The aptly-titled Augustine report, Seeking A Human Spaceflight Program Worthy of A Great Nation, has stirred up considerable debate within the space community and associated interests. Primarily, this debate has swirled around the practical question of means - i.e., should NASA continue to develop its own crew-transport launch vehicles, or should it move to more strongly support the development of commercial launch services and focus its own efforts beyond Low Earth Orbit (LEO)?
All of that is quite interesting, but far more profound is the question that appears to already have largely (and quietly) been settled in favor of a truly radical departure: Where do we go? For decades, this question has been articulated as a simple question of destination: Shall we go to the Moon first, then Mars? Shall we go to Mars first, and operate tangentially on the Moon? Or should we, perhaps, visit asteroids first, then decide what to do from there? The Augustine Commission poses a rather unorthodox option in the "Flexible Path": Everywhere. We go everywhere.
The report officialy titles the option "Flexible Path to Mars," and I fully agree with the committee's emphasis as a matter of publicity: Mars has the biggest and best-organized fanbase, and maintains an intense allure even among the general public as an attainable but virgin destination. It is also the juiciest target for long-term human settlement, or even, in the very distant future (millennial timescale), possibly terraforming into a second Earth.
So emphasizing the utility of Flexible Path to Mars exploration makes perfect sense, but the option is in fact much, MUCH bigger and more profound than simply a road to Mars. I quote from the report's description (pg. 40-41 of the document, 41-42 of the PDF):
The Flexible Path constitutes a steadily advancing, measured, and publicly notable human exploration of space beyond Earth orbit that
would build our capability to explore, enable scientific and economic return, and engage the public. The focus of the Flexible Path is to gain ever-increasing operational experience in space, growing in duration from a few weeks to several years in length, and moving from close proximity to the Earth to as far away as Mars.
Humans need to build the capability to explore other planets, and to operate far from the Earth. On the Flexible Path, critical scientific and technological components of human spaceflight would be addressed through incrementally more aggressive exploration missions. Determining the human physiological and operational impacts of (and the countermeasures to) long-term radiation environment (including galactic cosmic rays) and extended exposure to zero-gravity is necessary for a sustained human-exploration capability. The missions would build preparedness to explore by performing increasingly more complex in-space operations and by testing new elements.
In other words, the purpose of the Flexible Path is not actually to go anywhere in particular, it's to build the capability to go everywhere in the inner Solar System through a progression of increasingly distant, more challenging missions, some of which would have actual destinations (though not necessarily landings).
Were this program to be undertaken, manned space missions would no longer be viewed as routine, because each one would be breaking some new barrier, achieving some new milestone, and taking us tangibly one step closer to what this has always been about: The freedom of mankind to move beyond its cradle, and the intelligence to see both the wisdom and necessity of doing so.
The description of Flexible Path in the Augustine Commission report lays out the following missions, some of which could overlap or even occur simultaneously:
- Lunar orbit.
Aside from the purposes mentioned above (e.g., learning to deal with radiation beyond the terrestrial magnetic field), crews could learn to remotely operate robotic surface probes, repair orbital probes and telecom satellites, and develop advanced plans and procedures to ultimately make landing and manned surface operations as safe and effective as possible. As there is no atmosphere on the Moon, orbits could be as close to the surface as the topography safely allows - closer than humans are to Earth on an airline flight.
- Earth-Moon Lagrangian (EML) points .
Either following or overlapping Lunar orbital missions, others would be sent to EML points - regions of gravitational balance within the Earth-Moon system, where the net effect of gravity and inertia is to maintain a mass at or near them even as the system moves.
The so-called "colinear" Lagrange points, EML-1, EML-2, and EML-3 are considered "unstable" because they can be thought of as plateau peaks, and even a slight disturbance will cause a mass to be accelerated out of position. However, they can still be highly useful, because the net fields in their vicinity are weaker the closer one gets, allowing for cheaper station-keeping than being in LEO.
The "triangular" EML points (EML-4 and EML-5), however - so called because they are exactly 60 degrees off the line between the Earth and Moon - are such that they seem to be shallow gravity wells in empty space, when in fact it is simply the balance of the Earth's and Moon's gravity with various rotational effects that cause them to behave as if they were so.
It is for this reason they are considered "stable" Lagrange points, because displacing a mass from them would just cause the mass to orbit them rather than accelerate away. As is shown in the above image, such an orbit would be shaped like a bent oblong due to its arising from the interaction of the two gravity fields. These are the cheapest places to keep station, because the environment does the work for you.
Many theoretical "minimum energy" interplanetary trajectories have Lagrangian points as their beginning and endpoints due to their being equipotential, so EML-4 and/or EML-5 would make ideal locations for interplanetary waystations. They could also theoretically be used for habitat swarms, satellite junkyards (to minimize orbital debris), fueling depots, and many other uses, so thoroughly characterizing the environment will be enormously useful for the underlying goals of manned spaceflight.
A mission to EML-3, which is always on the opposite side of the Earth from the Moon, would have no special scenery other than the Earth itself, but it would be from a distance equal to that of the Moon, so it would still be an impressive achievement and generate some great photos. Missions to EML-1 and EML-2, which are closer to the Moon than the Earth and lie along the line between them, might possibly even be accomplished at the same time (or even in the same mission) as crewed journeys to Lunar orbit.
EML-4 and EML-5 missions could capture images of the Earth and Moon in the same frame at an equal distance from both, which might be interesting. Also, if crew were to orbit EML-4 or 5 at a considerable distance from barycenter, they could set the record for the furthest distance human beings have ever been from Earth, which would certainly be an inspiring milestone.
- Sun-Earth Lagrangian (SEL) points.
The principle setup of all Lagrange points is the same in a two-body system, so the diagram above is roughly the same for the Sun-Earth system as for the Earth-Moon system, although the difference in the ratio of masses changes some of the relative distances of the points. The characteristics and relative advantages of the "unstable" colinear vs. "stable" triangular L points is also the same, and a number of robotic probes are already operating at SEL-1 as heliospheric observatories, and two observatory probes are at SEL-2 (presumably within the Earth's shadow) to focus on dim objects outside the solar system.
Aside from setting distance records, these regions could also be used for habitat swarms, probe repair, and science. But more importantly, they allow for even lower-energy interplanetary trajectories than EML points, given the enormity of the Sun's gravity and the differing orbital factors (i.e., the Earth-Moon system orbits the Sun a lot faster than the Moon orbits the Earth, by a factor of 30).
- Neart-Earth Objects (NEOs).
The NEOs of most immediate concern, and indeed immediate opportunity, are asteroids and comets with Earth-crossing paths. This not only makes them potentially dangerous in the future, but makes it easier to reach some of them at perigee (closest approach to Earth) than it would be to reach Martian or even Lunar orbit, although this also depends on how fast they're moving relative to Earth. A mission to such an object would first involve rendezvous - matching speed with it - and the slower its motion relative to Earth is, the lower the delta-v (energy) required to both get near it and return when the mission is completed.
Missions to NEOs have the distinction that they could probably involve "landings," since asteroids and comets have so little gravity that no specialized landers would be required - a simple capsule with maneuvering thrusters would be able to guide itself to a landing, and then easily escape the object's gravity. Complications would include oddly-shaped gravity fields (see asteroid 25143 Itokawa, an Apollo asteroid, below) and in the case of comets, volatiles on the surface that might sublime due to the energy of the spacecraft on contact, but these are manageable complexities.
If astronauts chose to exit the vehicle in a spacesuit, although they could technically touch the surface with a boot, they couldn't "walk" - there would be too little gravity. Rather, they would mostly be floating tethered "beside" the asteroid, every once in a while tapping the ground lightly with a stick remain bobbing in place (probably tethered to the ship). This would likely be the first "landing" on another world since Apollo 17, so we can expect this to be received with enormous fanfare.
We would learn how to operate in the environment of irregular planetoids, how to deal with odd gravity fields and loosely-bounded material, and begin to better characterize the Earth-crossing objects that we know of. This would advance not only Earth defense, but the prospects for future mining or even habitat-development operations over the long term.
Note that these asteroids are not Main Belt asteroids, although they might have been perturbed from the Main Belt - we would be operating relatively close to the Earth-Moon system, so we would not have penetrated the Main Belt by having visited one of these objects. Still, it is possible that distance records might be broken in rendezvousing with a NEO.
- Mars orbit
Mars is the Big Game, and putting human beings into Martian orbit would be a profoundly enabling accomplishment, not to mention immensely inspiring. Making use of everything learned about radiation and microgravity exposure in previous missions, as well as orbital operation of surface probes and repair of satellites, Mars orbit could become the base camp from which manned landings would ultimately be launched and whose data and procedures would be developed expressly for that purpose.
It's easy to dismiss going there and then not landing as "sightseeing," but just imagine it for real: Imagine seeing Mars on your TV screen through the camera of an astronaut seeing it with his/her own eyes - seeing its rust-colored dunes and craters passing beneath in quiet magnificence and awesome detail, and knowing that you were beholding another world as you would if you were there. Knowing that History was upon you and all mankind, and the future advancing at an accelerating pace toward an infinite future.
- Phobos
From Mars orbit, Phobos (by far the more interesting of its moons) would be a natural target for exploration and landing. Imagine seeing Phobos in the foreground in front of the Mars seen in the image just above - that is a view we can expect to see and marvel at. "Marsrise." Given the color of Mars, it might actually be disturbing rather than beautiful like Earthrise, but still awesome.
As with NEOs, the low gravity of Phobos makes landing possible, and it is just massive enough to make establishing a base potentially feasible. Furthermore, Phobos is most likely a captured asteroid perturbed from the Main Belt, so its exploration, apart from enabling exploration of Mars, would give us a glimpse of the Main Belt that lies beyond it - the treasure trove of the solar system.
Once in Mars orbit, trips could also easily be made to Deimos:
- Venus orbit (not mentioned, but feasible)
Venus isn't specifically mentioned in the Flexible Path description, and I see no reason why it would be: Manned landings will not likely occur for centuries, assuming we ever deem it worthwhile, and the chances for either exobiology or human colonization on a meaningful time scale (i.e., one that NASA will have any likelihood of catalyzing) are minimal. However, it is another planet, and it's easier to get there than Mars.
The photograph above doesn't look like much, but just imagine its significance if it were the view through the window of a manned spacecraft. Would the world react less in awe, knowing that human beings were in orbit around another planet, and seeing the images of it in full-color HDTV (possibly even 3D), than they did when human beings set foot on the Moon? Who knows what could learned about climatology in orbit about a world as extreme as Venus?
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Together with Mars, the potential of Venus means that we could establish ourselves in orbit around two other planets, not to mention whatever we were doing in Lunar orbit, at the EML points, at the SEL points, with Earth-crossing asteroids, and on the surface of Phobos and/or Deimos. Were this to happen, the physical size of the human sphere would have expanded by orders of magnitude, and the seeds for radical advancement sown.
Each of these enumerated missions (except Venus, which isn't mentioned) is envisioned to take place consecutively (or in some cases simultaneously) on a timeline of about once per year starting around 2020-2025, and requiring a budget increase of only about 20% - and that's not counting savings from use of commercial services to LEO that seems likely to be far more substantial than NASA is currently willing to assume.
WE ARE GOING TO DO ALL OF THIS. Human beings are going to see all of this with their own eyes, in this generation. This is real. Provided the administration adopts the Flexible Path, it will happen. And this is merely what we already KNOW we can do, let alone what we will find out is possible when we finally begin to try.
Some inspirational music: