31 December 2017

There's a Hell of a Good World Next Door

Image credit: U.S. Air Force
I am fond of Mars - honestly, who isn't? It looks a little like some parts of Arizona, the southwest U.S. state where I live, so at first glance it seems cozily familiar. The cultural history of Mars is rich: it has been a favorite science-fiction setting for more than a century.

Most exciting to me, Mars might yet prove to be a home to life. We'll likely determine whether Mars lives by exploring the planet's delightfully complex geology. It seems probable, given how inhospitable is Mars's surface, that, if there is life on Mars, then it will be life in Mars. After all, much of Earth's biomass lives deep within its crust, happily metabolizing rocks and hot water. A few kilometers down, Mars and Earth might provide virtually identical habitats for life.

Mars exerts a powerful pull on our emotions. That being said, however, one has to exercise caution when emotions are part of the mix (as they always are). The thought of humans on Mars is exhilarating. Should humans, however, actually set booted foot on Mars?

I think the answer to that question must be yes - eventually. Humans should travel to every place they can. As we gain experience, improve our technology, develop new spaceflight concepts, and mull over data received from our robotic spacecraft, we become more capable. As we become more capable, we increase the probability that we can achieve success.

By "success," I mean several things. There's the obvious one: we increase the likelihood that humans will survive the Mars trip without short-term or long-term injury and be able to perform meaningful exploration. We also increase the likelihood that we will not clumsily interfere with the study of any native living things by accidentally introducing terrestrial biological contamination.

It would be really helpful if we had a place nearby where we could prepare ourselves for journeys throughout the Solar System. A good-sized world with a range of exotic alien environments and a complex geology. A world from which we might return rapidly if we got ourselves in over our heads. Bonus points for a world we can reach cheaply, using technologies we have at hand, and from which we can extract resources that could facilitate our journeys to more distant worlds.

Such a world exists. It bears boot prints nearly half a century old. Using technology shockingly primitive by modern standards, 12 humans walked, worked, and drove there. When they needed advice and assistance, they spoke with a support team back on Earth with a one-way radio time-delay of only 1.25 seconds. One spacecraft suffered a crippling oxygen tank explosion, but Earth was close enough that its three-man crew was able to return home safely.

I've expressed my views concerning this nearby world before on this blog. I've called it a part of Earth. Together with Earth, it forms a binary world unique in the inner Solar System. Mercury and Venus have no moons; Mars has two, but they more closely resemble middling-sized asteroids than they do planets. Earth, however, has as its near neighbor the planet-size Moon, a world which, were it a continent, would rank after only Asia in surface area. It is the fifth-largest moon in the Solar System; only Ganymede, Titan, Callisto, and Io, all moons of outer Solar System gas giant planets, are larger.

We have barely explored our planet's moon. Automated and piloted orbiters have surveyed its entire surface off and on over the past half-century, but no functioning spacecraft has landed on the Farside, the hemisphere of the Moon we cannot see. Nor has any spacecraft soft-landed near its poles, where ice hides in permanently shadowed craters at temperatures near those the New Horizons spacecraft measured at Pluto.

The ice at the lunar poles might supply life support consumables and rocket propellants for at least tens of thousands of years. By virtue of its low gravity - just half that of Mars and one-sixth that of Earth - and its lack of an atmosphere, the Moon could become an economical water supplier for an Earth-Moon infrastructure that might include habitats, spacecraft service stations, powerful observatories, lasers for boosting light sails, human-tended factories, and other facilities. Many of these facilities could be built at least in part from lunar titanium, aluminum, and glass. By the time the Earth-Moon infrastructure attains that level of sophistication, propellants needed for fast and frequent piloted journeys to Mars will amount to an incidental fraction of the total produced on the Moon.

Developing the Moon also gives us time to try to determine, using robots, whether life exists on Mars. It buys us time to decide what Mars life - and, indeed, life of other worlds - should mean for us and our posterity. Microbial life on or in Mars might not be a dead end; it might instead be biding its time. After all, for nearly all of its history, life on Earth was strictly microbial.

Gaining experience in the Earth-Moon system opens up many new opportunities beyond Mars. If we determine that long-term habitation of Mars is undesirable, then the lessons we learn and capabilities we acquire by developing the Moon and cislunar space could be readily applied to worlds throughout the Solar System. Consider this: Earth and its moon resemble more worlds in the Solar System than does Mars. The Moon resembles any number of vacuum worlds with significant surface gravity (Mercury, Ganymede, Iapetus, Miranda, Pluto), while Earth shares traits with Venus and Titan. Only Mars combines significant gravity with just enough atmosphere to raise dust storms.

If Mars pulls on our emotions, then it is probably not too bold to say - without any hint of superiority - that the Moon pulls on our minds. Of course, people who value the Moon have an emotional stake in it. It seems different to me, however, than the exuberance many feel toward Mars. I suspect that, if you have read this far, then you might see a difference, too.

Image credit: NASA

The post title is a play on the last line of e. e. cummings' free-verse sonnet "pity this busy monster, manunkind," published in 1944. That line reads - "listen: there's a hell of a good universe next door; let's go"

More Information

The Eighth Continent

Harold Urey and the Moon (1961)

"A Continuing Aspect of Human Endeavor": Bellcomm's January 1968 Lunar Exploration Program

Rocket Belts and Rocket Chairs: Lunar Flying Units

Apollo's End: NASA Cancels Apollo 15 & Apollo 19 to Save Station/Shuttle (1970)

23 December 2017

What If a Shuttle Orbiter Struck a Bird? (1988)

Final approach: the Shuttle Orbiter Discovery lands on the Shuttle Landing Facility at Kennedy Space Center, Florida, at the end of its longest mission (STS-131, 5-20 April 2010). Image credit: NASA
The first NASA astronaut to die in the line of duty was U. S. Air Force Captain Theodore Freeman. Little known today, Freeman was a member of the third astronaut selection group, which NASA introduced to the world on 18 October 1963. The group included 10 astronauts who would become famous - Michael Collins, Edwin Aldrin, Alan Bean, David Scott, Russell Schweickart, William Anders, Eugene Cernan, Walter Cunningham, Donn Eisele, and Richard Gordon - and three besides Freeman who would perish before reaching orbit - Clifton Williams, Roger Chaffee, and Charles Bassett. Of the seven pre-Shuttle NASA astronaut groups, Group 3 experienced more pre-flight astronaut deaths than any other.

The astronauts had at their disposal Northrop T-38 Talon supersonic training aircraft. They used them in two basic ways: for training sorties to accumulate flight time so that they could keep their piloting skills well honed and retain their flight status, and as readily available, speedy transportation to NASA and contractor facilities and training sites across the United States. Transportation flights also contributed to the flight time requirement.

On 31 October 1964, 34-year-old Freeman took off alone in a T-38 from Ellington Air Force Base, located between downtown Houston, Texas, and NASA's Manned Spacecraft Center (MSC). He began his training sortie by flying over MSC, then out over Clear Lake and Galveston Bay.

NASA's Third Astronaut Group. Theodore Freeman is in the back row, fourth from left. Image credit: NASA
As he returned to Ellington, a flock of Canadian geese took wing to one side of his flight path. As he made a turn, the flock rose up around his T-38, and one bird struck and shattered the plane's plexiglass forward canopy. Plexiglass shards entered the jet's twin engines through their air intakes. Moments later, the engines began to fail.

The eight-pound goose did not enter the T-38's intakes, though some sources report that it did. In fact, after striking the canopy, it struck the plane's rear seat, then spun away along the jet's upper fuselage.

Freeman tried to line up with an Ellington runway, but the engines flamed out and his plane began a steep dive at low altitude. He ejected, but before his parachute had time to open he struck the ground and was killed.

In October 1983, nearly 20 years after Freeman's untimely death, The Christian Science Monitor published a puff piece on NASA's efforts to keep wild pigs and alligators off the 15,000-foot-long, 300-foot-wide Shuttle Landing Facility (SLF) runway at Kennedy Space Center (KSC) in Florida. The story was timely because NASA aimed to achieve its first Orbiter landing at the SLF in January 1984. The space agency had planned to land Challenger at the SLF at the end of mission STS-7 on 24 June 1983, but had to divert it to Edwards Air Force Base (EAFB) in California after KSC became fogged in.

The north end of the SLF is about a mile from the Visitor Center for the Merritt Island National Wildlife Refuge (MINWR). MINWR and KSC both owe their origin to President John F. Kennedy's 25 May 1961 "moon speech." In 1962-1963, NASA acquired more than 140,000 acres of orange groves, swamp, and beaches to create a safety buffer around its Apollo Saturn V launch pads and other facilities. As landowners moved out, sometimes grudgingly, wildlife moved in.

On 28 August 1963, the space agency and the U.S. Fish and Wildlife Service agreed that the latter would manage the roughly 90% of KSC that NASA did not actively use. The interagency agreement assumed that KSC activities would increase over the course of the 1960s and 1970s and that its facilities would steadily expand. Apollo-era construction leveled off in 1966-1967, however.

Major facilities expansion did not begin again at KSC until April 1974, when the Morrison-Knudsen Company began work on the $22-million-dollar SLF. The facility, modeled on flight research runways at EAFB, was completed in 1976. It became KSC's airport, supporting astronaut T-38s, Gulfstream II Shuttle Training Aircraft, and other planes and helicopters. The first spaceworthy Orbiter, Columbia, arrived at the SLF atop a 747 carrier aircraft in March 1979.

The Shuttle Landing Facility. Image credit: NASA
A NASA spokesman told The Christian Science Monitor's reporter that KSC and MINWR played host to "all kinds of bald eagles, vultures, lots of brown pelicans, and ducks in winter." This was, however, not of great concern; the Shuttle Orbiter was a glider, he explained, so lacked air intakes that might ingest birds.

The Christian Science Monitor reporter wrote that the Orbiter had "triple-strength windows." This was a reference to the design of the six windows making up the flight deck windshield; each was three panes thick, with empty spaces between the panes. The outermost pane, the "thermal" pane, was attached to the fuselage structure; the innermost pane, the "pressure" pane, was attached to the crew cabin structure. Between these, also attached to the crew cabin structure, was a thick "redundant" pane.

The article affected an almost humorous tone as it described measures aimed at keeping alligators and wild pigs off the SLF. It seemed impossible that the Space Shuttle, a pinnacle of U.S. technological know-how, could ever be harmed by mere animals. Its author did suggest, however, that running over alligators basking in the Sun on the SLF runway might damage the Orbiter's "delicate landing gear."

On its second try, at the end of mission STS 41-B in February 1984, Challenger glided to a safe landing on the SLF runway. NASA hailed the landing, little more than five miles from the launch pad Challenger had left just eight days before, as a major step toward routine Shuttle flights and Shuttle launch rates of up to 25 per year.

A little less than two years later, on 28 January 1986, Challenger disintegrated 73 seconds after liftoff from KSC's Pad 39B, killing its seven-person crew. The disaster revealed that the Shuttle stack - twin reusable Solid Rocket Boosters, expendable External Tank, and reusable delta-winged Shuttle Orbiter - was much less robust than many had assumed.

Under intense scrutiny, NASA commenced a wide-ranging examination of Space Shuttle systems and operations. The U.S. civilian space agency soon found that many of its comfortable assumptions were incorrect.

Shuttle windshield: the Orbiter Endeavour during mission STS-123 (11-27 March 2008). Image credit: NASA

Karen Edelstein, with NASA's Johnson Space Center, and Robert McCarty of the Wright Aeronautical Laboratories at Wright-Patterson Air Force Base in Ohio, reported on results of their study of bird impacts on the Orbiter windshield. They determined that, far from being triple-strength, it was "a poor barrier to bird impacts."

In fact, computer modeling using a refined version of the U. S. Air Force Material and Geometrically Nonlinear Analysis (MAGNA) program showed that, in every case, a four-pound bird - for example, a typical turkey vulture - would penetrate all three windshield panes in less than a second and enter the flight deck if the Orbiter were moving above an indeterminate speed between 150 knots (172 miles per hour) and 175 knots (201 miles per hour). They noted that the Orbiter traveled at up to 355 knots (408 miles per hour) as it fell past 10,000 feet and 195 knots (224 miles per hour) as its rear wheels touched the SLF runway.

This meant that at no time during descent through altitudes where birds fly did the Orbiter's windshield provide protection from bird strikes. In fact, the crew on the flight deck remained vulnerable until about the time the Orbiter's nose gear touched concrete.

Edelstein and McCarty did not examine in detail a bird impact leading to a partial window failure; for example, broken thermal and redundant panes and an intact pressure pane. This scenario was expected to occur at speeds as low as 150 knots. One may speculate that at the very least a partial failure would make the affected window essentially opaque; it might also create extra drag, altering the handling characteristics of the Orbiter.

A turkey vulture. Its wingspan is about six feet. Image credit: Wikipedia
They noted that, short of a major redesign, there was little NASA could do to beef up the Orbiter windows. They urged designers of future space planes to seek materials more sturdy than glass when designing their windshields.

The Edelstein and McCarty paper did not lead to a major Orbiter redesign or new Orbiter window materials; NASA's allotted budget would not extend that far. Instead, the space agency redoubled its efforts to scare birds away from the SLF. Mostly it relied on loud noises.

For a time in the mid-1990s, however, KSC seriously considered putting falconers on its payroll. A June 1994 study noted that falcons had been used intermittently since the 1940s to kill or scare away birds at airfields in the U.K., the Netherlands, Spain, France, Canada, and the United States.

The study determined, however, that most of the more than 300 bird species that spent at least part of the year in MINWR had little experience with falcons, so were unlikely to be frightened by them. Falcons, for their part, were likely to be confused by wading birds such as herons and egrets.

The birds most threatening to Orbiters and other aircraft at the SLF, the 1994 study found, were various species of vulture. These were too large and numerous for falcons to tackle. It noted that groups of up to 30 individuals were frequently found around a single roadkill and that a "roost" of about 300 vultures had become established on the SLF runway's southern approach path.

The vultures, which weighed up to five pounds, took to the skies to ride thermals over KSC beginning in mid-morning. Mostly they glided lazily between 150 and 1800 feet above the ground. The air currents rising off the 526-foot-tall Vehicle Assembly Building were especially attractive to them. If the birds smelled a carrion buffet, however, they could fly rapidly, thwarting efforts to track and deter them. Loud noises, effective in driving away most other birds, were of little concern to vultures.

During the mid-morning launch of the Orbiter Discovery at the start of mission STS-114 on 26 July 2005, a vulture collided with the External Tank before the Shuttle stack cleared the Pad 39A launch tower. The bird probably weighed more than twice as much as the 1.7-pound chunk of External Tank foam insulation that had struck and breached Columbia's left wing leading edge on 16 January 2003, 82 seconds into mission STS-107. The foam chunk was estimated to have been moving at about 525 miles per hour when it hit the wing.

During Earth-atmosphere reentry on 1 February 2003, hot gases entered Columbia's left wing through the breach and rapidly destroyed its aluminum internal structure. NASA's oldest Orbiter broke up, killing the seven-member STS-107 crew.

Though the low-speed bird impact caused no obvious damage to the External Tank, NASA took notice because it occurred during launch of the first Shuttle mission since STS-107. The vulture might easily have struck a more vulnerable part of the Shuttle stack, or have struck it at a higher altitude, after the Shuttle had gained speed. KSC managers decided to apply SLF bird control techniques to the twin Shuttle launch pads. They also adopted a launch-day vulture "trap-and-release" policy.

By 2009, KSC's Bird Abatement Program relied on quick removal of roadkill to eliminate a major scavenger food source and pare down vulture numbers, bird detection radar and cameras, sirens, shotguns firing blanks and whistlers, and 25 liquid-propane-fueled "cannons." Installed along the SLF in 2007, the noise-producing cannons could be set off from the SLF runway control tower or by bird observers on the ground. They could also be set to fire automatically at random times and in random directions. Despite these measures, the risk to the Shuttle from bird strikes persisted until the Orbiter Atlantis rolled to a stop on the SLF runway at the end of STS-135, the final Shuttle mission, in July 2011.


"Space Shuttle Orbiter Windshield Bird Impact Analysis," ICAS-88-5.8.3, K. Edelstein and R. McCarty, Proceedings of the 16th International Council on Aeronautical Sciences Congress held in Jerusalem, Israel, 28 August-2 September 1988, Volume 2, pp. 1267-1274

A Review of Falconry as a Bird Control Technique With Recommendations for Use at the Shuttle Landing Facility, John F. Kennedy Space Center, Florida, U.S.A., NASA Technical Memorandum 110142, V. Larson, S. Rowe, D. Breininger, and R. Yosef, June 1994

"History of the Shuttle Landing Facility at Kennedy Space Center," E. Liston and D. Elliot; paper presented at The (40th) Space Congress in Cocoa Beach, Florida, 28 April-2 May 2003

Fallen Astronauts: Heroes Who Died Reaching for the Moon, Revised Edition, C. Burgess and K. Doolan with B. Vis, University of Nebraska Press, 2016, pp. 1-45

"NASA Tries To Keep The Hogs and 'Gators Off the Shuttle's Runway," G. Klein, The Christian Science Monitor, 12 October 1983
https://www.csmonitor.com/1983/1012/101225.html (accessed 17 December 2017)

"It's a Jungle Out There!" L. Herridge, 26 June 2006 - https://www.nasa.gov/mission_pages/shuttle/behindscenes/roadkill.html (accessed 14 December 2017)

"Bye, Bye, Birdies," C. Mansfield, 30 June 2006 - https://www.nasa.gov/mission_pages/shuttle/behindscenes/avian_radar.html (accessed 16 December 2017)

"Bird Team Clears Path for Space Shuttles," L. Herridge, 12 August 2009 - https://www.nasa.gov/mission_pages/shuttle/behindscenes/clearbirds.html (accessed 14 December 2017)

More Information

Where to Launch and Land the Space Shuttle? (1971-1972)

What If a Shuttle Orbiter Had to Ditch? (1975)

What Shuttle Should Have Been: NASA's October 1977 Space Shuttle Flight Manifest

29 November 2017

X-15: Lessons for Reusable Winged Spaceflight (1966)

An X-15 rocket plane separates from its B-52 carrier aircraft. During this 9 November 1961 flight, the 45th in the X-15 series, U.S. Air Force Major Robert White piloted X-15 No. 2 to a world-record speed of Mach 6.04 (4093 miles per hour). It was the first time a piloted aircraft exceeded Mach 6. Image credit: NASA
The X-15 a strong contender for the title of "Everyone's Favorite X-plane." Conceived in the 1952-1954 period, before Sputnik (4 October 1957) and the birth of NASA (1 October 1958), the North American Aviation-built rocket plane was intended to pioneer the technologies and techniques of piloted hypersonic flight - that is, of flight faster than Mach 5 (five times the speed of sound).

Between 1959 and 1968, three X-15 rocket planes, two modified B-52 bombers, and a dozen pilots took part in joint U.S. Air Force/NASA X-15 research missions. Before the start of each mission, an X-15 was mounted on a pylon attached to the underside of a wing of a B-52 carrier aircraft at Edwards Air Force Base, California. Wearing a silver pressure suit, a single pilot boarded the 50-foot-long X-15 as it hung from the pylon, then the B-52 taxied and took off from a runway.

Early X-15 missions were "captive" flights, meaning that the rocket plane stayed attached to the B-52, or gliding flights, meaning that it carried no propellants and relied on its wings, which spanned only 22 feet, to make a controlled - though fast and steep - descent to a landing. Early powered flights used stand-in rocket engines taken from earlier X-planes. By late 1960, however, the X-15's throttleable 600,000-horsepower XLR99 rocket engine was ready. The engine was designed to burn the nine tons of anhydrous ammonia fuel and liquid oxygen oxidizer in the X-15's tanks in about 90 seconds at full throttle.

Most missions followed two basic profiles. "Speed" missions saw the rocket plane level off at about 101,000 feet and push for ever-higher Mach numbers. The X-15 reached its top speed - Mach 6.72, or about 4520 miles per hour - during the 188th flight of the series on 3 October 1967 with Air Force Major William "Pete" Knight at the controls.

Knight flew X-15A-2, the former X-15 No. 2, which had rolled over during an abort landing on 9 November 1962, seriously injuring its pilot, John McKay. When NASA and the Air Force rebuilt X-15 No. 2, they modified its design to enable faster flights. McKay resumed X-15 flights after his recovery, though injuries he sustained plagued him until his death in 1975 at age 52.

For "altitude" missions, the X-15 climbed steeply until it exhausted its propellants, then arced upward, unpowered. X-15 reached its peak altitude - 354,200 feet (almost 67 miles) above the Earth's surface - on 22 August 1963, with NASA pilot Joseph Walker in the cockpit.

During altitude missions, the pilot experienced several minutes of weightlessness as the X-15 climbed toward the high point of its trajectory, above 99% of the atmosphere, then fell back toward Earth. Aerodynamic control surfaces (for example, ailerons) could not work while the X-15 soared in near-vacuum, so the space plane included hydrogen peroxide-fueled attitude-control thrusters so that the pilot could orient it for reentry.

It was during an altitude mission that the X-15 program suffered its only pilot fatality. On 15 November 1967, Major Michael McAdams piloted X-15 No. 3 to 266,000 feet despite an electrical problem that made control difficult. During descent, McAdams lost control of the space plane, which went into a flat spin at Mach 5, then an upside-down dive at Mach 4.7. McAdams might have recovered control at that point, but then an "adaptive" flight control system malfunctioned, thwarting maneuvers that might have damped out excessive pitch oscillations and compensated for increasing atmospheric density. The X-15 broke apart at about 65,000 feet.

Flights of early rocket-powered X planes, such as the first aircraft to break the sound barrier, the Bell X-1, took place over Edwards Air Force Base, but the X-15 needed more room for its speed and altitude flights. In both powered X-15 mission profiles, the B-52 released the X-15 about 45,000 feet above northern Nevada with its nose pointed southwest toward its landing site on Edwards dry lake bed. Two radio relay stations and six emergency landing sites on dry lake beds were established along the X-15 flight path. McAdams might have landed on Cuddeback dry lake bed, 37 miles northeast of Edwards, had he regained control of X-15 No. 3.

This NASA cutaway of the X-15 displays the aircraft's XLR99 engine, weight-saving aft skids, propellant tanks, wing, fin, and fuselage structure, cockpit, and forward landing gear. The lower tail fin was necessary for flight stability, but got in the way during landing, so was designed to drop away during approach.
During high-speed flight and Earth atmosphere reentry, the X-15 compressed the air in front of it, generating temperatures as high as 1300° Fahrenheit on its nose and wing leading edges. The rocket plane's designers opted for a "hot structure" approach to protecting it from aerodynamic heating. An outer skin made of Inconel X, a heat-resistant nickel-chromium alloy, covered an inner skin of aluminum and spun glass, which in turn covered a titanium structure with a few Inconel X parts. Heat caused the skin and structure to expand, warp, and flex, but they would return to their original shapes as they cooled. The X-15's cockpit temperature could reach 150° Fahrenheit, but the pilot usually remained cool in his pressure suit.

NASA's Project Mercury, which began officially on 6 October 1958, opted for a different approach to aerodynamic heat management: a blunt, bowl-shaped, ablative heat shield (that is, one that charred and broke away during atmosphere reentry, carrying away heat). As piloted Mercury capsule flights commenced (5 May 1961) and President John F. Kennedy put NASA on course for the moon (25 May 1961), public attention shifted away from the X-15 and Edwards Air Force Base and toward Mercury, Apollo, and Cape Canaveral, Florida. X-15 research planes continued to fly, however, pushing the hypersonic flight envelope well past their original design limits.

In the same period, some within NASA planned Earth-orbiting space stations. Before Kennedy's moon speech, a space station was seen as the necessary first step toward more advanced space activities. It would serve as a laboratory for exploring the effects of space conditions on astronauts and equipment and as a jumping-off place for lunar and interplanetary voyages. Station supporters often envisioned that it would reach orbit atop a two-stage Saturn V rocket, and that reusable spacecraft for logistics resupply and crew rotation would make operating it affordable. After the moon speech, station proponents hoped that, once Kennedy's politically motivated moon goal was reached, piloted spaceflight could resume its "proper" course by shifting back to space station development.

In November 1966, James Love and William Young, engineers at the NASA Flight Research Center at Edwards Air Force Base, completed a brief report in which they noted that the reusable suborbital booster for a reusable orbital spacecraft would undergo pressures, heating rates, and accelerations very similar to those the X-15 experienced. They acknowledged that the X-15, with a fully fueled mass of just 17 tons, might weigh just one-fiftieth as much as a typical reusable booster. They nevertheless maintained that X-15 experience contained lessons applicable to reusable booster planning.

Love and Young wrote that some space station planners expected that a reusable booster could be launched, recovered, refurbished, and launched again in from three to seven days. The X-15, they argued, had shown that such estimates were wildly optimistic. The average X-15 refurbishment time was 30 days, a period which had, they noted, hardly changed in four years. Even with identifiable procedural and technological improvements, they doubted that an X-15 could be refurbished in fewer than 20 days.

At the same time, Love and Young argued that the X-15 program had demonstrated the benefits of reusability. They estimated that refurbishing an X-15 in 1964 had cost about $270,000 per mission. NASA and the Air Force had accomplished 27 successful X-15 flights in 1964. The cost of refurbishing the three X-15s had thus totaled $7.3 million.

Love and Young cited North American Aviation estimates when they placed the cost of a new X-15 at about $9 million. They then calculated that 27 missions using expendable X-15s would have cost a total of $243 million. This meant, they wrote, that the cost of the reusable X-15 program in 1964 had amounted to just three percent of the cost of building 27 X-15s and throwing each one away after a single flight.

NASA test pilot Neil Armstrong flew the X-15 seven times in 1960-1962. Armstrong became a member of NASA Astronaut Group 2 ("The New Nine") in September 1962. He orbited the Earth as commander of Gemini 8 (March 1966) and became the first man to set foot on the moon during Apollo 11 (July 1969). Another X-15 pilot, Joseph Engle, became a member of NASA Astronaut Group 5 in April 1966. Engle flew the Orbiter Enterprise during Space Shuttle Approach and Landing Test (ALT) flights in 1977, commanded Columbia for mission STS-2 in November 1981, and commanded Discovery for mission STS 51-I in August-September 1985. Image credit: NASA
The last X-15 flight, the 199th in the series, took place on 24 October 1968. Flight experience gained and hypersonic flight data collected during the nine-year program contributed to the development of the U.S. Space Shuttle, though not exactly as Love and Young had envisioned.

When, in 1968, NASA Headquarters management first floated Space Station/Space Shuttle as the space agency's main post-Apollo piloted program, the Shuttle was conceived as a reusable piloted orbiter vehicle with a reusable piloted suborbital booster - that is, the design that Love and Young had assumed. By late 1971, however, funding limitations forced NASA to opt instead for a semi-reusable booster stack comprising an expendable External Tank and twin reusable solid-propellant Solid Rocket Boosters.

The space agency was also obliged to postpone its Space Station plans at least until after the Space Shuttle became operational. Saturn V was on the chopping block, so the semi-reusable Shuttle would be used to launch the Station as well as to resupply it and rotate its crews.

Shuttle Orbiter Columbia first reached Earth orbit on 12 April 1981, but no Orbiter visited a space station until Discovery rendezvoused with the Russian Mir station on 6 February 1995 during mission STS-63. The first Shuttle Orbiter to dock with a station - again, Russia's Mir - was Atlantis during mission STS-71 (27 June-7 July 1995).


Survey of Operation and Cost Experience of the X-15 Airplane as a Reusable Space Vehicle, NASA Technical Note D-3732, James Love and William Young, November 1966

"I Fly the X-15," Joseph Walker and Dean Conger, National Geographic, Volume 122, Number 3, September 1962, pp. 428-450

Hypersonics Before the Shuttle: A Concise History of the X-15 Research Airplane, Monographs in Aerospace History No. 18, Dennis R. Jenkins, NASA, June 2000

More Information

Space Station Resupply: The 1963 Plan to Turn the Apollo Spacecraft Into a Space Freighter

McDonnell Douglas Phase B Space Station (1970)

From Monolithic to Modular: NASA Establishes a Baseline Configuration for the Shuttle-Launched Space Station (1970)

An Alternate Station/Shuttle Evolution: The Spirit of '76 (1970)

Where to Launch and Land the Space Shuttle? (1971-1972)

25 November 2017

My Space Fleet (or, nostalgia concerning missed and lost toy spaceships)

Major Matt Mason, the moon, and a map. All stuff I've loved since forever. If I'd received this in a Christmas stocking at age eight, I'd have exploded. Alas, it appears to be a fan creation, not an authentic Mattel product. Image credit: I'm not sure, though it uses a NASA base map from after Luna 24 landed in 1976 and Mattel box art
I was born in 1962, just ahead of John Glenn's orbital Mercury-Atlas flight. The 1960s were a great epoch for space toys, but I fear that I missed out on most of those. My parents were not keen on encouraging my odd fascination with spaceflight. I had some Major Matt Mason dolls, but none of the large sets. It wasn't about poverty; I had a big metal garage with lots of moving parts, lots of Man from Uncle spy toys, and a baseball glove I never used. They just didn't see space as a "normal" sort of interest for a youngster. Perhaps they figured that I was peculiar enough already without adding space to the mix.

Oddly enough, though, they took me to see 2001: a Space Odyssey during its first theatrical run. (I think I had to seize hostages to induce them to take me - it's all hazy now.) I vividly remember building an Apollo LM model with my dad. I think that stands out because it was the only time he did something with me that was related to space.

The LM was great, but it was not enough for me. It was a display piece; I needed sturdy vessels with which I might conquer the Solar System.

I was eight or nine when I began to use materials I had at hand to make models of spacecraft of my own crude design. In the 1970-1975 period, in fact, I designed my own space program set in the then-distant year 2020. Arthur C. Clarke's Rendezvous with Rama and Earthlight were major sources of inspiration, as were the book and film 2001: A Space Odyssey. Bob McCall's first art compendium, Our World in Space, also influenced my vision. Some Star Trek influence was inevitable, though my space travelers didn't wander among the stars or tangle with aliens.

Foam cups, pins, dixie cups, pens, popsicle sticks, colored markers, pipe cleaners, tape, curtain weights, and rubber cement were my construction materials. The weights made excellent footpads; by far the heaviest parts of my spacecraft, the disk-shaped lead weights helped them to stand upright in the face of stray breezes and casual sideswipes from affectionate cats.

Perhaps in keeping with Star Trek, my ships included two propulsion systems. Chemical rockets permitted proximity operations near space stations and facilities on asteroids and other vacuum worlds. A far more advanced "photonic" drive enabled high-gee acceleration with minimal propellant expenditure. Think the Epstein Drive from The Expanse series.

The first spacecraft I built was an all-purpose explorer/police vessel in the tradition of Endeavour from Rendezvous with Rama or Star Trek's Enterprise. I envisioned a fleet of such craft. It was not designed to land, though it carried a small sortie vehicle and a 2001-esque service pod. Sortie vehicle and pod could be combined to yield a beefier sortie vehicle and the sortie vehicle could be broken down to create a second service pod.

Much of the action in my space program centered on the Asteroid Belt between Mars and Jupiter and the asteroidal moons and trojan asteroids of Jupiter. Asteroid settlement was well under way in 2020. My explorer/police vessel could "dock" with low-g small- and middle-sized asteroids with compatible facilities. It could also dock with and push smaller vessels with higher-g landing capability, much as the Apollo Command and Service Module pushed the Lunar Module.

The second vessel I built was a long-range explorer with higher-g landing capability. It had a beefy photonic drive, powerful chemical verniers, and a small crew compartment - perhaps room enough only for four people. Basically, it was a big engine cluster with scientific instrument pallets standing in as skin, eight adjustable landing legs, and a crew module on top.

A more conventional vessel needed weeks to travel between worlds of the Inner System and the Asteroid Belt and months to travel between the Outer System worlds. The long-range explorer could reach Pluto from Ceres in five weeks. It could also descend through atmospheres: an optional disposable heat shield (a thick paper plate) enabled Titan landings. Mysterious Titan was a major focus of scientific exploration in my space program.

The third vessel I designed, the Vulpecula-class space tug/freighter, was a small ship capable of pushing a standardized cargo module between worlds. It could accompany a cargo module to its destination or simply boost it on its way, then dock with an incoming cargo module and return to port. It could operate with or without a crew and could land on higher-g vacuum worlds bearing a cargo module.

Though I only built a pair of cargo modules, I imagined that they would take many forms. They could, for example, serve as tankers for refueling spacecraft. Another module was decked out as a passenger pod. The influence of the Franz Joseph space freighter in the Star Trek Technical Manual is unmistakable.

I also built a fast courier. Like the explorer/police ship, vessels of the Pegasus class weren't meant to land on higher-g worlds. They had a photonic engine identical to the explorer/police ship's engine, but could accelerate harder because they included only a small crew module, no auxiliary vehicles, and minimal instrumentation. They were meant to move people rapidly between scattered ships and worlds. For example, if an isolated trojan asteroid colony urgently needed a surgeon, one could be dispatched in a fast courier.

Finally, I built a long-range explorer capable of really epic trips. An extended version of the explorer/police ship, I envisioned that only a few would be built. Most traveled in pairs to interesting worlds beyond Pluto. (I'm not sure if I knew of the then-hypothetical Kuiper Belt - probably I just assumed there would be more planets past Pluto.) Their large crews hibernated in shifts. They traded speed for on-site crew expertise.

I didn't spend much time on Earth-to-orbit transportation. I assumed that rockets larger than the Saturn V would exist. That's all I remember.

Individuals and companies could own Pegasus-class fast couriers, Vulpecula-class freighters, and cargo modules. Some fast couriers became the equivalent of private jets. Some Vulpecula-class ships pushed cargo modules outfitted for asteroid prospecting.

Though I often lamented never acquiring Major Matt Mason's big moon base, in retrospect I am glad that I was thrown back on my own devices. Missing out on ready-made 1960s space toys helped to turn me creative.

What became of my space fleet? After Star Wars came out, I switched to building kit-bashed hyperdrive starships. The foam-cups-and-popsicle-sticks fleet grew dusty on a closet shelf. One summer day, as I prepared to depart for my first semester of college, I ceremoniously set fire to that fleet. The foam, rubber cement, and paper burned rapidly, leaving behind in moments only blackened pins and curtain weights. At college, my spaceships mostly became built of words, and it has remained so ever since.

18 November 2017

Pioneer Mars Orbiter with Penetrators (1974)

Pioneer Venus Orbiter (PVO) in Venus Orbit. The Pioneer Mars Orbiter (PMO) would have been based on this design. Image credit: NASA
The name "Pioneer" was applied to several different spacecraft designs, all of which were meant to spin to create gyroscopic stability. The first U.S. moon probe, launched by the Air Force in August 1958, bore the name. Though Pioneers 0 through 3 failed, Pioneer 4 flew by the moon at a distance of about 58,000 kilometers in March 1959. It became the first U.S. spacecraft to escape Earth's gravity and enter orbit around the Sun.

Pioneer 5 (March 1960), a unique design, was a pathfinder for future NASA interplanetary missions. Managed by NASA's Ames Research Center (ARC), it set a new record by transmitting until it was 36.2 million kilometers from Earth.

The Pioneer series seemed to draw to a close. In 1965, however, NASA ARC applied the name to its drum-shaped interplanetary "weather stations." The first, Pioneer 6, entered solar orbit between Earth and Venus in December 1965, where it monitored magnetic fields and radiation. Pioneers 7, 8, and 9 performed similarly prosaic (and generally little noticed) missions.

The first Pioneer design included a solid-propellant rocket motor on top; this was intended to slow the spacecraft so that the moon's gravity could capture it into lunar orbit. Pioneer 0, launched under U.S. Air Force auspices, was lost when its Thor-Able booster exploded 77 seconds after launch. Pioneers 1 and 2, launched under NASA auspices, also failed to reach lunar orbit, though the former attained a record altitude of 113,781 kilometers and returned useful data before falling back to Earth (October 1958). Image credit: NASA
NASA's Pioneer 3 and 4 lunar flyby spacecraft were launched on Redstone-derived Juno II rockets. Booster failure doomed Pioneer 3, but Pioneer 4, shown here attached to its small solid-propellant upper stage, performed a distant lunar flyby. Image credit: NASA
Pioneer 5, intended originally as a Venus probe set for launch in June 1959, was launched instead in March 1960 as a pathfinder for subsequent NASA planetary missions. Image credit: NASA
Pioneers 6 through 9 were drum-shaped spacecraft that measured "space weather" conditions in interplanetary space near Earth's orbit. Image credit: NASA
The name regained star status when Pioneer 10 left Earth in March 1972. It became the first spacecraft to brave the Asteroid Belt and fly past Jupiter. Pioneer 11 launched in April 1973, bound for Jupiter and Saturn. It went silent in 1995. Pioneer 10 sent its last signal from beyond Pluto in 2003.

The final Pioneer launches occurred in 1978. The Pioneer Venus Multiprobe spacecraft dropped four instrumented capsules on Venus, while Pioneer Venus Orbiter (PVO) surveyed the planet until 1992. The latter was informally designated Pioneer 12 and the former Pioneer 13.

Pioneer 10 and Pioneer 11, the only nuclear Pioneers, were Earth's first probes to traverse the Asteroid Belt and voyage through the outer Solar System. Image credit: NASA
Pioneer Venus Multiprobe deploys its one large and three small atmosphere probes. Against expectations, two probes survived landing and return data from the surface of Venus. No other U.S. spacecraft has landed intact on Venus. Image credit: NASA
If NASA ARC, the Planetary Programs Division of the NASA Office of Space Science, and Hughes Aircraft had had their way, the Pioneer name might also have been applied to a Mars spacecraft. In a 1974 report prepared on contract to NASA ARC, Hughes described a Pioneer Mars Orbiter (PMO) derived from the Hughes PVO spacecraft design. The PMO mission, set for launch in 1979, was intended as a follow-on to the twin Viking missions, which were scheduled to leave Earth in 1975 and seek life on Mars in 1976.

Hughes described the PVO upon which the PMO would be based as drum 2.5 meters in diameter and 1.2 meters tall with a 3.3-meter antenna mast on top and a solid-propellant Venus orbit insertion motor on the bottom. The company then cited differences between the PMO and PVO designs: for example, PMO's orbit insertion motor would need to be larger since it would arrive at Mars traveling faster than PVO would at Venus. In addition, PMO would operate in Mars orbit, about twice as far from the Sun as Venus, so solar cells would entirely cover its sides so that they could make enough electricity to operate the spacecraft's systems. PVO would operate in Venus orbit, so it would need to be only partly covered with solar cells.

The most obvious difference between the PVO and PMO designs were the Mars spacecraft's six 2.3-meter-long, 0.3-meter-diameter penetrator launch tubes. These would replace PVO's science instruments; apart from unspecified instruments in the penetrators, PMO would carry no science payload.

PMO, like PVO, would leave Earth on an two-stage Atlas-Centaur rocket. Because PMO would weigh more than PVO (1091 kilograms versus 523 kilograms), however, it would need a solid-propellant third stage to complete Earth escape. To make room for the third stage and penetrators, PMO's conical launch shroud would be 0.8 meters longer than its PVO counterpart.

PMO would need to reach Mars on 7 September 1980 so that its Mars orbit insertion motor could place it in its planned Mars orbit. To reach the planet on that date, PMO would need to depart Earth during one of 10 consecutive daily launch opportunities starting on 28 October 1979. 2 November 1979 would be the nominal launch date. The launch opportunities would only last from 10 to 15 minutes each.

The Centaur second stage would place PMO into a low-Earth orbit, then would ignite again 30 minutes later to begin pushing the spacecraft out of Earth orbit. The third-stage motor would then ignite to place PMO on course for Mars. PMO would weigh 1069 kilograms after third-stage separation. Launch on 2 November 1979 would yield a 310-day Earth-Mars transfer.

Following third-stage separation, PMO would use hydrazine thrusters to set itself spinning at 15 revolutions per minute (RPM) for stabilization. The antenna mast bearing the high-gain, low-gain, and two penetrator data reception antennas  would revolve in the opposite direction at the same rate, so would appear to stand still. Controllers on Earth would use the thrusters to carefully target PMO so that it would not accidentally hit Mars and introduce terrestrial microbes. They would perform a final course correction 30 days before Mars arrival.

One day out from Mars, on 6 September 1980, PMO would orient itself for its Mars orbit insertion burn and increase its spin rate to 30 RPM. The spacecraft's high-gain antenna would not point at Earth during the insertion burn. Controllers on Earth could, however, send PMO commands through the low-gain antenna.

Candidate PMO orbits. Image credit: Hughes Aircraft Company
PMO would reach Mars late in northern hemisphere summer, when the planet's south polar cap would be near its maximum extent. Hughes Aircraft proposed two possible elliptical Mars orbits - south polar and north polar - each with a period of 24.6 hours (one martian day) and a periapsis (low point) of 1000 kilometers. South polar orbit periapsis would occur above a point on Mars's surface 72° south of the equator, while north polar orbit periapsis would occur above a point at 37° north latitude. The spacecraft's high periapsis altitude would serve to forestall orbital decay, helping to ensure that PMO would not drop living terrestrial microbes on Mars. PMO would have a mass of 741 kilograms after orbit insertion.

The PMO mission's Mars orbit phase would last one martian year (686 terrestrial days). During this mission phase, PMO would deploy its six 45-kilogram penetrators singly and in pairs using a penetrator deployment system based on the Hughes-built TOW missile launcher. Before Earth departure the penetrators would be sealed inside their launch tubes and heated to kill hitchhiking microbes.

PMO deploys its first penetrator. The departing penetrator is at center right, while the exhaust plume from its small solid-propellant rocket motor gushes from the bottom end of the penetrator launch tube at lower left. On the bottom (left) side of the spacecraft, the Mars orbit-insertion engine bell is visible, as are the bottom ends of the six penetrator tubes. One tube is partly obscured by the exhaust plume, one by the orbit-insertion engine bell, and another by a neighboring penetrator tube. The top ends of three tubes are visible; one obscures the base of the counter-spun antenna mast mounted at the center of PMO's top (right) side. The high-gain dish antenna (center), two penetrator antennas, and the low-gain antenna are attached to the mast. Image credit: Hughes Aircraft Company
Penetrator deployment would occur near apoapsis (orbit high point), when the spacecraft's orbital velocity would be at its slowest. Hinged covers would open at both ends of the launch tube, then the penetrator's solid-propellant deployment rocket motor would ignite to launch it from the tube. Launching the penetrator in the direction opposite PMO's orbital motion would cancel out its orbital velocity and cause it to fall toward Mars. The dome-nosed penetrator, a Sandia Corporation design, would drop through Mars's atmosphere and implant itself in the surface up to 15 meters deep.

After impact, the penetrator would extend its antenna and begin transmitting data from its science instruments. PMO would record the penetrator data for relay to Earth through its high-gain dish. Chemical batteries in the penetrators would enable each to collect and transmit data from Mars for about eight days.

For their weak signals to be received, the penetrators would need to impact the surface not far from PMO's periapsis point. The orbiter could maintain radio contact with a given penetrator for at least eight minutes at a time. A PMO in south polar orbit would initially place its penetrators between 63° and 87° south; a north-polar-orbiting PMO would place them between 56° and 80° north. Periapsis would gradually shift north or south, however, permitting placement at other latitudes. With all six penetrators deployed, PMO would have a mass of 412 kilograms.

Viking 1 and Viking 2, each of which comprised a three-legged lander and an orbiter bearing cameras, were designed with certain assumptions in mind; for example, that microbial life on Mars would be ubiquitous, so that a scoop of surface dust and a jury of three biological experiments would readily reveal its presence. Unfortunately for the proposed 1979 PMO mission and NASA Mars exploration planning in general, the Viking biology experiments yielded equivocal results that were generally interpreted as indicative of a lifeless world. This, combined with the loss of the Mars Observer spacecraft as it attempted capture into Mars orbit in 1993, helped to create a two-decade gap during which no new U.S. spacecraft explored Mars.


Pioneer Mars Surface Penetrator Mission: Mission Analysis and Orbiter Design, Hughes Aircraft Company, August 1974

Pioneer Mars 1979 Mission Options, A. Friedlander, W. Hartmann, and J. Niehoff, Science Applications, Inc., 29 January 1974, pp. 61-99

Solar System Log, Andrew Wilson, Jane's, 1986, pp. 12-13, 16-17, 21

More Information

The Russians are Roving! The Russians are Roving! A 1970 JPL Plan for a 1979 Mars Rover 

Prelude to Mars Sample Return: the Mars 1984 Mission (1977)

12 November 2017

A CSM-Only Back-Up Plan for the Apollo 13 Mission to the Moon (1970)

The Apollo 13 crew of Commander James Lovell (left), Command Module Pilot John "Jack" Swigert (center), and Lunar Module Pilot Fred Haise (right). Image credit: NASA
Launch of Apollo 13, the planned third Apollo moon landing, was just two months in the future when NASA Manned Spacecraft Center (MSC) engineer Rocky Duncan proposed an alternate plan for the mission. He noted that Apollo 13 would mark the first flight of the Hycon Lunar Topographic Camera (LTC), a modified U.S. Air Force KA-74 aerial reconnaissance camera, which would be mounted in the Command and Service Module (CSM) crew hatch window for high-resolution overlapping photography of candidate future Apollo landing sites.

In Apollo Program parlance, this was dubbed "bootstrap photography." It took advantage of the piloted CSM, which had to loiter in lunar orbit anyway to collect the lunar surface crew after they completed their mission, to collect data useful for planning future Apollo missions.

Duncan noted that previous Apollo lunar missions had followed a "free-return" path that would enable them to loop behind the moon and fall back to Earth if their CSM Service Propulsion System (SPS) main engine failed. The Apollo 13 CSM, on the other hand, would fire its engine during the voyage to the moon to leave the free-return trajectory. This was necessary so that the mission's Lunar Module (LM) could reach its target landing site at Fra Mauro.

The Apollo 13 Saturn V rocket clears the tower. Image credit: NASA
A day after launch from Earth, the Apollo 13 crew ignited the CSM Odyssey's Service Propulsion System (SPS) main engine to leave the free-return trajectory that would automatically return them to Earth in the event of an SPS failure. This was required to permit the mission to reach its destination, the scientifically significant Fra Mauro landing site. Image credit: NASA
The MSC engineer then described a scenario in which the Apollo 13 LM was judged to be "NO-GO" soon after Trans-Lunar Injection (TLI), the maneuver that would boost them from low-Earth orbit and place them on course for the moon. TLI would occur about two hours after launch; it would use the Saturn V S-IVB third stage with its single J-2 engine. Following TLI, the CSM would separate from the segmented shroud - the Spacecraft Launch Adapter - linking it to the S-IVB stage; the shroud would then peel back to reveal the LM. The crew would dock their CSM with the port on top of the LM and separate it from the S-IVB stage. Presumably soon after maneuvering away from the S-IVB they would discover the fault that would render their LM unable to land on the moon.

Apollo 13 would then become a "CSM-only lunar alternate photographic mission." The CSM would remain on a free-return path until it reached the moon, then its crew would perform a standard two-impulse lunar orbit insertion (LOI) maneuver; that is, they would fire the SPS to slow their CSM so that the moon's gravity could capture it into an elliptical lunar orbit, then would fire the engine again at perilune (the low point of its lunar orbit) to circularize its orbit.

Duncan noted that some "desirable photographic orbits with high inclinations. . .require a three-impulse LOI." He argued, however, that "since the crew has not been trained for this type of LOI. . .this type of profile [should] not be flown."

In Duncan's alternate mission, Apollo 13 would capture into a lunar orbit that would take it over the craters Censorinus and Mösting C. These were, respectively, ranked first and eleventh in priority on the Apollo 13 list of targets for lunar-orbital photography.
Censorinus was the leading landing site candidate for Apollo 15, which at the time Duncan wrote his memo was planned as an H-class mission similar to Apollo 13 (that is, its LM would not carry a Lunar Roving Vehicle and would remain on the moon for only about a day and a half). Apollo 12 in November 1969 had been the first H-class mission, so had been designated H-1; Apollo 13 was H-2, Apollo 14 would be H-3, and Apollo 15 would be H-4, the final H-class flight.

Duncan advocated delaying the crew's scheduled sleep period by two lunar revolutions to enable them to photograph Censorinus and Mösting C. The photographic program would begin during Revolution 3 with vertical stereo photography using window-mounted Hasselblad cameras. Revolution 4 would see the first high-resolution vertical Hycon LTC photography, then the astronauts would conduct high-resolution oblique (side-looking) LTC photography during Revolution 5. They would perform "landmark tracking" using the CSM's wide-field scanning telescope (a part of its navigation system) during Revolutions 6 and 7, then would begin their delayed sleep period.

The Apollo 13 crew would awaken during Revolution 12 and fire the SPS to change their spacecraft's orbital plane (that is, the angle at which its orbit crossed the moon's equator). They would do this so that, beginning with Revolution 14, they would pass over Descartes, a suspected volcanic site in the moon's light-colored central Highlands, and Davy Rille, a chain of small craters of suspected volcanic origin. The astronauts would repeat the five-revolution photography sequence they used to image Censorinus and Mösting C. Duncan noted that Descartes ranked second on the Apollo 13 list of photographic targets, while Davy was fourth.

Duncan briefly considered a scenario in which the Apollo 13 LM was incapable of landing yet had a working descent engine which the crew could use to perform plane-change maneuvers in lunar orbit. He noted that the LM would block some CSM windows while it was docked. The astronauts might undock the CSM from the LM for photography and dock again for additional plane changes, or they might discard the LM after only a single plane change. Duncan favored a simpler approach: jettison the LM as soon as it was judged to be incapable of landing whether its descent engine was functional or not and use only the CSM SPS.

The astronauts would perform "target of opportunity" photography during Revolutions 18 and 19, then would sleep. They would wake during Revolution 24 and perform a plane change during Revolution 25 so that they could fly over Alphonsus crater, Gassendi West, and Gassendi East beginning with Revolution 27 and again carry out the five-revolution photography sequence. Alphonsus, where surface color changes and luminescence have been reported, was ranked ninth on the Apollo 13 target list, while the two sites in dark-floored Gassendi crater were ranked thirteenth and fourteenth, respectively.

Duncan estimated that, by the time the astronauts finished photographing the Alphonsus and Gassendi crater candidate landing sites, Apollo 13's cameras would likely have run out of film. He recommended that the crew fire the SPS to leave lunar orbit and return to Earth during Revolution 32 or two revolutions after the film ran out, whichever came first.

Apollo 13 left Earth on 11 April 1970. The LM Aquarius checked out as "GO" for a landing on the moon, and on 12 April the crew performed the SPS burn to leave the free-return trajectory. The next day, CSM Odyssey suffered an oxygen tank explosion in its Service Module (SM).

Because the extent of the internal damage to the CSM was unknown, NASA wrote off Odyssey's SPS and looked to the LM for salvation. Astronauts James Lovell, Jack Swigert, and Fred Haise used Aquarius's descent engine to get back onto a free-return trajectory.

During their lunar flyby, the crew photographed the moon through Aquarius's windows using hand-held cameras. Odyssey blocked part of their field of view, but there was no thought of discarding it: the crew needed the conical Command Module (CM), with its bowl-shaped heat shield, to reenter Earth's atmosphere at the end of their voyage.

Inside the lifeboat: after the explosion in the Apollo 13 CSM Odyssey, the Apollo 13 crew shut down Odyssey's systems and relocated to the still-functional LM Aquarius. The LM was designed to support two men for 36 hours, not three for four days. This meant that exhaled carbon dioxide built up in the cabin air. With assistance from engineers on Earth, the crew built a system (image above) that allowed the CSM's carbon dioxide-absorbing lithium hydroxide canisters to be used in the LM. CSM Pilot Jack Swigert, who would have performed "bootstrap photography" in lunar orbit had the third lunar landing attempt gone ahead as planned, is visible at right. Image credit: NASA
As Apollo 13 swung around the moon and began its fall back to Earth, its crew used handheld cameras to photograph the moon through windows in the LM Aquarius. This image, captured through one of the ceiling-mounted rendezvous and docking windows, shows parts of the Nearside and Farside hemispheres. Dominating the top half of the image is the crippled CSM Odyssey. To conserve electricity, its internal lights are off, making its windows dark. The out-of-focus lines on the rendezvous window were meant to enable the LM crew to gauge distance during rendezvous and docking with the CSM. Image credit: NASA
The Hycon camera was not used for photography, though it did provide a hose for the improvised adapter the crew made so that Odyssey's carbon dioxide-absorbing canisters could be used inside Aquarius. With help from the hose and the world-wide Apollo mission team, the crew safely reentered Earth's atmosphere and splashed down in the Pacific Ocean in the Odyssey CM on 17 April.

Apollo 14 (31 January-9 February 1971) became the first (and last) lunar mission to use the Hycon LTC. By the time it flew, NASA had cancelled Apollo 15 and 19 as part of its efforts to preserve its proposed Space Station/Space Shuttle Program. It had renumbered the remaining Apollo flights so that they ended with Apollo 17. Apollo 14, H-3, became the last H-class mission. The camera's chief target was Descartes, which had moved to the top spot among Apollo 16 landing site candidates. Apollo 16, planned as a J-class mission, would include a two-seat Lunar Roving Vehicle, an LM capable of remaining on the moon for three days, and a CSM with an ejectable subsatellite and a pallet of sophisticated sensors and cameras in its SM.

The Hycon camera captured 192 images, but malfunctioned while imaging the lunar surface about 70 kilometers east of Descartes. Though Apollo 14 returned no images of the site, Apollo 16 (J-2) landed at Descartes in April 1972.


Memorandum with attachment, FM5/Lunar Mission Analysis Branch to various, “Lunar alternate missions for Apollo 13 (Mission H-2),” Rocky Duncan, 13 February 1970

"Scientific Rationale Summaries for Apollo Candidate Lunar Exploration Landing Sites – case 340," J. Head, Bellcomm, Inc., 11 March 1970

"Significant Results from Apollo 14 Lunar Orbital Photography," F. El-Baz and S. Roosa, Proceedings of the 1972 Lunar Science Conference, Vol. 2, pp. 63-83, 1972

More Information

North American Aviation's 1965 Plan to Rescue Apollo Astronauts Stranded in Lunar Orbit

What If Apollo Astronauts Became Marooned in Lunar Orbit? (1968)

Apollo's End: NASA Cancels Apollo 15 & Apollo 19 to Save Station/Shuttle (1970)

29 October 2017

Chrysler's Transportation and Work Station Capsule (1965)

Chrysler-built Saturn IB first stages in the final phase of assembly at NASA's Michoud Assembly Facility, November 1967. The clustered Redstone rocket bodies are most obvious on the stage at far right. Image credit: NASA
In the 1960s, the Chrysler Corporation, an automobile company founded in 1925, manufactured the first stage of the Saturn IB, the first and last member of the Saturn rocket family to launch astronauts into space. After four successful unmanned test flights beginning in February 1966, Saturn IBs launched the Apollo 7 Command and Service Module (CSM), the first Apollo spacecraft to carry a crew (11-22 October 1968); the three CSMs that ferried crews to and from Skylab, the first U.S. space station (May 1973-February 1974); and the Apollo-Soyuz Test Project (ASTP) CSM and the Docking Module its crew used to link up with the Soviet Soyuz 19 spacecraft in Earth orbit (15-24 July 1975). The ASTP CSM was the last Apollo spacecraft to fly.

That Chrysler built the Saturn IB first stage should not be surprising. The company's Missile Division built intermediate-range Redstone missiles for the U.S. Army starting in 1950; the first flew in 1953. An upgraded Redstone, the Jupiter, served both as a missile and a space launcher. A modified Jupiter launched Explorer 1, the first U.S. Earth satellite, on 31 January 1958. Safety-enhanced Redstones launched suborbital Mercury spacecraft containing Alan Shepard, the first American in space (5 May 1961), and Virgil Grissom (21 July 1961).

The first Saturn I rocket lifts off, 27 October 1961. For this suborbital test of the Chrysler-built S-I first stage, the rocket carried a dummy S-IV second stage. Image credit: NASA
Redstone and its derivatives prepared Chrysler for its contributions to the 162-foot-tall Saturn I, which can reasonably be described as NASA's rocket for learning how to fly big rockets. Saturn I flew 10 times between October 1961 and July 1965. Chrysler's Saturn I first stage included eight Redstone rocket bodies clustered around a central Jupiter rocket body. The Jupiter and four Redstones were filled with liquid oxygen; the remaining four Redstones held RP-1 aviation fuel. Chrysler's Saturn IB first stage followed an identical pattern.

The last three Saturn I rockets each launched a Pegasus meteoroid-detection satellite, the first active payloads launched on a Saturn rocket. Pegasus 1 reached orbit in February 1965, Pegasus 2 in May 1965, and Pegasus 3 in July 1965. The Pegasus series was crucial for understanding the threat micrometeoroids posed to spacecraft and astronauts.

Shortly after Pegasus 1 reached space, at the Second Space Congress in Cocoa Beach, Florida, Chrysler engineers R. Dutzmann and E. Dunford described a small free-flying capsule for performing work outside spacecraft and space stations. They presented their paper in April 1965 during the six-week period that separated humankind's first spacewalk by Alexei Leonov (Voskhod 2, 18 March 1965) from the first U.S. spacewalk by Ed White (Gemini IV, 3 May 1965).

Dutzmann and Dunford's capsule design arose from a perceived need for new methods of protecting spacewalking astronauts - methods that would enhance protection but not compromise the ability to perform work. The Chrysler engineers explained, for example, that planned nylon fabric space suits might shield an astronaut from meteoroids if a coverall made of woven aluminum wire were added; the coverall would, however, make astronaut movement difficult.

Meteoroids were only one possible hazard of walking in space. Dutzmann and Dunford noted that objects in space have no weight, but retain their mass. They feared that a massive object - for example, a rocket stage - inadvertently set in motion might catch an astronaut unawares and crush him against another massive object.

The Chrysler engineers wrote that NASA planned to use a pure oxygen atmosphere at a pressure of 3.5 pounds per square inch (psi) inside its spacecraft and space suits. Experiments had shown that, should a space suit develop a leak, the astronaut would experience oxygen starvation if the pressure fell by just 0.8 psi. Increasing the flow of oxygen into the suit might keep pressure above the 2.7-psi critical level long enough for him to reach safety, but only if the suit perforation were small.

In addition, they noted that a space-suited astronaut would have no place to keep his tools. Attaching tools to the astronaut would impede movement.

The Chrysler engineers offered a brief assessment of past proposals for heavy (up to 2.5-ton) "taxis" that would include "comfortized" pressurized cockpits and mechanical manipulator arms. Such "luxuries," they wrote, could not realistically play a role in space operations before the 1970s. The technological leap required to move from a basic fabric space suit to a complex work vehicle was too great; also, tests had shown that existing mechanical manipulators were up to four times less efficient for doing work than astronaut arms and hands.

Side view of the interior of Chrysler's Transportation and Work Station Capsule with astronaut positions indicated. A = outline of astronaut position with capsule doors closed; B = outline of astronaut position at work site with capsule doors open. Work site attachment arms are shown in black outline in closed-door (retracted) position and in red in open-door (extended) position. Image credit: Chrysler Corporation/DSFPortree
Top view of the interior of Chrysler's Transportation and Work Station Capsule. A1 = left sliding door/window; A2 = right sliding door/window; B = hand controller for guiding capsule; C1 = left oxygen hose; C2 = right oxygen hose; D1 = left sticky pads at ends of arms for holding capsule at work site (arms shown retracted in closed-door position); D2 = right sticky pads at ends of arms for holding capsule at work site (arms retracted in closed-door position); E = tool storage; F = hydrogen peroxide propellant tank; G = pressure seal curtain deployment channel; H = Whipple Bumper hull. Image credit: Chrysler Corporation/DSFPortree
Dutzmann and Dunford thus proposed an intermediate developmental step in spacewalk technology: a three-foot-diameter, eight-foot-tall "Transportation and Work Station Capsule," normally kept unpressurized, that would provide the space-suited astronaut with an extra layer of protection from injury, a shelter in case of suit damage, improved mobility, worksite lighting, and places inside to store up to 30 pounds of tools. With a 230-pound space-suited astronaut inside and a full load of 30 pounds of hydrogen peroxide propellant, the cylindrical capsule would weigh just 550 pounds.

The capsule hull would comprise two layers of aluminum, each a fraction of an inch thick, separated by an empty space a little less than an inch wide. Meteoroids would strike the outer layer, break apart and partly vaporize, then strike the inner layer. Testing showed that this design, based on the Whipple Bumper concept, could provide meteoroid protection equivalent to that offered by a solid aluminum hull four times as thick. The Whipple Bumper was named for its inventor, comet astronomer Fred Whipple.

Dutzmann and Dunford suggested that the empty space between the aluminum layers be filled with aluminum honeycomb to improve structural strength. The lightweight Whipple Bumper hull meant that the Chrysler capsule's structure would weigh just 88 pounds.

The capsule's dome-shaped ends would each contain a thruster group. A total of 12 catalyst-bed thrusters, not too different from the Mercury spacecraft attitude-control thrusters, would draw hydrogen peroxide from a tank located at the capsule center of gravity. Upon contact with the catalyst, the hydrogen peroxide would turn to high-temperature steam and vent from the thruster nozzle. Each thruster could produce up to 10 pounds of thrust.

The astronaut, who would stand within the capsule, would open a pair of sliding doors with windows and lean out through the open doorway to perform tasks using tools gripped in gloved hands. Two pairs of telescoping arms with sticky pads at the ends, arranged one above the other, would extend through the 27-inch-by-78-inch door opening on either side of the astronaut's legs to hold the capsule in place at the work site.

A unique feature of Chrysler's capsule was its "pressure seal curtain" system. In the event of a suit puncture or tear, a transparent plastic sheet sleeve would rise up a deployment "channel" from a donut-shaped storage area in the capsule floor to surround and enclose the astronaut.

Dutzmann and Dunford offered a timeline for pressure seal curtain activation. They assumed that the astronaut's fabric space suit would most likely become damaged while the capsule was attached to a work site since at all other times the astronaut would remain inside the capsule with the doors closed.

They expected that a "pressurization emergency" would be detected 10 seconds after suit damage occurred. Five seconds post-detection, the capsule would automatically detach from the four arms holding it at its work site. This would clear the way for its sliding doors to shut 10 seconds after detection. Fifteen seconds after detection, the seal curtain would rise up and attach itself to the capsule "ceiling." Simultaneously, a backup oxygen supply mounted behind the astronaut's shoulders would activate, increasing flow into the astronaut's damaged suit. Air leaking from the suit would begin to fill the seal curtain volume 30 seconds after leak detection.

Much like the fabric space suit, the seal curtain would vent oxygen overboard to prevent buildup of exhaled carbon dioxide. Dutzmann and Dunford assumed that, to avoid oxygen depletion and carbon dioxide buildup within his helmet, the astronaut would open his visor soon after pressure within the seal curtain exceeded 2.7 psi.

The astronaut would then pilot the capsule back to its docking structure on the home spacecraft. If the capsule remained within 1000 feet of the docking structure, as Dutzmann and Dunford recommended, the trip would last less than 10 minutes.

The three Saturn I-launched Pegasus satellites would reveal that the threat from meteoroids in space was less severe than expected, but other dangers lay in wait for 1960s spacewalkers. The Soviet Union would for years claim that Alexei Leonov's spacewalk was a complete success, when in fact he could not control his movements, overheated, and became stuck sideways in Voskhod 2's inflatable airlock.

Ed White's excursion outside the Gemini IV spacecraft, less than a month after the Chrysler engineers presented their capsule design, was nearly as successful as Leonov's was claimed to have been. More careful analysis would, however, have pointed to potential problems - White's suit expanded during his spacewalk, and he exceeded the cooling capacity of his air-cooled space suit while struggling to squeeze into his narrow seat and close his balky spacecraft hatch.

Not until humankind's perilous third spacewalk on 5 June 1966 would the inadequacies of air-cooled space suits become obvious. During an ambitious attempt to fly free of the Gemini IX spacecraft using a 168-pound hydrogen peroxide-fueled Astronaut Maneuvering Unit (AMU) backpack, pilot Eugene Cernan tore his suit's outer layers, overheated, and became blinded by perspiration as he struggled against his suit's internal pressure. Cernan's AMU flight was called off and NASA was forced to descope its planned series of complex Gemini Program spacewalks (see "More Information" below).


"Design Considerations for a Free Space Transportation and Work Station Capsule," R. Dutzmann and E. Dunford, Proceedings of the 2nd Space Congress, April 1965, pp. 403-430

Chrysler's Ballistic Missile and Space Activities: First 20 Years, Chrysler Corporation, 1972

Walking to Olympus: An EVA Chronology, Monographs in Aerospace History #7, David S. F. Portree and Robert C. Trevino, NASA History Office, October 1997, pp. 1-5, 11 - https://history.nasa.gov/monograph7.pdf (accessed 12 November 2017)

More Information

The Spacewalks That Never Were: Gemini Extravehicular Planning Group (1965) (how Soviet deception concerning Leonov's spacewalk led NASA to plan complex Gemini spacewalks)

Rocket Belts and Rocket Chairs: Lunar Flying Units (1960s plans for rocket-powered lunar surface transportation)