Press Interview: Royal Society Publishing
Towards synthetic biological approaches to resource utilization on space missions
Ruth Milne: Why is synthetic biology in space an important issue?
Thank you very much for the opportunity to do this Q&A! First, allow me to provide some context. There will be manned long-duration space missions in the future, either to the Moon or to an asteroid or to Mars. The technologies to support such missions are currently under development, and most of these technologies are abiotic (although farming, or some form of it, is a notable exception). So my co-authors and I decided to investigate achieving some of these same mission-support objectives with technologies based on existing biological processes. Surprisingly, we found that not only were these current biological technologies competitive with abiotic technologies, when using common space metrics such as mass, power and volume, but we found that there was a potential for substantial cost savings as well, especially in mass. Because synthetic biology allows us to engineer biological processes to our advantage, we then tried to forecast how recent and future synthetic biology advances could help realize these savings.
Now, to answer your question: in a nutshell, we are claiming that synthetic biology in space is important because our analysis indicates that it has a good chance of being a disruptive space technology, by providing substantial savings over current techniques. Instead of discounting biological technologies in space outright, we are arguing for experimental work in this new area to confirm our analysis.
Why did you choose this topic to review?
Aerospace engineers don't really utilize biological processes in their technologies, and bioengineers are more concerned with technology applications that are closer to home. This review came about as we attempted to bridge this divide when discussing synthetic biology in space. We tried to appeal to both sides and showcase relevant results from traditionally disparate portions of the literature that backed our analysis.
What role does synthetic biology currently have in space science? What techniques are already employed?
Synthetic biology in space is very much a novel idea with a relatively limited current role in space science, particularly because the deployment of biological processes for space application is itself a non-traditional engineering approach. But efforts to explore and advance the field of space synthetic biology are already underway; there is the recent synthetic biology initiative at NASA Ames Research Center for instance, which two of my co-authors are a part of. Current endeavors at NASA Ames include investigating space food production, extremophile engineering, and developing construction materials from extraterrestrial soil or regolith. One goal of our paper is to advocate for an expanded role for synthetic biology in space science, with a view towards future mission deployment.
What useful resources are available on the Moon and Mars?
Since life on Earth is carbon-based and a number of the products around us utilize organic materials, having carbon compounds available would be really useful. And of course, we would need water and its elements, hydrogen and oxygen, to support life. Fortunately on Mars, carbon dioxide makes up more than 95% of the atmosphere, with nitrogen being another almost 3%. There are polar ice caps on Mars too. Thus, carbon dioxide, nitrogen, hydrogen and oxygen are the basic useful resources that we consider in our paper; they form a subset of the main elements required for life, which are carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. On the Moon, after some excavation, carbon dioxide, nitrogen in the form of ammonia, and water vapor are also available.
What are the target areas for development, and why those?
In our paper, we look at four target areas: fuel generation, food production, biopolymer synthesis, and pharmaceutical manufacture. We chose those areas to showcase the versatile potential of space synthetic biology, and also because advances in those areas can significantly impact long-duration space missions: fuel is required for transport, food is necessary for sustenance, biopolymers can be used as construction materials for objects (that are made by 3-D printing, for example), and therapeutics are essential because drugs expire faster in space than on Earth.
Why is it important to improve rocket fuel? How is synthetic biology helping?
According to the Augustine Committee report that was commissioned by President Obama back in 2009, fuel will be "about two-thirds of the mass on an Earth-to-Mars-to-Earth mission." So it makes sense to generate some of the necessary fuel in space rather than to take it all with us because of how expensive it is to launch that mass initially. The current thinking is to generate a methane-oxygen fuel blend on Mars for the return trip, by making use of available carbon dioxide. Lately, another fuel blend has also been gaining attention for its safety and efficacy; it blends nitrous oxide with some hydrocarbons. But it's not quite clear yet how this blend would be generated in space.
What we showed is that by substituting a known biological process (and its necessary ingredients) to generate the methane-oxygen fuel blend from carbon dioxide, we can potentially reduce both the mass of the required apparatus as well as the amount of feedstock that is required. Additionally, it turns out that there also exists biological processes to generate the nitrous oxide-hydrocarbon fuel blend, but they are not that efficient at the moment. So synthetic biology can do two things: help increase savings if a methane-oxygen fuel blend is chosen, or make the generation of a nitrous oxide-hydrocarbon fuel blend more efficient. In fact, we highlight steps that synthetic biology has already taken towards the latter goal, and we feel that synthetic biology can greatly help in this area.
How will synthetic biology improve astronauts' food?
Currently, astronauts' food for long-duration missions will be provided by some combination of shipped food as well as local crops, which also requires shipped mass for set-up and care. Typically, any shipped food is rehydrated before a meal to become "wet-food." An alternative is "dry-food," which consists of nutritious biomass like Spirulina that is produced by cyanobacteria and that we determined will require less shipped mass if deployed on a Mars mission. It turns out that this mass reduction is not true for a Moon mission because of the different mission time-periods involved. In any case, if synthetic biology improves the Spirulina biomass productivity rate to consistently attain approximately the reported maximum experimental values, then dry-food will be a viable option on all long-duration missions, not just Martian ones. Most importantly, synthetic biology can also improve the variety of textures and flavors of the biomass, so that the dry-food is palatable for the astronauts.
Why do drugs expire faster in space than on Earth? How is synthetic biology improving shelf life?
The faster expiry is due to space radiation. As a result, the acceptability of solid drug formulations flown in space is reduced by almost three-quarters when flown for a time-duration that is slightly less than that of a Mars mission. So the ability to manufacture drugs in space in near real-time is very important. Traditional chemical manufacturing techniques are fast and cheap of course, but these benefits are achieved because of a large-scale that would be tremendously massive to deploy, and also wasteful in a space setting since only small quantities of an active drug ingredient are often required. The current thinking is that drugs and other supplies will have to be shipped on an as-needed basis to astronauts in a medical emergency, which is very expensive, and could also endanger astronauts if the supplies do not arrive in time. As a possible workaround, we highlighted a colleague's recent synthetic biology manufacture of a common pharmaceutical, acetaminophen (also known as paracetamol and marketed under the tradenames Tylenol and Panadol), which only requires slight modification for space use. In general, we feel that such synthetic biology drug manufacture is a viable alternative to utilizing traditional drug production means in space, by also reducing the need for emergency shipments. After all, bacterial spores and rock-colonizing eukaryotes are known to survive with little protection in space for between 1.5 and 6 years, so it's conceivable that any designer bacteria will continue to be useful in space if suitably protected.
Will 3-D printing really enable printing of food and other materials in space?
There's some really good work out there on printing food, and of course, the Made in Space folks just recently sent up a 3-D printer with NASA to test out the printer's capabilities in space. We certainly think that 3-D printing will be a very important enabling technology for space travel, and we feel that synthetic biology can help efficiently produce the printer feedstocks that will be required, compared to the more costly option of shipping these feedstocks with the printer.
What's the most important synthetic biology product for space?
This question is hard to answer, since the competing technologies are still new and changing, and a long-duration manned mission is still a ways off. Certainly, we found that the most mass savings exist for the scenario where we substitute the shipped feedstock mass required to 3-D print a lunar or Martian habitat with the shipped mass required to biologically produce the feedstock on location, but this is because the whole concept of 3-D printing in space is still new and untested, and printer feedstock manufacture for space use has yet to be truly analyzed. Perhaps the most compelling space synthetic biology targets are those pharmaceuticals that assist astronauts in emergencies, but of course, we need to test synthetic biology performance in space first, and Earth-based testing in a simulated space environment is required before that. So it's difficult to say what may emerge to be most important at the end of this process, but we feel that the process definitely needs to be explored and given a chance.
How will future missions be different as a result of this technology?
Space synthetic biology is truly ground-breaking. Abiotic technologies were developed for many, many decades before they were successfully utilized in space, and biological technologies like synthetic biology are only now seeing development efforts. So of course these technologies have some catching-up to do when utilized in space. But it turns out that this catching-up may not be that much, and in some cases, the technologies may already be superior to their abiotic counterparts. If this claim is validated and the biological technologies are deemed "safe" for the astronauts and the extraterrestrial destination, then you may even see some biological technologies on the first long-duration manned voyage.
Additionally, nature's been doing product-manufacture with biological technologies for millennia...imagine if we could also deploy its chosen technique of evolution so that we can manufacture products in a way that allows us to tweak things in real-time and with the whole process requiring much, much shorter time-periods. Why then, not only will the space community achieve some of the savings that we claim are possible over select abiotic technologies, but we will also obtain adaptable production techniques that are capable of manufacturing a variety of outputs! Admittedly, we have a long way to go to achieve this, but it seems that the possibilities of space synthetic biology are both endless and practical.
What's your scientific background?
I am a control systems engineer. I was trained in mechanical engineering at the undergraduate level, specializing in mechatronics, and at the graduate level, I studied guidance and control systems for aircraft and spacecraft. My doctoral dissertation answered questions on evolution, adaptation and resilience that arise when considering a colony of space robots that can each produce a copy of itself after utilizing local resources, so as to save on the costs of launching multiple robots; this work turned out to model natural evolution and optimization in dynamic environments, and is applicable to any artificial self-reproducing system. I then did a brief postdoctoral stint learning a lot about diesel engine modeling for control, before my current postdoctoral appointment with the California Institute for Quantitative Biosciences. Essentially, the constant theme in my background is that of controlling various types of systems: mechanical systems (robots and automotive engines), aerospace systems (planes, satellites, even futuristic robots), and now different kinds of biological systems.
Have you always been interested in space?
Yes, although my first keen interest was in aeronautics; in fact, I got my glider pilot's license and my private pilot's license before my driver's license, and then I went on to become a glider pilot instructor soon after. But when I was in high school, the Mars Pathfinder/Sojourner mission really captured my imagination, and that made me want to specialize in aerospace robotics. My doctoral studies in this area made me realize that I also wanted to make biology more robotic, which I am now trying to do, and I hope to some day apply these biological robots in space, which is ultimately where I see the work in our paper headed.
What are you currently working on?
I try to develop ways of controlling different types of biological systems, both existing and novel ones. For instance, I am collaborating to model and control blood coagulation in trauma patients with abnormal clotting behaviors, and I am also investigating how to control and optimize different kinds of synthetic biological systems and circuits for numerous practical applications. Eventually, I hope to implement some of these biological control ideas in a space setting not just here on Earth, with the designed controllers and robots accomplishing various useful space-specific tasks.