Today we celebrate the 50th anniversary of the inaugural flight of Wernher von Braun’s magnum opus, the giant Saturn V moon rocket. This first flight was an unmanned mission, Apollo 4, and took place less than 10 months after the tragic launch pad fire that killed astronauts Gus Grissom, 40, Ed White, 36, and Roger Chaffee, 31.
The unmanned Apollo 4 mission was a complete success, paving the way for astronauts to go to the Moon. After another successful unmanned test flight (Apollo 6), the Saturn V rocket carried the first astronauts into space on the Apollo 8 mission in December 1968. On that mission, astronauts Frank Borman, Jim Lovell, and Bill Anders orbited the Moon for 20 hours and then returned safely to Earth.
“As of 2017, the Saturn V remains the tallest, heaviest, and most powerful (highest total impulse) rocket ever brought to operational status, and holds records for the heaviest payload launched and largest payload capacity to low Earth orbit (LEO) of 140,000 kg (310,000 lb), which included the third stage and unburned propellant needed to send the Apollo Command/Service Module and Lunar Module to the Moon. To date, the Saturn V remains the only launch vehicle to launch missions to carry humans beyond low Earth orbit.”
Reference (for quoted material above)
Wikipedia contributors, “Saturn V,” Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Saturn_V&oldid=808028027 (accessed November 9, 2017).
Between January 2 and 5 each year, the Earth reaches orbital perihelion, its closest distance to the Sun (0.983 AU). Between July 3 and 6 each year, the Earth reaches orbital aphelion, its farthest distance from the Sun (1.017 AU). These dates of perihelion and aphelion slowly shift across the calendar (always a half year apart) with a period between 22,000 and 26,000 years.
These distances can be easily derived knowing the semi-major axis (a) and orbital eccentricity (e) of the Earth’s orbit around the Sun, which are 1.000 and 0.017, respectively.
perihelion q = a (1-e) = 1.000 (1-0.017) = 0.983 AU
aphelion Q = a (1+e) = 1.000 (1+0.017) = 1.017 AU
So, the Earth is 0.034 AU closer to the Sun in early January than it is in early July. This is about 5 million km or 3.1 million miles.
How great a distance is this, really? The Moon in its orbit around the Earth is closer to the Sun around New Moon than it is around Full Moon. Currently, this difference in distance ranges between 130,592 miles (April 2018) and 923,177 miles (October 2018). Using the latter value, we see that the Moon’s maximum monthly range in distance from the Sun is 30% of the Earth’s range in distance from the Sun between perihelion and aphelion.
How about in terms of the diameter of the Sun? The Sun’s diameter is 864,526 miles. The Earth is just 3.6 Sun diameters closer to the Sun at perihelion than it is at aphelion. Not much! On average, the Earth is about 108 solar diameters distant from the Sun.
How about in terms of angular size? When the Earth is at perihelion, the Sun exhibits an angular size of 29.7 arcminutes. At aphelion, that angle is 28.7 arcminutes.
Every once in a while a really great documentary comes along. In the Shadow of the Moon is one of them. This 2007 British film, which like most documentaries (unfortunately), had a very limited theater engagement, is now widely available for rental or purchase.
The historical importance of this documentary cannot be overstated. There is nothing, and I mean nothing, like hearing about the first (and still only) human missions to the Moon firsthand from the astronauts who journeyed there. And, sadly, these pioneering astronauts are not going to be with us much longer. Some have already left us. In the ten years since this documentary was released, Edgar Mitchell, the last surviving member of the Apollo 14 crew, passed away in 2016, and Gene Cernan, the last man to walk on the Moon, passed away earlier this year. The eight surviving Apollo astronauts who shared their stories with us in this film are all octogenarians: Buzz Aldrin is 87, Michael Collins is 86, Alan Bean is 85, Jim Lovell is 89, David Scott is 85, John Young is 86, Charles Duke is 81, and Harrison Schmitt is 81.
The astronauts on Apollo 11, 12, 14, 15, 16, and 17 between 1969 and 1972 brought back a total of 840 lbs of moon rocks and soil. Each successive Apollo mission brought back a larger amount of lunar material.
The Soviets brought back a total of 0.7 lbs of lunar soil through their robotic sample return missions Luna 16 (1970), Luna 20 (1972), and Luna 24 (1976).
So, excluding lunar meteorites that have befallen the Earth, a total of 840.7 lbs of lunar material has been delivered to research laboratories here on Earth.
It has been over 40 years since we have brought anything back from the lunar surface. There are many interesting areas yet to be explored. Why not send a series of robotic geologists to the Moon in advance of human missions? The success of the Spirit, Opportunity, and Curiosity rovers on Mars show us the exciting work that can be done at a fraction of the cost of human missions. One enhancement would be the ability of the lunar robotic rovers to collect moon rocks and soil and return them to the mother ship for delivery to Earth.
But our 40+ year wait for additional lunar material may soon be over!
China plans to launch the Chang’e 5 lunar lander in November of this year. It is expected to land in the Oceanus Procellarum (“Ocean of Storms”) region of the Moon, scoop up at least 4.4 lbs of lunar soil and rock—including some at least six feet below the surface! The lunar haul will be launched into lunar orbit, where it will rendezvous with the sample return module that will bring it back to Earth. After a high-speed entry into Earth’s atmosphere, the sample return module will rapidly decelerate, then gently parachute down to the Earth’s surface, presumably somewhere in China.
Chang’e 5 promises to be one of the most exciting and important space missions this year. Stay tuned!
Between 1969 and 1972, a dozen human beings walked upon the surface of the Moon, amounting to a total lunar exploration time of 3d 8h 32m 26s. Gene Cernan returned to the Lunar Module at 11:40:56 p.m. CST on December 13, 1972. In the over 44 years since, no one has followed in his footsteps. Sadly, Gene Cernan, who died last month, never lived to see another human walk on the Moon. Ever since his Apollo 17 mission, he has held the dubious distinction of being the “last man to walk on the Moon”.
Only half of the twelve Apollo astronauts who walked on the Moon are still living. Will humans return to the Moon before the last of them dies?
Buzz Aldrin (1930-)
Neil Armstrong (1930-2012)
Alan Bean (1932-)
Gene Cernan (1934-2017)
Pete Conrad (1930-1999)
Charlie Duke (1935-)
Jim Irwin (1930-1991)
Ed Mitchell (1930-2016)
Harrison Schmitt (1935-)
Dave Scott (1932-)
Alan Shepard (1923-1998)
John Young (1930-)
Fortunately, robotic explorers orbiting and landing on the Moon in recent years have made some discoveries that provide a new impetus for humans to return to the Moon. One of those discoveries is evidence for sublunarean structures that could provide “roughed in” habitats for human settlement.
Mother Nature may have done us a great favor thanks to lunar volcanism.
Most volcanism on the Moon occurred between 3 and 4 billion years ago when the lunar maria formed.
Sinuous rilles provide evidence of past volcanic flows and may be the collapsed remains of lava tubes. There is some evidence to support that both Vallis Schröteri and Rima Sharp extend below the lunar surface as uncollapsed lava tubes. Vacant lava tubes beneath the lunar surface may be quite common.
Volcanism on the Moon may have continued almost up to the present day. Not only do numerous small volcanoes on the Moon suggest active volcanism within the past 50 to 100 million years, but the irregular mare patch Ina in Lacus Felicitatis (“Lake of Happiness”) may be a volcanic feature no more than 10 million years old.
Could there be vacant lava tubes beneath the lunar surface? On Earth, underground lava tubes can be found in Hawaii, Iceland, and many other locations around the world.
Further evidence that there may be caverns and vacant tubes underneath the lunar surface are the many deep pits that have been discovered—over 150 so far. Some of these pits may be openings into lava tubes beneath the surface, known as skylights.
NASA’s Gravity Recovery and Interior Laboratory (GRAIL) lunar orbiters mapped the gravitational field of the Moon in unprecedented detail, uncovering evidence of voids beneath the lunar surface. Ground-penetrating radar, gradiometric, and gravimetric measurements are now needed to confirm the nature of these voids and whether they would be suitable structures for human habitation, shielding lunar residents from radiation, temperature extremes, and micrometeorites.
The Marius Hills Hole (MHH), about 160 ft. wide and 160 ft. deep at 14.100˚N, 303.262˚E, has been identified as leading to an intact lava tube below the lunar surface (Kaku et al. 2017). The discovery was made after analyzing data from the Lunar Radar Sounder (LRS) instrument aboard the SELENE spacecraft. LRS was an 800-watt ground penetrating radar, sweeping between 4 and 6 MHz every 200 μsec. Each time these radio waves hit subsurface boundaries between rock and void, they reflected back towards the spacecraft and the lag times were used to estimate the depth and size of the voids.
Additional lava tubes or cavernous voids are thought to exist in the Marius Hills region, 13.5-13.8˚ N, 302.5-302.8˚ E.
The Lunar Advanced Radar Orbiter for Subsurface Sounding (LAROSS) mission has been proposed (Sood et al. 2016), and Gedex Inc., a Toronto-based geophysics company, is developing a rover-mounted gravimeter and gravity gradiometer (Urbancic et al. 2015). A gradiometer will be used to study the near-surface environment, and a gravimeter will go deeper.
These are exciting times for lunar exploration!
Beatty, K. 2014, (Geologically) Recent Volcanoes on the Moon?, Sky & Telescope blog, October 14, 2014
Blair, D. M., Chappaz, L., Sood, R. et al. 2017, Icarus, 282, 47:55
Kaku, T., Haruyama, J. et al. 2017, Geophysical Research Letters, 44
Sood, R., Melosh, H. J., Howell, K. 2016, 26th AAS/AIAA Space Flight Mechanics Meeting, AAS 16-464
Sumner, T. 2017, Science News, 191, 1, 5 (January 21, 2017)
Urbancic, N., Stanley, S., Ghent, R., et al. 2015, 46th Lunar and Planetary Science Conference #1616