAL CHANNEL PROPERTIES Umbilical channels offer connectivity between the Payload and Customer EGSE systems. Umbilical channels are offered in umbilical groups consisting of six (6) channels. The transmission properties of each of these channels is specified in Table 4-3. Table 4-3: Umbilical Channel Electrical Properties Umbilical Channel Name Example Usage Maximum One-Way Resistance (Ω) Maximum Allowable Steady-state Current (A) Controlled Characteristic Impedance BATT_CHG_1 Battery charging 5 3.5 -- BATT_CHG_2 BATT_SNS_1 Battery sensing 13.5 3.5 -- BATT_SNS_2 COMM Communication 18 2.5 100 Ω COMM The example usage column in Table 4-3 represents the expected usage of the channel, but is not a requirement. The Customer can use the umbilical signals as required for the Payload, with the following restrictions The electrical properties of the signal must be de-rated to the advertised capabilities of the cable. No AC signals maybe transmitted.
