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Revision as of 19:19, 16 May 2021
|Johan van Tien||1455788||MEemail@example.com|
The great unknowns of space might soon be less unknown; various government and private space exploration companies have started projects to discover Mars, the nearest planet where life might be possible. But, it might not the only one, as possible conditions for primitive life can be found on a moon of Saturn as well: Titan.
Titan features a dense atmosphere of nitrogen and methane. It is the only other spacial body to have surface liquids (beside Earth). Beneath its surface, it possibly features a layer of ice and liquid water. Although the conditions are not perfect for earth-like life, it could form the base for lifeforms of other kinds.
The goal of this project is to design a system to search for life (or traces thereof) on the surface of Titan. As Titan is far away from earth, communication is restricted; this means the system will have to independently be able to discover the unknowns of the planet. Using AI the device will have to navigate, identify points-of-interest, and hopefully discover life on Titan.
The conditions on Titan are harsh. [...]
Since Titans distance from earth, communication is delayed by 70 to 90 minutes. This means that if the vehicle gets stuck, it will cost over an hour before that information arrives on earth, and then double it before commands to get unstuck arrives back at the device. This complicates control of the device, thus it will have to be able to navigate and discover independently, with as few human interventions as possible.
Something about Astrobiology
The device should be able to do the following:
- To safely arrive at Titan
- Move around on Titan without need of human intervention
- Identify (evidence of) lifeforms
- Communicate findings back to earth, possibly via a satellite or other external device
This paper describes GESTALT, a program used to autonomously navigate the Martian surface.
There is blind-drive, which is the simplest method to reach a goal. It speaks for itself, it is a blind drive, there is no hazard detection.
With the AutoNav, the rover detects obstacles and hazards and autonomously avoids this. The paper then goes more in-debt about AutoNav. The approach has its similarities with the Robots and AI course NetLogo assignment.
An idea for a deliverable is to try and alter/expand/improve that assignment or use it as a base to come up with a path-finding algorithm. Another idea is to chose an instrument we like, and further work on that. For example further investigate the SAM, and maybe try to improve on its size. Which now has the size of a microwave.
In space exploration, the lines between User, Society and Enterprise are often more vague than in other fields. This is because one entity can be in all three groups at once, with the main example being NASA.
NASA is a User of the satellites and spacecrafts that are in space, using them to conduct research in many different topics.
NASA is also Society, since it is a government driven and funded entity. NASA has its own administrator, but the decision making is also heavily influenced by Congress.
Lastly, NASA has a major role in Enterprise, not to make profit themselves (since they’re funded by the Government), but to fund other companies that build rockets and satellites.
So the Governmental space administrations usually fall in all three categories. Besides that, there are the companies, who usually fall in the groups User and Enterprise, and the scientists, who fall in the groups User and Society.
- Space agencies
- Governmental: NASA, ESA, JAXA, Roscosmos
- rockets: ULA, SpaceX, Boeing, Blue Origin
- satelites: JPL, Lockheed Martin, Orbital ATK, Universities
(To be edited) Satisfying our curiosity further our understanding of
- planetary biochemistry
- formation of planets/moons
Long term: Everyone
(to be edited) Enterprise:
- Space agencies
- Governmental: NASA, ESA, JAXA, Roscosmos)
- Commercial: SpaceX, Blue Origin
To approach the project, milestones are created in hopes of setting realistic goals which can be acheived on a weekly basis. These goals will span for the entirety of the project timeline. Note, these will change throughout the project, as the type of deliverable is still not set in concrete. Once this is decided many of the milestones can be removed or ammended. Below the milestones can be found in a chronological order. These will be used later to create a project plan which can be modified throughout the project.
- Project Decision
- Project Plan
- Research (25 papers - 5 P.P.):
- Complete USEr research
- List of topics for WIKI
- RPC List
- Start looking into design solutions
- Specify Deliverable
- Prototype/deliverable development of idea
- potential deliverable programs/software
- what would be used to create deliverable/software.
- Update project plan for prototype/deliverable
- Additional research (if necissary)
- Begin developping prototype
- Addapt WIKI page with new information
- Run primary test on prototype
- Fix any issues with prototype and further develop it
- Complete Prototype
- Test Prototype deliverable
- Final testing of deliverable
- Fill in missing information from WIKI
- Finalize WIKI
- Get to Titan, the device must be able to reach Titan.
- Durability, the materials the device is made of must be able to sustain the environment, meaning it should not erode quickly or react chemically with Titan's atmosphere or surface.
- Survivable, the device should be able to handle temperatures as low as 90K, and be able to deal with winds of up to 34m/s (122km/h)
- Longevity, there must be an energy source on the device that enables the device to collect sufficient data.
- Autonomy, with light having to travel 60 to 90 minutes from Earth to Titan the device must be able to operate (partly) autonomously since it cannot be directly controlled from earth due to the massive 'input lag' caused by the distance between Earth and Titan.
- Consistent communication, the device should be able to communicate in a consistent format with Earth.
- Navigation, the device should be able to navigate Titan without getting itself stuck.
- Ethical treatment, when life is encountered the device should be able to recognize this and act accordingly.
- Flexible ways of travel, the device should be able to travel across both land and lakes/rivers and should be able to traverse canyons as well.
- Redundancy, when vital components stop working, it should have redundant backup parts such that it is able to function again afterwards.
- Simulation, the device should have a proper model to simulate the device's behavior on Earth for verification.
- Obtaining data, the device should be able to obtain data via camera, infrared, and XXX(?).
- In case of rover: Geo-locate, the device should be able to identify its location on the surface.
- In case of Satellite: Orbital-location, the device should be able to identify its current position with reference to its orbit.
- Use ready data: data obtained from the device should be formatted in a way that it is ready for use. E.g. maps should be directly renderable in GIS.
- Constant data flow, such that information passes to and from the device continuously.
- sustainability, the material used should have the potential of being recovered, and if not, should be safe to leave on titan without causing damage to the enviroment, or when in orbit would not create space debris.
- Universal Program, the code written for the operation of the device (in all cases) should not restrict the availability of potential imput from other software, and should allow a large range of possible contribution.
- Maximum size, the device must fit into the rocket so it can be transported.
- Maximum weight, the device cannot weigh more than (to be determined) in order for the rocket to launch properly.
- Cost/Realizability, the device/mission has to be approved by a governmental Space Agency (probably NASA), to get funding.
Logbook and Structure:
For a thoroughly catalogued timetable of the work contributed by team members, the Logbook Group 5 is used.
The hours mentioned within this logbook correspond to the Project Plan Adaptable Structure, where-in a continuously modified to-do list is given, as well as the priority of each task, and how far developped these tasks are.
Conditions of Life
To be able to 'find life', the priliminary problem is determining how this can be done. Therefore, before describing how we can find life on Titan, an investigation into what signs of life are has to be made. The following subsection is dedicated to this, as well as elaborating on the different forms of life. Once this has been thoroughly covered, the instruments used to do this can be further explained.
There are three mayor components that need to be met in order for life to be able to exist on a planet:
- Energy, this is needed in order to fuel chemical reactions like metabolism. A form of energy would be warmth which would be a concern for Titan as it has an average surface temperature of 90 to 94 K. This doesn't make life on Titan impossible though since certain extremophiles might still be able to live there. For example, the tardigrade is a micro-animal discovered on Earth that is able to survive temperatures near zero Kelvin.
- Protection from UV radiation, ultra violet light can damage or even break complex molecules which impedes the existance of complex life. Luckily, Titan's atmosphere is able to block most UV radiation similarly to Earth's ozone layer is able to do this meaning this condition is satisfied everywhere on Titan.
- Complex chemistry, Life as we know it on Earth is able to extract energy from its environment in order to survive via various methods. These methods require certain specific molecules to exist as building blocks on the planet. These methods create different molecules that would otherwise never have existed as waste products. These waste products and building blocks are called biosignatures and are a great indication of life having existed in either the present or past.
The organisms on Titan will not be similar to those usually found on earth, but rather be what we call 'extremophiles', organisms that thrive in what normally is considered harsh conditions. The lack of oxygen but availability of methane in the atmosphere suggest that if there is life on the surface of the moon, it will likely be adapted to use it. These organisms use what is called "reverse methanogenesis", in which methane and sulfate are transformed into bisulfide, bicarbonate and water. These chemicals, and their derivatives, could be indications of life. If a researcher would want to investigate this kind of life, a good chance would be to send the rover to one of the methane lakes on the surface.
Alternatively, there could be a type of anaerobe organism, who does not require oxygen. Various types can be found on Earth, which range from having a metabolism that could survive in case it lacks oxygen to being poisoned and killed by any oxygen. These organisms can be sorted into three categories:
- Facultative anaerobes (which can use oxygen, but can also thrive without it)
- Aerotolerant organisms (which can deal with oxygen but does not use it)
- Obligate anaerobes (which cannot thrive in environments with oxygen)
It is likely that if there's life on Titan of this type, it would be of the latter two types. The chemical processes used in these kinds of lifeforms instead of the regular air-based cycle can vary greatly. And with each alternative cycle, there are different extraneous substances that can be traced. However, using the (known components of the) environment of Titan, we can identify a set of likely process and use their by-products as potential markers for Titan life.
These traceable by-products consist of various metals in certain electron configurations and (bi-)sulfide. table with all the processes
Biosignatures are “features that must be sufficiently complex and/or abundant so that they retain a diagnostic expression of some of life’s universal attributes” (Des Marais et al. 2008). Another essential characteristic is that their formation by nonbiological processes be highly improbable. Informational biopolymers like DNA or polypeptides, for example, would be examples of biosignatures that are highly unlikely to arise in the absence of biology. These concepts govern the selection of candidate biosignatures, which are ranked by how well they pass three criteria: reliability (i.e., a feature that is more likely to be produced by life), survivability (i.e., the ability of the biosignature to be preserved or otherwise persist in its environment), and detectability (the likelihood that the biosignature can be observed or measured) (NASEM 2017; Meadows 2017; Meadows et al. 2018b). Using these rankings, features of life were listed by NASA in the 'Ladder of Life Detection'.
NASA’s curiosity rover is equipped with several cameras and sensors. Generally speaking they consist of the following:
- Radiation Detectors
- Environmental sensors
- Atmospheric sensors
The cameras are used for visualization and orientation during descent and exploration.
- Mahli – microscopic imaging – Identify minerals in a rock or debris->Indication of life
- Mardi - provides view during descent for better exploration path planning – For NASA data is send back to earth after landing so the so-called Earthbound planners can plan the route for the rover. This could be an interesting part to further look into as this could possibly be extended with some AI-features. Like recognizing patterns and planning the route itself.
Spectrometers are commonly used in chemical analysis. These devices can separate matter by their mass for example.
- APXS – radiation detection for types of elements
- ChemCam – uses laser and spectrometer to vaporize and analyze the chemicals
- CheMin – spectrometer
SAM (sample analysis)
- Gas chromatograph
- Mass spectrometer
- Tunable Laser Spectrometer
- RAD – radiation assessment detector – for future human exploration
- DAN – detection subsurface water
- REMS – weather station
- MEDLI – collect engineering data during descent into atmosphere – material study
Conclusions that can be drawn from this, is that there are different sensors for different end-goals. Observation, navigation, material study via various ways(taking samples or collecting data on radiation), a weather station and collecting data entering the atmosphere. Keep in mind this is only from NASA’s Curiosity rover. NASA’s perseverance rover is an upgraded version with solar-powered drone, which I have not looked into much deeper.
From what we have discussed so far, it is best to focus our interest in the material study and navigation.
Further investigation into Ingenuity (the mars helicopter)
Because Ingenuity is only built to test if a 'drone' of sorts can fly on Mars, it does not have the same collection of sensors and cameras as the curiosity rover or preservance. That being said, there is an extremely high level of engineering dedicated to the flight of Ingenuity, which could be taken into account when considering our own hardware end product. Whilst Ingenuity is the pinacle of technological advancements (considering it is the first UAV to fly on Mars), it is still quite rudementary with the following Hardware:
- Body: 0.136 m x 0.195m x 0.163m (cubic shape)
- Landing 'legs' 0.384 m (length)
- Rotor Diameter: 1.2m
- Height: 0.49 m
- Landing mass: 1.8 kg with 273 g tatal mass of batteries
- Power output: 350 W
Further investigation into Ingenuity Gives the following flight characteristics:
- Rotor speed: 2400 rpm
- Blade tip speed: <0.7 mach
- Operation time: 1-5 flights within 30 sols
- Flight time: Max. 120 seconds per flight.
- Maximum flight range: 600 m
- Maximum radio range: 1000 m
- Maximum planned attitude: 10 m
- Maximum speed:
- Horizontal: 10 m/s
- Vertical: 3 m/s
- Battery capacity: 35-40 Wh
From these fundemental statistics of the Ingenuity copter, we can conclude the following. Whilst this is an impressive feat to achieve (flight on Mars of a UAV), it is not nearly sufficient for what we would be planning and therefore several adaptations would need to be made. Most notably, as greater flight times would be expected (with greater max. alttitude & range), a greater radio communication range would be required. For any of this to be implemented, greater dimensions would be required. This also means that greater batteries would be needed, and much larger rotor speeds would be almost manditory. Therefore, further investigation into how this can be done needs to be made.
In hopes of satisfying the USEr, we want to focus on key aspects of the project, most notably the deliverable. This can be done by taking several assumptions, most notably the spacecraft used, the size of the payload, the weight of the payload and any other details which would prove relvant to the problem, but irrelevant to the final deliverable. In hopes of doing this, the assumptions made will be further elaborated here.
In order to reach Titan's orbit, a sufficiently large exit velocity is required (to escape Earth's gravitational pull). To do this, some rudimentary calculations are needed. This will broken down into several categories starting with computing the required escape velocity. After this we will determine the power output required to do so, and how much fuel this would consume. Lastly, we will select a rocket which can meet all of these conditions. Using this information, we use the payload capsule volume available to select a deliverable which suits these dimensions. We can of course already make the assumption that the falcon X heavy rocket is the most capable rocket to bring us to titan. This can be said because it has the largest payload capacity of any operational rocket (Approximately 63,800 kg in LEO). We can re-compute the payoad capacity for a trans-Titan journey, but seeing as this is the rocket with the highest available payload that is operational, it does not leave many alternate options.
We can determine the escape velocity using the following equation:
The relevance of this comes from the requirement of knowing how fast the rocket needs to be moving to escape the gravitiational pull of Earth. All of the values of this equation are known, notably G = 6.674 x 10^-11 [N*m^2/kg^2], M = 5.972 x 10^24 [kg] & r = 6371 km. This gives us an escape velocity of approximately 11.19 km/s.
Power Required & Fuel Consumption
Knowing the escape velocity of earth, we can now compute the energy requirement to reach titan, which, evidently, would also mean the fuel requirement, and the desired power output. To compute this, the following is required.
Here in, we take into account the mass of the rocket (total mass, therefore rocket, fuel and payload) = (m) = 1,420,788 [kg] and the desired escape velocity = (v) = 11.19 km/s. This allows us to compute the desired Energy required to reach escape velocity, which is 8.8953 x 10^13 [J]. For this calculation, we have assumed that the rocket had maxed out payload and fuel, therefore removing any doubts of additional mass. We can now use this energy requirement to determine how much fuel is reuqired, and how much mass we have left over for our payload.
Because the Falcon Heavy uses RP-1 (some form of refined karosene) mixed with liquid oxygen, we know it has an energy density of 0.81 g/ml. This can be used to determine the required mass to reach the desired energy output, and conclusively formulate a total ammount of fuel required.
One way of computing this could be done (rather crudely) with the Tsiolkovsky rocket equation (show below), but this would require far too much detail and work dedicated to a part of the project which is not relevant to the USEr, and therefore annother approximation will be made. A previous Mission to Saturn occured with the Cassini-Huygens rocket where in a rocket with a mass of approximately 5,600 kg was launched using 3,132 kg of propellants at launch. Therefore we can take a similar Mass to fuel ratio (5.6 : 3.132) for the Falcon Heavy rocket. This is what we will use as our Standard Minimum fuel requirement.
Lastly, now that we know most of the details of the Falcon X Heavy rocket, we can come to a conclusion that is is most suited for this journey. We can now begin to investigate the payload and which rover that will be used.
Alternate method: (to be checked with group):
We could use the cassinni rocket, saving us from making inaccurate approximations. This would work because the rover also fits within these dimensions, and the fuel has already been considered for it. Additionally it made a trip to saturn as well as orbitted and tracked the gass giant for 4 whole years. This would work perfectly as well for the project, and save some of the more complex assumptions from errors due to uncertainty.
Rocket: 6.8 [m] Tall - Approximately the size of a school bus. weight - 5,612 [kg], Probe: 2.7 [m] wide, 318 [kg].
Note: Cassini Carried 12 instruments! therefore, the probe dimensions are not our maximum constraints.
Because the payload varies with the distance the rocket travels, we need to make an approximation for how much mass we can consider within the payload capacity to dedicate to the rover itself. To make this approximation we will look at previous missions to Mars and other planetary bodies in hopes of coming to a decisive conclusion.
Weight: (rover+payload) Mars 317,083,743 km – 16800 kg Pluto 5,059,488,081 km – 3500 kg Titan 1,609,344,000 km – estimated 13800kg
Now that we have the weight we can bring to titan, we can also begin looking at our available dimensions. Fortunately this is something given in the information of the Falcon X Heavy, and we can simply plug those in below:
Dimensions: (payload constrained) Height: 13.1m Diameter: 5.2m
Because we seek to determine the perfect rover for this experiment, the final decision is to be made between two existing rovers: the Curiosity rover and Preservance. These have the following dimensions:
Curiosity: 899kg 3x2.7x2.2m Perseverance: 1025kg 3x2.7x2.2m
The main difference between Curiosity and Perseverance is related to the goal of the rover. Where Curiosity studies rocks onsite, Perseverance collects rocks and also has new gadgets attached to the arm.
‘’ The power source is called a "Multi-Mission Radioisotope Thermoelectric Generator" or MMRTG for short. The MMRTG converts heat from the natural radioactive decay of plutonium into electricity. This power system charges the rover's two primary batteries. The heat from the MMRTG is also used to keep the rover's tools and systems at their correct operating temperatures. ‘’
Plutonium Dioxide energy source. Over 30 years a reliable source of energy for NASA. With increasing power(Curiosity 100W(2011), Perseverance 110W(2020)). I looked into solar energy. However due to the distance from the sun to Titan, the solar energy on titan is about 0.1 percent of that of earth. Although there is little to no difference between day and night, so a constant power supplied by the sun, using solar energy would require an abnormal amount of solar panels, which would not be efficient.
State of the Art:
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- ↑ FAQ on the Dragonfly rotorcraft destined for Titan 
- ↑ Wikipedia - Tardigrades - 
- ↑ University of Colorado - Early Earth Haze Likely Provided Ultraviolet Shield for Planet, Says New CU-Boulder Study - 
- ↑ link
- ↑ "A conspicuous nickel protein in microbial mats that oxidize methane anaerobically", by ... 
- ↑ Methane lake article - 
- ↑ 7.0 7.1 Accessed 16/05/2021 link
- ↑ Section of wiki article - Accessed on 13/05/2021 - 
- ↑ NASA - Ladder of Life Detection - 
- Nature (magazine) on Lakes On Titan - link
- Nature (journal) on Lakes On Titan - link
- On Terrain features on a part of Titan - link
- On extremophiles in astrobilogy - link
- On finding evidence of fossilized bacteria (on earth) - link
- Image based species identification - link
- On rover-to-orbiter communication - link
- DragonFly mission concept - link
- Space exploration for life - link
- The (progress of) development of autonomy technologies required to explore Titan - link
- A page containing all info published by NASA about the Cassini mission - link
- A page containing loads of information about Titan itself published by NASA - link
- Geological map of Titan published by NASA - link
- Impervious surface mapping - link
- Achievements in space robotics - link
- Dragonfly mission page - link
- Gravity assisted space travel - link
- The Oberth effect - link
- NASA Scientists Discover ‘Weird’ Molecule in Titan’s Atmosphere - link
- Pictures of Saturn and Titan - link
- Modular Software for an Autonomous Space Rover - link
- Real time map building - link
- ESA Cassini-Huygens page - link
- DragonFly concept paper - link
- NASA Curiosity rover - link
- MARDI - link
- NASA perseverance rover - link
- Global path planning on Mars - link
- Ingenuity Copter - 
- Ingenuity Copter (Nasa) - 
- Alternate ice planets - 
- Exoplanet investigations - 
- Preservence rover - 
- Life in the universe -