1 Asteroid Sample Return AEM 4332 FDR 5/7/2008 Becky Wacker Carla Bodensteiner Ashley Chipman John Edquist Paul Krueger Jessica Lattimer Nick Meinhardt Derek Steffes Sam Zarovy

Mission Goal Acquire a 1 m deep, 100 g core sample of the asteroid

Mission Objectives 1.Leave orbit about the asteroid and position for landing. 2.Land on the asteroid with drill and return vehicle intact. 3.Attach the spacecraft to the asteroid that withstands a 10 N reaction force and a 0.1 N/m torque from the drill for 24 hours. Structures | Propulsion | GN&C | Telecommunications | Becky 3

4 Requirements Spacecraft must weigh no more than 750kg including: – 50kg payload package (drill and stereo cameras) – 200kg return vehicle The spacecraft must land and support drilling operations for 24 hours Landing must not exceed 15 g’s Spacecraft must support drilling operations: – 10 N reaction force – 0.1 N/m torque

5 Expectations Explain the results of all system and hardware trade studies including rationale for final selections Provide spacecraft layout drawing(s) Demonstrate compliance with all requirements Provide high-level block diagram of the spacecraft subsystems Define system and hardware requirements sufficiently to allow future subsystem architecture definition and hardware trade studies Demonstrate that the landing loads do not exceed requirements and can be supported by the structural/mechanical configuration

Assumptions Orbiter will supply pictures of asteroid to give targeted landing area Asteroid is only gravitational pull in area Orbiter can place lander in preferred initial placement Major Tasks 1 and 2 are most important Key asteroid physical properties a. Rotation period is 5.0 hours b. Semimajor axis: 1.5 AU c. Radius: 10 km (assume spherical shape) d. Mass is 1x10 16 kg e. Surface rock distribution is gaussian with 0.25% probability of a 0.5 m rock in a 5 m 2 area. f. Surface gravity: m/s 2 6

7 Major Tasks 1) Perform a trade study of approach, landing and anchoring options which considers: a. Control system architecture b. Structural impact loads c. Anchoring mechanism d. Propulsion system options 2) Develop a spacecraft layout including a. Mechanical/structural configuration b. GN&C sensor locations and field-of-view (FOV) clearances c. Location and orientations of reaction control system thrusters d. Telecommunication component locations including antenna FOV clearances

Major Tasks Cont. 3) Identify major hardware components of each spacecraft subsystem a. Guidance, Navigation, and Control b. Command and Data Handling c. Electrical Power d. Telecommunications e. Propulsion f. Structures and mechanisms g. Thermal control system 4) Define the key system and hardware requirements 5) Determine landing loads and associated structure/absorber sizing 8

9 Team Organization

Layout

Attachment Method

Initial Trade Study IdeaHow worksProsCons Spikes on ImpactDrive stakes in when land from legs Don’t need separate propulsion system (less weight) Highest probability for success Leaves nothing behind HarpoonShoot something out and reel ourselves in Compensation torques Probably use more fuel Way more mechanisms involved Possibly get tangled to roll back up. Thrusters Propulsion Only Use thrusters to hold in place Extra fuel Torque when drilling Need momentum wheel, “spikey feet” Cork ScrewScrews into ground like a cork screw into a cork Not a high resulting force Complicated mechanisms and possibility of stirring soil instead of screwing in Spikes Post-ImpactTwo arms with small explosion that would rotate and come back while nailing into the ground Would work…kinda Able to retry Even more complicated than harpoon

Initial Trade Study Cont. ThrustersHarpoonSpikes on ImpactSpikes Post- Impact Corkscrew WeightBad GoodOkayBad Mechanical Complexity GoodBadGoodOkayBad Fuel Consumption BadGood OkayGood Power Requirements GoodBadGood Bad DependabilityGoodBadOkayGoodBad Applied LoadsGood BadOkayGood ReusabilityGoodBad Okay

Attachment Method Use Mechanical fastening system based on Hilti Gun model DX E72. Assume built weight for guns to be same as hilti gun (2kg ea.). Use F=m(v/t) to determine force from anchor deployment. t is assumed to be 0.01 s Determine required Thrust and Fuel based on Force. Deploy two anchors simultaneously at 45° to reduce thruster requirements. Assume 30s to deploy all 4 anchors Use Anchor based on future research.

Attachment Method.22 caliber powder actuated fastening tool Drives up to 2.8” nails into concrete or steel 2 kg each 15 Structures | Propulsion | GN&C | Telecommunications | Becky

Reaction Force Ballistics information found at: Used: Remington.22 Short CB Cap Bullet Weight = 1.87 g Velocity = m/s Force from Attachment = (213.36/.01)*(1.87/1000)=39.898N per anchor

Spike deployment requires a 21 N force from the 4 thrusters pointing in the +Z direction using a safety factor of 1.5 Attachment Method Cont. Spacecraft +28N -28N +28N Gun #1 Gun #2 17 Structures | Propulsion | GN&C | Telecommunications | Becky

Thrust and Fuel Requirements Using Moments = 0 and forces = 0, 21N force required from all 4 thrusters pointing in the positive Z direction. X direction forces cancel each other out, resulting in 56 N force. 56/4=14*1.5(safety factor)=21N/per thruster (Need Fuel Req. From Nick)

Further Work Required Make gun space worthy -solid rocket propellant instead of gun powder -space worthy construction material Test force required to insert nails -soil testing experiments Determine spike specifications -force experiments