A Strain-Free Lock and Release Mechanism for an  Elastically  Suspended T wo-Axis Gimbal 

Armond A sadurian*, Richard Pugh*, Jim Hamm ond* 

Abstract 

A sin gle-point -actu ated, m ulti deg ree-of-freedom restrainin g launch latch m echanism  was develope d for a  two-d egree-of-freed om tilt table a ntenna  gimbal. The design of th e launch lat ch prote cts the gimbal pivot s  and a ctuato rs throug h lau nch vibration, and p recludes any high force s on sensitive gimbal compone nts a s  a result of operation of the  latch mecha nism itself. At the same time, string ent requi reme nts on stiffne ss  for the latche d gimbal an d payload a re met. 

The la unch latch d esign was carried th rough  to qualific ation  largel y as i nitially conceived; h owever, detail  design cha nges and improveme nts were mad e during devel opment a s a result of prototyping a nd  developm ent testing. 

Introduc tion 

Both the stru cture a nd the  actuation pat hs of efficient ly designe d spaceflight me chanisms are typ ically not  sized to  carry the ine rtial loads generated by la unch vibration a cting on the mech anism p ayload. Whe n  this is the case, ad ditional  structural lo ad path s are requi red during the lau nch pha se. Sub sequently, the  structure so introdu ced must be remo vable on  command  to al low norm al on-orbit o peration of the   mech anism. 

Mech anism p ayload s typically are articulated in one  or two deg rees of free dom (althoug h there can b e  more ), and constraine d otherwise by  the mech anism joints. If the mech anism p ower sources are ca pable  of position holding in the l aunch phas e, usually power off, then the phase  of the mechani sm is nominally  fixed. The l aunch lo ck device the n must supp ort th at mechani sm configu ration with p arallel loa d paths,  which are adequately sized for l aunch load s; so that  no damage or degradatio n of the structure, lin ks, or  beari ngs occurs d uring lau nch.   

Addition of redun dant parallel l oad paths to  a completed  mechanism creates con cern that lo cal  overloa ding of mech anism element s by t he simple act of engaging the lockin g device could occur. T his is  a prim ary d esign drive r for the lo cking device it self. Stiffness p arameters of th e lockin g dev ice el ement s  must be tailo red in su ch a way as to avo id high load s in cross-axis direction s when the lock is enga ged.   

Functio nally, launch lat ches vary from a sim ple single de gree o f freedo m co nstrai nt (e.g., pin joi nt), to   more comple x multiple de gree of fre edom re straints, depen ding on paylo ad size a nd m ass an d oth er  requi rements.  The su bject of this pape r is a cla mping-type launch latch, whi ch fully restrai ns the payloa d. 

Launch L atch Requirem ents 

The gimb al actuators control the out put platform an gular ori entation  actively in th e power-on condition an d  maintain it passively in t he p ower-off co ndition. Howeve r, in t he la unch phase of th e missi on, b oth  stiffness and load ca rrying cap ability must be enha nced in all six degre es of fre edom. For thi s appli cation,   a laun ch latch has b een d esigned inte gral to the mai n gimbal pivo t. 

                                                       * Moog, Chat sworth O perations, Ch atsworth, CA 

Procee dings of the 37th Aeros pace Mec hanisms Sy mpos ium, Joh nson S pace Ce nter, May 19-2 1, 200 4  97