Progress in Reducing Vibration Levels on NPSCuL

Transcription

1 Prgress in Reducing Vibratin Levels n NPSCuL W. Lan, V. Kaushish, J. Newman 2015 Spring CubeSat Develpers Wrkshp 23 APR 2015 Naval Pstgraduate Schl Space Systems Academic Grup Mnterey, CA 93943

2 NPSCuL Overview NPSCuL is an ESPAcmpatible paylad with a capacity f 24 1U CubeSats using P-PODs and 6U dispensers 2 successful launches, OUTSat and GEMSat, n the Atlas V Aft Bulkhead Carrier (ABC) in 2012 and upcming launches, ULTRASat and GRACE, in May and August /23/2015 Prgress in Reducing Vibratin Levels n NPSCuL 2

3 Prgress in Reducing Vibratin Levels n NPSCuL 3 Need fr Reducing Vibratin Levels 1.00E+01 Test-T-Insane Levels (TTIL) methdlgy applied t CubeSats n NPSCuL during randm vibe ~15 G RMS at MPE fr the P-POD is cnsidered harsh Rigidly munted, cantilevered, thin-plate structure causes amplificatin at P-POD interface Discurages mre sensitive and cmplex paylads frm gaining access t space via ABC Current envirnment is cnsidered cach-class X- Axis G RMS (Wrst- Case) ASD, g^2/hz 1.00E E E E Frequency, Hz GEMSat Acceptance NASA GEVS (100 lb r less) Level Base (Input) P- POD Interface* Acceptance (MPE +0dB) Prtqual (MPE +3dB) Qual (MPE +6dB) *Envelpe f OUTSat acceptance test data (Flight P- PODs and CubeSats)

4 Prgressin f Vibratin Reductin Methds fr NPSCuL Implemented frce-limited vibratin testing (FLVT) t minimize ver-test caused by test set-up Effective in reducing the resnance at the fundamental frequency Redesigned NPSCuL t increase stiffness Mves fundamental frequency frm ~50 Hz t ~75 Hz Increased stiffness results in reduced benefit frm FLVT in verall G RMS fr the ABC input Obtain lwer input frm LV prvider N flight data fr full test frequency range available t create test envelpe 4/23/2015 Prgress in Reducing Vibratin Levels n NPSCuL 4

5 Prgress in Reducing Vibratin Levels n NPSCuL 5 FLVT n NPSCuL Semi-empirical methd is used t calculate frce limit per NASA-HDBK- 7004B Has been repeatedly shwn t be the least cnservative methd while still meeting test requirements Results in a ntch in the acceleratin input at the fundamental frequency Frce rll-ff is assumed after fundamental frequency t 500 Hz Des nt prvide relief past the frcelimited range Test data shws there is a significant amunt f energy abve 500 Hz at the P-POD interface Nt a mechanism, and is nt intended t be, fr changing the resnant prperties f the system ASD (g^2/hz) Input at ABC Interface Frequency (Hz) Frce Limited Input (Example) Unntched Input

6 Prgress in Reducing Vibratin Levels n NPSCuL 6 Redesigned NPSCuL - Isgrid Isgrid techniques were utilized t reduce amplificatin by increasing stiffness withut increasing verall mass Mves fundamental frequency frm ~50 Hz t ~75 Hz NPSCuL adapter ring and base plate were unified int a single part t reduce amplificatin frm rcking mdes Increased stiffness results in reduced benefit frm FLVT in verall G RMS fr the ABC input N significant change in G RMS between isgrid and baseline NPSCuL when using FLVT set-up *Reference: Kaushish, V., Frce limited vibratin testing and subsequent redesign f the Naval Pstgraduate Schl CubeSat launcher, Mnterey, CA: Naval Pstgraduate Schl, 2014.

7 Next Step Islatrs n NPSCuL Implement islatrs with FLVT t reduce P-POD envirnment n NPSCuL Eight (8) COTS islatrs incrprated between adapter ring and baseplate Attaches t the LV interface using eight (8) f the 24 fastener lcatins n the 15 ESPA standard 4/23/2015 Prgress in Reducing Vibratin Levels n NPSCuL 7

8 Prgress in Reducing Vibratin Levels n NPSCuL 8 Islatr Installatin Cnfiguratins Cnical brad-temperature-range (BTR) silicne islatrs (LORD AM ) cnstrained using tw (2) methds Methd 1: Fastener that ges thrugh supprted unit is threaded int supprting member Elastmer is cnstrained in cmpressin, tensin, and shear Effectively lwers the CG f NPSCuL by 0.9 with little reductin in jint stiffness Methd 2: Typical installatin fr true islatin behavir Elastmer is allwed t deflect as intended by vendr Generally recmmended fr use in cmpressin nly Significant change t jint stiffness and lwers the CG Use in tensin is assessed n a case-by-case basis Methd 1 Methd 2

9 Prgress in Reducing Vibratin Levels n NPSCuL 9 Islatr Test Set-Up All NPSCuL cnfiguratins, integrated with 8 P-POD Mass Mdels (P2M2s) and a SAD EDU, were subjected t the fllwing tests in each axis Fixed-base 0.5 G sine sweep, Hz Un-ntched and frce-limited ABC levels, 7.6 Grms randm acceleratin input (MPE) FLVT is still necessary t reduce cnservatism during test Cnfiguratins are referred t as fllws: Cnfig 1: Baseline (n islatrs, riginal NPSCuL structure) Cnfig 2a: Baseline with cnstrained islatrs (Methd 1) Cnfig 2b: Baseline with islatrs, typical installatin( Methd 2)

10 Dynamic Prperties f Cnstrained Cnfiguratin Islatr system is nt effective in lateral directins when cnstrained First fundamental frequency in X, Y axes shifted lwer by 15 Hz Mst likely attributed t a lwer CG Islatrs behave as expected in Z axis Indicative f much lwer respnse after the 1 st fundamental mde 4/23/2015 Prgress in Reducing Vibratin Levels n NPSCuL 10

11 Prgress in Reducing Vibratin Levels n NPSCuL 11 Dynamic Prperties f Typical Installatin Cnfiguratin Typical behavir fr basemunted islatrs n a bx-like structure Results in tw (2) distinct mdes in each axis and n amplificatin f higher rder mdes Islatin system appears t prduce a tuned-mass damper effect Anti-resnance f islated system ccurs at fundamental frequency f baseline NPSCuL Peak at 1560 Hz in Z-axis is an FLVT plate mde Lwer apparent mass results in lwer respnse in all axes

12 Prgress in Reducing Vibratin Levels n NPSCuL 12 Perfrmance Summary Significant reductin in P-POD interface envirnment with islated NPSCuL Lwer CG nly cntributes ~30% f ttal G RMS reductin Qualificatin G RMS levels wuld be less than current acceptance G RMS X- Axis G RMS (Wrst- Case) Grms Overall Grms, ABC Frce- Lmited X Axis Level Acceptance (MPE +0dB) Prtqual (MPE +3dB) Qual (MPE +6dB) Base (Input) P- POD Interface, Cnfig 1 P- POD Interface, Cnfig 2b Cnfig1 Cnfig2 Cnfig2a *Envelpe f develpment test data (P2M2s)

13 Prgress in Reducing Vibratin Levels n NPSCuL 13 Cmbined Effects f FLVT and Islatin Islatin system alne is effective in reducing G RMS, but cnservatism is still further reduced with FLVT Frce-limited vibratin test setup is still beneficial and plays an integral part in reducing the P-POD respnse Overall Grms Envelpe, ABC Unntched Overall Grms Envelpe, ABC Frce- Limited Grms Grms X Y Z Axis Cnfig1 Cnfig2 Cnfig2a 0.00 X Y Z Axis Cnfig1 Cnfig2 Cnfig2a

14 Benefits fr the CubeSat Cmmunity Prvides a COTS islatin system fr NPSCuL and CubeSats Islatin system fr larger satellites (greater than 500 lbs) exist, but are ften missin-specific Applicable t ther ESPA-class spacecraft f similar size Cst f NPSCuL islatin system is ~$2000 fr 35-85% reductin in randm vibratin envirnment Cnsiderable cst reductin ver existing industry custmized spacecraft islatin fr similar perfrmance* Prpsed islatin system is cmpatible with ESPA and PSC MLB interfaces and can be easily altered fr use with any ESPA-class interface Main design parameters include mass and munting cnfiguratin n LV *References: Wilke, P., Jhnsn, C., Grsserde, P., Sciulli, D., Whle- Spacecraft Vibratin Islatin n Small Launch Vehicles, Smart Structures and Materials 2000, Damping and Islatin, Jhnsn, C., Wilke, P., Pendletn, S., SftRide Vibratin and Shck Islatin Systems that Prtect Spacecraft frm Launch Dynamic Envirnments, 38 th Aerspace Mechanisms Sympsium, /23/2015 Prgress in Reducing Vibratin Levels n NPSCuL 14

15 Cnclusin and Path Frward Effective and lw-cst slutin t prvide a first-class ride t space fr CubeSats and small spacecraft Investigating ther COTS islatrs f cmparable size that can be used in tensin, cmpressin, and shear withut cmprmising islatr effectiveness Typical islatr installatin cnfiguratin in tensin with current islatr may be investigated Qual test will be perfrmed with final islatr selectin 4/23/2015 Prgress in Reducing Vibratin Levels n NPSCuL 15