Asteroid Sample Return

Progress as of 3/12/2008

GN&C

Sensor Data

Star Tracker

• Galileo Avionica A-STR Autonomous Star Tracker

• FOV: 16.4 X 16.4˚• Power Consumption: 8.9 W at 20˚C

13.5 W at 60˚C• Size: 195 (L) X 175 (W) X 288 (H) mm• Mass: 3 kg

IMU

• Honeywell Miniture IMU• Mass: 5 kg• Size: Unknown• Power Consumption: Unknown• This device has very little information

available to us.

Altimeter

• Yet to be decided upon discussion with Steve

High Level Control System

Control Inputs – Reaction Jets Vehicle Dynamics

Sensors-Star Tracker

-IMU-Altimeter

Planned Trajectory

Telecomm

• Waiting for answers to questions

Approach of Asteroid

• GN&C has developed a code that gives the required delta v based on the point where the free fall begins.

• This will be finalized once the structures group determines what impact loads are acceptible.

Propulsion• Propulsion has developed a code to determine fuel

needs based on the delta v requirements and thrust for attachment.

• Code provides suggestions for tanks and thrusters required for mission based on data retrieved through web research of thrusters and tanks.

• Final fuel requirements are based on thrust requirements for attachment, which depends on final structure design

Structures Work so Far

Force needed to hold Spacecraft

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Finding Needed Torque offset due to drill

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Initial Sketch of Spike and Holding MethodSpike 3 inches in length and ¼ inch in diameter

Spike exits through hole in foot and head of spike clamps down on foot

Barbs on spike increase surface area and holding power in ground

Attachment Method• Use Mechanical fastening system based on Hilti Gun

model DX E72.• Assume built weight for guns to be same as hilti gun. • Use F=m(v/t) to determine force from anchor

deployment.• t is assumed to be .01 s• Determine required Thrust and Fuel based on Force.• Deploy one anchor at a time to reduce thruster

requirements.• Assume 30s to deploy all 4 anchors• Use _____ Anchor based on research.

Hilti Gun DX E72

• .22 caliber powder actuated fastening tool

• Drives up to 2.8” nails into concrete or steel

• 2 kg each • Modify Design using

space worthy materials

http://www.us.hilti.com/holus/modules/prcat/prca_navigation.jsp?OID=-16951

Reaction Force

Ballistics information found at: http://www.korabrno.cz/bal-22.htmlUsed: Remington .22 Short CB Cap

• Bullet Weight = 1.87 g• Velocity = 213.36 m/s• Force from Attachment =

(213.36/.01)*(1.87/1000)=39.898N per anchor

Thrust and Fuel Requirements

• Using Moments = 0 and forces = 0 • T1=40(L/L=a) + (40-M)• T2=40(L/L=a) - (40-M)• T1 – thrusters on same side as anchor• T2 – thrusters on opposite side as anchor• M – Mass*g • g=.006

Anchor Specifications Ideas

Trade Study

• (Final trade study between mech. And thruster methods will go here)

• At this point estimated fuel usage for 24 hr bun is ~ 300kg

Initial Trade StudyIdea How works Pros Cons

Spikes on Impact Drive stakes in when land from legs

Don’t need separate propulsion system (less weight)Highest probability for successLeaves nothing behind

Harpoon Shoot something out and reel ourselves in

Compensation torquesProbably use more fuelWay more mechanisms involvedProbably get tangled to roll back up.

ThrustersPropulsion Only

Use thrusters to hold in place

Extra fuelTorque when drillingNeed momentum wheel, “spikey feet”

Cork Screw

Spikes Post-Impact Two arms with small explosion that would rotate and come back while nailing into the ground

Would work…kindaAble to retry

Even more complicated than harpoon

Initial Trade Study Cont.Thrusters Harpoon Spikes on Impact Spikes Post-

ImpactCorkscrew

Weight bad bad goodish okay Bad

MechanicalComplexity

Good (best)

BAD good okay BAD

FuelConsumption

BAD good good okay good

Power Requirements

good bad good good Bad

Dependability good bad okay good Bad

Applied Loads good good bad okay good

Reusability good bad bad okay okay

Methods in bold font further researched to come to final decision.

Mass Budget

• Mass budget is under construction.