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Twenty years and $86 billion = One human visit to an asteroid (from Wilhite et al., 2011)

A plan for a human mission to a near Earth object (NEO; an asteroid), designed by engineers from Georgia Tech and the National Institute for Aerospace (GT/NIA), was recently posted online.  Keying in on lowering program total costs, this architecture eliminates the need for a new heavy lift launch vehicle (HLV) by advocating the placement and use of space-based propellant depots.

Doug Stanley, one of the co-authors of this study, previously led NASA’s 2005 Exploration Systems Architecture Study (ESAS).  ESAS (a.k.a. Project Constellation, NASA’s chosen blueprint to implement the Vision for Space Exploration) was widely reviled by many in the space community as an Apollo Redux-style, unaffordable approach to lunar return.  The 2009 Augustine Committee Report concluded that without a significant increase in NASA’s budget, a return to the Moon under the Constellation architecture was not achievable.  President Obama’s Administration subsequently announced it was terminating both Constellation and lunar return.

This new study is an interesting approach to the problem of staging a human asteroid mission.  It is written partly in response to the recent NASA Human Exploration Framework Team (HEFT) study, which designed and estimated costs for an asteroid mission in 2026 (the date called for in the Administration’s re-design of our strategic direction in space).  The HEFT architecture was briefly famous two months ago, when it was pointed out that it had incorrectly concluded that NASA is unable to build a heavy lift launch vehicle under the Congressionally mandated cost and budget envelope of its recent authorization.

The new GT/NIA study proposes that commercial launch services, coupled with Earth orbital propellant depots, can create the infrastructure needed to stage a human mission to a NEO in 20 years (by 2031).  While reviewing details of the study, I was specifically drawn to their cost estimates; the GT/NIA study concludes (depending on the specific launch options selected) that a human asteroid mission can be accomplished (by the time specified for a total program cost) for between $73B and $97B (constant FY2010 dollars).  This number contrasts with the HEFT study estimate of $143B (an approach that develops and uses a 100 mT heavy lift launch vehicle).

What benefit do we gain with this expenditure?  By 2031, we will have conducted a human mission to an asteroid, thereby reaching the first rung of the Augustine challenge for America’s space program to conduct a “series of space ‘firsts’.”  We’ll have emplaced a fuel depot system that can support future human missions to other asteroids, or the moons of Mars (also called for in Augustine’s 2009 “Flexible Path” approach).  As NASA will have no launch capability in the future, fuel supplied to these space-based depots will be dependent on commercial deliveries of propellant from Earth.  This will be the “new way” of space – depots with fuel supplied by commercial vendors for sortie missions to various and as yet unspecified destinations.  All of these missions will be dependent on the necessity of everything needed for space operations being launched (currently, deemed prohibitively expensive) from the surface of the Earth.

I have argued elsewhere that the “launch everything from Earth” template we’ve been locked into for the last 50 years has imprisoned us.   Because of the “tyranny of the rocket equation,” we’ve been capability limited – hobbled by upfront launch requirements that consume otherwise useful reserves of mass and power – just to get into space.  Propellant depots do not address this fundamental conundrum; they simply obviate the need for a very big launch vehicle by allowing us to stage complex, heavy missions from Earth in smaller increments.  Propellant depots are a necessary but insufficient element in a long-term space faring strategy.  To truly change the rules of spaceflight, we need to learn how to access and use what we find in space to create new capabilities in space. This involves learning how to use extraterrestrial resources of material and energy.

The Moon was picked as the first destination of the original Vision for Space Exploration because it contains resources in an accessible and readily usable form.  By skipping past the Moon, it is certain that we will not use space resources for decades because, in order to access and begin using asteroid materials, we will need long-term, if not permanent, presence in the vicinity of the asteroid to characterize, experiment, and learn how to process its resources into usable forms.  Initially, robotic missions can begin the characterization of resources, but robots are not sophisticated enough to set up and begin operating a production pipeline, which requires both repetitive and intelligent interaction with the processing.  Unlike the Moon, the duration of human presence around a given NEO will be extremely limited by the ironclad laws of celestial mechanics.

It’s interesting to compare the new GT/NIA plan with the lunar return architecture that Tony Lavoie and I recently published.  Our architecture also uses propellant depots, initially supplied from Earth but ultimately supplied from the Moon.  It creates an expandable, fully functional resource outpost on the Moon, complete, with a reusable, extensible Earth-Moon transportation system capable of exporting rocket propellant to cislunar space within 16 years, at a program cost of $87B.

The affordable lunar return architecture begins the dissolution of space logistics from Earth’s apron strings, leaving in place a legacy infrastructure that can eventually take us beyond cislunar space.  Such a system has important scientific, economic and national security value.  In contrast, as much as I applaud the GT/NIA effort, their plan spends between $73-97B over 20 years for a single human mission to an as-yet unselected destination, and in the end, has us still launching everything from the Earth.

As painful as this upheaval in the space community has been, it need not be in vain.  Both economic and scalable function is required for space operations.  A healthy, viable national space program needs purpose and a return on investment.  By returning to the Moon and using its resources, we get what we need in order to get what we want.

The solar corona is a stream of energetic particles flowing from the Sun, the solar wind

A recent article about the role of global magnetic fields in the loss of planetary volatiles caught my attention.  The article addresses planetary climate issues as they relate to Earth, Mars and Venus, but what struck me was this statement:

We don’t have a direct record of the sun’s history, but astronomers can study other stars that are similar to our sun at an earlier age.

But in fact, we do have an excellent historical record of the Sun’s history – preserved on our nearby Moon.

The Sun constantly emits streams of high-energy particles, consisting mostly of hydrogen atoms and ions (protons).  This stream, called the solar wind, has been monitored and studied since satellites were first launched.  High-energy solar wind flows around the protective bubble of Earth’s global magnetic field and into interplanetary space.  Some of these charged particles become trapped between magnetic lines of force, creating spectacular displays of aurora, known as the “northern lights.”

The Moon does not have a global magnetic field, so its surface is directly exposed to the solar wind.  These charged particles and neutral atoms impinge directly upon the surface, where some of its atoms are retained on the grains, thus creating a recoverable record of matter from the Sun. The antiquity of the lunar surface means a preserved solar record extending back at least several billion years – the average age of the surface units of the Moon.

We have measured solar wind gas implanted onto the dust grains of the Moon using the Apollo samples and have a good indication that this record contains some significant information.  One curious and obscure relation in the solar wind record recovered from the Moon suggests that the ratio of some isotopes of nitrogen (specifically, the ¹⁵N/¹⁴N ratio) has increased over the last couple of billion years.  This increase is not predicted in current models of stellar evolution; the current interpretation is that it reflects the addition of a meteoritic component, but changes in the solar output have not been ruled out.  So the Sun may be evolving and changing in ways we do not fully understand.

The Sun literally is responsible for our existence – without it, life on Earth would not be possible.  Media coverage of climate change tends to ignore the critical fact that the primary driver of climate on Earth and all terrestrial planets is the Sun.  Before we can understand how and why climate changes on Earth (and it has repeatedly throughout geological history), we must understand what historic role the Sun has played in this complex exchange.

At any given time, only the uppermost few millimeters of the Moon’s regolith is exposed to the Sun.  Because the regolith is continually excavated, buried, mixed and turned over by the bombardment of meteorites, we have a very complex record to decipher.  Such a chaotic, random process would seem poised to destroy exactly the very information we need to access and study, similar to the destruction of scientific clues about past climatic conditions on our geologically dynamic Earth.  But our nearest neighbor has provided a process that preserves the solar record in ancient regoliths, whereby the solar record is isolated and sequestered for very long periods of time.

The dark maria of the Moon is made up of a myriad of individual lava flows, erupted sporadically but continuously, since 3.9 billion years ago, possibly to as recently as less than 1 billion years ago. These fresh surfaces are readily exposed to the solar wind, which implants its atoms onto the dust grains.  From the moment the lava flow cools, this fresh surface is slowly ground up and broken apart by meteorite impact (regolith formation). Then, as new lava flows are extruded, they cover the pre-existing surface regolith, forever sealing it off, along with its preserved solar record, from active surface processes.  Thus, thousands of individual lava flows in the maria have buried and preserved millions of ancient regolith deposits, all potentially available for study, allowing us to see not only the output of the current Sun, but the solar wind record of some ancient Sun as well.

Thus, the dusty regolith of the Moon acts like a tape recorder, detailing the output of the Sun throughout time.  How might we find and access these ancient regoliths and read the preserved solar record?  These deposits are accessible wherever there is an exposed section of bedrock in the lunar maria.  On the Moon, such exposure occurs within the walls of craters, sinuous rilles and other structural depressions.  Not only did we photograph such exposures during the Apollo missions, we may already have sampled a “fossil regolith” from a unit that is more than 3.84 billion years old.  Finding and sampling more of these buried units will allow us to reconstruct the output and history of the Sun over the course of at least the last 4 billion years.

Here is yet another reason to return to the Moon: to understand the history of our Sun, the primary driver of climate and life on Earth.  It is ironic that many people who are most ardent in their concern about Earth’s changing climate disparage lunar return because “we’ve been there.”  By dismissing the Moon, they are missing one of the most important chapters necessary in understanding the grand story of the past, present and probable future of the Earth and the Solar System.  That chapter – holding vital answers necessary for an informed debate about our constantly changing climate – patiently waits for us on the Moon.

Marius Hills on the Moon (left) and Marion Island, Indian Ocean, Earth (right) -- Twins?

Come home with your shield, or on it – Spartan women to their husbands, marching off to war.

From the giant Olympus Mons shield on Mars (600 kilometers across and 27 km high) to the large volcanoes of Venus, shield-building was thought to be a common expression of volcanism on all rocky Solar System bodies; the Moon appeared to be a conspicuous exception.  In geology, a shield volcano is a volcanic construct with a broad, low profile made up primarily of thin lava flows with little ash deposits.  Earth’s shield volcanoes range in size from a few to more than 200 km for the Big Island of Hawaii, the extent of its base on the sea floor beneath the surface of the Pacific Ocean.

Our understanding of lunar volcanism has been informed and shaped both by images and samples.  The large-scale shield volcanoes so prominent on Mars, Venus and Earth were believed to be absent on the Moon.  Before the Apollo 11 astronauts visited Mare Tranquillitatis in 1969, we understood that the dark maria of the Moon were volcanic lava plains.  Orbital images showed us a landscape of domes, small cones, sinuous lava channels (rilles) and collapse pits – surface features created by volcanic activity.  Many of these small volcanic features tend to be clustered in provinces concentrated on the western near side.

Rocks from the maria are basalts, the most common type of igneous rock in the Solar System.  They are rich in iron and magnesium and poor in silica.  On Earth, when such rocks are molten, the resulting magma has a very low viscosity (i.e., they are very fluid, spreading onto flat surfaces in thin sheets).  We understand lunar lavas to be similarly fluid, having erupted in thin sheet-like flows onto the airless surface of the Moon.  The maria formed as this geologic process of massive high-volume eruptions built up stacks from the thin, fluid flows which extend for hundreds of kilometers.  Scattered within the ancient maria are numerous small volcanic constructs, previously believed to be the only manifestation of central-vent volcanism on the Moon.

When the Moon’s topography was mapped with laser altimetry (first by Clementine in 1994, then at greater resolution by the Japanese Kaguya spacecraft and NASA’s Lunar Reconnaissance Orbiter mission), it showed clusters of many small volcanoes occurring on topographic highs that are quasi-circular, with low relief and shield-shaped.  Pat McGovern, Walter Kiefer (colleagues at the Lunar and Planetary Institute) and I were intrigued by this correspondence.  We studied these areas by mapping volcanic features, integrating the new topographic data, and examining their gravity signatures (the amount the local gravitational attraction is enhanced or depleted from normal).

We found that these large shield-shaped topographic swells are made of basaltic lava and display concentrations of volcanic features.  Such a structure found on Venus or Mars would be classified as a shield volcano; therefore, we interpret these features on the Moon as shield volcanoes.  We have found seven of these large structures on the Moon, ranging in size from 66 to almost 400 kilometers in diameter and from 600 to over 3200 meters in height.  Such sizes and shapes are very similar to large shields on Earth, Venus and Mars.  The average slopes on these volcanoes are very low, typically less than a few degrees, as would be expected for structures made from very fluid lava.  These lunar shields display abundant volcanic features, including domes and cones, sinuous rilles (lava channels and tubes) and collapse features – all common morphologies in terrestrial shield volcanoes.

Topographic map of the Marius Hills shield on the Moon from LOLA laser altimetry. A broad topographic swell with many small cones and domes on it.

Although we believe these features are shield volcanoes, this new interpretation is not without some difficulties.  Unlike most shield volcanoes on the other planets, none of the lunar shields has a central collapse pit (caldera).  However, many shields – especially those on Venus – likewise do not show central calderas.  Additionally, while evidence for some lunar shields such as the Marius Hills is pretty convincing (e.g., shield shape, high gravity signature indicating dense stacks of lava), the evidence for others is not as clear.  The largest feature we identified, the Cauchy shield, possesses the correct topographic shape and has numerous small cones, rilles, and vents on it, but remote sensing data suggest that the lava thickness in eastern Mare Tranquillitatis is relatively thin, which might mean that Cauchy is not a thick stack of lava as Marius appears to be.  We still think that Cauchy is a shield volcano, but acknowledge that our interpretation is tentative and we will continue studying these enigmatic features to better understand their history.

But the real story here is not whether these features are true shield volcanoes or not, but rather, how the advent of new, high-precision data (high resolution topography) can cause scientists to reexamine areas and processes long thought understood and perhaps come to surprisingly different interpretations.  We are currently in the midst of a revolution in lunar science.  The 42^nd Lunar and Planetary Science Conference held this month in Houston highlighted new scientific findings about the history and processes of the Moon.   New, high-quality data coming from an international flotilla of lunar orbital mappers – Chandrayaan, Kaguya, Chang’E and LRO – has scientists seriously reconsidering our current understanding of the processes, history, resources and potential of the Moon.

NASA spending as fraction of federal budget by year, in constant dollars.

On February 15, 2011 a symposium entitled “U.S. Human Spaceflight: Continuity and Stability” was held at Rice University’s James A. Baker Institute of Public Policy.  Organized by George Abbey, the resident space expert at the Baker Institute, one might have suspected that it would be Shuttle-centric and indeed, it was.  Many pertinent points relevant to the current discussion about NASA’s human space program and its future (or lack thereof) came out of the presentations at this symposium.

The program featured several speakers, all of whom played major roles in the Shuttle program.  I found comments by Robert F. “Bob” Thompson most interesting.  Bob Thompson is one of the true “old guard” – an original member of Bob Gilruth’s Space Task Group at NASA Langley, a group pre-dating the Mercury Program.  Thompson was head of the Apollo Applications Program (Skylab) and the first manager of the Space Shuttle program.  Many of his remarks resonate strongly with points I have made here and elsewhere about serious problems being dismissed or ignored in the unseemly rush to re-vamp NASA from an operational space flight agency into a check-writing bureaucracy for New Space endeavors.

Thompson’s theme was a considered and educated look at what discarding the country’s Space Shuttle Program means.  Both his talk and the talk by Howard DeCastro (Shuttle Program Manager at the United Space Alliance, which operates the Shuttle system for NASA) carefully outlined the history of the Shuttle program and the possibility of flying the Shuttle commercially until a new system becomes available, thereby retaining our national spaceflight capability.  They covered the many compromises made both in Shuttle’s conception and in its execution, as well as its unique capabilities.  The Shuttle can both deliver and retrieve payloads from space; it is a fully integrated transport and servicing system in low Earth orbit.  The famous Hubble Space Telescope would be a useless piece of junk instead of a national treasure without the Shuttle missions that first allowed for the repair of its defective vision and then returned to service the instrument in space multiple times over the ensuing decade.

An often ignored but critically important issue is the supporting infrastructure for spaceflight.  Thompson made the analogy that when people see a Shuttle Orbiter, they really are seeing just the “tip of an iceberg.”  The Shuttle is more than an orbiter vehicle; it is also the servicing facilities at the Cape that process and prepare the orbiter for launch.  It is the ET fabrication facilities at Michoud and the SRB plant at Promontory as well as the Space Shuttle Main Engine (SSME) that has performed flawlessly over the 133 flights to date.  It is the mobile crawler and the launch towers at Pad 39-A.  And it is the trained cadre of people that put all the pieces together and make them work in concert to deliver and return people and equipment from space.   Thompson rhetorically encompassed his argument thusly: The Shuttle is a “dumb vehicle that cost too much” but is a “fully functional part of a space transportation system – an 18-wheel, extended cab work vehicle.”  He told the audience that Orion, Soyuz and Progress were more like “taxis” and “pickup trucks.” He said that the Constellation vehicles (chosen to implement the 2004 Vision) were bad decisions, followed on now by an even worse decision.

Thompson used a familiar graphic, the chart showing NASA’s fraction of the annual federal budget over decades (see above).  The large spike centered around 1966 represents peak spending for the Apollo program.  Thompson made two specific observations about this graph.  First, Richard Nixon (who took office in 1969) is often damned as the President who “killed Apollo.”  But the graph shows that the ramp-down in spending for Apollo began two years earlier in 1967, in Lyndon Johnson’s administration.  The Vietnam War required some of NASA’s money, so Apollo-Saturn production managers were told to build the equipment needed to fulfill Kennedy’s decadal goal and shut down thereafter.

Additionally, Thompson made the very significant point (one usually ignored by many engaged in space policy debates) that the “Apollo spike” paid for the infrastructure – the buildings, laboratories, test and training facilities, and launch systems – that Apollo used and that the Shuttle uses to this day.  By terminating the Shuttle with no follow-on, the fate of most of this infrastructure is the scrap heap.  Note that the “Apollo spike” in funding happened forty years ago.  To design and build the supporting infrastructure for human spaceflight in the mid-1960s, we annually spent ten times the fraction of the budget that we do now.  Given the reality of the nation’s finances, NASA will be lucky if they can continue to get one-half of one percent of federal spending per year.  This does not seem to be a good time to throw away three functioning Shuttle orbiters, thereby discarding a working national space faring capability, one carefully built and paid for over the last 50 years.

Several New Space companies are working on vehicle designs, which, if successful in creating a replacement space “work vehicle,” will need their own supporting infrastructure.  These efforts will necessitate creating all the facilities mentioned above for their vehicles and systems.  The cost of any given single launch is rolled into one number, but it must cover a multitude of expenses.  Amortized over many decades, they may eventually pay for it all, but only if they can get enough business to fly their vehicles regularly and often.  With NASA as their principal customer, will enough flights be purchased to take these New Space companies to the level they need in order to make a profit and survive?

Finally, Thompson asked, what is exploration if not living and working in space and contributing to the economy?  He understands that exploration is more than going somewhere and planting a flag or collecting some rocks.  Each time NASA launches a Shuttle, it puts 100 tons in space.  By replacing the orbiter body with a cargo faring, we are creating a heavy lift launch vehicle.  This Shuttle side-mount launch vehicle is something that fits the requirements placed on NASA for a new heavy lift vehicle.  Its reliability has been consistently improved over the course of more than 30 years of flight experience and is more than adequate for many different kinds of missions throughout cislunar space.  This is where the focus of our space program ought to be – and a zone of space specifically mentioned in the new agency authorization.

Preserving, adapting and using what we already have is smarter than destroying capability and starting again from scratch.  We are putting faith in the emergence of space systems that will do what we want, when and where we want.  We are told that to nurture and foster other providers of space access, we must throw away the bird in our hand and plant a revolutionary new bush, hopeful that it will grow and attract a variety of new birds.  I leave it to you to decide the wisdom of such a restrictive course.  Plant the bush but don’t throw away the only bird we now hold.  We must be fully conscious about the realities of non-existent systems and preserve the space transportation capability on which America can rely.