8
$\begingroup$

According to the cubesat design specification electrical requirements (3.3.7 in revision 13) a Cubesat shall include an RBF pin:

3.3.7 The CubeSat shall include an RBF pin.

  • 3.3.7.1 The RBF pin shall cut all power to the satellite once it is inserted into the satellite.
  • 3.3.7.2 The RBF pin shall be removed from the CubeSat after integration into the P-POD.
  • 3.3.7.3 The RBF pin shall protrude no more than 6.5 mm from the rails when it is fully inserted into the satellite.

I'm wondering how these kind of RBF pins are realized according to the cubesat standard, but also whether there are other mechanisms that have been used in other missions.

I tried doing extensive internet searches, especially for publications or technical documents, as I am very much interested in the actual electrical solution of a RBF pin and whether anyone ever tried a solution where for example you don't pull something out but put something in.

From what I gather even if you put in an RBF pin according to the cubesat standard there are still currents flowing around, as the RBF pin is to short the Base and Collector of a transistor thus preventing it from opening. But this needs pull up resistors and causes current bleed even if the satellite is to be off. It seems kinda silly to have a constant power flow that drains your batteries when you don't want the satellite to do anything.

Could anyone tell me of other RBF pin mechanisms, specifically ones where there is a galvanic isolation of the batteries and the rest of the satellite using an RBF pin? I'd be very happy about technical documents or papers that I could look into.

Thanks!

$\endgroup$
  • 1
    $\begingroup$ Is this a duplicate of How are remove before flight (RBF) pins made? $\endgroup$ – DylanSp Jun 15 '17 at 14:48
  • $\begingroup$ @DylanSp Different questions, even if they were the same that one doesn't have an answer. $\endgroup$ – Jake Blocker Jun 15 '17 at 16:10
  • $\begingroup$ I'm no expert, but I've read through that standard out of curiosity. It just states that power must be cut when the pin is inserted. Where did you get the information about shorting the base to collector of a transistor? $\endgroup$ – Steve Jun 15 '17 at 16:23
  • 1
    $\begingroup$ Could the pin not move a mechanical switch (or two) that breaks a circuit? $\endgroup$ – Steve Jun 19 '17 at 15:28
  • 2
    $\begingroup$ @user46794 I do not think that Steve means "break" in the sense "to permanently disable or ruin." In electrical work, "break" means "to interrupt the current path," and does not imply that the interruption is permanent. "Breaking" a circuit is usually a temporary change. $\endgroup$ – Wayne Conrad Jun 22 '17 at 18:06
1
$\begingroup$

Most of the time Remove Before Flight mechanisms disconnect the batteries from everything else. The system might still obtain some power though the solar panels, or via an external connector (Still on the ground), but will not be able to power themselves via the batteries. The ones that I have seen are purely mechanical in nature.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.