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Flexible Path -- Metro Map to Nowhere (Augustine Report)

Hot rumor has it that, like Christmas, the Obama Administration’s response to the Augustine Committee Report, Seeking a Human Space Program Worthy of a Great Nation, is imminent.  Much excitement is discernible in the space blogosphere that a major change is at hand.

The Augustine Committee report concluded that NASA cannot execute the existing Program of Record (POR) of moving humans beyond low Earth orbit (LEO) to the Moon at existing or projected levels of funding.  The report offered up “Flexible Path” (FP), an alternate beyond LEO mission architecture of sending humans to asteroids and other destinations.

Flexible Path is billed as a low-cost alternative to the POR.  It avoids going to the Moon, a destination viewed by the Augustine Committee chairman as a repeat of Apollo (a defensible position, at least in terms of the current plans by NASA’s Exploration Systems Architecture Study).  FP describes a trans-LEO architecture that uses fuel depots and visits Lagrangian-points, asteroids and the moons of Mars.  By not building a “costly” lander spacecraft for descent into the gravity well of the Moon, NASA can “save” money.  The Augustine Report envisions human trips (in terms of total mission duration and remote-from-Earth operations) to L-points and asteroids as intermediate steps to human missions to Mars, their chosen “ultimate destination” of human spaceflight.

Many space advocates see great advantages to FP.  It relies on the idea of propellant depots, where fuel is cached at staging locations (e.g., Earth-Moon L-1; see below) and human vehicles are re-fueled in space for voyages beyond – trips destined for places at which no additional significant propulsive maneuvers are required.  Thus, its targets are theoretical points in space or objects with very low surface gravity, such as near-Earth asteroids (rocky objects with orbits between Earth and Mars, not those in the asteroid belt, between Mars and Jupiter) or the small, asteroid-like moons of Mars.  The latter are particularly interesting in that they could allow humans to control (teleoperate) robots on the surface of Mars with a near-instantaneous response, eliminating the tens-of-minutes time delay of radio communication with Earth.  Such operations might permit true field geological exploration of the surface of Mars without the necessity of descending into the planet’s relatively deep gravity well.

The Lagrangian points (also called libration or L-points) are quasi-stable spots in space that are stationary with respect to two or more objects.  For example, if you draw a line between Earth and Moon, it will revolve like the hand on a clock around the center of the Earth.  If a satellite is put at a point on that line such that its period of revolution is identical with the Moon’s, it will appear to be stationary in space relative to both Earth and Moon, even though it is flying through space just as fast as the Moon.  L-points are found in relation to any two bodies, including Earth-Moon, but also Earth-Sun.  They have many advantages as observation points, where satellites or telescopes can point and stare at targets in space for long dwell times and as staging areas for trips to other destinations.

So what’s the problem with FP?  At first glance, it appears to be an innovative way to move people beyond low Earth orbit at a relatively low cost.  Advocates claim that human trips to destinations never visited by people are more exciting than repeating what we did 40 years ago and that by investing in things like depots, we get a flexible, extensible space infrastructure that will ultimately permit routine access to all destinations.  Why complain about such a thing?  Especially as many have advocated exactly such an approach for the return to the Moon, an approach sorely lacking in NASA’s existing plans.

To be blunt, the difficulty with Flexible Path lies in its motivations, assumptions and likely implementation.  Development of FP by the Augustine Committee was driven largely by their determination that NASA’s chosen architecture for lunar return (ESAS) is unaffordable.  Assuming that movement of people beyond LEO is desirable, FP offers an allegedly low cost path to accomplish such.  But to what end?  The Augustine report is a bit vague as to the objectives and goals of the various FP missions.  Mentioned is the servicing of telescopes at the L-points; the problem is there are none, at least at the moment.  The James Webb Space Telescope is not yet launched, nor is it designed for human servicing.  The L-points are empty spots in space; there’s nothing there except what we put there.  In that sense, as a destination for people, it is no different from low Earth orbit, except that being outside the Van Allen belts (which protect astronauts on the ISS and Shuttle,) the radiation hazard is much greater.

The Augustine Report indicates that human missions to asteroids—Near Earth Objects (NEO), could yield valuable information, including gathering strategic information for the possible mitigation of asteroid collision with the Earth.  Yet such targets are potentially dangerous.  Some NEO asteroids have very high rates of rotation (on the order of an hour or less) making close approach very hazardous, except near the poles.  Many asteroids are loose piles of rubble and co-rotating pieces of debris in the near field of such bodies could pose a hazard to a human vehicle.  The Orion spacecraft must be completely depressurized to allow astronauts to egress and explore an asteroid with EVA, so having all the crew in suits would be required.  Exploratory capability would be very limited, on a scale similar to that of Apollo 11, the first lunar landing.

The several weeks-to-months duration of such mission will likely require the development of a “mission module,” with significant life-support, power, and environmental control.  Thus, selecting this path over the lunar surface does not relieve the agency from the task of developing and qualifying a completely new spacecraft, so the alleged “savings” of not building a lander are gobbled up by expenditure on the mission module.  Lockheed-Martin, contractor for the Orion spacecraft, has come up with a clever “kissing Crew Modules” concept whereby two Orion spacecraft are docked together, doubling the available interior space and consumables.  However, this arrangement complicates the mission design.  With two separate vehicles (requiring two dangerous re-entries), this configuration (with no airlock or docking module) has little exploratory flexibility.  With such architectural difficulties and the “safety first,” risk-aversion-at-any-cost sensibility expressed in the report, a NEO mission is probably a non-starter, or more likely, it will morph into a multi-year “study.”

The programmatic assumption behind FP is that lunar return is “boring” and trips to new destinations will somehow “excite” the public and sustain the NASA budget.  The problem with this reasoning is that it’s not public excitement that is needed – it’s public support.  People will support things that aren’t exciting, if there is some perceived value to it.  A return to the Moon to develop and utilize its material and energy resources and create new space faring capability may not be “exciting” but it certainly is productive and useful.  It allows us to build an extensible, maintainable, expandable, affordable transportation system, serving many purposes, thereby moving beyond the existing spaceflight paradigm: Design, Launch, Use, Discard (and Repeat.)  The Committee’s assertion – that building a lander to get into and out of the Moon’s gravity well makes lunar return unaffordable – is ludicrous.  It’s not the Altair lunar lander that’s eating NASA’s lunch; it’s the development of two entirely new (and arguably unnecessary) Ares launch vehicles.

Repeating what we did 40 years ago is not the reason for lunar return, although, I understand the confusion.  Here was a great missed opportunity for the Committee – they could have pointed out that NASA flubbed the implementation of its lunar mission from the beginning, largely because the agency never really grasped the rationale behind going to the Moon, thereby leaving others unable to embrace or articulate the mission.  Perhaps the Committee didn’t point this out because they didn’t understand it either.  Or perhaps because so much money has already disappeared down the black hole of Ares development, it was deemed easier to frame the report in the familiar terms of hardware procurement rather than focus on the objectives of the mission.

The above dissection of U.S. space policy leads us to the question of how NASA would implement Flexible Path.  The lesson to be drawn from NASA’s Exploration Systems Architecture Study – whose fiscally unsustainable architecture led to the creation of the Augustine Committee in the first place – is that the agency only knows one way of conducting business: the Apollo template.  This business model calls for big rockets, big infrastructure, a large marching army, and big budgets.  Who believes NASA would implement FP differently than how they’ve planned a return to the Moon?  The Augustine Committee itself (largely made up of former NASA employees and agency contractors) claims that “heavy lift launch vehicles are essential for human trips beyond LEO,” a clear expression of the Apollo mindset, yet a statement that, objectively speaking, simply isn’t true.

In other words, changing the focus of our destination from the lunar surface to Flexible Path doesn’t solve anything.  Building big rockets and throwing away 95% of the vehicle leaves no lasting infrastructure in space and prevents access to the material and energy resources of the Moon, negating the original intent and beauty of the Vision for Space Exploration (VSE) – to learn how (or whether, if you prefer) to use those resources to build sustainable, extensible space faring infrastructure.  The chorus of approval that you hear in the space press for FP is based largely on wishful thinking.  Flexible Path, if implemented by NASA, will reflexively follow the existing panem et circenses paradigm, abandoning any hope of ultimately changing an outdated spaceflight business model.

A $3 billion vaccine won’t rid NASA of this disease.  Only a renewed sense of purpose can save the patient.

Another time, another place

A recent discovery from the Spitzer Space Telescope may yield new insight into the origin of our own Moon.  Although this discovery was in the news some time ago, the advent of the Augustine report and the LCROSS mission results have eclipsed it.

The Spitzer Telescope found evidence for a planetary collision around the star HD 172555, about 100 light-years away from our Solar System.  This evidence was a heat signature associated with spectral evidence for silicon monoxide gas (a fairly rare substance) and glassy silica dioxide, a common form of silica glass found associated with volcanoes on Earth.  These substances were found associated with a large cloud of silicate debris:  the ground-up and pulverized parts of the outer portions of two rocky planets.  The evidence suggests that two planets collided with each other at relative speeds exceeding 10 kilometers per second.

This set of circumstances is (more or less) the same that we expect in the aftermath of the currently favored model for the origin of our own Moon.  Traditionally, Earth’s Moon was considered to have formed in one of three different ways.  One model called for Earth and Moon to accrete (assemble) from a collection of small bodies simultaneously; with great imagination, this model was called “co-accretion.”  The second idea called for the Moon to form somewhere else in the Solar System and then be “captured” into orbit by a near-miss encounter with the Earth.  The last model of “fission” suggested that the Moon was ripped from the body of the Earth at a very early stage of our history when it was molten (or nearly so) and spinning very quickly.  This spun-off piece of molten slag then became our Moon.

Although each of these models had its proponents in the days before and immediately after the Apollo missions, none of them seem to simultaneously satisfy all the constraints those program results provided.  The general composition of the Moon is very similar to the mantle of the Earth, suggesting some variant of the fission model might be the answer.  The problem with fission was its physical implausibility, as the early Earth was not like binary stars cited as analogs by the model’s proponents.  The near-identical oxygen isotopes of Earth and Moon indicated that co-accretion might be correct, but why would such planetary formation create two different objects (Earth and Moon) instead of a single body?  Capture was an attractive way of explaining the subtle differences between Earth and Moon, but not their similarities and it was not an easy model to reconcile dynamically with the Moon’s orbital properties.

The advent of the “Giant Impact” model of lunar origin supposedly severed this Gordian Knot of lunar origin.   Although first proposed in the mid-1970’s, it seemed to emerge fully grown from the forehead of Zeus at the 1985 Origin of the Moon conference in Kona, Hawaii.  In one fell swoop, the “big whack” explained all the salient features of the Earth-Moon system, including its oxygen isotopes (both Earth and proto-Moon formed at the same position near the Sun), its depletion in volatiles (such a large impact would vaporize the planets’ mantles and this material would be depleted in volatiles), and the high degree of angular momentum in the Earth-Moon system (an off-center impact would speed up the Earth’s rotation while the Moon was spun off into orbit around it).

Although many scientists embraced the Giant Impact model, a few dissidents remain.  Much of the model’s attraction stems from its apparent ability to explain any particular fact about or constraint on the Moon.  Lack of volatiles troubling?  No problem – the big whack would drive them away.  High spin rates on the early Earth?  The impact hit off-center.  Moon’s bulk composition like the Earth’s mantle?  The Moon came from the Earth’s mantle.  Is it too unlike the Earth’s mantle?  No problem – it comes mostly from the mantle of the (now destroyed) impactor planet.  In other words, the model is largely unconstrained and elastic enough to fit any fact or observation.

Scientists tend to be uncomfortable with such models; not only do they lack predictive power, they seem too much like “Just-So” stories.  However, finding something unexpected that matches the predictions of a model tend to give that model veracity and “completes” the jigsaw puzzle.  The new Spitzer findings might well be that missing piece of the puzzle.  They suggest that planetary collisions do happen (we didn’t really doubt that, but it’s nice to have a concrete example).  The presence of silicon monoxide gas indicates very high temperature, non-equillibrium processes – exactly what would be expected from a giant impact.

We may well find systems in various stages of evolution as we continue to observe the nearer stars and examine their planetary systems.  Having oither examples of multiple planetary systems allows us to “field check” our suppositions about the history of our own Solar System.  Some of the apparently contrived “Just So” stories may just be correct.