You really shouldn't miss the images of the booster return.

by Eric Berger - Jan 16, 2023 1:14pm EST

The Falcon Heavy rocket made its fifth launch in five years on Sunday evening from Florida. However, this was the first launch of the triple-core booster in twilight, and this rare evening light provided some spectacular new insights into the liftoff and return of the rocket. //

Now the second-most powerful rocket in the world after NASA's Space Launch System, the Falcon Heavy always puts on a great show, with its 27 Merlin engines firing at once. It holds the record for the rocket with the most first-stage engines to reach orbit—at least, it will until SpaceX's Starship rocket flies later this year.

The 30-foot-long, robotic, X-37B military ship — which has gained fame both for its secret missions as well as its ability to stay in orbit for so long — ended its most recent trip at NASA’s Kennedy Space Center in Florida on Saturday, according to Space Force and USA Today. //

The unmanned little spacecraft, which looks like a mini-shuttle, spent a record-breaking 908 days in orbit, or 118 days more than its previous record, USA Today said.

The reusable Boeing vehicle, now done with its sixth mission, has traveled 1.3 billion miles over the course of 3,774 days in space. It has been whizzing around Earth on various trips since 2010.

While X-37B’s primary missions are mainly secretive, it does perform secondary tasks that are publicized, the outlet said.

Several NASA experiments were completed during the record-breaking mission, the military Space Force said in a statement.

We would like to specifically stress an extremely dangerous trend that goes beyond the harmless use of outer space technologies and has become apparent during the latest developments in Ukraine. Namely, the use by the United States and its allies of civilian, including commercial, infrastructure elements in outer space for military purposes. Apparently, these States do not realize that such actions in fact constitute indirect participation in military conflicts. Quasi-civilian infrastructure may become a legitimate target for retaliation. Western actions needlessly put at risk the sustainability of peaceful space activities, as well as numerous social and economic processes on Earth that affect the well-being of people, first of all in developing countries. At the very least, this provocative use of civilian satellites is questionable under the Outer Space Treaty, which only provides for the peaceful use of outer space, and must be strongly condemned by the international community.

This is not the first time Vorontsov has made such comments, as he made similar remarks last month to the United Nations Office for Disarmament Affairs working group. However, it is not clear to what extent Russia might be able to follow through on its threat to target commercial satellites.

While he wasn't sure what to expect, Shatner did not predict this. He had been excited to travel to space, and had thought about it for nearly 60 years, but didn't think he'd be overwhelmed with sadness, or that he'd go through "the strongest feelings of grief" that he's ever experienced.

There's a name for what Shatner felt: it's called the "overview effect." The term was coined by space philosopher Frank White in his 1987 book of the same name.

"The overview effect is a cognitive and emotional shift in a person's awareness, their consciousness and their identity when they see the Earth from space," White told NPR. "They're at a distance and they're seeing the Earth ... in the context of the universe."

This context was what struck Shatner the most.

"It was the death that I saw in space and the lifeforce that I saw coming from the planet — the blue, the beige and the white," he said. "And I realized one was death and the other was life."

According to White, everyone who travels to space experiences an "overview effect" — an emotional or mental reaction strong enough to disrupt that person's previous assumptions about humanity, Earth, and/or the cosmos. Everyone's overview effect is unique to them, but there are reactions that are more common than others.

"We cannot work with a partner who is completely trampling on those values." //

Half a year after Russia's invasion of Ukraine, the implications of this war for the European space industry have been profound. Most notably, Europe has severed all connections with the Russian launch industry and canceled a joint mission to place a European rover on Mars with the help of a Russian rocket and lander. //

Soon after the Russian invasion, relations between the two space programs broke down. Russian workers at Europe's main spaceport in French Guiana walked off the job and returned home. A launch of OneWeb satellites on a Russian rocket, brokered by the European Space Agency, was scrubbed. Those 36 satellites remain stranded in Kazakhstan, and OneWeb recently took a $229 million writedown.

Prior to the war, Europe had relied on Russia's Soyuz rocket for its medium-lift needs—for payloads larger than its Vega rocket could accommodate but not large enough to necessitate the more expensive Ariane 5 rocket. That partnership had been expected to continue even as Europe brought a new generation of rockets, the Vega-C and Ariane 6, into service. But no longer. //

"I cannot see a rebuild of the cooperation we had in the past," Aschbacher said. "I am speaking here on behalf of my member states. They all have very much the same opinion. And this is really something where the behavior of ESA will reflect the geopolitical situation of the member states on this point. And I think this is very clear."

The Mars Oxygen In-Situ Resource Utilization Experiment can make oxygen at anytime during the Martian day or year.

NASA confirmed Wednesday that it has awarded five additional crew transportation missions to SpaceX, and its Crew Dragon vehicle, to ferry astronauts to the International Space Station. This brings to 14 the total number of crewed missions that SpaceX is contracted to fly for NASA through 2030.

As previously reported by Ars, these are likely the final flights NASA needs to keep the space station fully occupied into the year 2030. While there are no international agreements yet signed, NASA has signaled that it would like to continue flying the orbiting laboratory until 2030, by which time one or more US commercial space stations should be operational in low Earth orbit.

Under the new agreement, SpaceX would fly 14 crewed missions to the station on Crew Dragon, and Boeing would fly six during the lifetime of the station. That would be enough to fill all of NASA's needs, which include two launches a year, carrying four astronauts each. But NASA has an option to buy more seats from either provider. //

SpaceX started flying operational missions to the space station in 2020, with the Crew-1 mission. Although Boeing's Starliner has a crewed test flight early next year, likely in February, its first operational mission will not come before the second half of 2023.

Additionally, there is some question about the availability of rockets for Starliner. Boeing has purchased enough Atlas V rockets from United Launch Alliance for six operational Starliner missions, but after that the Atlas V will be retired. During a news conference last week, Boeing's program manager for commercial crew, Mark Nappi, said the company is looking at "different options" for Starliner launch vehicles. These options include buying a Falcon 9 from a competitor, SpaceX, paying United Launch Alliance to human-rate its new Vulcan rocket, or paying Blue Origin for its forthcoming New Glenn booster. //

Since we now know how many flights each company will be providing NASA through the lifetime of the International Space Station, and the full cost of those contracts, we can break down the price NASA is paying each company per seat by amortizing the development costs.

Boeing, in flying 24 astronauts, has a per-seat price of $183 million. SpaceX, in flying 56 astronauts during the same time frame, has a seat price of $88 million. Thus, NASA is paying Boeing 2.1 times the price per seat that it is paying SpaceX, inclusive of development costs incurred by NASA. //

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ColdWetDog wrote:
Interesting that the $90 million lasts charged by Roscosmos isn't too far off the SpaceX cost.

The Russians were seen to be price gouging - and in a way that's true, the Soyuz development costs have been paid back years ago - but it wasn't too outrageous of a price in retrospect.

Of course, giving the money to SpaceX has many other advantages.

It's not a good comparison regarding Roscosmos seat price because the SpaceX "seat price" actually includes the complete capacity of the Dragon and it's trunk for cargo up mass and down mass.

Under the current limits, set by NASA in 1989, the effective dose limit for an astronaut's career is based on a maximum 3% lifetime excess risk of cancer mortality. That risk is evaluated with a sliding scale based on age and sex, ranging from a lower career limit of 180 millisieverts (mSv) of radiation for a 30-year-old woman to an upper career limit of 700 mSv for a 60-year-old man.

So why is there a lower career limit for radiation exposure for female astronauts than for male astronauts?

According to R. Julian Preston, a special government employee with the U.S. Environmental Protection Agency's Radiation Protection division, NASA's lower radiation threshold for female astronauts was based on the following finding: When women and men were exposed to high levels of radiation for similar periods of time, women had more than twice the risk that men did of developing lung cancer. //

"It has been generally considered — based largely on the survivors from the atomic bombs in Japan — that, particularly for lung cancer, that women were more sensitive" to ionizing radiation than men were, Preston, who serves on committees for the National Council on Radiological Protection and Measurements, told Live Science. //

However, NASA's radiation thresholds are expected to change in the near future. In 2021, NASA asked a panel of experts convened by the National Academies of Sciences, Engineering and Medicine to assess the space agency's plan to change its career radiation limit to 600 mSv for all astronauts of all ages. NASA determined that limit by applying the agency's cancer risk model to the most susceptible individuals: early-career women. NASA calculated the average risk of exposure-induced death for this group and converted that risk, which allows for a much larger margin of error than previously, to a dose. That 600-mSv dose translates to the exposure an astronaut would receive during four six-month expeditions on the ISS. For comparison, the average annual dose of radiation received by a person on Earth is about 3.6 mSv, according to NASA, versus 300 mSv per year on the ISS.

Appearing before a House Science Committee hearing on NASA's Artemis program, Martin revealed the operational costs of the big rocket and spacecraft for the first time. Moreover, he took aim at NASA and particularly its large aerospace contractors for their "very poor" performance in developing these vehicles.

Martin said that the operational costs alone for a single Artemis launch—for just the rocket, Orion spacecraft, and ground systems—will total $4.1 billion. This is, he said, "a price tag that strikes us as unsustainable." With this comment, Martin essentially threw down his gauntlet and said NASA cannot have a meaningful exploration program based around SLS and Orion at this cost.

Later in the hearing, Martin broke down the costs per flight, which will apply to at least the first four launches of the Artemis program: $2.2 billion to build a single SLS rocket, $568 million for ground systems, $1 billion for an Orion spacecraft, and $300 million to the European Space Agency for Orion's Service Module. NASA, Martin said, had checked and confirmed these figures.

What is striking about these costs is that they do not include the tens of billions of dollars that NASA has already spent developing the Orion spacecraft since 2005 and the Space Launch System rocket since 2011. If one were to amortize development costs over 10 flights of the SLS rocket and Orion spacecraft, the $4.1 billion figure cited by Martin would easily double. //

Later during the hearing, US Rep. Brian Babin (R-Texas), asked whether the incremental costs of flying more than one Artemis mission a year would bring the cost down. Martin said he did not know for sure. Moreover, NASA is not planning to fly more than one Artemis mission a year, so the question is somewhat moot.

Martin, however, appeared to doubt that there would be significant cost savings due to the inefficiency of the program and its large aerospace contractors.

"Part of it goes to the efficiencies of the underlying contractors, like Boeing," Martin said. "One of the problems we saw in development of the SLS and Orion—it's a challenging development of course—but we did notice very poor contractor performance on Boeing's part, poor planning, and poor execution."

Then, unprompted, Martin continued to criticize the programs set up by Congress to fund the rocket and spacecraft. House and Senate members told NASA to use "cost-plus" contracts, which ensure that companies involved in the development and operation of these systems receive all of their costs, plus a fee. This tends to disincentivize timely work completed within a set budget. (Remarkably, NASA was told to continue using cost-plus contracts even after the development program.)

"We saw that the cost-plus contracts that NASA had been using to develop that combined SLS-Orion system worked to the contractors' rather than NASA's advantage," Martin said. //

In reality, no one should expect Congress to care about the high cost of the SLS and Orion program. The legislature created the programs this way. //

In fact, key members of Congress have been critical of NASA every time the agency has tried to break free of cost-plus contracting and use a more commercial approach through fixed-price contracts. That congressional skepticism has persisted even as the commercial approach has borne fruit. As tensions with Russia rise, for instance, NASA only has independent access to space because of the Crew Dragon spacecraft.

Lest anyone doubt this, House Science Committee Chair Eddie Bernice Johnson (D-Texas) took aim at NASA's commercial space efforts in her opening statement at the hearing. The context of her statement concerns NASA's desire to purchase commercial services for spaceflight in the future rather than oversee their development in-house like it did with SLS and Orion.

"I find the sum of these actions to be very troubling," Johnson said. "And it raises the question of whether NASA will even retain the capabilities and workforce within the agency that will be needed to get US astronauts to Mars if all of these privatization plans are realized."

At least it answers the question of where congressional priorities lie.

Russia's unprovoked invasion of Ukraine this week will have devastating consequences for the people on the ground. Although the terrestrial implications of this war are far greater than those for spaceflight, there will nonetheless be ripple effects felt by space programs around the world. //

The most prominent space issue concerns the fate of the International Space Station, which is operated by 15 nations but led by the United States and Russia. The countries rely on one another: Russia provides fuel and thruster capability to periodically re-boost the space station to a higher altitude, and NASA gyroscopes provide stability, and its solar panels generate the vast majority of electricity. At present, the station cannot operate without the consent of both partners.

After Biden's comments on Thursday, the head of Russia's main space corporation, Dmitry Rogozin, lashed out in a series of tweets in which he characterized Biden's actions as "Alzheimer's Sanctions." //

All of this translates into fewer resources pouring into the Russian space program and a further diminution of its activities. Without investment, the country is unlikely to be able to afford any semblance of deep-space activities or the creation of its own space station as a follow-on to the International Space Station.

This very likely will push Russia to cooperate further with China, where it has already initiated discussions about joining the Chinese lunar exploration program. But this Chinese lifeline will almost certainly come with costs. China will be interested in partnering with Russia to promote the idea that it is leading an international exploration program—but Russia should have no illusions about who will be driving the bus and who will be along for the ride.

As SpaceX charges forward with full and rapid rocket reuse, the company's stretch goal is to fly each "ship" every six to eight hours. These "ships" are the Starship launch system's upper stage, which is 50 meters tall and designed to carry payloads into orbit or be refilled there to fly to the Moon or Mars. The first-stage "booster" could fly even more frequently, as much as once an hour, he predicted. The first stage makes a six-minute flight to space and back and is intended to be loaded with propellant on the ground in just 30 minutes. //

SpaceX has unquestionably come a long way since 2016, when Musk first revealed the full scope of his plans to build a launch system that could establish a self-sustaining settlement on Mars. By his own estimates, such a venture would require 1 million tons of food, water, and construction materials. The settlers will need to build an entire industrial base to mine the red planet, and manufacturing consumer products will require a huge infrastructure base to refine and shape materials.

This is an incredible logistical challenge. Consider that throughout the last five decades, during the entirety of its Mars exploration program, NASA has landed a grand total of a couple of tons on the surface of Mars.

For his settlement plan, therefore, Musk proposed an unprecedented rocket and spacecraft. During a 90-minute speech in Guadalajara, Mexico, five years ago, Musk spoke of his “Interplanetary Transportation System,” or ITS. This was a huge and fully reusable launch system with a second-stage spaceship that could be fueled in low Earth orbit and then flown to Mars fully laden with supplies or dozens of settlers. Eventually, after more name changes, the ship would be christened Starship.

The 2016 speech was striking in its candor. Musk laid bare his entire vision for the first time for all the world to see. It was easy to criticize, and many did. The general viewpoint among the established space community at the time was that such a vision was preposterous.

And who could blame the critics? Only four weeks before Musk gave his speech, SpaceX had blown up its second Falcon 9 rocket in a year, losing the Amos-6 satellite on the launch pad on September 1. The company was also going to be years late delivering a Crew Dragon capability to NASA and its astronauts. And for all the talk of reusable rockets, SpaceX had not yet re-flown a single Falcon 9 rocket. Critics watched the Guadalajara speech and saw Musk the Charlatan—over-promising, grasping for government money, and spewing lies about the future when he couldn’t deliver in the present.

But in the five and a half years since Musk’s first Mars moment, the billionaire has answered those critics. SpaceX has not lost a single rocket since Amos-6. In fact, the Falcon 9 booster recently set the record for the longest streak of successful launches by any rocket ever. SpaceX also has become a reliable provider of crew transportation services to NASA, years ahead of its competitor Boeing, which NASA paid 60 percent more for the same service to low Earth orbit. And Falcon 9 rocket first stages have now flown 11 times, with no end in sight.

https://outline.com/yrHtaL

I actually had an interesting conversation with Elon Musk about this. The question was, what would it take to build a self-sustaining settlement on the surface of Mars? It would take one million metric tons of stuff, propellant, the 3D printers, the stock for the 3D printers, food, agriculture, domes, wherever you're gonna live, all of it, to get to the point where you could have all that on Mars and those people could then survive without intervention from Earth. So one million metric tons, if you think about that, it takes a very large rocket and a whole sort of sophisticated spacecraft. The Curiosity mission was what, a couple billion dollar mission to get to Mars? And that Rover was one ton. That's the challenge we're talking about, sending one million Perseverances or Curiosities worth of mass to Mars. It's an enormous challenge. //

Right now we're focused on stepping one foot on Mars and then 10 and then a hundred, slowly building up to have a permanent human presence. There's no physics reason preventing us from inhabiting Mars, it's a matter of technology and engineering and patience, and most importantly, money. But there's no reason why we can't eventually be on Mars. Humanity will have a presence on Mars. Well, I'm not going.

SpaceX has been launching Falcon 9 rockets thick and fast of late. With 10 launches since the beginning of December, the company has flown rockets at a rate greater than one mission a week. And another launch could happen as soon as today, shortly after noon (18:13 UTC), with a Starlink satellite launch planned from Florida.

Lost amid the flurry of activity are some pretty significant milestones for the Falcon 9 rocket, which made its debut a little more than a decade ago. //

The Falcon 9 rocket has now launched a total of 139 times. Of those, one mission failed, the launch of an International Space Station supply mission for NASA, in June 2015. Not included in this launch tally is the pre-flight failure of a Falcon 9 rocket and its Amos-6 satellite during a static fire test in September 2016.

Since the year 2020, the Falcon 9 has been the most experienced, active rocket in the United States, when it surpassed the Atlas V rocket in total launches. Globally, the still-flying Russian Soyuz and Proton rockets have more experience than the Falcon 9 fleet. The Soyuz, of course, remains the king of all rockets. It has more than 1,900 launches across about a dozen variants of the booster dating back to 1957, with more than 100 failures.

The Falcon 9 reached a notable US milestone in January, equaling and then exceeding the tally of space shuttle launches. During its more than three decades in service, NASA's space shuttle launched 135 times, with 133 successes. To put the Falcon 9's flight rate into perspective, it surpassed the larger shuttle in flights in about one-third of the time.

There is no way to know how many missions the Falcon 9 will ultimately fly. At its current rate, the rocket could reach 500 flights before the end of this decade. However, SpaceX is also actively working to put its own booster out of business. The success of the company's Starship project will probably ultimately determine how long the Falcon 9 will remain a workhorse. //

Speaking of safety, this is where the Falcon 9 rocket has really shone of late. Since the Amos-6 failure during its static fire test, SpaceX has completed a record-setting run of 111 successful Falcon 9 missions in a row. It probably will be 112 after Thursday.

There are only two other rockets with a string of successful flights comparable to the Falcon 9. One is the Soyuz-U variant of the Russian rocket, which launched 786 times from 1973 to 2017. The other is the American Delta II rocket, which recently retired. (Eventually, the Atlas V rocket could also exceed 100 consecutive successes before its retirement later this decade.)

The 20th-century was marked by competition between two Cold War adversaries, the Soviet Union (USSR) and the United States, to achieve superior spaceflight capability.

The space race led to great technological advances, but these innovations came at a high cost. For instance, during the 1960s NASA spent $28 billion to land astronauts on the moon, a cost today equating to about $288 billion in inflation-adjusted dollars.

In the last two decades, space startup companies have demonstrated they can compete against heavyweight aerospace contractors as Boeing and Lockheed Martin. Today, a SpaceX rocket launching can be 97% cheaper than a Russian Soyuz ride cost in the ’60s.

The key to increasing cost efficiency?

SpaceX rocket boosters usually return to Earth in good enough condition that they’re able to be refurbished, which saves money and helps the company undercut competitors’ prices.

On Christmas morning of 2021, the James Webb Space Telescope successfully launched from Earth. Thomas Zurbuchen, now NASA's associate administrator for science, had made the call. If Webb was going to fail, he would take the blame.

Not only did Webb launch, but its Ariane 5 rocket performed the flight with such precision that the spacecraft was able to save precious fuel for maneuvering, thereby extending its lifetime. Over the next two weeks, engineers and scientists executed hundreds of steps to unfold and fully extend the telescope and its massive sunshield. And then, finally, on Monday, the spacecraft performed one final major burn of its thrusters, falling into a halo orbit around the L2 point.

This means that the Webb space telescope has reached its final destination, a 180-day orbit around this L2 point, which keeps the telescope in line with the Earth as both the instrument and planet orbit around the Sun. Here, while using a minimum amount of fuel to hold its position, Webb can use its sunshield to keep the infrared telescope and its instruments cold.

The work is not done. The telescope has 18 primary mirror segments, which are moved by 132 actuators. These actuators have already been tested and shown to work. Now, over the next three months, telescope operators will fine-tune the alignment of these mirrors. During this process, scientists will use a Sun-like star named HD84406 to focus the mirrors. This star is located about 240 light years from Earth and can be found in Ursa Major near the bowl of the Big Dipper.

At the same time, in the wake of the sunshield, these mirrors and their scientific instruments will continue to cool in order to be able to detect the weak, ultra-distant signals of heat from the Universe's oldest galaxies. //

What is it about HD84406 that makes it the one to use for focusing the mirrors?

There are probably lots of criteria, but I only know two of them:

1. It's in the same 1/3 of space that JWST can see (i.e. the telescope doesn't have to look towards the Sun to see it)
2. It has to be relatively bright (HD84406 is not visible to the naked eye but can be seen with binoculars).

I can't find a reference now, but IIRC it was also selected because it's isolated with nothing behind it that's close (in interstellar terms), so it's easier to determine if the focus is good because there's less background light.

A Washington-state based aerospace company has exited stealth mode by announcing plans to develop one of the holy grails of spaceflight—a single-stage-to-orbit space plane. Radian Aerospace said it is deep into the design of an airplane-like vehicle that could take off from a runway, ignite its rocket engines, spend time in orbit, and then return to Earth and land on a runway. //

The current design of Radian One calls for taking up to five people and 5,000 pounds of cargo into orbit. The vehicle would have a down-mass capability of about 10,000 pounds and be powered by three liquid-fueled engines. The idea would be to get as close to airline operations as possible, by flying, landing, re-fueling, and flying again. //

If Radian can succeed technologically, large markets would likely open. A vehicle like Radian One would be well suited to fly people to commercial space stations in low Earth orbit, which NASA seeks to foster development of by 2030. These planes could also perform Earth observation work and play a role in bringing back space-manufactured goods. There is also the potential for point-to-point travel on Earth.

There can be no question that this is a hugely challenging endeavor that many people have tried before. Will Radian find the right stuff, at the right moment in time? We'd like to think so.

Space anemia is tied to being in the void and can stick around awhile

Space isn’t easy on humans. Some aspects are avoidable—the vacuum, of course, and the cold, as well as some of the radiation. Astronauts can also lose bone density, thanks to a lack of gravity. NASA has even created a fun acronym for the issues: RIDGE, which stands for space radiation, isolation and confinement, distance from Earth, gravity fields, and hostile and closed environments.

New research adds to the worries by describing how being in space destroys your blood. Or rather, something about space—and we don’t know what just yet—causes the human body to perform hemolysis at a higher rate than back on Earth. //

The team’s results showed that in space, the astronauts’ bodies destroyed around 3 million red blood cells every second. This is 54 percent higher than what happens in human bodies on Earth, where the rate is 2 million every second. //

It’s also uncertain how long a person in space can continue to destroy 54 percent more red blood cells than their Earth-bound kin. “We don’t have data beyond six months. There’s a knowledge gap for longer missions, for one-year missions, or missions to the Moon or Mars or other bodies,” he said.

Considering the looming possibility (or reality, if you’re a billionaire or aging Star Trek actor) of space tourism, Trudel’s research could pose a warning for some would-be space-farers. People with heart problems, angina, abnormal hemoglobin levels, or a propensity for blood clots might be at risk for complications out in the void, he said. The work may also help us learn about space injuries—a body’s ability to heal a cut might be affected by this shift in red blood cells.

How on Earth do you patch the software on a computer orbiting the Moon? Very carefully.

FRANK O’BRIEN - 1/30/2020, 12:30 PM

In the afternoon of January 31, 1971, the flight thundered away from the Kennedy Space Center on its Saturn V launch vehicle after only a brief 40 minute hold for weather. After restarting the S-IVB third stage for trans-lunar injection (TLI), the command module Kitty Hawk and her crew were on their way to the Moon. //

However, less than four hours before the scheduled landing, controllers noticed that according to the indications on their consoles in Mission Control, the LM's Abort pushbutton appeared to have been pressed. When asked via radio, Shepard confirmed that no one on board Antares had pressed the Abort button—which meant there was a short-circuit or other electrical issue somewhere inside the LM's complicated guts.

This was potentially a mission-ending problem: if the button was pressed and the engine was firing, the LM would immediately begin its abort procedure as soon as the lunar descent started, making a landing impossible.

Under hard time pressure, the ground had to quickly figure out what was wrong and devise a workaround. What they came up with was the most brilliant computer hack of the entire Apollo program, and possibly in the entire history of electronic computing.

To explain exactly what the hack was, how it functioned, and the issues facing the developers during its creation, we need to dig deep into how the Apollo Guidance Computer worked. Hold onto your hats, Ars readers—we're going in. //

Once again the LM’s orbit carried it behind the Moon and out of communications, leaving the crew with just a smattering of procedures and few options. The normal work of finishing the system configurations continued, and the crew maneuvered to the descent attitude, tidied up the cabin, and put on their helmets and gloves. In the meantime, Don Eyles’ team was feverishly working to find a better solution to the Abort bit issue.

Working the problem involved unraveling a complex, daisy-chained series of events. The main landing program, P63, does not perform all of the landing computations itself. Rather, it orchestrates a large number of Jobs and Waitlist Tasks, each performing a necessary part of the effort. Another Job running concurrently was the SERVICER, which sampled attitudes and accelerations that fed into the guidance equations. SERVICER, in turn, scheduled Routine R11 as a Waitlist Task, running every 0.25 seconds. R11 first checked whether aborts are enabled (via the LETABBIT flag), and if so, it then checked the status of the Abort bit. With aborts allowed, and the abort signal set (presumably because the crew pressed the Abort pushbutton), P63 is terminated, the AGC's Major Mode switches to P70, and the abort process begins. //

This was the breakthrough. If R11 could be spoofed into believing that an abort was already in progress, then it didn’t matter if the Abort button was pressed or not—the button's state would be ignored.

But how did R11 actually inform itself about whether or not an abort was executing? The answer was in plain sight on the DSKY: The Major Mode display, under the label “PROG”. //

In less than two minutes after the descent to the Moon had started, the Abort pushbutton had been successfully disabled and the computer was happily managing the descent. All indications were that the next lunar landing would be successfully accomplished in eight more minutes. //

As Antares passed through 32,000 feet (about 9,700 meters), Mitchell became concerned and informed controllers that the radar hadn’t locked on. Houston replied with a suggestion to pull the circuit breaker for the radar, and then power the system back on, which did the trick. Solid radar data began flowing into the computer, and the crew quickly agreed to accept it. Just a few minutes later, Shepard made a smooth and on-target touchdown at the Fra Mauro highlands.

After the mission, when asked if he would have attempted to land without the radar, the notoriously hard-charging Shepard reportedly replied, “You’ll never know.” In Gene Kranz’s Failure is Not an Option autobio, Kranz recounts that Flight Director Jerry Griffin was convinced that Shepard would indeed make an attempt to land without radar, and would just as certainly have had to abort when fuel ran out. //

The idea that a single errant switch could derail a lunar landing attempt was unacceptable. After the mission, a new variable in the AGC code was introduced that allowed the crew to "mask out" (that is, to ignore) the Abort and Abort Stage pushbuttons. The scenario assumed that a failing switch would be recognized well before the descent began, and commands could be entered in time to prevent an inadvertent abort. Like the fix used for Apollo 14, this would make initiating an abort through a pushbutton impossible, and any urgent situation would have to be performed on the Abort Guidance System. //

The recovery from Apollo 14’s Abort switch failure can only be described as brilliant and heroic. But the most important enabler of this effort was that the software, while fiendishly complex, could be understood by a small team of developers. Modern hardware and software, with its extensive protection schemes, virtualization and dynamic program management simply would make such a simple hack impossible. Faced with a comparable problem today, even if the fix were trivial, the solution likely would require large amounts of code to be recompiled, tested and uploaded to the spacecraft. This may not be possible given the short timeframe necessary to save the mission.

In the end, Apollo 14’s fix truly represented the “Spirit of Apollo," where talented teams made the impossible happen.

The five layers of the sunshield are incredibly delicate. Each plastic-like sheet has the same thickness as a human hair and had to be stretched across a tennis-court-sized area. All of this had to be done in microgravity, an environment that could not be simulated in ground tests.

"It was the first time we deployed this system in zero-g, and we nailed it," said Alphonso Stewart, Webb deployment systems lead. "It's a really good testament to the work done by the teams."

So much could have gone wrong. During tests as recently as 2018, the sunshield layers were snagging during ground-based tests. It's not difficult to understand why. According to NASA, the unfolding and tensioning of the sunshield involved 139 of the telescope's 178 release mechanisms, 70 hinge assemblies, eight deployment motors, some 400 pulleys, and 90 individual cables totaling more than 400 meters in length.

By getting through the sunshield deployment process, therefore, NASA has surmounted the most complex aspect of unpacking the telescope in space and setting it up for operations.

"The sunshield deployment certainly was the most complex in terms of moving parts having to all work in harmony, and systems that were interrelated with one another," said James Cooper, the Webb telescope's sunshield manager. "The stuff that’s left from a deployment point of view is more conventional, such as hinges and motors."

Lots of hurdles to come, but a good start for the new observatory.