The ST5 aluminum pusher shown in Figure 3 contai ns a spring of type LHL-1000A-13 that imparts the  400-N spin up force. The spring’s compression is adj usted by a threaded rod. The tip of the pusher  pushes against a stainless-steel-440C roller ball on the YZ Hardpoint on the spacecraft. Additional  TufLite® bushings are located between the pusher and the aluminum pusher housing mounted on the YZ  Mechanism stanchion. 

The spacecraft is fixed in the X, Y, and Z direct ions by the XYZ mechanism shown in Figure 4. A  stainless steel shaft on the deployer fits into and is driven by a key in the aluminum XYZ hardpoint on the  spacecraft. These two surfaces in metal to metal contact are impregnated with Polytetrafluoroethylene  (PTFE) to reduce friction. TufLite® bushings in the XYZ hardpoint encircle the XYZ shaft. On the other end  of this XYZ shaft there is a butterfly key. There is a spring of type LC-080-8 compressed inside the XYZ  housing. When the XYZ shaft turns 20 deg, the butterfly  key fits into the keyed slot and the XYZ shaft  retracts out of the spacecraft. To provide restraint in the Z direction, a 410-st ainless-steel cone reacts  against an aluminum-7075 cup on the XYZ hardpoint. A similar XY-only mechanism, on the opposite side  of the spacecraft acts coaxially and completes the hinge line. There is no Z-direction restraint needed.  

There are several stages required for the deployer desi gn to spin up the spacecraft and deploy it from the  LV. First, a LV separation pulse causes the Pinpuller to pull the pin from the clevis in the YZ mechanism,  which releases the YZ hardpoint clevis.  The spacec raft is then driven by the pusher to rotate about the  XY and XYZ hardpoints. The key in each of these two hardpoints forces the two shafts to spin with the  spacecraft. At about 7-deg, the pusher completes its throw and the spacecraft has reached its final  rotational velocity. The spacecraft, now no longer in contact with the pusher, continues to rotate about the  coaxial XY and XYZ shafts until it reaches a 20-deg angle. Finally, the two driven XY and XYZ shafts  retract out of the slots in the XY and XYZ mechani sms. The spacecraft is then unrestrained and spins  with a rate of 3.35 rad/s (32.4 rp m) about the Z-axis.  Its translational  speed is ~.72 m/s (28 in/s) at an  angle of 20 deg from the interface plane normal.  

Low Shock Pinpuller 

The TiNi Aerospace Model P50-1310-4RS Pinpuller was selected for its flight- demonstrated reliability,  compatibility with existing LV separation pulses, and low shock imparted to the surrounding structure. Its  ball-lock detent mechanism is initiated by a Nitinol shape-memory-alloy wire trigger [2]. It fires with a  margin of 1.5 under the 400-N (90-lbf) shear load im parted by the ST5 pusher. The Pinpuller pin is coated  with Braycote lubricant to minimize friction as it  retracts. Extensive suba ssembly-level testing at  operational temperatures and worst-case electr ical parameters verified this margin.   

The Pinpuller originally came with a 222-N (50-lbf) nom inal retraction force. Assuming a friction coefficient  of 0.4 and a 445-N (100-lbf) shear load led to a low analyt ical margin of 0.2 for release of the spacecraft.  This was unacceptable for a mission critical elemen t. The spring was upgraded to music wire, which gave  a retraction force of 310 N (70 lbf). The mission spin rate requirement was also relaxed to lower the  required pusher force to 400 N (90 lbf).  

Pinpuller Testing 

Subassembly testing was conducted on the YZ mechanism  to verify that the Pinpuller could operate with  a margin of 1.5 above the flight pusher shear load of  400 N (90 lbf). To do this, an Instron® Universal  Test Machine was used to apply the normal shear load on the pin in a temperature-controlled test cell.  The Pinpuller was tested under the goal 1000 N (225 lbf) l oad at five temperatures: cold survival at -35  oC, cold qualification at -20 oC, ambient +20 oC, hot qualification at +50 oC, and hot survival at +60 oC.  

Discussions with LV providers introduced the possibilit y that the current to the Pinpuller might be limited  to 5 A, as opposed to the initially planned 7.5-A limit. Because of this possibility, the Pinpuller was also  tested at the 5-A current levels at all five temperat ures. In total, there were 44 test conducted with the  Pinpuller under a 1000-N (225-lbf) shear load: six trials  for each current case at ambient temperature and  four trials for each current ca se at the four temperatures. 

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