mass. The results of a coupled lo ads analysi s will be appli ed to  an  ETU b oom on the te st fixture to  make sure it can survive the drop  transient and captive carry response. Afte r a technical interchange  meeting with OSC the su pport stru cture  was rede signed to raise t he  freque ncy fro m 22 to 37 Hz. 

Test Resul ts 

A cap ability test of the  spacecraft and  boom  was perfo rmed  with  prelimi nary suppo rt struct ure response data to det ermin e probl em  areas. The b oom su rvived  the dr op tra nsient excitation, which was  modele d as a 10 G pe ak 10 Hz in put and a random vib ration  environ ment that had a  peak of 0.2 g2/ Hz below 60 Hz. A s imilar  environ ment with a pea k input of 0.4 g2/ Hz below 60 Hz, ho wever,  caused the e lbow hinge to fail with what loo ks like a sin gle ev ent  overloa d. The appli cation  of this load based on th e softer support  structure was a gamble  that did not pay o ff. The random response  that is expect ed with the n ew stiffe r sup port structu re is expected t o  have a pea k value clo ser to 0.2 g2/Hz below 6 0 Hz. No a ction is  being ta ken until the new levels are in and the b oom is teste d to  them. 

Figure 17.    On Launc h Adap ter   Curre nt Flig ht Boom Sta tus 

The boom  comprises three  1.9-cm (3/4") diamete r M55J graphite compo site tube segme nts with Titani um  adapte rs at each e nd to m ount "ca rpenter tape" spring hinge bl ades. Each  hinge  is made up of fou r "carpente r-tape" blad es sta cked t wo thick on each  side. T hese blades are formed from a Beryllium-Copper alloy strip (0.15-mm  (0.006 ”) thick) th at ha s been te mpered to m eet design n eeds. When   stowed, the boom folds ar ound three si des of the spacecraft. It is supported  with stand -offs at either en d of the middle segme nt to keep it off the sola r  panel s. A lo w-sho ck, SM A pin pull er from Ti Ni Ae rospace, Inc. is used in  conjunction with a kine matic retentio n cage to re strain the se nsor head  durin g the la unch pha se of the missio n. The therm al treatment consists of  gold platin g the hinge s and blan keting everyt hing el se e xcept the   magneto meter mou nt tang  which is coated with SiO.  Titanium screws a re  used throughout the boom syste m. This boom  syste m is ab out to  undergo  flight qualifica tion testing.    Figure 18.  ST-5 on ELV  Deplo yer Mount 

The Futu re? 

In order to f ully sati sfy th e scie nce require ment s for a  magneti cally clea n boom system, at le ast the wri st joint  nearest the magneto meter sho uld be compl etely non-  metallic to re duce therm al magneti c contamination. This  is pro bably a chieva ble wit h more d evelopment work.  The  cente r boom section b etween the wrist and elb ow should  be po sitively restrained. T his will ta ke anothe r actuator  but is rea dily doabl e and will greatly improve the boo m's  ability to re sist rando m vibration. A  custom cable made  from p rinted  circuits on  Kapton would further en hance  the system being lighte r and able to be run i nside the  tube. The large exte rnal cable loo ps currently over  hangi ng the  joints contib ute to the n on-linear re sponse of  the system.  Figure 19.  Flight hardwar e  85