Science A-54 – Life as a Planetary Phenomenon (Spring 2008)
Section 6: Mars Week
All image credits: NASA/ESA
Talk about the design, history, and evolution of real missions to Mars for a bit.
Then start building and testing our own Lego mars rovers.
1. A Brief History of Mars Exploration
First Flyby Missions:
Mariner 3-4 1964, M3 failed on launch. M4 became the first flyby of another planet.
Mariner 6-7 1969, Proved there were no canals or cities. First close-ups of south pole.
Early U.S. Orbiters & Landers:
Mariner 8 1971, Orbiter, failed
Mariner 9 1971, First planet orbiter, discovered Olympus Mons & Vallis Marineris
Viking 1 1976, Orbiter
Viking 2 Orbiter
Viking 1 Lander
Viking 2 Lander
Russian Attempts to Reach Mars:
11 failed attempts before first success (Mars 2 Orbiter, 1971)
Followed by 4 more orbiter failures, 2 more orbiters successes (10 days of data)
2 lander failures, then 1 capsule landed (150 seconds of data). Last attempt was in 1996.
Currently planning a sample return mission from Mars' moon Phobos-Grunt in late 2011 or early 2012.
The Mid 1990's: The Mars Dark Ages
Mars Observer 1992, Blew up (really) just before arrival.
Mars Climate Orbiter 1998, Burned up in atmosphere upon arrival
Mars 96 Russian, launcher failed, fell to Earth
Mars Global Surveyor 1996, First major orbiter in 20 years
The Modern Mars Golden Age
Mars Pathfinder First airbag landing, first rover
Mars Polar Lander 1999 Crashed
Mars Exploration Rover 1 Spirit, Gusev Crater, planned for 90 day mission, currently over 2267 days, geology mission
Mars Exploration Rover 2 Opportunity, Meridiani Planum
Mars 2001 Odyssey High Resolution, mineral mapping
Mars Express Europe’s first orbiter, Super Hi res. plus color and 3D.
Beagle Lander Crashed (British)
Deep Space 2 Penetrators Crashed/Lost
Mars Reconnaissance Orbiter Ultra high resolution
Mars Phoenix Lander Polar Lander Dedux, landed May 25, 2008, confirmed water-ice on mars, showed soil is alkaline (pH 8-9)
Missions Largely Underway
Mars Science Laboratory Lands via Sky Crane. Size of Mini, 60% built, scheduled Oct 14, 2011. Will assess whether Mars ever was or is habitable, able to support microbial life!
Mars Trace Gas Mission Scheduled for 2016, orbiter to map sources of methane and choose Exomars landing site
ExoMars Europe’s planned rover, Mobile Viking-like experiments, faced horrible budget cuts, launch delayed 7 years to 2018 with a much reduced science mission. Mission: to search for biosignatures.
Missions In Planning Stages:
Mars Atmosphere and Volatile EvolutioN (MAVEN), expected launch 2013
Mars Sample Return, possible launch 2018, return 2020-2022
Mars Deep Drill, unknown launch, nominally 2018
Mars Astrobiology Field Laboratory – unknown launch
Notable Non-Mars Missions
Galileo Orbited Jupiter for many years. Stunning moon images. Bad antenna
Cassini Last of NASA's huge flagships. Currently flawlessly orbiting Saturn.
NEAR Orbited & landed on an asteroid (although never designed to land!)
Hayabusa Attempting the first sample return from beyond the moon
Rosetta Enroute to orbit and land on a comet
Deep Impact Probed the subsurface of a comet (now exoplanet hunting!)
DAWN Enroute to orbit the two large asteroids Juno and Ceres
New Horizons aka the Pluto Express. Flys by Pluto-Charon system in 2014
MESSENGER Enroute to orbit Mercury for the first time.
Kepler Hoping to detect the first Earth-like planet
Planned/Proposed Planetary Missions:
Juno Jupiter Polar Orbiter 2011
Neptune Orbiter - cancelled
OSIRIS-Rex - U.S. Asteroid Sample Return
Europa Orbiter - cancelled
Europa Lander – cancelled
Europa Jupiter Space mission – 2020 joint NASA and ESA
2. Spacecraft Design Basics
1. The Essential Components
Multiple radiation hardened computers
Power sources (Solar, Nuclear, Batteries)
Communications (Dish Antenna & Low Gain Antenna (as fail-safe))
2. Objectives and the instruments chosen to meet those objectives
Science Missions and Engineering Missions
Using Proven Technology
"Faster, Better, Cheaper"
"Budget, Schedule, Quality: Pick two."
Both Pathfinder & the movie Waterworld cost ~250M$ (2005 USD)
4. Always trade-offs:
Very tight instrument mass restrictions (mass overruns cascade!)
Orbiters vs. landers
For landers: mobility vs. a stationary platform
5. Choice of landing sites
Safety vs. interest
6. Gradual evolution of missions from one to the next:
3. Example Missions
1. Launched: 1975
2. Twin missions, each with an orbiter and a lander.
3. Landing sites: Chryse Planitia (22.48° N, 49.97° W and Utopia Planitia (47.97° N, 225.74° W)
Mass: 2,325 kilograms (5,125 pounds) with fuel
Objective: High resolution surface mapping
Science instruments: High-resolution camera, atmospheric water-vapor mapper, surface heat mapper,
Mass: 576 kilograms (1,270 pounds)
Power: nuclear (70 watts per lander)
Objective: Life detection
a. CCD stereo color cameras
b. Soil sampler
c. Apparatus for gas exchange experiment, pyrolysis (color assimilation) experiment, labeled
release experiment ; coupled gas chromatograph/mass spectrometer
d. Seismometer (measures abundance of heavy elements)
e. Temperature and Wind sensors
f. X-ray fluorescence spectrometer
6. Cost: $1 billion 1975 dollars (roughly $4 billion in 2010 dollars)
7. Fun fact: Carl Sagan provoked his Viking colleagues into using valuable payload space for a camera by pointing out that their microbial experiments might miss larger life forms, like Martian polar bears
Mars Pathfinder Lander:
1. Launched: 1996
2. One rover, named Sojourner (11.5 kg)
3. Objectives: To demonstrate rover technology and provide geochemical measurements to groundtruth orbital data.
4. Power: solar
5. Landing site: downstream from the mouth of a giant catastrophic outflow channel (Ares Vallis)
6. Cost: $266 million in 1996 dollars, including mission operations (ca $370 million in 2010 dollars)
Mars Exploration Rovers (MER):
1. Launched: 2003
2. Objective: Geological exploration, with particular emphasis on the question of past water on Mars.
3. Landing sites: Gusev crater (interpreted as possible ancient lake) and Meridiani Planum (hematite)
4. Two rovers
a. Mass: 185 kg
b. Power: Solar (100 watts to drive)
5. Cost: $850 million (~1 billion in 2010 dollars) for the pair
Mars Science Laboratory (MSL):
1. Launch: 2011 (expected)
2. One rovers
3. Landing Site: To be determined
4. To expand the exploration program begun by MER; designed for long term (> 2 Earth years) operation, and at least 55 km of travel
5. Mission Goals:
1. Determine the nature and inventory of organic carbon compounds.
2. Inventory the chemical building blocks of life as we know it: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur.
3. Identify features that may represent the effects of biological processes.
4. Investigate the chemical, isotopic, and mineralogical composition of the Martian surface and near-surface geological materials.
5. Interpret the processes that have formed and modified rocks and soils.
6. Assess long-timescale (i.e., 4-billion-year) Martian atmospheric evolution processes.
7. Determine present state, distribution, and cycling of water and carbon dioxide.
8. Characterize the broad spectrum of surface radiation, including galactic radiation, cosmic radiation, solar proton events and secondary neutrons.
6. Mass: est. 900 Kg (9 feet in length)
7. Cost: est. $2.3 billion
Mars Express (European Union):
1. Launch: 2003 (and still going)
2. Orbiter (success) and Lander (failed)
3. Objectives: The Orbiter was designed to provide unprecedented scope and resolution in the imaging and geochemical analysis of the martian surface; it will:
image the entire surface at high resolution (10 meters/pixel) and selected areas at super resolution (2 meters/pixel);
produce a map of the mineral composition of the surface at 100 meter resolution;
map the composition of the atmosphere and determine its global circulation;
determine the structure of the sub-surface to a depth of a few kilometers;
determine the effect of the atmosphere on the surface;
determine the interaction of the atmosphere with the solar wind.
The lander, Beagle II, carried a suite of life detection instruments, but apparently crash-landed into Mars
4. Mass: 113 kg orbiter payload and 60 kg lander
5. Power: Solar
6. Cost: 300 million euros ($471 in 2010 dollars)
Mars Reconnaissance Orbiter (MRO)
1. Launch: 2005
3. Objectives: mapping surface topography, mineralogy, and magnetic properties; also monitors weather phenomena (dust storms, etc.)
4. Power: Solar (980 watts)
5. Mass: 1,031 Kg of hardware, with about an equal mass (at launch) of propellant)
Cost: $720 million
4. Lego Robotics Mars Rovers
You are not building this, but here’s an example:
Learn what it’s like to be an engineer; this is more important than a working robot.
Build a pair of simple Mars Rover analogs that can drive around the section room's "U" shape of conference tables: autonomously, dodging random obstacles, and without falling off!
Intro to Lego Robotics:
USB or Bluetooth link to a desktop computer
5 demo programs
Advanced programs are downlinked from a desktop machine.
4 Input Channels for Sensors (1,2,3,4); in order from left to right in the picture below
Touch Sensor – sends a signal when getting pushed in
Microphone – records sound levels
Light Sensor – records red light levels
Ultrasonic Sensor – detects distance
3 Output Channels (A,B,C)
For 3 Servo Motors.
A servo motor is just a motor that can be commanded to a specific number of rotations, not just a given power level)
Structurally, there are three types of connections (L to R):
Standard Lego: Bricks
Lego Technic: Pins and beams (this should be the majority of your structure)
Shafts and Gears: X-shaped
Many pieces are able to connect between two of these types of connections.
Many strange/special elements to turn corners: building a three-dimensional structure is often the hardest part
Split into two teams
Team 1: Tracks
Team 2: Wheels
Split into sub-groups to build/integrate/test the required components:
Ultrasonic “cliff” sensor
Back “cliff” sensor
Add NXT brick to Chassis
Integrate all the components
Testing, testing, testing
Everyone should have a good opportunity to participate. You can have managers and subcontractors or some other organization.
1 full Lego NXT Robotics Kit for each team.
1 set of spare parts to share between teams.
3 touch sensors, 1 ultrasonic sensor for each team
Plenty of cables
Program Options / Expectations:
Writing the computer program to run your robot is as difficult and time-consuming as building, sometimes more so. The program we have written does the following:
[ Constantly drive unless something happens to the three forward sensors (left/right bumper and ultrasonic). If a bump is detected, stop and move backwards (turning away from the obstacle). If a cliff is detected (by detecting a distance greater than ~6 inches), stop and move backwards (also turning away). As the robot moves backwards, it will check for the back touch sensor: if it is undepressed, it will stop moving backwards. ] The algorithm in the square brackets is constantly repeated until the program is turned off.
For the program to work this is how the NXT brick needs to be wired:
A – left motor
B – right motor
1 – left touch sensor (bumper)
2 – right touch sensor (bumper)
3 – back touch sensor (back cliff sensor)
4 – ultrasonic sensor (forward cliff sensor)
Note that the chassis is oriented so that the motor connectors are in the back. The front sensors must be placed on the other side.
Create your organization
Plan your chassis: Modifications? Mounting points? Wheels?
Divide into sub-groups
Build your Prototype Sensor Modules, do preliminary testing by simulating how these will be used
Integrate your sensors onto your chassis
Wire everything up
Modify your Sensor Modules
Try out the course
Try out some alternate designs?
“Perfect is the enemy of good enough”: your robot won’t be perfect, it just needs to be good enough to fulfill the objective.
Use the right tool for the right job.
Everything takes longer than you think it will.
The last step, full system testing, is the most important and will take a long time.
Keep in mind space for cable connections
NXT box mounting to the chassis need not be perfect. Just good enough to drive!
Think about placing at your forward bumpers various distances ahead of the wheels.
Think about your where to place your ultrasonic sensor (above/below forward/behind the bumpers)
Think about hitting a wall straight on as well as at and angle
Think about approaching a cliff at a sharp angle as well as head on.
Test your individual parts and then test them all together. If they fail, redesign them. Iterate.
Though functional robots work quite well, you should always be ready to catch your robot.
Negotiating between teams for scare parts?
Please help clean up your robots.
What did you learn about being an engineer?