H T S AG H T S HTHGA APA. February 23 rd, 2005 BepiColombo Technology Status Review ESTEC, Noordwijk. BepiColombo: TSR, February 23 rd, 2005

Transcription

1 H T S H T S AG February 23 rd, 2005 BepiColombo Technology Status Review ESTEC, Noordwijk Page 1/14

2 H T S APA Design Overview Two axes antenna pointing mechanism, equipped with: Preloaded thin section four point contact bearings Structure and main gear wheel made of Dispal Stepper motors with planetary gearheads and integrated anti backlash pinions Rotary joints and waveguides for X- and Ka-band Inductosyn position indicator Cable wrap design with open housing Page 2/14

3 H T S Preloaded thin section four point contact bearing Offers possibility for lightweight mechanism 440C material for all components Can be used up to 319 C (special heat treatment required) Candidate dry lubricants: MoS 2 (up to 400 C) WS 2 Dicronite (up to 800 C) Silver (up to 800 C) Small built in preload, final preload achieved by fits in housing and shaft Material selection for adjacent structural parts is the most crucial issue Analysis tool for proper preload calculation required and developed Heritage for space mechanism (but in much more benign thermal environment) Page 3/14

4 H T S Bearing analysis for housing and shaft structure made of Aluminium Preload = f(temp, fit tolerances) Calculated figures Starting torque = f(temp, fit tolerances) Lines indicate calculated figures Red dots indicate measured values min. total preload on bearing max. total preload on bearing measured torque predicted min torque predicted max torque preload (µm) torque (Nm) temperature ( C) temperature ( C) Materials with similar CTE required Page 4/14

5 H T S Bearing analysis for housing and shaft structure made of Dispal min total preload max total preload Preload [ m] Temperature [ C] Preload = f(fit tolerances mainly) Starting torque is almost constant over temperature range Bearing stiffnesses are almost constant over temperature range Page 5/14

6 H T S Dispal: A powder-metallurgical material Spray-compacted AlSi 17 Ingot moulded AlSi 17 ;-Aluminium, processed by spraycompacting, a powder-metallurgical process extremely fine-grained and homogeneous micro-structure isotropic material characteristics Properties can be varied in a wide range according to specific needs Solves CTE mismatch problem for bearing fits and preloads Same low density as Aluminium Qualification of material for each batch required Loss of strength at elevated temperatures (but less than Aluminium) Page 6/14

7 H T S Properties of Dispal R m R p0,2 A 5 E ρ α = Tensile strength ultimate = Tensile strength yield = Elongation at break = Modulus of elasticity = Density = Coefficient of thermal expansion Page 7/14

8 H T S Surface treatment of Dispal (for use as gear wheel material) NISLIDE Nickel layer Dispal Standard Aluminium surface treatment processes are not possible due to high content of Si NISLIDE process investigated Chemical refined nickel-phosphor layer with homogeneous integrated PTFE particles, built up on a pure nickel layer True to size application Machinable Measured hardness: 450 ± 50 HV Page 8/14

9 H T S Stepper motor European supplier: Phytron US-supplier: CDA Intercorp Dedicated bearing fits for working temperatures from -270 C to +300 C 2 motors procured for the HTHGA pointing mechanism breadboard: stainless steel bearings, Dicronite lubricated ceramic bearings, no lubrication Reasonable hardware cost Co-operation is quite difficult Limited (no?) space heritage Materials with similar CTE allow temperature working range from -270 C to +300 C for the same unit Extreme expensive Good co-operation Large space heritage Page 9/14

10 H T S Planetary gearhead Swiss-supplier: Gysin Stainless steel design with similar CTE allow temperature working range from -270 C to +300 C for the same unit Integrated anti backlash pinion (HTS design) Lubrication defined by HTS DLC (diamond like carbon) coating of gears DLC known as excellent lubrication system in atmospheric condition For vacuum application implementation of additional H2 molecules required Dicronite coating of bearings No lubrication of main gear pinion Page 10/14

11 H T S Rotary Joint German-supplier: Spinner GmbH New supplier for space application Huge heritage in terrestrial applications Design Aluminium housing Stainless steel bearings with Dicronite lubrication Current design temperature = 180 C structural integrity up to 300 C reduction of RF-performance for higher temperatures Page 11/14

12 H T S Inductosyn position indicator No European supplier found US-supplier: Inductosyn International (Ruhle) Temperature limit for BB unit = 170 C No thermal limitations for the measurement principle as long as the unit maintains its structural integrity Technical solutions up to 300 C are feasible, however it would be quite expensive Reasonable cost for units up to 240 C Page 12/14

13 H T S Harness Cables Connectors No space qualified harness for temperatures >200 C found Harness for industrial applications for temperatures >300 C available Military and commercial aircraft specified harness for temperatures up to 260 C No space qualified connectors for temperatures >125 C found High temperature connectors for industrial applications: Standard materials: up to 200 C Glass-ceramic design: up to 450 C Page 13/14

14 H T S Summary & conclusion Components with high temperature limitations Bearings: <= 319 C space qualified Actuators: <= 300 C space qualified Dry lubrication: > 300 C lubrication system to be qualified Position indicators: <= 300 C technically feasible Cables: > 300 C industrial application Connectors: > 300 C industrial application Rotary joints: n.a. temp. limited by materials and bearings continuous drop of RF performance Nislide coating: <=260 C industrial application Conclusion: It is technically feasible to build and qualify a pointing mechanism for continuous operation at an environmental temperature of 250 C. Page 14/14