The Case for Mars, page 38
The Mars rock discoveries have changed all that. Now exobiology and paleontology have moved to the fore. And while seismology and meteorology can be done well, and geochemistry done badly, with robotic probes, exobiology and paleontology cannot be done competently without human explorers on the surface. Fossil hunts require the ability to hike miles across unimproved terrain, to climb up boulder fields, to do both heavy work and delicate work, and to exercise subtle forms of perception and intuition, all of which are far beyond the capabilities of robotic rovers. To find the fossil beds that will reveal the ancient Martian biosphere in its true glory will take human explorers, real live rock hounds, on the scene. To drill deep into the ground to bring up subsurface water in which Martian life may yet exist will take human prospectors and drill-rig teams working out of a permanent Mars base.
President Clinton has called for putting “the full intellectual resources and technological prowess of the United States behind the search for life on Mars.” If this commitment is to be honored, then the United States will have to send human explorers to Mars. Administrator Goldin is leery, at least publicly, of using the NASA team’s findings as a reason to launch an immediate, aggressive campaign of Mars missions, especially human missions. Having weathered several years of fairly vicious budget cuts and sensing a distinct hostility toward new, possibly big programs on the Hill, Goldin has been cautious. “Our missions should be driven by scientific potential,” he notes, “and the potential for economic opportunity.” If we go to Mars, via robotic missions or human missions, we should know “why we’re there.” Goldin wants mission planning to be “science driven,” not the result of an “emotional” response.
Goldin, of course, has to play to an audience that includes not only the president and Congress, but also White House science advisor Jack Gibbons, a long-time skeptic of human space exploration, and therefore may deem it wise to keep his comments enthusiastic but conservative. A slightly different view of the future was offered by Richard Zare during the August 7 press conference. “It’s very important to this country to really keep its sense of exploration, the pioneering spirit, the same thing that brought our forebears to the New World,” he said. “I think there are new wrlds to explore in space and elsewhere, but we people must be willing to invest in them. When we turn inward, when we forget to make these investments, when we lose that will, such nations perish.”
I couldn’t have said it better.
Mars Direct promises to land a crew on the planet within a decade. The plan makes this possible by using local Martian resources to manufacture fuel for the trip home. The crew hab is the tuna-can shaped object on the left; the conical ERV stands to the right. (Artwork Robert Murray, courtesy Lockheed Martin)
As an added benefit, Mars Direct hardware can be used for missions to the Moon, as shown here. (Artwork Robert Murray, courtesy Lockheed Martin)
The Ares heavy lift booster, composed of shuttle-derived propulsion technology, will directly launch crew and equipment to the Red Planet. (Artwork Robert Murray, courtesy Lockheed Martin)
Viking orbiter views of the surface gave clear evidence for Mars’ watery past, as can be seen in this image of water-carved channels found to the west of the Viking 1 landing site. (Photo courtesy NASA)
Given that Earth and Mars shared similar climates in the distant past, there is a chance that life could have evolved on the Red Planet, in this instance in the form of Martian stromatolites. (Artwork by Michael Carroll)
Mars Global Surveyor aero-brakes into orbit. (Artwork Michael Carroll, courtesy NASA/JPL)
Two robotic missions to the Red Planet—Mars Global Surveyor and Mars Pathfinder—will launch late 1996. The Mars Aerial Platform mission could return information invaluable to piloted missions and a Mars Sample Return mission employing locally produced propellants could demonstrate this critical technology.
The Mars Aerial Platform (MAP) mission will employ superpressure balloons to fly cameras over the surface of the Red Planet for hundreds of days. (Artwork Robert Murray, courtesy Lockheed Martin)
The Mars Pathfinder lander with Sojourner rover. (Artwork courtesy NASA/JPL)
The Mars Sample Return mission will return several kilograms of soil to Earth for analysis. (Artwork Pat Rawlings, courtesy NASA/JSC)
Mars Semi-Direct step 1 : Propellant production on Mars. (Artwork courtesy NASA/JSC)
In the fall of 1992, NASA broke with the “Battlestar Galactica” paradigm and adopted Mars Semi-Direct as their baseline.
Mars Semi-Direct step 2: Arrival of crew in surface hab. (Artwork courtesy NASA/JSC)
Mars Semi-Direct step 3: Crew departure. (Artwork courtesy NASA/JSC)
Mars Semi-Direct step 4: Rendezvous with ERV. (Artwork courtesy NASA/JSC)
Departure from Earth as envisioned for a traditional “Battlestar Galactica” Mars mission. (Artwork by Michael Carroll)
The first Mars missions will focus on the search for evidence of past or present life and for resources for the future. (Artwork Pat Rawlings, courtesy NASA)
Larry Clark (left) and the author perform initial checkout of the In-Situ Propellant Production plant developed by a team at Martin Marietta under contract to NASA Johnson Space Center. This demonstration unit clearly showed that making propellant on Mars is a viable concept. (Photo courtesy NASA)
NASA administrator Dan Goldin (right), shown here with the author and the Martin Marietta ISPP machine, became a supporter of Mars Direct. (Photo R. Zubrin)
The author talks Mars mission strategy with Speaker of the House Newt Gingrich. (Photo R. Zubrin)
Mars Direct making press. This photo of Robert Zubrin (left), David Baker (center), and Ben Clark (right) ran as the cover of Rocky Mountain News magazine shortly after Baker and the author began presenting the plan at conferences around the country. (Photo courtesy Rocky Mountain News)
Mars Direct habitats can be mated up with the aid of inflatable tunnels to create an initial Mars base in fairly short order. (Artwork by Cr Emmart)
An Earth Return Vehicle descends to land at a growing Mars base. (Artwork by Michael Carroll)
A mature base, established over a geothermal energy source, will provide a testbed for establishing technologies crucial to settling Mars. (Artwork by Carter Emmart)
Ballistic NIMF. (Artwork Robert Murray, courtesy Lockheed Martin)
NIMF Rocketplane. (Artwork Robert Murray, courtesy Lockheed Martin)
NIMFs—Nuclear Rockets using Indigenous Martian Fuels—as rocketplanes or as ballistic spacecraft would afford Mars explorers and later colonists unlimited mobility on a planetary scale.
Exploration team on a partially terraformed Mars. (Artwork by Michael Carroll)
The New Created World. (Artwork by Michael Carroll)
Liquid water once coursed over the face of Mars and, given the technological capabilities of the twenty-first century, it may once again. Several decades of terraforming could transform Mars into a relatively warm and slightly moist planet suitable some day for explorers without space-suits, although breathing gear would still be required. Returning oceans to Mars is actually a possibility for the distant future.
GLOSSARY
Aerobraking: A spacecraft maneuver using friction with a planetary atmosphere to decelerate from an interplanetary orbit to one about a planet.
Aeroshell: A heat shield used to protect a spacecraft from atmospheric heating during aerobraking.
Apogee: The highest point in an orbit about a planet.
Atmospheric pressure: The pressure an atmosphere exerts. On Earth at sea level, the atmospheric pressure is 14.7 pounds per square inch. This amount of pressure is therefore known as one “atmosphere” or one “bar.”
BEIR: Biological effects of ionizing radiation.
Bipropellant: A rocket propellant combination including both a fuel and oxidizer. Examples include methane/oxygen, hydrogen/oxygen, kerosene/hydrogen-peroxide, etc.
Buffer gas: An effectively inert gas that is used to dilute the oxygen required to support breathing or combustion. On Earth, the 80 percent nitrogen found in air serves as a buffer gas.
Conjunctionem> The position of a planet behind the Sun as seen from another planet. When Earth and Mars are in conjunction, they are on opposite sides of the Sun.
Conjunction mission: A mission that flies about half of the way around the Sun to travel from one planet to another. Conjunction missions have the lowest propulsion requirements.
Cosmic ray: A particle, such as an atomic nucleus, traveling through space at very high velocity. Cosmic rays originate outside of our solar system. They typically have energies of billions of volts and require meters of solid shielding to stop.
Cryogenic: Ultra-cold. Liquid oxygen and hydrogen are both cryogenic fluids as they require temperatures of-180° and -250°C, respectively, for storage.
Delta 2: An expendable launch vehicle manufactured by McDonell Douglas, capable of throwing 1,000 kg on a direct trajectory from Earth to Mars.
Delta-V (also written ΔV): The velocity change required to move a spacecraft from one orbit to another. A typical delta-V required to go from low Earth orbit to a trans-Mars trajectory would be about 4 km/s.
Departure velocity: The velocity of a spacecraft relative to a planet after effectively leaving the planet’s gravitational field. Also known as hyperbolic velocity.
Direct entry: A maneuver in which a spacecraft enters a planet’s atmosphere and uses it to decelerate and land without going into orbit.
Direct launch: A maneuver in which a spacecraft is launched directly from one planet to another without being assembled in orbit.
Electrolysis: The use of electricity to split a chemical compound into its elemental components. Electrolysis of water splits it into hydrogen and oxygen.
Electron density: The number of electrons per cubic centimeter. The higher the electron density of an ionosphere, the better it reflects radio waves.
Endothermic: A chemical reaction requiring the addition of energy to occur.
Epicycle: A small circle whose center travels along the path of a larger circle. Ancient and medieval astronomers described the motion of the planets by envisioning that each planet traveled in a circle—the epicycle—whose center moved along a larger circle centered on the Earth.
Equilibnum constant: A number that characterizes the degree to which a chemical reaction will proceed to completion. A very high equilibrium constant implies near complete reaction.
ERV: Earth return vehicle.
ET: External tank.
EVA: Extravehicular activity.
Exhaust velocity: The speed of the gases emitted from a rocket nozzle.
Exothermic: A chemical reaction that releases energy when it occurs.
Fairing: The protective streamlined shell containing a payload that sits on top of a launch vehicle.
Fast conjunction mission: A conjunction-type mission (see above) inwhich some extra propellant is used to shorten the flight time.
Free-return trajectory: A trajectory which, after departing Earth, will eventually return to the Earth without any additional propulsive maneuvers.
GCMS: Gas chromatograph mass spectrometer.
Geothermal energy: Energy produced by using naturally hot underground materials to heat a fluid, which can then be expanded in a turbine-generator to produce electricity.
Gravity assist: A maneuver in which a spacecraft flying by a planet uses that planet’s gravity to create a slingshot effect which adds to the spacecraft’s velocity without any requirement for the use of rocket propellant.
Heliocentric: Centered about the Sun. A heliocentric orbit is one that trans-verses interplanetary space and is not bound to the Earth or any other planet.
Hohmann transfer orbit: An elliptical orbit, one of whose ends is tangent to the orbit of the planet of departure, and whose other end is tangent to the orbit of the planet of destination. The Hohmann transfer orbit is the purest incarnation of the conjunction-class orbit, and as such is the lowest-energy path from one planet to another.
Hydrazine: A rocket propellant whose formula is N2H4. Hydrazine is a mono-propellant, which means that it can release energy by decomposing, without any additional oxidizer required for combustion.
Hyperbolic velocity: The velocity of a spacecraft relative to a planet before entering, or after effectively leaving, the planet’s gravitational field. Also known as approach or departure velocity.
Hypersonic: A speed many times the speed of sound; in common usage Mach 5 or greater.
Ionosphere: The upper layer of a planet’s atmosphere in which a significant fraction of the gas atoms have split into free positively charged ions and negatively charged electrons. Because of the presence of freely moving charged particles, an ionosphere can reflect radio waves.
Isp: A commonly used abbreviation for specific impulse (see below).
ISPP: In-situ propellant production.
JSC: Johnson Space Center, Houston, Texas.
kb/s: kilobits per second.
Kelvin degrees: The Kelvin or “absolute” scale is a method of measuring temperature which starts with its zero point set at “absolute zero,” the temperature at which a body in fact possesses no heat. Thus, 273 degrees Kelvin is the same temperature as 0° centigrade, the freezing point of water. Each additional degree Kelvin corresponds to one additional degree centigrade.
kHz: kilohertz, a measure of frequency used in radio. One kHz equals 1,000 cycles per second.
km/s: kilometers per second.
kW: kilowatts.
kWe: kilowatts of electricity.
kWe-hr: The total amount of energy associated with the use of one kilowatt of electriciy for one hour.
kWh: The total amount of energy associated with the use of one kilowatt for one hour.
LEO: Low Earth orbit.
LOR: Lunar orbit rendezvous.
LOX: Liquid oxygen.
MAV: Mars ascent vehicle.
Methanation reaction: A chemical reaction forming methane. In the Mars Direct mission, the methanation reaction is the Sabatier reaction in which hydrogen is combined with carbon dioxide to produce methane and water.
MHz: megahertz, a measure of frequency used in radio. One MHz equals 1,000,000 cycles per second.
millirem: 1/1,000th of a rem (see below).
Minimum energy trajectory: The trajectory between two planets requiring the least amount of rocket propellant to attain (see Hohmann transfer).
m/s: meters per second.
MOR: Mars orbit rendezvous.
MSR: Mars sample return.
MSR-ISPP: Mars sample return employing in-situ propellant production.
MWe: Megawatts of electricity.
MWt: Megawatts of heat. One megawatt equals 1,000 kilowatts.
NEP: Nuclear electric propulsion.
NIMF: Nuclear rocket using indigenous Martian fuel.
NTR: Nuclear thermal rocket.
Opposition: The position of a planet in the opposite direction from the Sun as seen from another planet. When Earth and Mars are in opposition, they are on the same side of the Sun, and thus closest to each other.
Opposition mission: A mission that flies most or all of the way around the Sun (~360 degrees) to travel from one planet to another, swinging into the inner solar system in the process in order to increase speeds. Opposition missions have the highest propulsion requirements.
Perigee: The lowest point in an orbit around a planet.
Pyrolyze: The use of heat to split a compound into its elemental constituents.
