“Circular economy” methods such as recycling and reuse have made significant advances (see the Waste to Base Challenge), but a limited amount of waste generated aboard a crewed spacecraft cannot be recycled. Non-recyclable waste could take up crucial space, and some waste products can pose risks to the spacecraft and crew. Effectively controlled jettison operations can mitigate risks to spacecraft and avoid creating hazards or contaminants, while protecting livable volume and increasing fuel efficiency for the spacecraft. NASA is seeking an efficient and reliable jettison concept that will keep astronauts and spacecraft safe as we venture farther into deep space on roundtrip missions to Mars.
Trash jettison operations are complex and could be risky. During the transit phases of a crewed Mars mission, there is no option for returning to Earth early, or sending up a repair team or spare parts. This challenge is therefore complex and important for a successful crewed Mars mission. Examples of material generated during prolonged spaceflight include biological waste from astronauts, spent components, protective packaging, and damaged parts. The amount of non-recyclables produced per week during a crewed Mars mission is expected to have a volume of approximately 0.2m3 with a mass of 50kg for a crew of four. This is roughly the amount of trash that would fill a standard 55-gallon drum.
Purpose of the Challenge
The purpose of this challenge is to generate detailed jettison mechanism designs for ejecting non-recyclable material from a spacecraft during a crewed Mars mission. Winning design concepts may be considered for further development by NASA.
The Mission Profile
There are several different crewed mission profiles that will require jettison operations, with the longest being 3 years. Such a mission would be made up of 6-9 months in transit from Earth to Mars, around 18-24 months on or near the Martian surface, and 6-9 months for the return journey from Mars to Earth. An illustration of some of the potential mission profiles is given below but this jettison mechanism challenge refers specifically to the transit phases from Earth orbit to Mars orbit and the return. Surface operations on Mars are not included, but the solution must still be available for the return journey so consideration must be given to how the system will be stored and maintained during long surface operations. Jettisoned objects will orbit the Sun but, given the huge distances from Earth and vast volume of space, these are very unlikely to ever interfere with future space missions.
Even if technological developments allow significant improvements in recycling, reuse and repurposing, there will still be certain waste products that will need to be jettisoned. The exact composition of these will be determined by any recycling technology adopted, but could include urine salts, carbon residue, wet or dried fecal matter, waste food, used hygiene products, plastic packaging, protective foams, metals, and ceramics.
Trash Jettison Mechanism Design Criteria:
There are a number of key requirements that successful jettison mechanism solutions must deliver. These include:
- The trash jettison mechanism, and any supporting systems, must be able to process minimum waste levels of 0.2m3 volume and 50kg per week. This will be made up largely of biological astronaut waste and packaging associated with consumables such as food, but periodically could include broken parts, worn out clothing, medical waste, packaging, and expired mission equipment.
- The jettison mechanism must be integrated safely with the spacecraft and not interfere with other systems or activities.
- The jettison mechanism must be simple to operate, minimize the crew time needed to operate the system, and minimize direct crew exposure to waste products.
- The jettison mechanism must be highly reliable and robust since the mission depends on reducing spacecraft mass by offloading waste products. Designs should either prevent jams in the first place or have some technique that clears jams and blockages. Ease of repair and effective maintenance regimes will also be key as failure during the mission could be mission and life-threatening. Wherever possible, designs should use off-the-shelf components with a high Technology Readiness Level (TRL) that have already proven to be reliable, preferably within a space setting.
- Designs must be able to operate in extremes of temperature (hot and cold) and cater for cyclical temperature swings that result from facing towards and away from the sun.
- Additional hardware jettisoned with the trash (for example a container, fly-away piece, or wrapper to enclose the waste) must be minimized. The preference is for no additional hardware. Trash bags such as those already used by NASA are reasonable to assume.
- The waste earmarked for jettison will not be suitable for recycling or reuse but, if necessary, can be processed to make storage and jettison easier or safer. For example, waste could be shredded, compacted, or crushed; however, if pre-jettison processing steps such as this are proposed, details should be included in the design.
- The power budget available on the spacecraft for trash jettison is a maximum of 500W. Pre-jettison processing techniques must also operate within this 500W power budget while also ensuring crew and ship safety. Besides staying below this maximum power, designs should strive to reduce energy consumption as much as possible.
- The jettison mechanism must eject the trash with sufficient velocity to clear the spacecraft so as to avoid the possibility of collision. If a variable or high energy jettison system is proposed, a strategy for handling the reaction force on the spacecraft must also be presented.
- The preferred exit route for trash is either the small scientific/utility airlock or the larger crew EVA airlock that will both be fitted to the spacecraft. The final designs of the two airlocks have yet to be finalized, but for planning purposes the HAL Scientific and Orbiter EVA airlocks described below should be used as a guide. Technical specs for these airlocks can be found at the Resources Tab but key dimensions are given in the table below. Please note that while some design changes to the two airlocks can be considered as part of submissions, wholescale redesigns that markedly change the dimensions, shape, or function of the airlocks are not feasible.
|Airlock Parameter:||HAL Scientific Airlock||Orbiter EVA Airlock|
|Interior Dimensions||Approximately cylindrical with:
Length – 0.610m
Diameter – 0.610m.
|Approximately cylindrical with:
Height – 2.108m
Diameter – 1.6m
|Hatch Size and Dimensions||Width – 0.528m
Height – 0.629m
Thickness – 0.0218m
|Approximately circular with:
Diameter – 1.105m
Hatches connect to airlock walls, not endplates.
|Mounting Plate||Width – 0.660m
Height – 0.865m
|Mass||374.2kg when empty.|
Typical Dimensions of a Scientific/Utility Airlock and an EVA Airlock
- The decision has yet to be made on whether to have the jettison mechanism as a ‘primary’ system permanently fitted for continual use or as a ‘secondary’ backup system that is only fitted if required. Solvers are free to consider one or both options, but other airlock operations should not be constrained by the jettison mechanism when it is not being used.
- The final design of the spacecraft has not yet been determined, but the mass and volume allowance for any part of the system within the spacecraft must be practicable given the tight mass and volume limitations of crewed missions. The preference is for compact solutions. However, the jettison mechanism and trash to be ejected must fit in either the EVA or scientific/utility airlock, so these should be taken as the upper limits when considering volume.
- Any designs that do not use the specified air locks must explain clearly how trash from inside the spacecraft will be moved to the exterior and jettisoned without causing hull integrity or safety issues.
Other Jettison Considerations:
- Typical dimensions of trash bags and fecal waste containers can be found in the Resources tab. The jettison system must be able to accommodate these shapes, and ideally all irregular shapes.
- Jettisoning of material will be required throughout the transit phases of the mission. Depending on the location of the spacecraft, the jettison activity will face different challenges. A single jettison concept must be able to deal with multiple scenarios and mission waste streams. See the Resources Tab for some current policy documentation and discussion on potential future space waste regulations.
- Material cannot be simply dumped overboard without considering the potential future impact of jettisoned waste. Where possible, jettison mechanism designs should incorporate features for reducing the risk of space debris and the biological contamination of Mars.
This is a tough challenge focused on delivery of a detailed technical concept, so the prize purse reflects this. While a prototype jettison mechanism is not required at this stage, submissions must have enough technical detail to show how the concept works and how it will integrate with a crewed platform. Winning submissions are likely to include detailed technical drawings and/or blueprints as a minimum. Some suggested information requirements are listed in the table at the Resource Tab. However, the minimum information required is given below:
Minimum Submission Information Requirements
As a minimum, submissions must include:
- Mass estimate of the jettison mechanism and any supporting systems such as a shredder or crusher.
- Mass estimate of any wrapper or extra bag or piece ejected with the trash, and the total wrapper/bag mass requirement for the entire mission.
- Dimensions and volume of the jettison mechanism and any supporting systems.
- Construction materials.
- Power requirements.
- Detailed description of the jettison mechanism and how it works.
- Mechanism mounting/fitting instructions.
- Stowage plan for when the trash jettison mechanism and any supporting systems are not in use.
- A narrative on how the jettison mechanism will support the mission.
- A description on how to use the jettison mechanism.
Additional Submission Information Requirements
The best submissions are also likely to include information such as:
- Technology Readiness Level (TRL) of sub-components.
- Reliability data and/or estimates for the jettison mechanism and sub-components.
- Maintenance and repair schedules.
- Operating temperature ranges.
- Prototype cost estimates.
- Crew interaction/interface and training requirements.
- Detailed description on how designs will be integrated with the spacecraft.
There is a total of $30,000 available in cash prizes and the potential to work and collaborate with NASA. The top five shortlisted submissions will be invited to pitch their design online to a NASA panel in a 10-minute presentation followed by a 20-minute Q&A session. The three finalists will be given the opportunity to attend a virtual workshop with NASA to explore their concepts in more detail. Exceptional entries may be selected for further collaboration with the NASA team.