Electro-luminescently Cooled Zero-boil-off Propellant Depots Enabling Crewed Exploration of Mars

Aaswath Pattabhi Raman
University of California, Los Angeles

Exploration of Mars has captivated the public in recent decades with high-profile robotic missions and the images they have acquired seeding our collective imagination. NASA is actively planning for human exploration of Mars and laid out some of the key capabilities that must be developed to execute successful, cost-effective programs that would put human beings on the surface of another planet and bring them home safely. One crucial area where new missions and enabling technologies are needed is the long-duration storage of cryogenic propellants in various space environments; relevant propellants include liquid Hydrogen (LH2) for high specific impulse Nuclear Thermal Propulsion (NTP) which can be deployed in strategic locations in advance of a mission. Such LH2 storage tanks could be used to refill a crewed Mars Transfer Vehicle (MTV) to send and bring astronauts home quickly, safely, and cost-effectively.

We propose a breakthrough mission concept: a cryogenic liquid storage depot capable of storing LH2 with ZBO even in the severe and fluctuating thermal environment of LEO. Our innovative storage depot mission employs thin, lightweight, all-solid-state panels attached to the tank’s deep-space-facing surfaces that utilize a long-understood but as-yet-unrealized cooling technology known as Electro-Luminescent Cooling (ELC) to reject heat from cold solid surfaces as non-equilibrium thermal radiation with orders of magnitude more power density than Planck’s Law permits for equilibrium thermal radiation. Such a depot and tank would drastically lower the cost and complexity of propulsion systems for crewed Mars missions and other deep space exploration by allowing spacecraft to refill propellant tanks after reaching orbit rather than launching on the much larger rocket required to lift the spacecraft in a single-use stage. To achieve ZBO, a storage spacecraft must keep the storage tank’s temperature below the boiling point of the cryogen

(e.g., ≈20 K for liquid H2). Achieving this in LEO-like thermal environments requires both excellent reflectivity toward sunlight and thermal radiation from the Earth and other nearby bodies as well as a power-efficient cooling mechanism to remove what little heat inevitably does leak in, a pair of conditions ideally suited to the the ELC panel concept that enables our mission. By enabling ZBO LH2 storage in LEO, our mission will enable cost-effective, and flexible crewed exploration of Mars. Our mission will also demonstrate capabilities with ancillary benefits to cryogenic storage in terrestrial applications and solid-state cooling technologies more generally.

2024 Phase I Selection

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A Revolutionary Approach to Interplanetary Space Travel: Studying Torpor in Animals for Space-health in Humans (STASH)

Ryan Sprenger
Fauna Bio Inc.

The use of non-model organisms in medical research is an expanding field that has already made a significant impact on human health. Insights gleaned from the study of unique mammalian traits are being used to develop novel therapeutic agents. The remarkable phenotype of mammalian hibernation confers unique physiologic and metabolic benefits that are being actively investigated for potential human health applications on Earth. These benefits also hold promise for mitigating many of the physical and mental health risks of space travel. The essential feature of hibernation is an energy-conserving state called torpor, which involves an active and often deep reduction in metabolic rate from baseline homeostasis. Additional potential benefits include the preservation of muscle and bone despite prolonged immobilization and protection against radiation injury. Despite this remarkable potential, the space-based infrastructure needed to study torpor in laboratory rodents does not currently exist, and hibernation in microgravity has never been studied. This is a critical gap in our understanding of hibernation and its potential applications for human spaceflight. We propose to remedy this situation through the design and implementation of STASH, a novel microgravity hibernation laboratory for use aboard the ISS. Some unique and necessary design features include the ability to maintain STASH at temperatures as low as 4°C, adjustable recirculation of animal chamber air enabling the measurement of metabolism via oxygen consumption, and measurement of real-time total ventilation, body temperature, and heart rate. The STASH unit will also feature animal chamber sizes that will accommodate the expected variety of future hibernating and non-hibernating species, boosting its applicability to a variety of studies on the ISS by enabling real-time physiological measurements. The STASH unit is being designed in collaboration with BioServe Space Technologies to be integrated into the Space Automated Biological Laboratory (SABL) unit. This will allow for the achievable and practical application of this research to advance our understanding of both hibernation and mammalian physiology in space. The short-term goals of the STASH project are novel investigations into the basic science of hibernation in a microgravity environment, laying the foundation for application of its potential benefits to human health. These include determining whether hibernation provides the expected protection against bone and muscle loss. The medium-term goals of the project begin developing translational applications of hibernation research. These include using STASH both for testing bioactive molecules that mimic the transcriptional signatures of hibernation and for evaluating methods of inducing synthetic torpor for their ability to provide similar protection. As a long-term goal, during a crewed mission to Mars, human synthetic torpor could act as a relevant countermeasure that would change everything for space exploration, mitigating or eliminating every hazard included in NASA’s RIDGE acronym for the hazards of space travel: Space Radiation, Isolation and Confinement, Distance from Earth, Gravity Fields, and Hostile/Closed Environments. Research performed using STASH will be an essential first step toward acquiring fundamental knowledge about the ability of hibernation to lessen the health risks of space. This knowledge will inform development of both biomimetic drug countermeasures and the future infrastructure needed to support torpor-enabled human astronauts engaged in interplanetary missions. We feel that STASH is the epitome of the high-risk, high-reward projects for which NIAC was established.

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LIFA: Lightweight Fiber-based Antenna for Small Sat-Compatible Radiometry

Zhang, Beijia Zhang, Beijia
Massachusetts Institute of Technology (MIT), Lincoln Lab

Very large space-based RF antennas can be large and expensive to manufacture and deploy. These problems become more challenging for cases when an array of antennas are needed such as for correlation interferometers that provide high spatial resolution of Earth and space. The proposal will specifically examine the potential applicability of novel fiber-based antennas to L-band radiometry for the purpose of generating high resolution soil moisture and sea surface salinity data. Initial estimates indicate that a x10 improvement on resolution may be possible with long fiber-based antenna arrays. Lincoln Laboratory has been investigating the ability to produce large flexible RF antenna arrays embedded in polymer fibers. These lightweight fibers are flexible enough to be coiled and uncoiled, thus facilitating transport and deployment. The metal that forms the antenna structure and other conductive elements is embedded inside a polymer boule that is heated and drawn to form a novel type of fiber. The resulting fiber thus has multiple materials embedded inside for the ability to support sensing capabilities and other functionalities. Thus, this fiber fabrication process may also lead to a cost-effective means to create very large antennas. This work will include analysis of the required antenna performance and the ability of fiber-based antennas to meet those requirements, deployment strategies, satellite specifics, space tolerance of components and materials, a preliminary system-level design, and concept of operations.

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Swarming Proxima Centauri: Coherent Picospacecraft Swarms Over Interstellar Distances

Thomas Eubanks
Space Initiatives, Inc.

Tiny gram-scale interstellar probes pushed by laser light are likely to be the only technology capable of reaching another star this century. We presuppose availability by mid-century of a laser beamer powerful enough (~100-GW) to boost a few grams to relativistic speed, lasersails robust enough to survive launch, and terrestrial light buckets (~1-sq.km) big enough to catch our optical signals. Then our proposed representative mission, around the third quarter of this century, is to fly by our nearest neighbor, the potentially habitable world Proxima b, with a large autonomous swarm of 1000s of tiny probes.

Given extreme constraints on launch mass (grams), onboard power (milliwatts), and coms aperture (centimeters to meters), our team determined in our work over the last 3 years that only a large swarm of many probes acting in unison can generate an optical signal strong enough to cross the immense distance back to Earth. The 8-year round-trip time lag eliminates any practical control by Earth, therefore the swarm must possess an extraordinary degree of autonomy, for example, in order to prioritize which data is returned to Earth. Thus, the reader will see that coordinating the swarming of individuals into an effective whole is the dominant challenge for our representative mission to Proxima Centauri b. Coordination in turn rests on establishing a mesh network via low-power optical links and synchronizing probes’ on-board clocks with Earth and with each other to support accurate position-navigation-timing (PNT).

Our representative mission begins with a long string of probes launched one at a time to ~0.2c. After launch, the drive laser is used for signaling and clock synchronization, providing a continual time signal like a metronome. Initial boost is modulated so the tail of the string catches up with the head (“time on target”). Exploiting drag imparted by the interstellar medium (“velocity on target”) over the 20-year cruise keeps the group together once assembled. An initial string 100s to 1000s of AU long dynamically coalesces itself over time into a lens-shaped mesh network #100,000 km across, sufficient to account for ephemeris errors at Proxima, ensuring at least some probes pass close to the target.

A swarm whose members are in known spatial positions relative to each other, having state-of-the-art microminiaturized clocks to keep synchrony, can utilize its entire population to communicate with Earth, periodically building up a single short but extremely bright contemporaneous laser pulse from all of them. Operational coherence means each probe sends the same data but adjusts its emission time according to its relative position, such that all pulses arrive simultaneously at the receiving arrays on Earth. This effectively multiplies the power from any one probe by the number N of probes in the swarm, providing orders of magnitude greater data return.

A swarm would tolerate significant attrition en route, mitigating the risk of “putting all your eggs in one basket,” and enabling close observation of Proxima b from multiple vantage points. Fortunately, we don’t have to wait until mid-century to make practical progress – we can explore and test swarming techniques now in a simulated environment, which is what we propose to do in this work. We anticipate our innovations would have a profound effect on space exploration, complementing existing techniques and enabling entirely new types of missions, for example picospacecraft swarms covering all of cislunar space, or instrumenting an entire planetary magnetosphere. Well before mid-century we foresee a number of such missions, starting in Earth or lunar orbit, but in time extending deep into the outer Solar system. For example, such a swarm could explore the rapidly receding interstellar object 1I/’Oumuamua or the solar gravitational lens. These would both be precursors to the ultimate interstellar mission, but also scientifically valuable in their own right.

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Detoxifying Mars: the biocatalytic elimination of omnipresent perchlorates

Lynn Rothschild
NASA Ames Research Center (ARC)

Water is the lifeblood of human survival and civilization and is critical for our sustained exploration beyond Earth. Fortunately, Mars has plenty of water to sustain our aspirations in the form of subsurface ice. Unfortunately, it is not clean water – it is contaminated by toxic perchlorates. Perchlorate and chlorate are potent oxidizers that cause equipment corrosion and are hazardous to human health even at low concentrations. It is therefore critical that Martian water be detoxified to remove these contaminating solutes before it can be used in propellant production, food production, or human consumption. The scale of anticipated water demand on Mars highlights the shortcomings of traditional water purification approaches, which require either large amounts of consumable materials, high electrical draw, or water pretreatment.

What if we could make the perchlorates just vanish? This is the innovative solution we propose here, taking advantage of the reduction of chlorate and perchlorate to chloride and oxygen being thermodynamically favorable, if kinetically slow. This is the promise of our regenerative perchlorate reduction system, leveraging synthetic biology to take advantage of and improve upon natural perchlorate reducing bacteria. These terrestrial microbes are not directly suitable for off-world use, but their key genes pcrAB and cld, which catalyze the reduction of perchlorates to chloride and oxygen, have been previously identified and well-studied. This proposed work exploits the prior work studying perchlorate-reducing bacteria by engineering this perchlorate reduction pathway into the spaceflight proven Bacillus subtilis strain 168, under the control of a robust, active promoter. This solution is highly sustainable and scalable, and unlike traditional water purification approaches, outright eliminates perchlorates rather than filtering them to dump somewhere nearby.

For Phase I we will explore whether this approach is feasible through these objectives:

1. Engineer the genes PcrAB and cld into B. subtilis 168 under the control of the strong promoter pVeg and test and quantify the efficacy of perchlorate reduction under the modeled conditions.
2. Develop B. subtilis strains that secrete the enzymes to test intra- vs extracellular efficacy.
3. Perform a trade study comparing the performance of biological water detoxification from Objs. 1 & 2 to traditional engineering approaches in terms of mass, power, and crew time.
4. Delineate a plan to infuse this technology in human Mars missions. Development of our detoxification biotechnology will also lead to more efficient solutions to natural and particularly industrial terrestrial perchlorate contamination on Earth. It will also shine a spotlight on the potential of using life rather than only industrial solutions to address our environmental problems, which may spur further innovations for other terrestrial environmental challenges such as climate change. The system will be launched as inert, dried spores stable at room temperature for years. Upon arrival at Mars, spores will be rehydrated and grown in a bioreactor that meets planetary protection standards. Martian water will be processed by the bioreactor to accomplish perchlorate reduction. Processed water can then be used or further purified as required.

2024 Phase I Selection

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