1 / 11

Space Environment

See Table: SMAD p. 305 for directory to Spacecraft design constraints. Space Environment. Radiation (SMAD 214) UV Ionizing TID SEU Disturbances (SMAD 366 - 367) Gravity Gradient Magnetic Solar Pressure Aerodynamic Self-disturbances. Vacuum ( various ) Outgassing TVC

trixie
Download Presentation

Space Environment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. See Table: SMAD p. 305 for directory to Spacecraft design constraints Space Environment • Radiation (SMAD 214) • UV • Ionizing • TID • SEU • Disturbances (SMAD 366 - 367) • Gravity Gradient • Magnetic • Solar Pressure • Aerodynamic • Self-disturbances • Vacuum (various) • Outgassing TVC • Vacuum welding • Heat transfer • Drag (SMAD 144, 209) • Atomic Oxygen (SMAD 211) • Debris (SMAD 840) • Natural • Synthetic Engin 176

  2. Space Environment - i • Vacuum • Outgassing http://epims.gsfc.nasa.gov/og/ • Max TVC in % is specified - usually 0.5% • Problems with outgassing: • Destroys materials (brittle, flaking, delamination, adhesives, colors) • Re-condense on sensitive surfaces (especially cooled ones - optics) • Disturbance torques (usually minor) • Vacuum welding • Zero lubricant or contaminant to separate surfaces Galileo: Vacuum Welded Engin 176

  3. Space Environment - ii • Vacuum • Outgassing • Vacuum welding • Heat transfer (see future lecture but for now…) • Heat balance is radiative only (sun, earth, space) • => periodic inputs in LEO, t = 1/r2, • All collected solar energy goes somewhere (solar panels as radiators) • No fluid convection - even in pressurized regions • Fans are suspect and often don’t help • Lightweight structures and adhesives (eg RTV) are poor conductors Engin 176

  4. Space Environment - iii • Drag • 1/2 rv2 x A x Cd (calc @ 300 km = STS / Station)= 0.5 x 10-11 kg/m3 x (7500) 2 m2/s2 x 22 m2 x 2 = 0.001 kg m / s2 (Newton) to 0.01 N for 10x r => Acceleration = F/m ~ 10-4 N = 10-5 g and Orbit lifetime 10 to 50 days (note Cd > 1 and dependence on ballistic coefficient) • Solar Activity • Roughly factor 10 variation over solar cycle • Atomic Oxygen • Only a factor with propulsion (otherwise you’ll deorbit first) Engin 176

  5. Space Environment - iv • Debris • Natural • Synthetic • Rockets and spacecraft are commonly debris controlled but accidents do (rarely) happen • Arthur Clarke “end of LEO” prediction • Collision mechanics, the cheese cutter and tethers Engin 176

  6. Space Environment - v • Radiation • UV: materials degradation problem - optics, adhesives, organics • Ionizing • SEU: EDAC, fast processing, hard storage, watchdogs & rebooting • SEL: Current detection, watchdogs & power cycling • TID: Accumulated damage, mainly from protons - well characterized and quantified - 10 krad is standard part tolerance - how do laptops work in STS? (LEO, low I, shield, short duration) Engin 176

  7. Space Environment - vi • Disturbances (SMAD 366 - 367) • Gravity Gradient • Magnetic • Solar Pressure • Aerodynamic • Self-disturbances (eg bearing noise, magnetics, crew motion & mechanisms) Engin 176

  8. Environmental Torques Torque Drivers Torque Magnitude Key Equation Assumptions (Newton-meters) Aerodynamic Area, Length, 2.5 x 10-4 T= 1/2rAV2(cp-cg) h=300 km; A=1m2 Orbit Altitude cp-cg = 0.1m Gravity Inertia ∆ 3.0x10 -6 T=3(w)2 x ∆I 100 minute orbit Gradient Orbit Altitude ∆I = 1 kg - m2 Stray Magnetic Current Loops 5.0 x 10-6 T = Dipole X Bfield LEO Bfield Magnetics 1A-t-m2 current loop Solar Pressure Area vs. CG 4.5 x 10-7 T=4.5x10-6 xAx (cp-cg) 1 m2 @ 0.1m Leaks / Leak rate, location 2.0 x 10-4 T=m’Ve(L-Cg) 0.1 gm/s, Ve=20m/s Outgassing L - Cg = 0.1m Torque Bearings 1.0 x 10-8 (Empirical) Manufacturer’s Noise Lubrication Specification Thermal Materials 5.0 x 10-1 T=dX/dt2 x M x (∆Cg) dX/dt = 1 m/s in 10s Flex 5kg, ∆Cg =1m Meteor Meteor Mass 10-1 T=Mm x Vm = ∆Cg Mm = 10-6 kg, non-spinner Vm = 106 ∆Cg = 0.1m Engin 176

  9. For Next Week (Feb.6) • 7 - Radio & Comms • 8 - Thermal / Mechanical Design. FEA • 9 - Reliability • 10 - Digital & Software • 11 - Project Management Cost / Schedule • 12 - Getting Designs Done • 13 - Design Presentations • 1 - Introduction • 2 - Propulsion & ∆V • 5 - Attitude Control & instruments • 4 - Orbits & Orbit Determination • 3 - Launch Vehicles • Cost & scale observations • Piggyback vs. dedicated • Mission $ = 3xLaunch $ • The end is near? • AeroAstro SPORT • 6 - Power & Mechanisms • Reading • SMAD 18 • SMAD 17 (if you haven’t already) • TLOM 16: Launch sites Engin 176

  10. Homework Questions Review • 2 - Trip to Phobos: Space Environment • Assume cubic spacecraft of 2m characteristic length • What is P(impact) with object of dimension 1 mm3 or larger during 4 year interplanetary cruise? • What is Total Ionizing Dose (TID) for the cruise? • What is largest disturbance torque during cruise? What might be #2 and #3? • 1 - Propulsion system for Phobos Landing • Requirements: • Electricity (~100W) (optional) • 1 km/s ∆V - 4 years post launch • Small bursts for ACS en route+ soft landing • 100N deceleration burns (pulse or vernier) • Pick a Propulsion System • Justify via (1 or more of these) • Calcs • Tradeoffs vs. alternatives • Qualitative (bullets?) advantages • Sketch major elements of system • Tanks, pressurization, fluid mgt. • Valves, nozzles, electrical • Thrust Vector Control Engin 176

  11. Design Work and Reading • Design Milestones: • Form teams (3 - 4 members) • Mission Statement • RequirementsDefinition • Reading for lecture #3 • SMAD 18 • SMAD 17 (if you haven’t already) • TLOM 16: Launch sites For your calendar: Feb 26; 2:00 PMEN 194 S07 (Entrepreneurship) Engin 176

More Related