- Press Release
- August 8, 2022
Astronauts Enthused About Mars – But Cautious About Human Factors
Despite nearly 100 shuttle missions, years of extended stays on Mir, and trips to the Moon, we still do not have all the answers when it comes to sending humans to Mars – safely. While the problems are not insurmountable, they will have to be thoroughly addressed – by both doctors and engineers – before humans can travel to – and work safely upon – Mars. Veteran astronauts Scott Horowitz and John Grunsfeld spoke at the Mars Society Convention in Toronto about their own experiences as astronauts and what lies ahead as we prepare to send people to Mars.
Regardless of which mission scenario you subscribe to, it is going to take many months for people to make the first trips to Mars. Advanced propulsion could shave months off of the travel time, but most experts agree that even the most optimistic plans show approaches using advanced, non-chemical propulsion as being somewhat down the road. Most mission scenarios – including NASA’s officially unofficial design reference mission plan – currently show this trip happening without artificial gravity.
Humans, like all other forms of life on Earth, evolved as a species, and grew up as individuals, in the presence of gravity. Even aquatic organisms are directly affected by gravity despite the buoyancy they may experience. Indeed, gravity is the only environmental factor whose character and strength has remained virtually unchanged throughout life’s entire tenure on Earth. Taking a living system out of an environment it has no previous ability to adapt to can cause a variety of changes. Some changes are compensated for – others are not.
Spaceflight is both benign and rough on humans. Half of the humans who go into space are affected with nausea and vomiting which can appear rather swiftly upon entering space and may last for several days. This cannot be predicted and can be only partially treated or prevented. The effects eventually pass within a few days after which life in microgravity becomes a thrilling adventure. Readaptation to life on a planet happens rather swiftly upon return with no lingering after effects.
Meanwhile, as the crew learns to cavort in weightlessness and develops a whole new frame of reference, their bodies are falling apart. Without the ubiquitous presence of a gravity field to resist, the body seeks to strike a new equilibrium – one that reflects the dramatically reduced physical stress encountered in microgravity. Bones are dynamically maintained structures that react swiftly to alterations in the stress under which they are placed. In space, a progressive loss of bone mass occurs – one that is directly proportional to the amount of time spent in microgravity. Upon return to Earth, a permanent loss of up to 15-20% of bone mass in weight bearing portions of the skeleton is seen in all humans.
While this bone loss is similar in some ways to osteoporosis observed on Earth, the pharmacological countermeasures used on Earth have no effect upon this phenomenon in space. The effect of exercise in microgravity has yet to be shown to have clear effects upon minimizing this bone loss. In addition to bone loss, a marked decrease in muscle mass is seen – including cardiac muscle – although this is more or less reversed after return to Earth.
These serious microgravity issues not withstanding, there is considerable pressure upon a zero-G design for a Mars mission at NASA and elsewhere. It is less complex, lighter, and uses much less energy than one where all or part of the spacecraft is set in motion. Using this approach, however makes the assumption that countermeasures – such as exercise and/or pharmacological agents will exist in time so as to be able to minimize the deleterious effects of prolonged microgravity exposure on the crew. This is important not only for their long term health prospects upon return to Earth, but also for their ability to perform their mission when they arrive at Mars.
The only other solution, should zero-G design be used, is to get to Mars as fast as possible – this is where advanced propulsion comes in. Mention was made by the astronauts of research being conducted at NASA JSC by a team assembled by Astronaut Franklin Chang-Diaz on a new propulsion system (VASIMR -the Variable Specific Impulse Magnetoplasma Rocket). While the use of such a propulsion system is still many years off, it does promise to cut travel time between the planets from months to weeks. The shorter the exposure to microgravity, the less deleterious the physiological effects on the crew will be.
Being able to function on Mars after a long space trip is of tantamount importance. Not only does the crew have to manage a ship as it enters Mars atmosphere and lands, but they also have to deal with the reconfiguration of the ship’s systems once it has landed. They also have to be prepared for contingencies after landing – including damage that might occur after a rough landing and assembly of hardware on the surface. Horowitz and Grunsfeld both expressed concerns about the ability of a crew to perform all of these tasks after many months in microgravity.
Studies have already been done aboard Space Shuttle missions to allow pilots to practice their landing skills after prolonged stays in space. This is being done to be certain that the ability to orient oneself and fly is not decoupled after long periods in microgravity. Moreover, as G forces reassert themselves, the amount of blood going to the brain can decrease leading to possible light headedness, fatigue, or disorientation – something a Space Shuttle pilot cannot afford to experience.
According to Grunsfeld the Mars crew “needs to be in the best shape of their lives” upon arrival. Given the current state of knowledge, humans arriving on Mars would be in the same bad condition as humans returning to Earth from Mir. The lower Martian gravity would not make much difference. Not having a crew in tip top condition would place landing activities and any post landing surface activities at risk. Indeed, these two astronauts felt that surface activity on Mars would be rather limited for the first several weeks under even the most optimal circumstances for any crew travelling to Mars in microgravity.
One thing you will hear rather often at Mars Society conventions is how quickly humans can readapt to life on Earth upon return from long duration spaceflight – such as trips to Mir. Astronaut Shannon Lucid’s steps up to the podium with President Clinton after her 6 month stay on Mir are regularly cited – the reason for her apparent fitness in front of the cameras is usually ascribed to having “done all of her exercises”. This is somewhat inaccurate. Scott Horowitz, a runner, said that he took his ability to run as sort of a personal barometer of his fitness level. After a 16 day flight he said that it took him 3 1/2 weeks to return to his pre-flight running capability.
According to Horowitz the crews returning from Mir had incredible resolve to show they public that they could stand up upon landing – and that they are OK after the experience of living in space for a long time. “That is good for about 6 hours” he said and that standing upright at these post flight media events is followed by a 6 week rehabilitation period. According to Horowitz, when astronaut John Blaha came back from Mir he told the press that he was a “basket case” and that he could not move.
Life on the way to and from Mars is only part of the issues facing Mars mission planners. According to Horowitz and Grunsfeld, the spacesuits to be used on the surface of Mars need to be vastly more attuned to human ergonomics than any currently in existence. Space suits are self contained spacecraft.. Regardless of where you use a space suit, each motion works against the suit’s attempt to retain a certain shape while under pressure. The suits used in microgravity do not have to contend with prolonged human movement across the surface of a planet. The suits needed for Mars will.
The suits designed for use on the Apollo missions, while able to allow the crew to perform their tasks, were eventually rendered useless by the end of their brief usage on the Moon. Apollo 17 astronaut Jack Schmitt spoke of how the lunar dust had managed to work its ways into all of the suits joints such that they did not function at the end of his third EVA. The space suits to be used on Mars need to be designed for as many as 300 trips across the surface – trips that will last for many hours and will require the users of the suits to perform a wide array of movements. Current Mars suits designs exhaust their wearers after 10 to 15 minutes of use. The suits also need to be designed for routine maintenance on Mars by the crew, not a contractor back on Earth.
Clearly much more work needs to be done on ‘space rating’ humans for prolonged microgravity exposure before critical decisions need to be made on spacecraft design. Facilities will be operational aboard the International Space Station in the coming years that will seek to address these problems. Unfortunately, the Centrifuge Accommodation Module which will house a large variable force centrifuge for animal research into gravitational physiology, will not be in launched to the space station until mid-2006. As such, any design of a Mars mission that does not include some means of producing artificial gravity for the crew runs the risk of being redesigned in the face of future data. All the more reason to get this research underway as soon as possible.
Advanced surface space suits also need to be developed. Given that this will require many years and some considerable expense, now is the time to start work. A prototype Mars spacesuit built by Hamilton Sunstrand was tested out at the Mars Arctic Research Station on Devon Island this summer. While the suit received generally positive reviews, it clearly indicates that a substantial amount of work lies ahead.
Grunsfeld and Horowitz were genuinely optimistic about the prospect of sending humans to Mars. In so doing, they urged all involved to learn from the lessons gained – not just from Apollo – but from the current International Space Station project as well. They favored a small “skunkworks” like effort where the design team was kept as isolated as possible from external political and managerial pressures. They stated that they felt that a mission to Mars was possible in the span of time covered by the next administration – 8 years.
In closing the two astronauts noted that we went to the moon in the 1960’s with far less experience than we have today. Back then we couldn’t even launch rockets without having them blow up on a regular basis. A few years later we were walking on the Moon.
° Biography of Astronaut John Grunsfeld, NASA JSC
° Biography of Astronaut Scott Horowitz, NASA JSC