Smoothing out Plot-knots
After watching Andy Weir’s movie Project Hail Mary (2026), I went straight home with itching fingers to write a scathing post on the voluminous rubbish stuffed into the movie. “Andy Weir is worshipped as a science fiction god, yet his stories are nonsense,” I intended to write.
But I couldn’t do it because Andy Weir is an author, and I have a place in my heart for creative people, no matter their failings. If I eviscerated him, someday someone might do the same to me.
Then I thought of the many stories I’d critiqued over the years from budding authors who got themselves into what I call “plot knots” (story events made more complicated than they needed to be) and didn’t know how to fix them.
So, instead of criticizing the scientific flaws of Project Hail Mary, I’m going to describe how to handle the story’s “plot-knots” to make the story smoother and more believable without requiring extra words or the movie costing more money to make. And the critics would have less to say.
Unless they’re the jerk kind. Only living in hell for 10,000 years will have any effect on those folks.
Technical info
Before getting into my “perhaps-you-could-consider-writing-it-this-way” advice, I will provide some general information about neutrinos and propulsion via light emission to get those topics out of the way before the fun stuff begins.
Regarding neutrinos
Here are some interesting facts about neutrinos:
About 65 billion neutrinos from the Sun pass through every square centimeter of your body every second. In fact, they pass all the way through Earth and come out the other side unaffected.
If a neutrino were to somehow slow down or even stop, it would still be a neutrino. If you had a pile of them on your desk, they would just sit there and look back at you.
One way neutrinos form is through sufficiently high-energy collisions of photons (particles of light), which decay into neutrinos and other particles. Such reactions occur within the Sun's core.
The Astrophage in Project Hail Mary works similarly: It somehow gathers photons from the Sun and traps them within its cell. The Astrophage then somehow turns them into energy, which somehow creates neutrinos in the process. (I need to take a breath.) This keeps happening until the Astrophage cell is fully charged with energy.
The novel gives the energy density of fully charged Astrophage at about 7 x 1016 J/kg. If it weighs about the same as ordinary matter (which it appears to do in the book and in the movie), then Astrophage’s volumetric energy density is around 1020 J/m3, compared to the paltry energy density of the Sun’s core of merely 1014 J/m3, making the energy density of fully charged Astrophage about a million times greater than the energy density of the Sun's core.
While the existence of such a substance (Astrophage) in nature is astonishingly improbable, it doesn’t technically violate known laws of physics regarding energy storage. Note that a material containing 9.0 x 1016 J/kg of energy, no matter its size, would collapse into a black hole because that value is the energy density of black holes. This may be why Astrophage cells are black (just my opinion), because they’re very close to being little black holes.
Regarding light as propulsion
If you were floating in deep space and you turned on a flashlight, you would accelerate in the opposite direction of the beam of light. Yes, emitting light produces a thrust, just like a little rocket engine.
For example, 1 gigawatt of directed light results in about 0.742 pounds of thrust.
Thus, while floating in space, if you turned on a 1-gigawatt flashlight, and if you and your space suit together weighed 250 pounds, you would accelerate at:
That’s less than one-third of one percent of 1 g on Earth. Not very spectacular. However, if you turned on a 1-terawatt flashlight (that’s a thousand gigawatts), you’d accelerate at 3 g’s. Off you go, spaceman!
This is, in principle, what Astrophage does.
Yet, there’s an issue. The Petrova line in the novel and the movie portrays the band as being between the Sun and an orbiting planet, such as Venus. If Astrophage traveled in a group, their propulsion mechanism would be weakened.
See the following figure portraying an Astrophage cell emitting light:
Light is emitted to the left (in the figure above), so the cell accelerates to the right. This works well for a single cell. But when multiple cells are near each other, light from the first cell on the right pushes against the cell behind it, slowing down the second cell.
Imagine a number of rockets arranged in a single line, one after the other. The thrust from the first rocket would push against and slow down the second rocket, and so on. Thus, Astrophage would travel more efficiently if the cells spread out instead of keeping together in a band. Maybe they don’t know this, and someone should tell them.
Eliminate the “Huh?” moments
One way to make a story better is to avoid making readers (or viewers) say, “Huh?”
In a story, if a character is sitting at her desk at home, and she lifts up her pen in the air and then lets it go, and it stays there in the air, and there is no explanation for this, the readers/viewers are going to say, “Huh?”
There are many “Huh?” moments in Project Hail Mary that could be fixed without the need to increase word count or add a second coat of paint to the fake Styrofoam walls.
While Project Hail Mary is a novel, I’m choosing examples from the movie, making sure they also occur in the novel as far as I can tell from reading the story. I’ve also time-stamped each example from the Amazon Prime version of the movie, so you can review each scene I’ve highlighted and judge it for yourself.
Fixing the science
Let’s get to the good stuff:
Issue at 16:51
Grace pokes a single cell of Astrophage under a microscope with a sharp instrument, and the cell pops. Grace then announces that Astrophage consists of living cells. “Huh?” Lots of things “pop” when poked. Soap bubbles, balloons, and bubble wrap.
Solution
Instead, he can say, “Now we can find out what it’s made of.” Is there a requirement in the entire story that Astrophage must actually be alive? Viruses aren’t technically alive. Rust destroys things, and it’s not alive. A few trillion tiny black holes infesting the sun could seriously impact it, and they wouldn’t be alive.
Issue at 29:00
Grace says, “Those little guys store a lot of energy.” “Huh?” How could he know that so early in the story? What test did he run to learn that?
Solution
Have the scientists who’ve been developing the Hail Mary mission and spacecraft give Grace that information. They would know more than he would at that point.
Issue at 29:30
Eva Stratt says, “There won’t be enough fuel for a round trip.” “Huh?” I’ve worked on at least a hundred engineering projects, and there are always ideas for solutions to problems. There are more ideas than atoms in the universe.
Solution
Have Eva Stratt say, “There won’t be enough fuel for the first round trip. We are working on a second, unmanned spacecraft carrying only fuel, but we don’t believe it will be ready in time. The world needs this mission to start now.”
Her answer needed a bit more “oomph” so it wouldn't come across as 2D and contrived.
Issue at 33:15
This one I saw coming. I’m sitting in the audience pleading repeatedly to myself, “Please, don’t make it so!” Grace is preparing the bodies of his two deceased fellow astronauts to be “buried in space,” where he opens an airlock and releases the bodies into space. The problem is he’s walking around. Things fall to the floor. There clearly is a gravitational force, which means the spaceship’s engines are on, so the spaceship is either accelerating or decelerating. This becomes clearer a few minutes later when the ship's engines turn off because it reached orbit around Tau Ceti, and Grace becomes weightless.
As he’s about to let the bodies out into space (with the ship's engines on), my head is screaming, “No—don’t let them float!”
Out they float beside the ship, magically continuing to accelerate (or decelerate) at the same rate as the ship.
If you’re accelerating or decelerating, and you let something go, it will fall behind you or ahead of you. It won’t stay next to you like a doting puppy.
Health tip: Don’t drive a car with your arm hanging out of the window because if you get into an accident and the car stops suddenly (decelerates), your arm will “keep going” and either come off or you’ll have a serious shoulder injury.
Solution
This is the case where the novel gets it right, but the movie gets it wrong. According to the novel, the ship accelerates at 1.5 g (50% stronger than Earth’s gravity). The book describes it this way: “...the airlock decompresses to 10 percent of an atmosphere … Then it releases the outer door. With a whoosh, Olesya is gone. And, with the constantly accelerating ship, the body simply falls away.”
It should be “super falls away,” because the g-load on the ship and on Grace is stronger than it is on Earth. If I were Andy Weir, I would have screamed about this error until they fixed it.
That scene made me see the movie as a cartoon than a serious, dramatic story.
Issue at 36:00
“Blip-A Detected.” “Huh?” What’s the likelihood that when orbiting a gigantic star, Grace’s ship would park within visual distance of Rocky’s ship? (You must realize that over 26,000 satellites orbit Earth, and none of them come in contact with each other.)
But let’s do some math.
Let’s assume Grace’s ship begins its orbit within 100 miles of the Petrova line, at a distance from the Tau Ceti star equivalent to between Mercury’s orbit and Venus’ orbit. If we assume that Grace can see Rocky’s ship no farther than 20 miles away, what is the likelihood that Grace will see Rocky’s ship? The answer is: 0.0000034%.
Or expressed differently, one chance out of 29 million. Wow. Space is big.
Solution
Have the ship say, “Blip-A approaching.” In the novel, Rocky had been in orbit around Tau Ceti for decades. Rocky notices an incoming ship slowing down by expelling great amounts of energy at the Petrova frequency, so Rocky moves his ship to Grace’s ship. The novel does it right. Conversely, the movie provides pablum. Mr. Weir should be angry about that, too.
Issue at 37:09
After getting close to Rocky’s ship, Grace becomes afraid and tries to navigate his ship away from Rocky’s. He does this by pushing 12-16 buttons and switches around him in quick succession and then grabs the joystick to steer the ship. “Huh?” How would Grace know which buttons to push and levers to pull, given he had told the ship previously, repeatedly, that he’s not a pilot?
Solution
Either show that Grace has practiced steering the ship beforehand or have him simply move the joystick without pushing 12-16 buttons and switches. The scene can still be cute and cuddly without all those switches. Astronauts portrayed pushing many buttons in movies is a tiring, overused sci-fi trope. Again, in the novel, Grace learns to fly the ship over time through trial and error. His self-training bits were not included in the movie, making it appear that Grace can accomplish any task by magic.
Issue at 38:45
“Blip-B detected... Blip-C detected,” which turn out to be small canisters sent from Rocky’s ship containing 3D models providing mission information. Deciding that the first canister (“Blip-B”) wasn’t harmful, Grace dons a spacesuit to go out and grab “Blip-C.” “Huh?” Astronauts train for weeks on how to use spacesuits. Spacewalks in real life are extremely dangerous. And with Grace’s constant tripping and hitting against things before reaching the canister, his suit should have received numerous tears, and Grace should have died.
Solution
Similar to the previous issue, show Grace having to don a spacesuit on previous occasions to repair something outside the ship, where he had proper time to prepare. The scene of Grace clumsily going out at breakneck speed for “cuteness purposes” to grab “Blip-C” takes away all tension and turns something extremely dangerous into a knee-slapping joke.
During that entire scene (while trying my hardest not to make critical comments about it to my wife sitting next to me), I was thinking, “If the aliens are smart, why don’t they just toss the container into the open airlock door so Grace doesn’t have to do a spacewalk. Incredibly, this is exactly what happens later with “Blip-D” (46:30). This shows that I’m as smart as extraterrestrials.
Issue at 42:25
Xenonite: A super-strong, thermally insulating material that also has a transparent phase made entirely of xenon. “Huh?” Xenon is a noble gas, meaning it doesn’t react chemically with anything, including with itself.
Solution
Make it from something else with a creative enough name to please the most persnickety sci-fi fans. In real life, new metal alloys are constantly being developed. One, called Custom 465, is hated by machinists because it’s so strong it damages the machines trying to machine it. Recently developed alloys are even stronger. Forming/cutting processes cannot keep up with real-life super-strong metal alloys.
Issue at 43:00
Grace activates the ship’s centrifugal gravity system by pushing random buttons. “Huh?” (This also occurs at 52:40, where the ship explicitly tells him, “It is not advised to modify the centrifugal settings of the ship.” I’m impressed that I know as much as the Hail Mary ship.)
Solution
Between tense scenes, show Grace sitting in a corner studying manuals while licking lollipops to maximize cuteness—which appears to be the main theme of both the novel and movie. One manual could be titled, “Centrifugal Gravity System.” These scenes can be brief, a second or two. The scenes help readers and viewers understand how Grace can do what’s necessary.
Issue at 44:0
Grace opens “Blip-C.” The container looks about 3 inches in diameter and 11 inches long, for a volume of roughly 78 cubic inches. Rocky’s world has an atmosphere of 29 atmospheres, or 426 psi. Opening such a container would injure Grace’s eardrums and eyes. The force behind the sudden release of the lid would be three thousand pounds, clearly enough to break Grace’s hand or remove it from his wrist. But no matter, because with all that force against the lid, Grace wouldn’t be able to unscrew it.
Solution
Add a button or opening on the container that slowly releases the pressure. Grace realizes that ammonia is being released into the room, so he cutely and clumsily moves it (tripping twice) into one of the glass-enclosed glove boxes where experiments are performed. This way, there is still all the adorableness without the thinking people in the theatre wanting to walk out in disgust.
Issue at 53:49
Grace opens the outer airlock door expecting the vacuum of space on the other side, when in fact it was 21.1 kPa (according to the display on Grace’s wrist), and Grace is blown against the back of the airlock. This is more of a lowercase “huh” because the ship’s designers couldn’t have anticipated an atmospheric pressure on the outside of the door.
However, 21.1 kPa (kilopascals) equals 3.06 psi, or 21% of regular atmospheric pressure.
The equivalent altitude on Earth of 3.06 psi is about 37,550 ft, or 8,500 feet higher than Mt. Everest. At 37,550 ft, the human body cannot absorb oxygen on its own. After Grace takes off his helmet at the request of Rocky, Grace should struggle to breathe for about 20 to 30 seconds before experiencing hypoxia and loss of consciousness, along with other nasty physiological reactions such as the Bends.
Solution
After being thrown back by the outer airlock door, have the pressure display on Grace’s wrist say, “40 kPa” instead. All would be well.
Issue at 57:33 (and throughout the story)
Rocky’s personality matches Grace’s. While this is a “preference/taste” criticism (one person’s opinion vs. another), it is fictional pablum. In the novel, Rocky is a brilliant scientist and, while still being a bit quirky, has a superior intellect to Grace’s. In the movie, turning Rocky into a goofy sidekick sweeps away any remaining dramatic tension in an unimaginatively dangerous situation.
Imagine watching Saving Private Ryan with a lovable, dopey sidekick in every scene. Or Dunkirk, Jane Eyre, Interstellar, Inception, Cape Fear, Apollo 13, The Hunt for Red October, or any other movie with actual tension.
To prove my point, there is exactly one scene in Project Hail Mary where Rocky was deadly serious. And boy, was it felt! The scene was around 1 hour and 54 minutes when Rocky breaks out of his ball, fixes the ship's decaying orbit around Adrian, and gives medical care to Grace. Not a single goofy word came from Rocky’s mouth. Mouth?
You know I’m right on this.
Solution
While Grace and Rocky can be adorable and cute, the story shouldn’t make that relationship the movie's sole theme. Even the Eva Stratt character is adorable in her own way. By now, an estimated 20 million people have seen Project Hail Mary. They all likely disagree with me on this point. I can’t help it if the world is intellectually dying. I’m trying to help.
Issue at 1hr:17min
Rocky boards the Hail Mary in a transparent Xenonite ball while making constant quippy criticisms about the interior of the ship and Grace’s untidiness. I cannot believe that the deluge of words coming from Rocky was practiced ahead of time between Grace and Rocky. This turned the scene into verbal-communication-magic.
But that’s not my biggest issue with this scene.
According to the novel, Rocky weighs 370 pounds. A 1-yard-diameter sphere of ammonia gas at 29 atmospheres weighs 126 pounds. And what about Rocky’s ball? Given that his ball is made of 100% xenon, let’s use the real-life density of frozen xenon (0.126 pounds/cubic inch). I know Rocky’s ball isn't made of frozen xenon, but it’s all we have right now. If we assume Rocky’s ball’s sides are about 0.25 inches thick, we can calculate the ball’s mass at 129 pounds. Now we can add up the masses:
370 lbm + 126 lbm + 129 lbm = 625 pounds!
That much weight tossed willy-nilly around a fragile laboratory environment would cause serious damage!
Solution
I don’t know what to say about this one. I understand the appeal of seeing Rocky flopping in his ball all over the place while criticizing the room’s messiness, so I’ll let this one go even though it hurts me.
Issue at 1hr:40min
The Astrophage collector scene was rushed and confusing to watch. Lots of things happening, swishy camera movements, and so on. It’s difficult for the audience to “feel the moment” when it’s not entirely clear what’s going on. It felt like a big, hot, swirling mess that I just had to wait through until it was over.
And it was entirely unnecessary.
Solution
The Hail Mary ship can provide thrust at 1.5 g’s for years at a time. If the Adrian planet was about the size of Earth, the ship could have simply stopped its orbit, pointed away from the planet at a thrust of 1-g, and just sat there in a “hovering” pose (like a helicopter) rather than in orbit around the planet. The relative velocity between the ship and Adrian’s atmosphere would be zero, and they could collect all the Atmospheric samples for as long as they needed. Calmly. Quietly. While telling each other jokes.
“But that’s not exciting!” you say.
Fine. But then make the scenes comprehensible and less rushed, so the audience doesn’t feel like firehoses are being thrust into their faces.
At least half the audience wondered why they didn’t gather the Astrophage my way anyway.
Issue at 1:hr:54min
Grace is knocked unconscious as the Hail Mary is about to be destroyed by Adrian’s atmosphere. Rocky sees the problem, breaks out of his ball to fix the ship’s course, and provides medical help to Grace.
This scene has several problems. How does Rocky know which buttons to push or levers to pull to save the ship? (More button-pushing magic.) How does Rocky, who lives in an ammonia-rich atmosphere at 426 psi at over 400 degrees Fahrenheit, survive outside his ball for more than a few seconds?
Most importantly, what happens to a medium-sized room when a 1-yard-diameter spherical container containing 426 psi bursts? It isn’t just a small “woosh” of gas coming from the hole.
In a medium-sized room on Earth, the pressure wave coming from the hole in the ball would cause serious injury to anyone nearby, including hearing loss and pulmonary (lung) injury. Doors, windows, ceilings, and walls would be damaged. The energy release would be equivalent to 0.66 kg of TNT, which is over two and a half sticks of dynamite. The room Rocky and Grace were in would be destroyed. End of movie.
Solution
Have Rocky’s world have an atmospheric pressure closer to Earth’s. Problem solved. This isn’t rocket science.
Issue at 2hr:2min
How could the microscopic “Predator” organism from the planet Adrian, which Grace names Taumoeba, kill Astrophage if Astrophage is immune to electromagnetic interaction—meaning immune to ordinary chemical reactions?
I’m proud of myself for noticing this issue.
This will be a difficult issue to explain because the novel and the movie don't explain it well. Apparently—I say this because the novel doesn’t explicitly state this—while Astrophage is immune to electromagnetic interactions, it’s not immune to other interactions, such as interactions via the “weak nuclear force.”
Okay, everyone’s brain just exploded.
I only theorize this because neutrinos (back to those again) operate in the realm of “weak nuclear forces.” If the Taumoeba predator could somehow take advantage of weak nuclear forces (an astronomical leap in believability), Taumoeba could disable Astrophage.
Solution
To avoid beyond-PhD-complexity, make Astrophage susceptible to chemical reactions like regular matter, delivered by the Taumoeba predator. That wouldn’t weaken the story, because how do you kill a band of Astrophage stretching between the Sun and Venus using manmade chemicals? It’s still an unsolvable problem. Yet the plot becomes less ultra-complex and easier to believe if an extraterrestrial microscopic organism could do it using regular chemistry.
Issue at 2hr:20min
How does Grace find Rocky’s ship after they parted ways after several days or weeks? Note that space is really, really, really big. By then, Grace assumes that Rocky’s ship has run out of Astrophage fuel, so Grace can’t find Rocky’s ship by tracking Petrova energy emitted from Rocky’s ship.
Solution
In the novel (not the movie—this is another place where Andy Weir should be angry), Grace knows the general direction that Rocky’s ship has traveled. And even if Rocky’s ship has run out of fuel, his ship is still moving toward his planet. Grace heads in the general direction of where he thinks Rocky’s ship would be. He then causes the Hail Mary to emit Petrova energy in the forward direction and uses the ship’s Patrovascope to look for any reflected light in that frequency until he locates Rocky’s ship.
However unlikely that plan would work given the immensity of space, I’ll hand it to the novel for being clever. The issue in the movie could have been fixed by having Grace mutter something about “reflected Petrova light” while he trips over something.
One final point
Toward the end of Chapter 5 in the novel, Grace is told that fully charging 200,000 kg of Astrophage, necessary for the voyage to Tau Ceti, will require 1023 joules of energy. Just how much energy is that? It’s 32 times the amount of energy the entire United States consumes in 1 year. Or, it's the equivalent energy of 25 million Space Shuttle launches. Where did they get all that energy?
Critics are somewhat/questionably good at pointing out issues in stories, but they fail at giving advice on changing stories.
However, in the name of helping to reduce “plot-knots,” my overall thought after preparing this post is that most of the story's astronomical issues would go away if the Hail Mary simply went to our own Petrova line between Venus and the Sun, and Rocky’s ship had come to our solar system. Rocky could then help save the Hail Mary spaceship—which had experienced a terrible accident causing the death of the other two astronauts, destroying the ship’s communication system, and marooning Grace to certain death. Remember that in the novel, Rocky does find Grace’s ship, not the other way around.
This way, we could still have all the goofy/feel good/snarky/clumsy/adorable moments, still have an Astrophage-powered rocket, but without the mountain of on-the-edge-of-believability issues. The story could be more character-based, with trauma and conflict in a more relatable range for the average person.
We could come up with a host of ideas for why Rocky would bring his ship to our Petrova line, but such suggestions are pointless because the story is already written.
Another point
I'm sorry. I can't help it. From 11 light-years away, our Sun would be plainly visible to the naked eye. For example, from Earth, it would look like the star Megrez in the Big Dipper.
Given that Grace and Rocky are the best of friends, why didn't Grace point out our Sun to Rocky? What's sweeter and friendlier than saying, "Hey, buddy. Check it out. There's my home, right there."
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