Posted on by Nancy Atkinson

13 Things That Saved Apollo 13, Part 8: The Command Module Wasn’t Severed

This view of the damaged Apollo 13 Service Module (SM) was photographed by a maurer 16mm motion picture camera from the Lunar Module/Command Module following SM jettisoning. Credit: NASA

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Note: To celebrate the 40th anniversary of the Apollo 13 mission, for 13 days, Universe Today will feature “13 Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill.

When the Apollo 13 crew jettisoned the crippled Service Module as they approached Earth, they saw the extent of the damage from the explosion of an oxygen tank. “There’s one whole side of that spacecraft missing!” Jim Lovell radioed to Mission Control, his voice reflecting his incredulousness at seeing the damage of a 13-ft panel blown off the spacecraft. However, the situation could have been more dire. The heat shield on the Command Module could have been damaged. What’s more, NASA engineer Jerry Woodfill said that instead of the panel blowing out, the explosion could have — and maybe should have –severed the Command Module from the Service Module.

Graphic of the CSM. Credit: NASA

Photos taken by the Apollo 13 crew after the service module was jettisoned in preparation for the command module’s reentry via the heat shield revealed that not only was the panel missing from the side of the spacecraft — blown into the vastness of space by the exploding pressure of the detonating oxygen – there was also damage to the Hi Gain Antenna, at the right of the vehicle drawing above, indicating the panel had catapulted into space, striking the antenna. What the images couldn’t show, and what the Apollo 13 crew couldn’t see was if there was any damage to the Command Module’s heat shield.

“The structural design of the interior of the Service Module is that it has a long open tunnel-like volume in the center of the module, about 30 inches by 13 feet,” said Woodfill. “The tunnel is much like a chimney such that gases, liquids, or particles could readily move through it toward the main engine bell at the right and the heat shield at the left. The tunnel is not sealed so that the explosive force of the burning oxygen from the exploded O2 tank 2 could escape into and around the tunnel in the direction of both the heat shield and main engine.”

Woodfill said concern was voiced in Mission Control that shrapnel from the exploding tank had entered the tunnel, and perhaps ultimately caused damage to both the heat shield and main engine. The main engine wasn’t the biggest issue, as the crew was able to use the lunar lander’s descent engine. (see our previous article , “Using the LM for Propulsion.”) But there was only one heat shield, and it had to work to enable the capsule and the crew to survive the fiery reentry through Earth’s atmosphere.

Thankfully, as it turned out ,the heat shield wasn’t damaged.

The recovery of the Apollo 13 Command Module. Credit: NASA

But almost miraculously, Woodfill said, the command module and service module remained connected following the explosion, while the internal pressure of the explosion rocketed the exterior panel into space.

“The attachment strength of the Service Module panel to the structure required a considerable internal pressure of 24 pounds per square inch for severing it from the service module,” Woodfill said. “A much lower pressure was required to separate the Command Module with its heat shield from the Service Module, only 10 pound per square inch. One can only speculate on why the panel blew and the crew capsule/service module attachment remained intact.”

Since there is no air pressure in space, Woodfill explained, the force which held the vehicles together was the strength of their mechanical attachments.

“Two pressures were at work,” he said. “Each attempted to overcome respective attachment forces: the force which attached the Service Module to the Command capsule and the force which attached the Service Module panel to the Service Module. Because the explosive pressure force of the oxygen was immediately applied in great strength to the panel, this overwhelming force would be expected to blast that panel apart from the vehicle, exceeding the 24 pound per square inch attachment strength. However, venting of residual explosive oxygen into the framework of the Service Module could well be expected to overcome the attachment strength between the two vehicles, separating them.”

Yet, it did not. Why?

Sequence photo from 16mm motion picture film of test at Langley Research Center which seeks to determine mechanism by which Apollo 13 panel was separated from Service Module. Credit: NASA. Click image for more information

“Apparently, the presence of ‘tankage’ and other structure acted to mitigate and dissipate the sudden pressure spike before it reached the interface between the vehicles,” Woodfill said. “However, if a shard from the exploded O2 tank 2 had punctured any of the adjacent tanks, likely a secondary explosion of any of them would have propagated both the explosion and build up of pressure. In that event, certainly, the vehicles would have experienced either a fatal separation or fatal damage to the heat shield.

A piece of shrapnel did fracture the plumbing between the oxygen tanks that allowed the oxygen to leak out of Tank 1, causing the complete loss of power in the Command Module, for without oxygen the fuel cells couldn’t work.

Some may say that having the Service Module attached to the Command Module wasn’t important – it was just dead weight anyway. However, other problems could have developed without the Service Module attached, according the Apollo 13 Failure Report. Having the heat shield exposed to low temperatures for a long period could have damaged it, and internal Command Module thermal problems could arise if the Service Module was jettisoned too early.

Additionally, flight control problems were anticipated if the Command Module wasn’t attached.
The immediate loss of the Service Module would have meant immediate loss of the residual power from the fuel cells while the crew and mission control wrestled to understand the problem. This would have required a much greater power drain on those emergency batteries to the extent that one wonders if the later “trickle-charge” from the lander’s batteries would have been sufficient for reentry.

The crew of Apollo 13, Jim Lovell, Jack Swigert and Fred Haise, during a post-flight debrief. Credit: NASA

Of course, since the Service Module was jettisoned before the crew re-entered (and the SM itself later burned up in the Earth’s atmosphere) no one could do any “forensic analysis” or an engineering “autopsy” on that part of the spacecraft.

“To me, it is amazing that, one, the heat shield wasn’t damaged from the explosion, and two, the connection that could withstand higher pressure ended up blowing, while the weaker connection stayed together,” said Woodfill.

But those were among the many things that saved Apollo 13.

Next: Part 9: Which tank was damaged

Earlier articles from the “13 Things That Saved Apollo 13” series:

Introduction

Part 1: Timing

Part 2: The Hatch That Wouldn’t Close

Part 3: Charlie Duke’s Measles

Part 4: Using the LM for Propulsion

Part 5: Unexplained Shutdown of the Saturn V Center Engine

Part 6: Navigating by Earth’s Terminator

Part 7: The Apollo 1 Fire

Part 8: The Command Module Wasn’t Severed

Part 9: Position of the Tanks

Part 10: Duct Tape

Part 11: A Hollywood Movie

Part 12: Lunar Orbit Rendezvous

Part 13: The Mission Operations Team

Also:

Your Questions about Apollo 13 Answered by Jerry Woodfill (Part 1)

More Reader Questions about Apollo 13 Answered by Jerry Woodfill (part 2)

Final Round of Apollo 13 Questions Answered by Jerry Woodfill (part 3)

Never Before Published Images of Apollo 13’s Recovery

Listen to an interview of Jerry Woodfill on the 365 Days of Astronomy podcast.

Posted on by Jean Tate

Hubble’s 20th: At Least as Good as Any Human Photographer

NGC 3314 (click for larger version)

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Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 2000 to April 2002.

The International Center for Photography gave its 2000 Infinity Award to the Hubble Heritage Project, in the Applied Photography section. And what did that team choose to showcase their award? The above image of NGC 3314! Clearly the Hubble has had a deep impact far beyond the astronomical community and space fans.

Columbia’s last flight, before the one that ended in disaster, was STS-109, or the Hubble servicing mission 3B, in March, 2002. In terms of imaging capability, it was the most dramatic; the Advanced Camera for Surveys (ACS) was installed (replacing the Faint Object Camera), and NICMOS’ cooling system was replaced (giving the Hubble ‘night vision’ again – it could see in the infrared once more). I’ll be covering the cornucopia of science results from ACS in later articles.

My pick for the Hubble image most of you, my readers, would put at the top your ‘what I remember from these two years’ is Stephan’s Quintet.

Stephan's Quintet (Credit: ESA)


Hubble Space Telescope Faint Object Spectrograph (Credit: NASA)

What we see on a webpage or in a magazine, when we look at a Hubble image, resembles a photograph. What an astronomer sees is data, glorious data, in all its numerical detail (astronomers even invented a special file format for their data, called FITS, short for flexible image transport system; more about it here). And among the most critical aspect of astronomical data is its calibration, e.g. the function which relates pixel values to things like flux (which may be measured in janskys, or ergs per second per square meter per hertz). But how do you calibrate an instrument that’s aboard the Hubble? You turn to the Instrument Physical Modelling Group, part of the Space Telescope European Coordinating Facility! This highly specialist team actually models the Hubble’s instruments, in software, from first (physics) principles, and from those models produces robust software for taking the raw data from a Hubble instrument and producing calibrated, science-grade data. They then make their results public, for anyone and everyone to use; for example the Faint Object Spectrograph Post-Operational Archive (you can read the details of their work in ST-ECF Newsletter 29).

Another behind-the-scenes activity is the production of the Hubble Guide Star Catalog, essential for the Hubble’s smooth operation (and a major boon to amateurs); 2001 saw a major new release (II).
A MACHO (Credit: European Space Agency, European Southern Observatory and the MACHO project team)

Every now and then a (faint) star will pass close to the line of sight of a more (bright) distant star, and we will see the (distant) star brighten in a characteristic way (due to gravitational lensing). One kind of such lensing is the object of many astronomers’ desire, a MACHO (massive compact halo object); even more desirable is to see both the lensed and lensing stars, as separate points of light, some time after the event. Hubble observed just such a rarity.
Comet LINEAR (Credit: NASA and Hal Weaver (The Johns Hopkins University, Baltimore, MD))

Comets are fragile things; their very tails tell tales of constant erosion at the hands of sunlight. And when they die, do they do so with a bang, or merely a whimper? Hubble captured an example of the latter (Comet LINEAR is no more).
Horsehead Nebula (Credit: NASA, NOAO, ESA and The Hubble Heritage Team (STScI/AURA))

But the Hubble isn’t only for astronomers, even amateur astronomers; it’s there for us all, to take pictures that awe and inspire us. And by popular demand, the famous Horsehead nebula, as never seen by anyone using a telescope down here on Earth.

It was during these two years that Universe Today began its coverage of the Hubble (and other astronomy and space topics); for example Hubble Reveals Backward Galaxy (however, I can’t find any Universe Today stories from this period with Hubble images; can you help me out please, dear reader?)

Tomorrow: 2002 and 2003.

Previous articles:
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System

Posted on by Jean Tate

Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant

HDF-S (Credit: R. Williams (STScI), the HDF-S Team, and NASA). Click for a larger version

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Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 1998 to April 2000.

In October 1998, Hubble complemented the original Hubble Deep Field with Hubble Deep Field South (HDF-S). Three instruments – NICMOS, STIS, and WFPC2 – stared at a tiny spot in the sky for ten days (more images here).

Hubble got dizzy in November 1999; the fourth (of six) gyroscopes failed, and the observatory was put into safe mode. The third servicing mission, planned for mid-2000, was split in two, with 3A being done in December 1999. Along with replacing all the gyros, Hubble got a computer upgrade … to a 486 model (did you ever own a PC with a 486 CPU?)

I reckon the image which most of us remember best from these two years is this one of M57, yet another planetary nebula.

M57 (Credit: The Hubble Heritage Team (AURA/STScI/NASA))


Wendy Freedman (CARLA BEFERA PUBLIC RELATIONS)

“Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant” is one of the most heavily cited papers in astronomy, perhaps even science, period. It also happens to be one of easiest to read, and is likely to serve as a model for a long time. It is based on a great deal of ‘Hubble time’ (dedicated observations), but should anyone want use all the data from all that time, they are free to do so. Wendy Freedman is the lead author on that paper, and led this Hubble Key Project (HKP) from start to finish.
NGC 4603 with Cepheids marked (Credit: Jeffrey Newman (Univ. of California at Berkeley) and NASA)

At its heart, this HKP is a repeat of Edwin Hubble’s work, some seven decades earlier – observing lots of Cepheid variables in some 19 nearby galaxies, with the Hubble, and using the period-luminosity relationship to estimate the distances to them (Of course, there’s a very great deal more to it than that!). No prizes for guessing who the Hubble is named after, and why.
Copernicus, by Hubble (Credit: John Caldwell (York University, Ontario), Alex Storrs (STScI), and NASA)

The end of the Key Projects freed up more time for the Hubble to observe other things; some of which may surprise you. For example, many people think the Hubble cannot look at the Moon, much less take pictures of it.

To make some of Hubble’s best eye-candy more accessible, the Hubble Heritage Project was set up, in 1998. And what more appropriate eye candy is there, in a story about the Hubble, than Hubble’s variable nebula?
NGC 4650A (Credit: The Hubble Heritage Team (AURA/STScI/NASA))

And one of the things the Hubble Heritage team did was run a competition for the best image; the polar ring galaxy NGC 4650A won (was that your choice?); if you think this looks odd, it is … I rotated it 90 degrees (there’s no up or down in space).
HDF-S by NICMOS (Credit: R. Williams (STScI), the HDF-S Team, and NASA)

To close, two much less often seen HDF-S results, from NICMOS (above) and STIS (below).
HDF-S by STIS (Credit: R. Williams (STScI), the HDF-S Team, and NASA)

Tomorrow: 2000 and 2001.

Previous articles:
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System, Hubble Deep Field South

Posted on by Ken Kremer

WORF and Klingons occupy ISS

Japan Aerospace Exploration Agency (JAXA) astronaut Naoko Yamazaki, STS-131 mission specialist, works inside the Window Observational Research Facility (WORF) in the Destiny laboratory of the International Space Station while shuttle Discovery was still docked. WORF is a platform for cameras, multispectral scanners, and other sensors to capture science imagery of Earth imagery through Destiny's earth facing window. WORF is named after the Klingon character Worf beloved in the Star Trek Universe (top left). The WORF patch (lower left) is inscribed with Commander Worf’s name in Klingon script and was created by Tony Boatright. Credit: NASA images. WORF Patch: NASA/Tony Boatright. Mosaic: Ken Kremer

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WORF has finally joined the crew aboard the International Space Station (ISS). That’s great news for NASA as well as members and fans of the Klingon High Council who are delighted to occupy a prime location for exquisite surveillance of the Earth and Federation activities.

WORF is the acronym for the Window Observational Research Facility, a new science imaging platform on the ISS, which is named after the popular Klingon character from the “Star Trek: The Next Generation” science fiction television series. The surface panel on WORF sports a beautiful patch with a Klingon language inscription – spelling out the name WORF in Klingon script (see photo). Although seemingly innocent, Universe Today has learned that the Klingon High Council may have more sinister plans afoot for WORF involving future imperial undertakings.

WORF was permanently installed inside the US Destiny Lab module over the labs optical quality glass window by the STS 131 crew. Credit: NASA
The WORF science rack was one of the major new pieces of scientific equipment delivered to the ISS by the seven person crew of Space Shuttle Discovery during the highly successful STS 131 mission which blasted to space on April 5, 2010. WORF was packed into the ‘Leonardo’ resupply module which was the primary payload inside Discovery’s cavernous cargo bay.

WORF was designed by Earthlings to function as a photographic darkroom for precision remote space sensing of the Earth. As such, it’s also the only rack on the station that ISS astronauts and cosmonauts can actually physically float into and then maneuver equipment around to conduct their science research. “The working volume to accommodate instruments is about 23 cubic ft (0.8 cubic m)”, according to Dennis Toney of Boeing, Huntsville, Al, who I interviewed at the Kennedy Space Center during the STS 131 launch.

Panels, shelving and brackets inside WORF provide numerous attach points for digital cameras, multispectral and hyperspectral scanners, camcorders, sensors and other instruments to capture Earth imagery through Destiny’s nadir – Earth facing – window.
The experiments will focus on studies of atmospheric and climate properties, land and sea formations, geology, agriculture, ranching, environmental and coastal changes, and also be linked to public outreach and education efforts.

“EarthKAM is an example of a remotely controlled digital camera system that will be commanded to take pictures by middle school students across the US using web based tools”, Toney explained to me. The kids will learn how to work as real scientists. See WORF graphics provided to the author by Boeing/Denis Toney.

Graphics show WORF ‘darkroom’ science rack loaded with cameras and spectral payloads (left) and after closing with hatch (right) to exclude stray light from entering the payload volume. Crewmembers control the experiments loaded inside WORF using a laptop computer mounted on the front of the rack. NASA will use WORF for high resolution Earth observation experiments. Middle school students will be able to remotely control the EarthKAM digital camera payload inside WORF to take photos of the earth and learn how to work as real scientists. Graphics courtesy of Boeing/Dennis Toney were specially provided to the author for this story.

Astronauts installed the WORF darkroom inside the US Destiny Laboratory module and purposely “placed it in a bay directly over the labs 20 inch (508 mm) diameter observation window to provide direct access to the window from inside WORF”, said Toney.

“WORF provides the infrastructure to maximize the usability of the window. Up to 5 science payloads can be accommodated at once”, explained Toney. Numerous instrument connector ports and jacks for Ethernet computer connections, power, video and cooling are built directly into the rack to transmit the multispectral and high resolution experimental imaging data to the ground.

The Destiny window is the highest quality optical glass science window ever flown on any manned spacecraft. The window is constructed from 4 panes of optical quality glass pressed together that permit greater than 95% transmission across most of the visible spectrum and 90% transmission in the near infrared.

Jeff Williams, Expedition 13 Science Officer, at the U.S. Destiny Laboratory Science Window on the ISS. Williams recently served as the ISS Expedition 22 Commander.WORF was mounted on top of the Destiny window by the STS 131 crew.

The photographic and spectral gear – up to 350 mm aperture – mounted inside WORF can be remotely operated from Earth or by astronauts on board, who may also work in a hand held mode as required by the particular piece of equipment to maximize the scientific return.

An external shutter protects the window from micrometeoroid and orbital debris floating outside the station. The hinged cover can be manually opened and closed by the crew inside the cabin with a hand crank.

The “Leonardo’ Multi-purpose Logistics Module (MPLM) weighs over 27,000 pounds and is one of three such modules built by the Italian Space Agency. The module serves as a space moving van and was loaded with 16 science and storage racks – including WORF – holding over 17,000 pounds of science supplies and experiments, crew life support provisions, spare parts, a new astronaut sleep quarter and a minus 80 degree freezer to stow science samples collected by the resident ISS crew.

The Leonardo resupply module and Ken Kremer inside the Space Station Processing Facility at the Kennedy Space Center as the module was being prepared for launch aboard shuttle Discovery on the STS 131 mission. WORF science rack and over 17,000 pounds of science equipment and supplies were loaded inside Leonardo. Credit: Ken Kremer

After Discovery docked to the ISS, Leonardo was hoisted out of Discovery’s cargo bay and berthed to the station for the duration of the flight. The massive orbiting outpost is 98% complete – by habitable volume – and weighs in at 800,000 pounds and spans the length of an American football field.

Space Shuttle Discovery undocked from the ISS on Saturday morning (April 17) in preparation for a Monday April 19 landing at 8:51 AM. Credit: NASA
The STS 131 mission of Space Shuttle Discovery is nearing a close. Discovery undocked from the ISS early this morning at 8:52 AM and about 213 miles above earth and is set to land at KSC on Monday morning at 8:51 AM, weather permitting.

Authors Note: This paragraph is just for fun excepting Federation Counterintelligence agents. Unbeknownst to the crew members and NASA, top secret Klingon military surveillance technology was embedded deep within the WORF unit, according to a source who requested anonymity. Whilst the STS 131 crew was innocently hooking up umbilical line connections to the ISS electrical and computer systems, they unwittingly activated the Klingon Empires cloaking chip previously hidden inside WORF by time traveling Klingon spies dispatched by the High Council. The chip instantaneously began transmitting encoded data via sub space frequencies to eagerly waiting intelligence operatives working for the Klingon Chancellor. Stay tuned for more on WORF and the Klingon infiltration of the ISS.

Earlier STS 131 related articles by Ken Kremer:

Mother of Pearl Colored Clouds form above Kennedy after Discovery Blast Off

Spectacular Radar Failed Belly Flip (Video) and Docking links Discovery to ISS

Antenna Glitch hinders Data Flow from Inspection of Discovery

Discovery Dazzles with Two Dawns in One Day

Discovery Unveiled on Easter Sunday to the Heavens Above

Countdown Clock Ticking for Discovery Blast off on April 5

Soyuz Blasts off with Russian American Crew for Easter ISS arrival

Read more about the WORF Facility and the WORF Patch here:

NASA WORF Website

collectSpace.com Forum discussion on WORF patch

Dennis Toney (Boeing) and Ken Kremer discuss the science goals of the WORF facility at the Kennedy Space Center Press Site during the STS 131 launch of shuttle Discovery on April 5, 2010. Discovery delivered WORF to the ISS. Credit: Ken Kremer
Posted on by Jean Tate

Hubble at 8: So Many Discoveries, So Quickly

Planetary Nebula
Planetary Nebula M2-9 (Credit: Bruce Balick (University of Washington), Vincent Icke (Leiden University, The Netherlands), Garrelt Mellema (Stockholm University), and NASA)

Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 1996 to April 1998.

The ability of the Hubble Space Telescope to be serviced by astronauts, using a space shuttle as a platform, is one of its design features. This proved its worth very early, with the first servicing mission installing COSTAR. The second such mission – a ten day effort with Discovery as the workhorse – took place in February 1997; two new instruments were installed (and two removed), the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Space Telescope Imaging Spectrograph (STIS), and many other, smaller, upgrades and repairs made.

Yesterday’s article featured the Pillars of Creation; today’s captures the beauty of a star’s death.
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STScI's home, John Hopkins University, Homewood Campus (Credit: John Hopkins Univerity)

How does the Hubble work? Who runs it? The Space Telescope Science Institute (STScI) is responsible for the scientific operation of Hubble as an international observatory; it has a combined staff of approximately 500, of whom approximately 100 are PhDs. Among the prime tasks of the STScI are the selection of the Hubble observing proposals, their execution, the scientific monitoring of the telescope and its instruments and the archiving and distribution of the Hubble observations.

The Space Telescope-European Coordinating Facility (ST-ECF) offers support for the preparation of Hubble observing proposals and the scientific analysis of observations. It also operates the Hubble Science Archive, which makes data available to the astronomical community via the Internet.

With the exception of observations like the Hubble Deep Field – which are available for immediate release – the data from Hubble observations are the exclusive property of the observers for one year, after which all scientific data are made available to anyone and everyone, via the internet. And guess what? Thousands of papers have been published, using such freely available data!

Asteroid Trail Crosses Galaxy NGC 4548 (Credit: R. Evans and K. Stapelfeldt (JPL) and NASA)

One example of the tremendous value of the Hubble archive is all the asteroids it inadvertently images; because of the Hubble’s sensitivity, motion, and resolution, the orbits of many of these can be determined from just the serendipitous images (discoveries made by ground-based telescopes usually require follow-up images days apart). And yes, many papers have been written, based on these images, “Asteroid Trails in Hubble Space Telescope” for example.
GRB 970228 (Credit: STScI and NASA)

Sometimes something happens in the sky and you want to point powerful telescopes at it, quickly, before it disappears. By far the most interesting yet fleeting ‘something’ is gamma-ray bursts (GRBs). Although known for decades, none had been seen in any other electromagnetic waveband … until February 28, 1997. Right after its servicing mission, Hubble caught the afterglow of GRB 970228, located in very distant galaxy. A milestone in astronomy.

Volcanoes, active ones, were discovered on Io, by accident, in 1979, as volcanic plumes rising above the limb. Who could have imagined that such plumes would be imaged not twenty years later, from low-Earth orbit, with Jupiter as the backdrop?

In 1920 Betelgeuse’s diameter was estimated, using a 6 meter interferometer mounted on the front of the 100-inch Mount Wilson telescope. In 1996, the Hubble made a direct observation of Betelgeuse, resolving it; only the second star to have ever been seen as anything but a point of light (what was the first?).
Antennae Galaxies (Credit: Brad Whitmore (STScI) and NASA)

The Antennae galaxies, NGC 4038/NGC 4039, are not only highly photogenic (how many amateurs count their snaps of these among their most prized?), but great natural laboratories for studying galaxy collisions, star formation, etc. Hubble’s 1997 images provided the basis for hundreds of papers.

Tomorrow: 1998 and 1999.

Previous articles:
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System

Posted on by Jean Tate

Hubble’s 20 Years: Now We Are Six

pillars of creation
Eagle Nebula Pillars of Creation as seen by Hubble Space Telescope in 2005. (Credit NASA, ESA, STScI, J. Hester and P. Scowen (ASU)


Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 1994 to April 1996.

After the famous Apollo 8 “Earthrise” image, comet Shoemaker-Levy 9’s impact with Jupiter, in July 1994, strikes us as the most stark reminder of the fragility of our home. And the Hubble gave us the clearest pictures of just how destructive that collision was; those dark blotches are bigger than the Earth.

Equally memorable, from Hubble’s early childhood years – ages five and six – is the “Pillars of Creation” image.
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Richard Griffiths (Credit: CXC)

Much of the Hubble’s time in the first few years was devoted to the Hubble Space Telescope Key Projects, two of which I mentioned yesterday, “on the Extragalactic Distance Scale”, and the “Quasar Absorption Line” Key Project. There is a third, the Medium-Deep Survey (MDS), lead by Richard Griffiths, who is now at Carnegie Mellon University. Here’s a nice bit of trivia: astronomers spend an inordinate, a humongous amount of time doing surveys; they even build entire observatories devoted exclusively to them (think Sloan Digital Sky Survey, of Galaxy Zoo fame)! And here’s a question for you: why? Why are surveys soooo important to astronomers?
Hubble images of distant spiral galaxies (Credit: NASA, Richard Griffiths/JHU, Medium Deep Survey Team)

Anyway, MDS is interesting for another reason too; it’s a “parallel mode” project … while the Hubble is pointed at its main target, a nearby field is also observed, using WF/PC or the Faint Object Camera (or, later, WFPC2); two results for the price of one! However, perhaps more than any other observations, the MDS ones before the Hubble had its vision fixed (see yesterday’s article) suffered from the mis-figuring of the primary mirror. And it’s a tribute to the ingenuity and perseverance of Griffiths and his colleages that they were, eventually, to wring so much good science from the data (you guessed it, hundreds and hundreds of papers).
Uranus, rings, and moons (Credit: Kenneth Seidelmann, U.S. Naval Observatory, and NASA)

Jupiter wasn’t the only solar system object of interest to Hubble; Uranus, its rings and inner moons captured on film (well, CCD); the first surface features on Pluto were snapped; Saturn’s Aurorae imaged; the Galilean moons of Jupiter mapped; etc, etc, etc.
Credit: J. Bahcall, Institute for Advance Study, Princeton, F. Paresce, STScI & ESA, and NASA

My own favorite Hubble recollection from these two years is (another!) paper by John Bahcall, “M dwarfs, microlensing, and the mass budget of the Galaxy“, which basically proved that the Milky Way’s halo is composed principally of non-baryonic dark matter. I remember reading it and thinking, “nah, that can’t be right, you guys can’t conclude that from that data!”, but the more I gnawed at it, the more it struck me just how simple, yet profound, this work was (pay attention you fans of Universe Puzzle, there’s a clue to a future puzzle here).
Hubble Deep Field (R.E. Williams/STScI/NASA; Werry/Blanton/Hogg (NYU), Lupton (Princeton))

Finally, towards the end of the time I’m covering in this article, Hubble took the famous Hubble Deep Field. The version posted here you may not have seen before, because it uses a different color transform, by Robert Lupton (more images using this technique here).

Tomorrow: 1996 and 1997.

Previous articles:
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System

Posted on by Nancy Atkinson

13 Things That Saved Apollo 13, Part 6: Navigating By Earth’s Terminator

Earth's Terminator, showing darkness and daylight, July 1969, as seen from NASA's Apollo 11 Spacecraft.

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Note: To celebrate the 40th anniversary of the Apollo 13 mission, for 13 days, Universe Today will feature “13 Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill.

The rupture and explosion of Apollo 13’s oxygen tank crippled the spacecraft, endangering the lives of the crew and making a Moon landing not an option. But more problems arose as the perilous flight progressed. Keeping the spacecraft on the right trajectory was a huge challenge for Mission Control, and especially for the crew. Normally, the ship’s computers allowed for much of the navigation, but due to the loss of the Service Module as an electrical power source, even backup navigation and targeting functions were unavailable. The Lander’s limited battery power required the shutting down of its guidance computer. The astronauts also needed to use an on-board sextant to confirm their location by sighting-in the stars, similar to how ancient sailors navigated. “There are thirty-seven stars – and one is the sun,” said Apollo engineer Jerry Woodfill, “that provided an accurate way of aligning the spacecraft’s computer platform to allow the astronauts to steer their way through the heavens.”

But the explosion of the tank had enshrouded the Apollo 13 spacecraft with debris. Commander Jim Lovell and his crew couldn’t discern the stars from the particles that glimmered in the sunlight. “The situation was, without the ability to see the stars, you couldn’t navigate,” Woodfill said.

But NASA had a backup navigation plan, thanks to an insightful NASA contractor employee. This novel way of navigating had only been tried once before in space. And coincidentally, the astronaut who used it was Jim Lovell, during his previous flight — Apollo 8 — which orbited the Moon in December of 1968.

An employee of TRW – which was the contractor for many of the navigational systems and procedures for NASA — thought of an unusual backup navigation plan one day. “This fellow is a friend and neighbor of mine,” said Woodfill, “and by his account of the story to me, he said that a thought came to him one day about Apollo astronauts using stars to navigate. What if the stars couldn’t be seen? Now, that was highly unlikely, as there are no clouds, fog, or smoke to conceal stars from viewing by astronauts. But, nevertheless, the thought simply wouldn’t cease. Soon a follow-up idea came to mind. Why not use the Earth’s terminator?”

The nominal flight plan for a mission to the Moon. Credit: Apollo 13 report.

The terminator is the line which delineates between night and day on Earth; where the Sun is shining and where it is dark.

Woodfill’s friend figured out the geometry and wrote a computer program to validate the idea. He submitted the proposal to the navigation board, which approved the technique so that it was entered into the computers in the Mission Control Center.

Through unusual, and what could be called happenstance circumstances, Lovell experimented with the backup plan during Apollo 8.

Lovell served as navigator for the first manned mission to orbit the Moon. He made a star sighting in preparation for the return to Earth, and entered the coordinates into the Apollo spacecraft’s primitive computer using the “DSKY” (display and keyboard). Instead of pressing the ENTR (enter) key, he inadvertently pressed the adjacent CLR (clear) key erasing the entire navigational alignment.

“Lovell consulted with Mission Control whether to repeat the sextant star sighting,” Woodfill said, “and someone realized this would be an opportunity to test the backup ‘seat of the pants’ means of navigating using the Earth’s terminator. And it worked! But then everyone forgot about it, until…guess when?”

Apollo 13's view of the Moon. Credit: NASA

Initially, the Apollo 13 crew was able to use the Sun as a “marker” to help in guiding the spacecraft to confirm they were on the right path, and were able to fire the LM engines for course corrections using the transferred guidance platform from the Command Module.

But as Apollo 13 headed back to Earth, the Reentry (RETRO) and Guidance, Navigation and Control (GNC) officers looking at the trajectory analysis noticed the spacecraft was coming in too “shallow,” that is, Apollo 13 was headed to skip off the atmosphere and out into space forever. Something seemed to be “blowing” the spacecraft off course. Later, it was discovered that cooling vapor from the lander was responsible. Since no lander had been present for previous missions on a return trip from the Moon, such a mysterious “wind” had never been encountered prior to Earth re-entry.

Another burn was needed, but no help from the guidance system would be available, as powering the lander’s guidance system, its gyros, the computer, etc. would use too much electrical power.

Here’s where the backup navigation approach that Lovell experimented with on Apollo 8 came to the rescue.

“If a ‘dead-reckoning’ approach could be used, no electricity would be needed,” said Woodfill. “Simply point the vehicle correctly, start the engine and stop it based on Mission Control’s prescribed time for its operation.” Lovell eyed up the Earth’s terminator line and controlled the “yaw” of the spacecraft, Haise controlled the “pitch” and Swigert timed it with his accurate Omega Speedmaster watch.

Graphics from the Apollo 13 report on using Earth's terminator for navigation.

The Navigation report for Apollo 13 describes it this way:

“The cusps of the Earth terminator were placed on the Y axis of the COAS. The illuminated part of the Earth was placed at the top of the reticle. Pitch attitude was achieved by placing the Sun in the upper portion of the AOT (see below). This procedure aimed the LM +Z axis at the Earth and aligned the LM +X axis retrograde along the local horizontal. An AGS body axis alignment was performed, followed by transitioning the AGS to the automatic attitude hold mode. A maneuver to burn attitude was performed, followed by another body axis alignment.”

Navigation graphics from the Apollo 13 report.

Woodfill said he enjoyed Hollywood’s re-enactment of the procedure in the “Apollo 13” movie. Though the spacecraft gyrations about the heavens are wholly exaggerated, the scene where Tom Hanks, Bill Paxton, and Kevin Bacon set-up and execute the terminator burn is generally accurate.

Suffice to say, the procedure worked for Hollywood dramatics, but more importantly, it worked to save the lives of Lovell, Haise and Swigert.

Tomorrow, Part 6: Fire

Other articles from the “13 Things That Saved Apollo 13” series:

Introduction

Part 1: Timing

Part 2: The Hatch That Wouldn’t Close

Part 3: Charlie Duke’s Measles

Part 4: Using the LM for Propulsion

Part 5: Unexplained Shutdown of the Saturn V Center Engine

Part 6: Navigating by Earth’s Terminator

Part 7: The Apollo 1 Fire

Part 8: The Command Module Wasn’t Severed

Part 9: Position of the Tanks

Part 10: Duct Tape

Part 11: A Hollywood Movie

Part 12: Lunar Orbit Rendezvous

Part 13: The Mission Operations Team

Also:

Your Questions about Apollo 13 Answered by Jerry Woodfill (Part 1)

More Reader Questions about Apollo 13 Answered by Jerry Woodfill (part 2)

Final Round of Apollo 13 Questions Answered by Jerry Woodfill (part 3)

Never Before Published Images of Apollo 13’s Recovery

Listen to an interview of Jerry Woodfill on the 365 Days of Astronomy podcast.

Posted on by Jean Tate

Hubble’s 20 Years: Time for 20/20 Vision

Credit: NASA/STScI


Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 1992 to April 1994.

“And we have liftoff, liftoff of the Space Shuttle Endeavor, on an ambitious mission to service the Hubble Space Telescope”

Without a doubt, Servicing Mission 1 in early December 1993 was the high point of the Hubble Space Telescope’s third and fourth years in space.

For starters, it successfully replaced the high speed photometer instrument with COSTAR (Corrective Optics Space Telescope Axial Replacement), which, as its name implies, corrected for the mis-figured primary mirror and so permitted the three instruments not replaced to make the high quality images intended (they were the Faint Object Camera, the Faint Object Spectrograph, and the Goddard High Resolution Spectrograph).

It also replaced the WF/PC (Wide Field Planetary Camera) with an upgraded WF/PC (called WFPC2), and made several other repairs and replacements which considerably improved the Hubble’s performance and robustness.
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John Bahcall

Well before the Hubble was launched much of its observing time was pre-allocated, especially to two Hubble Key Projects, “on the Extragalactic Distance Scale”, and the “Quasar Absorption Line” Key Project. The former is well-known (and I’ll cover it in a later Hubble 20th birthday article); the latter hardly known at all outside the astrophysics community. It was the brainchild of the remarkable John Bahcall, and much of the Hubble’s time in its first four years was devoted to it. There are 13 main papers on its results, with hundreds more based on them. In a word, this project revolutionized our understanding of the space between galaxies and galaxy clusters, all the way from just beyond the Milky Way to billions of light-years distant.
The lucky 16 amateurs (Credit: NASA/STScI)

It wasn’t only professional astronomers who used the Hubble in these two years; 16 amateurs did too! Do you know what they found? If you had the chance, what would you use the Hubble to observe?
Comet Shoemaker-Levy 9 (Credit: Dr H.A. Weaver, T.E. Smith; STScI/NASA)

Perhaps the most captivating images the Hubble took in these two years are the ones of Comet Shoemaker-Levy 9 on its way to a collision with Jupiter (I’ll cover the collision itself tomorrow). Do you remember, back then, that asteroid and comet threats to life on Earth just became a whole lot more believable?
eta Carinae (Credit: J.Hester/Arizona State University/NASA)

3C273's jet (Credit: R.C. Thomson&C.D. Mackay, IoA, Cambridge, UK; A.E. Wright, ATNF)

Hubble sent back images of many more objects in these two years, including a much better one of eta Carinae (compare this one with the one in yesterday’s article) and the optical jet of the iconic quasar 3C273.

Tomorrow: 1994 and 1995.

Previous article:
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System

Posted on by Nancy Atkinson

Obama Wants Mission to Asteroid by 2025, Mars by mid-2030’s

President Barack Obama during his speech at Kennedy Space Center on April 15, 2010. Image credit: Alan Walters (awaltersphoto.com) for Universe Today

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Speaking at Kennedy Space Center, President Barack Obama discussed his plans for NASA which includes sending astronauts to a nearby asteroid by 2025 and going to Mars by the mid-2030’s. “Let me start by being extremely clear,” Obama said. “I am 100 per cent committed to the mission of NASA and its future because broadening our capabilities in space will continue to serve us in ways we can hardly imagine.” Obama’s plan, which includes the $6 billion in additional funds for NASA over the next five years that was previously announced and using a scaled-down version of the Orion spacecraft as a rescue vehicle for the International Space Station.

Also, Obama committed funds for research now to build a heavy-lift rocket starting in 2015 — or earlier — to launch astronauts and payloads to missions beyond the Moon.

“By 2025 we expect new spacecraft designed for long journeys to allow us to begin the first ever crew missions beyond the Moon into deep space,” Obama said. “So, we’ll start by sending astronauts to an asteroid for the first time in history. By the mid-2030s, I believe we can send humans to orbit Mars and return them safely to earth, and a landing on Mars will follow.”

Obama at KSC. Image credit: Alan Walters (awaltersphoto.com) for Universe Today.

Obama said his program of partnering with commercial space companies allows for more missions launched from Kennedy Space Center, an acceleration of advanced technologies that will allow for better space transportation systems and a shortening of the dependence on Russian rockets.

The president made no mention of any extension to the space shuttle program, which was one rumor that floated around before his speech.

Norm Augustine, before the president's speech. Credit: Alan Walters (awaltersphoto.com) for Universe Today

Speaking after the President, Norm Augustine – who headed the Augustine Commission review of NASA’s future, said that the new program is very close to one of the options his panel offered (option 5-B) and this path would be “worthy of a great nation, and be able to transform NASA from transportation to exploration.” Augustine also pointed out that we seem more eager to accept current Russian technology than to encourage future of our own private industry.

Buzz Aldrin flew with President Obama to Kennedy Space Center in Air Force One. Image credit: Alan Walters (awaltersphoto.com) for Universe Today

The White House Chief Science Advisor John Holdren said Obama’s plan is a “faster pace to space, with more missions sooner and more affordably.” He said it’s a more visionary approach as it expands commercial capability and allows NASA to devote its resources to exploring deep space.

Obama discussed his space plan at the Operations and Checkout Building at the Kennedy Space Center, the same building used to build the Orion spacecraft. This is the first time in 12 years a sitting U.S. president has visited KSC.

The plan was originally unveiled on Feb 1, 2010, and the proposal to cancel the Constellation program and use commercial companies for trips to LEO was met with harsh criticism from members of Congress and many former astronauts, including a letter from Neil Armstrong, Gene Cernan and Jim Lovell who called the plan “devastating” the legacy of US space leadership.

Today, however, before the president’s speech, Elon Musk from SpaceX – whose Falcon 9 spacecraft will launch a test flight perhaps next month – issued a statement that lauded Obama’s plan to end Constellation.

“The President quite reasonably concluded that spending $50 billion to develop a vehicle that would cost 50% more to operate, but carry 50% less payload was perhaps not the best possible use of funds. To quote a member of the Augustine Commission, which was convened by the President to analyze Ares/Orion, ‘If Santa Claus brought us the system tomorrow, fully developed, and the budget didn’t change, our next action would have to be to cancel it,’ because we can’t afford the annual operating costs.”

“Cancellation was therefore simply a matter of time,” Musk continued, “and thankfully we have a President with the political courage to do the right thing sooner rather than later. We can ill afford the expense of an “Apollo on steroids”, as a former NASA Administrator referred to the Ares/Orion program. A lesser President might have waited until after the upcoming election cycle, not caring that billions more dollars would be wasted. It was disappointing to see how many in Congress did not possess this courage.”

By choosing KSC to make his speech Obama hoped to bring home that his program will add more 2,500 jobs compared to plan under previous administration.

“We will modernize KSC, creating jobs as we upgrade launch facilities, and bringing the potential for more jobs as companies come here to compete for launch projects. This is an area prime to lead in this competition.”

Afterwards, NASA Administrator Charlie Bolden said, “It’s special when a president talks about you but it’s even more special when he comes to visit.”

Readers, what are your thoughts on Obama’s program for NASA, and his speech?

A gallery of images from the President’s speech by Alan Walters, in attendance representing Universe Today.

Space personalities Neil deGrasse Tyson and Jim Bell at Obama's speech at KSC. Image credit: Alan Walters (awaltersphoto.com) for Universe Today
Bill Nye, The Science Guy
Leland Melvin was one of many astronauts in attendance at KSC. Credit: Alan Walters (awaltersphoto.com) for Universe Today
Senator Bill Nelson (D-Florida) and NASA Administrator Charlie Bolden introduced President Obama. Image Credit: Alan Walters (awaltersphoto.com) for Universe Today
Posted on by Nancy Atkinson

13 Things That Saved Apollo 13, Part 5: Unexplained Shutdown of the Saturn V Center Engine

Apollo 13 launch. Credit: NASA

Note: To celebrate the 40th anniversary of the Apollo 13 mission, for 13 days, Universe Today will feature “13 Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill.

While oxygen tank number two on the Apollo 13 spacecraft was an accident waiting to happen, another problem on the Saturn V rocket could have destroyed Apollo 13 before it reached Earth orbit. During the second-stage boost, the center – or inboard — engine shut down two minutes early. The shutdown wasn’t a problem, as the other four engines were able to compensate for the loss by operating for an extra four minutes. But why the engine shut down is a mystery that may have saved the mission.

“A catastrophic failure should have ensued,” said Apollo engineer Jerry Woodfill, “and would have, except for the unexplained behavior of the engine’s shutoff system. In fact, even the NASA Apollo 13 accident report fails to deal with the seriousness of the event.”

When the center engine shut down, it caused a few moments of uneasiness for Mission Control and the crew. Speaking after the flight, Commander Jim Lovell said that when NASA gave them the OK to carry on with the flight, “We all breathed a sigh of relief on the spacecraft. Hey, that was our crisis over with and we thought we’d have a smooth flight from then on.”

Woodfill said that the quick assessment in Mission Control was that a minor electrical signal failed to keep the engine operating so that it shut down prematurely. But that wasn’t the problem.
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What happened was the Saturn V rocket experienced dangerous so-called “pogo” thrust oscillations, a problem NASA knew about. While a fix had been planned for Apollo 14, time did not permit its implementation on Apollo 13’s Saturn V.

“While a clerical error caused Apollo 13’s oxygen tank to explode,” said Woodfill, “because its heater design had not been updated for 65 volt operation, and the tank was a virtual bomb (see Part 1), similarly NASA’s failure to fix a known serious booster flaw should have destroyed Apollo 13.”

The Saturn V rocket had five J-2 engines, each producing 200,000 pounds of thrust, together creating the 1 million pounds of thrust needed for a mission to the Moon.

On previous Saturn flights, these pogo oscillations had occurred during launch. The phenomenon occurred as the fuel lines and structure of the rocket resonated at a common frequency. The resonance tended to amplify in force and potential destruction with each bounce of the “pogo” mechanism. So damaging was the phenomena on the unmanned Apollo 6 mission that an entire outer panel of the Saturn 5 ejected into space.

Launch of Apollo 6. Credit: NASA

“The oscillations are like a jack hammer and it was so dreadful on Apollo 6 that it tore off a panel on the booster, and threatened the mission,” said Woodfill. “Apollo 6’s orbit was supposed to be circular, but because of the pogo effect and failure of second stage engines, the orbit became an elongated orbit of about 60 by 180 miles.”

Woodfill said if Apollo 13 had ended up in that type of orbit, it would have been bad but not fatal. However, Apollo 13 was a much different situation than Apollo 6.

The Apollo 6 mission carried a mock lunar lander of more modest mass than the “full-up” lander which Apollo 13 carried to orbit. With the added mass for Apollo 13, the pogo forces were suddenly a magnitude greater in intensity. A mission report said that the engine experienced 68g vibrations at 16 hertz, flexing the thrust frame by 3 inches (76 mm).

Woodfill said that if the center engine had continued running a few more seconds, the oscillations may have destroyed the vehicle. “That engine was pounding horizontally up and down, a quarter foot, at the rate of 16 times a second,” he said. “The engine had become a two ton sledge hammer, a deadly pogo stick of destruction, putting enormous forces on the supporting structures.”

What shut the engine down?

“It is, to this day, not fully understood, but it had something to do with fooling the engine’s thrust chamber pressure sensor that pressure was too low,” said Woodfill. He has studied the mission report, but says the complete analysis of why the engine shut down isn’t included.

“Though the shutdown command came from a low thrust chamber pressure sensor assessment, actually, the engine was operating correctly,” he said. ” The sensor had nothing to do with the pogo phenomenon. For some inexplicable reason, it was like something sucked the pressure out of the chamber and a sensor turned the engine off. But no one knows exactly why.”

Woodfill said those who later examined the situation said it was altogether lucky that the sensor shut down the engine. “Something intervened, stopping the engine from pounding its way from the mount into the fragile fuel tanks. This would have destroyed the Apollo 13 launch vehicle.”

As it was, the engine shutdown likely saved the Apollo 13 mission.

Tomorrow, Part 6: Navigation

Other articles from the “13 Things That Saved Apollo 13” series:

Introduction

Part 1: Timing

Part 2: The Hatch That Wouldn’t Close

Part 3: Charlie Duke’s Measles

Part 4: Using the LM for Propulsion

Part 5: Unexplained Shutdown of the Saturn V Center Engine

Part 6: Navigating by Earth’s Terminator

Part 7: The Apollo 1 Fire

Part 8: The Command Module Wasn’t Severed

Part 9: Position of the Tanks

Part 10: Duct Tape

Part 11: A Hollywood Movie

Part 12: Lunar Orbit Rendezvous

Part 13: The Mission Operations Team

Also:

Your Questions about Apollo 13 Answered by Jerry Woodfill (Part 1)

More Reader Questions about Apollo 13 Answered by Jerry Woodfill (part 2)

Final Round of Apollo 13 Questions Answered by Jerry Woodfill (part 3)

Never Before Published Images of Apollo 13’s Recovery

Listen to an interview of Jerry Woodfill on the 365 Days of Astronomy podcast.