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Comment by TeMPOraL | Hacker News Reader

KSP was possibly my best entertainment spending ever. It definitely is the best game for me in terms of costs / time played. If you haven't played it yet, do yourself a favour and buy it now. If you have a kid with even tangential interest in space, get a copy for them.

Side effects of playing KSP include:

- getting an intuitive feel for basic orbital mechanics

- finding yourself reading up on actual math to better understand what's happening with your rockets (and how to build more efficient one)

- no longer being able to watch most space movies due to frustration caused by the filmmakers not grokking basic orbital physics

(RE the last point - after Gravity, Interstellar, The Martian and The Expanse series, getting basic spaceflight wrong should no longer be accepted in popular media. Looking at you, makers of The 100.)

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> no longer being able to watch most space movies due to frustration caused by the filmmakers not grokking basic orbital physics

Meh. I've a degree in Physics and I still enjoy Star Trek.

I agree with the rest.

And I think all of us here love hacker movies.

Sneakers, Hackers, Swordfish, etc. :)

Yes, but we love them despite the horrible misconceptions they hoisted on the general public, and the generally horrible accuracy. :)

But RISC is nonetheless good.

In what way was swordfish like Sneakers/Hackers? The latter are cyberpunk-ish, a bit ideological.

Swordfish is more of a "caper" movie with a cheap tacked-on hacking bit. Bad guy wants money, uses hacker and LOTS OF CRIME to get it.

Yeah those three movies are not the same when it comes to the hacking.

I realised in Swordfish that the 'hacking' bit (with the 3D shapes rather than anything real) isn't meant to be literally hacking, but instead emotive of it, for the 98.2% of the audience who doesn't know what actually goes on.

Hackers has a couple scenes like that, I don't have a problem with the device.

But in Swordfish it's completely ancillary to the movie that it's computer hacking that's going on. The goal is money, not any part of any "hacker ethos" or anything.

Just in that they all have unrealistic depictions of hacking.

It's definitely the worst of the three.

I absolutely hated watching Mr. Robot. Gave up after 4 episodes.

Any reasons why?

That's surprising. Mr. Robot has the most realistic depiction of hacking I have seen in mainstream media.

Same. Massive reason why I watched the show.

I remember watching the first few episodes and Elliot is doing one of his monologues about the technology he uses and his hacking activities and I was like hold on! That all mostly made sense! What's going on here? :)

I love Mr. Robot one of the best shows on TV IMO.

My personal favorite https://www.youtube.com/watch?v=hkDD03yeLnU

...Or https://m.youtube.com/watch?v=URVS4H7vrdU

Do you consider Office Space a hacker movie?

I consider Office Space a documentary.

A real hacking movie would be deathly boring. My favorite hacking in movies is either when it's cheesed up to the max (visually interesting) or happens off screen (more realistic).

I love the 10 minute or so montage in wargames where David just goes to libraries to do basic honest research on falken, in order to figure out what his password is. Of course, he should have tried Joshua like a week before he actually did, but you can't have everything.

And that's not counting knowing where the school password post-it note is kept, and getting yourself sent to the principal on a regular basis so you can keep looking it up.

Or just letting your computer run for an entire day to determine which phone numbers in a given set of area codes have modems on the other end.

Wargames does take a few shortcuts for storytelling, and it is a bit silly in the best possible way, but the actual hacking is genuinely good, and not boring.

Wargames was brilliant. How does everyone feel about the remake: http://www.imdb.com/title/tt0865957/? I've decided not to let it ruin my memories of the original so far.

According to the reviews on IMDB you linked to, that was a good call. Stick to it.

Oh grief, Swordfish is laugh out loud hilarious. I cannot for the life of me think of a movie that tries so hard to be one of the cool kids.

I enjoy when older, unrealistic movies become more realistic over time.

Remotely hacking the sprinkler system in Hackers was so unrealistic when it came out but today it's scary how real that could be.

I too have a degree in Physics but have trouble enjoying sci-fi entertainment that includes basic physics screw ups in its story. I about pull my hair out when I hear them insert quantum entanglement in random places to make up for a lack of creativity and/or ability to hire a decent science adviser.

Well, I was just watching yesterday an episode from TNG, where Geordie detects a "deuterium leak", and Riker immediately asks "toxic?"

Dude, it's hydrogen, you need to have different concerns there.

At least they did acknowledge that firing a weapon in a deuterium-rich atmosphere might not be wise, depending on concentration.

Eh, just push the non-chewy bits to the edge of the plate and enjoy the rest of the culinary confection.

As a nitpick, deuterium actually is toxic. The hydrogen bonding in molecules that substitute deuterium for light hydrogen is affected, such that if you drink enough heavy water, you will experience symptoms similar to radiation poisoning. It interferes with how your chromosomes line up during cell division.

Presumably, if you inhale enough dideuterium monoxide vapor, you may experience a similar effect. It would not be acutely toxic, though--more like an occupational exposure level of hazard. Deuterium gas is likely as harmless as light hydrogen gas.

If a retcon is necessary to preserve one's enjoyment of the show, Riker may have already been aware of the hazard level for humans, but was asking for a more informed opinion from the chief engineer, who has presumably read and memorized all the MSDS sheets, for the benefit of any nonhuman organisms on board. Vulcans and Romulans, for instance, experience an anaesthetic effect from TLTDH, similar to the effect of NO2 on humans. It would not be out of character for Star Trek to invent a bizarre species-specific toxicity if the plot demanded one.

This is the best Internet comment I have seen this month on HN or anywhere else. Thank you!

Well, they were not about to drink heavy water, they were just breathing air with some percentage of heavy hydrogen.

How much D2 can you breathe in before you suffocate anyway?

Of whatever amount you do breathe, how little is absorbed?

Of the tiny amount that is in fact absorbed, how much ends up exchanging D atoms with your body?

I don't know the answers to these questions, but my bet is the airborne process is orders of magnitude less efficient than drinking D2O.

Their main concerns should be:

1. Suffocation from lack of O2

2. Risk of explosion if the D2 percentage is in the danger zone

3. If that think was leaking out of a reactor, maybe there were some byproducts leaking out with it? Like, I dunno, tritium? That would be really, really nasty to breathe in.

You'd probably enjoy Greg Egan's work then.

I enjoy Star Trek too, but mostly thanks to growing up with it. It's what got me interested in science and technology in the first place. I also very much enjoy the story and the message of TNG and later Trek series. It's the future I'd love to happen.

Same! And I have theories about it. It's either because

1.) In general Star Trek isn't really about physics, its about sociology or (in the better episodes) political science.

2.) Star Trek gets physics so wildly wrong that its not as grating as a show/movie that tries really hard for realism and still fails utterly. If there's an uncanny valley of scifi physics, Star Trek is definitely standing miles from the opposite side.

The only consistent exception to this is Voyager which does start to get on my nerves as a particle astrophysicist. I mean c'mon guys thats too many made up particles. Settle down.

>1.) In general Star Trek isn't really about physics, its about sociology or (in the better episodes) political science.

I've never watched Star Trek, though curiously I know another show set in space about politics, the anime Legend of the Galactic Heroes; it runs about 100 episodes with a few feature films too. If you're interested in politics, specifically in this case the play between a democracy and rule by one person.

It's also rather quaint, the imperial military is styled in a 19th century German style complete with uniforms, and the republic is styled in a modern futuristic style, not without berets though.

It's great fun, but I don't suggest it be discounted because it's an anime, which is a response I have received before.

The ten books the series is based on are currently getting an 'official' translation, I think they've now published 4 books out of 10 in English. It's not very different from the series but definitely not as time-consuming.

How do you feel about The Flash? To me, it was fine at first, but as the show went on, too much habdwaiving was used, even for a tv show of its genre and it's becoming increasingly annoying (to me at least). I'm no physicist, though.

Interstellar had really bad orbital mechanics. You remember when they used the staged rocket to get off earth? Do you remember later, when they landed on that other planet with 1.5 times the mass of earth? Do you remember the machine that they used to leave that planet?

Remember when he let go of the spacecraft and fell into the black hole?

I recall a distinct lack of spaghettification.

I don't recall the exact scene, but wouldn't the different relative centers of mass, and the corresponding difference in distance from the black hole cause some drift. I assume it would be slow. Possibly VERY slow, so it likely wouldn't look like falling, but I think they would separate, right?

I read that as you fall into a black hole, there comes a point where the gravitational difference between your head and toes would be large enough to rip you apart. (Not that you wouldn't have other problems anyway :-) )

If they're as close to a decently-sized black hole as dramatic movie pictures require, I suspect they would be close enough for the separation not to be gentle at all, assuming their individual limbs wouldn't separate.

they were spinning, right?

I haven't see the movie, but this only makes sense if the spacecraft is actively using thrusters, and the human obviously is not.

It's unspoken, but I assume the staged rocket was used to conserve the antimatter the ship was carrying for its rocket-less launches.

I wouldn't be surprised if that's in the script somewhere but ended up on the cutting room floor.

Except if the antimatter engines were so reliable, why risk blowing up your last hope to conserve the obvious surplus of antimatter you had for the mission anyway?

There were several plotpoints about how there was NOT surplus of antimatter (or whatever propellant they used).

And in case of "blowing up" they could use those am engines as LAS (they apparently had enough thrust), so what risk are you speaking about?

Seriously, bitching about science stuff in Interstellar, very large but actually very well crafted scifi is kind of dumb. It's big enough that you find SOME mistakes, but most of the time you'll be wrong (or blaming them for not explaining every detail), and it has pretty correct science overall. Just hating for sake of hating.

I think you're giving them too much credit. Happy that it didn't "unsuspend disbelief" for you, but it's too easy to make creative excuses for movie fridge logic.

Christopher Nolan seems like a pretty smart guy. It must have crossed his mind at some point.

Plus, the ship's engines don't appear to use propellant - they use the standard sci fi "eeire blue glow" trope. Seems like antimatter is the best explanation to me.

> Christopher Nolan seems like a pretty smart guy. It must have crossed his mind at some point.

Also, he had Kip Thorne as an advisor. I remember criticism of the "slow-time planet" (including by Bad Astronomy) being shot down by Kip pointing out he actually calculated it as an edge-case solution for a specific rotating black hole.

Mass has little do escape velocity, it's density. Consider that any planet/sun could be shrunk until it's a black hole, with effectively infinite escape velocity.

Earth density: 5.51 g/cm³, escape velocity: 11.2 km/s

Jupiter density: 1.33 g/cm³, escape velocity: 59.5 km/sec

I think it's more than just density.

first of all, mass contributes more to escape velocity than density. V_e=k*(m^(1/3)d^(1/6)). (scaling the mass is quadratic compared to scaling the the density). Second, the density of rocky planets is bounded from below pretty close to the density of earth.

A black hole has the same escape velocity as a star of the same mass, as long as you are well outside the swarzchild radius. Inside or near it, the effect of general relativity makes things very weird.

In case of mostly anything else, Newtonian physics apply correctly, and the relevant thing is mass (and distance from the center). The escape velocity from a body is sqrt(2GM/d) where d is the distance from the center of mass, M is the mass of the object, and G is the universal gravitational constant.

Note that if the sun was replaced with a black hole of the same mass, the orbit of the earth wouldn't change.

escape velocity is calculated from the surface.

Not necessarily, for example we'd measure escape velocity from our system as starting from Earth, so effectively we'd be 1 AU above Sun's surface.

even the way time passes faster on The planet with tidal waves is complete bullshit. It does not match any of the assumptions aT all and is just used as a stupid trope.

It's so weird, looking at a perfectly normal movie and the only thing you can think about is "What? It doesn't work that way!" like if everything started falling up with no explanation and the characters found that perfectly normal.

But I'll disagree on Gravity and Interstellar getting spaceflight right. Unless you are going for very basic.

I'm going for the very basic. The kind of which immediately destroys any suspension of disbelief I would have. Gravity was good enough in my book, and is also somewhat rescued by the way you could feel the vastness of space when watching it in 3D.

The protagonist-seeking-debris that ignores orbital mechanics pretty much destroyed my suspension of disbelief with Gravity.

I could suspend pretty well up until the point where the dude just had to nobly sacrifice himself for no reason. All I could see at that point was the emergency drama screenwriter shooting a blunderbuss filled with space station shrapnel into the unsuspecting back of the realistic physics consultant.

Why did they need a 2 stage rocket to get from earth to LEO and yet they had a lander that could both descend and ascend from an earth-similar gravity well in a single stage?

The earth rocket had a significantly larger payload than the lander. IIRC, the lander only carried a crew of ~3 people, whereas the earth rocket had to launch with a larger crew, life-support for an extended stay in space, and enough fuel to get to and from Jupiter.

edit: I forgot that they had another ship waiting for them in LEO already, so maybe the fuel point doesn't apply. But, it's still plausible that the earth rocket had to carry a much larger payload than the lander had to carry.

Oh, don't mind that... How did they maintain acceleration around that planet near a black hole for 7 years? And who the hell would think that was a good idea? (Wouldn't it be passing under the ship nearly the speed of light, and thus every few seconds anyway?)

Conservation of fuel. Especially as the fuel for "classic" two stage rocket would be vastly cheaper than magic-fuel they used later in the movie.

Why everybody brings up this honestly stupidest ctiticism about the movie is beyond me. It's like you lack both imagination and understanding how space missions work.

Gravity was a good movie. And for a movie set in space, it's pretty realistic...ish. But it's orbital physics are terrible. Just terrible. I mean, most movies don't even try. Guardians of the Galaxy and Star Wars don't deal with orbital physics at all. Gravity tries, and gets it all wrong.

That really is the crux of the issue here. When a movie gets something so essential to the plot wrong, you rightfully dislike the makers for being so damn lazy and not bothering to do their homework.

When it's only tangentially related, we're far more forgiving.

It can even get downright dangerous when policymakers start getting their ideas from them. For example, shows like "24" that have suspects giving up accurate and truthful information under torture, when any expert in the field of interrogation knows it doesn't work that way.

> When a movie gets something so essential to the plot wrong, you rightfully dislike the makers for being so damn lazy and not bothering to do their homework.

Actually, that's when I feel compelled to give it a pass. We watch movies all the time that start on a ridiculous assertion. Allowing one major mistake I have to let go, but in the beginning and service of the plot as a whole is okay with me, as long as most of the rest is done well. Having something that just plain seems wrong but without any reason beyond laziness is what really gets me.

For example, without allowing for the core problems of orbital physics of the debris and the relative distance and speed if different space stations, there is no movie. I found the rest of the movie enjoyable enough that I allow for those mistakes in service of the whole (in a similar way that I allow for a lot more in a superhero movie).

> For example, shows like "24" that have suspects giving up accurate and truthful information under torture, when any expert in the field of interrogation knows it doesn't work that way.

There's a more insidious explanation for this specific case: Viewers are being conditioned to accept torture as a legitimate interrogation technique, at the direction of $AGENCY.

> ... Star Wars don't deal with orbital physics at all.

Except at the times when a ship is disabled in an attack, and then changes course and "sink" into the nearby planet.

But yeah, I do agree. It's much easier to watch that kind of atrocity in a movie that makes no effort to look realistic than it is to watch something like gravity.

That actually makes sense if you get rid of the assumption that they were in orbit in the first place.

Once you have cheap, powerful thrusters like starwars/startrek has (thrusters that can hold the mass of the whole ship against gravity in any direction, independent of the main engine), it makes little sense to actually bother going into orbit, unless you actually want to turn the thrusters off.

Instead, just pick a point on the planet and hover over it. Or pick a circular orbit-like path around the planet for maximum coverage. Just pick whatever position or path through space makes the most strategic sense.

If you have a ship operating like this, and it loses power to it's thrusters... then of course it will 'sink' into the nearest planet as gravity suddenly becomes the primary force acting on the ship.

I have KSP and I've played around with it. I liked it, however what I didn't like was piloting a launch by hand.

Maybe later in the game you don't have to do that or something, I don't know because it wasn't the experience I was looking for. I was hoping for flight computers and programming trajectories.

There are a lot of mods that allow you to do exactly that.

My favorite that does exactly as you mention is KOs (Kerbal OS). It's basically a programmers interface for it, allowing for really precise control.

A YouTuber, Scott Manley, has a pretty good (albeit old) video on the topic.

https://www.youtube.com/watch?v=FPDPzsnlHOI

Vanilla KSP makes you do everything by hand. That's part of the fun, IMO, but after you get good at landing and docking it can turn into a chore when you need to fly multiple missions to e.g. build a colony. However, there are many mods that will let you automate some or all parts of the gameplay.

Two particular mods worth mentioning are MechJeb, the autopilot for everything, and kOS, which lets you code up your own guidance system.

try mechjeb.

MechJeb doesn't do proper roll, pitch, gravity turn launches either. It does a pre-programmed ascent profile.

In reality all the control of a space launch takes place in the first seconds when the vehicle is subsonic. After that it's just pointing to the direction of travel because any angle of attack in the atmosphere would cause excess aerodynamic stress.

That's why launch controllers say "nominal" that often. There's nothing that can be done, just hoping that the vehicle stays within the planned bounds.

All the accumulated errors from atmospheric conditions and other randomness are corrected by the second stage burn once outside the atmosphere.

Other commenters have mentioned both Kerbal OS or MechJeb. Kerbal OS will let you geek out on programming your own routines while MechJeb will just handle the "boring stuff" for you like maintaining a particular vector while you do the "cool stuff" like navigation and mission planning. Some say these mods are like cheating, but once you can get a ship into orbit with your eyes closed, repeating that every time isn't really the fun part anymore.

The most egregious example I recall recently was in the Flash TV show, where a character lamented that the energy required for their weapon against the main villain was more than the sun could provide. Except, of course, the writers got it wrong by orders of magnitude.

I could call Shakespeare a Jazz musician, and and still be closer to being correct than they did.

They also got a guy that zips around the place at speeds he should burn up in the atmosphere to be fair though

Wait, did Gravity do something besides getting basic spaceflight wrong in visually compelling ways?

I think those were examples of movies that got it mostly right. Had to read it twice, myself.

It had a couple mulligans like the different space stations being in really similar orbits, but otherwise was pretty good.

The orbit of the debris cloud is kind of nonsensical, since it is co-orbital to the station but somehow faster.

If the cloud was orbiting at the same speed, but a different axis, wouldn't the collision be as depicted?

It wouldn't come back to collide with the protagonist every 90 minutes then.

Yeah, it'd be every 180 minutes. There'd be two orbits, the circular 90 minute orbit of the ISS and an elliptical, 180 minute debris orbit that has a common perigee with the ISS but a farther out apogee. The debris would thus be moving faster at perigee and would be able to wreak havoc every second orbit of the ISS. Of course the chance of such coincidental orbits happening by accident would be insanely low; you'd need some explanation as to why the object that blew up was in that kind of orbit in the first place.

Actually ... if you imagine two debris fields spaced opposite in the elliptical orbit, or simply a debris ring, then you would have the devastation occurring every 90 minutes. It's even less likely trying to think of how this could happen accidentally, but you could certainly set up a situation like this intentionally.

The period of the debris cloud interactions is about equal to the orbital period of Hubble's orbit. If the orbit was a different inclination but otherwise similar and so crossed Hubble's orbit, it would do so at two points and so the period would be half of the orbital period (it would also require extremely unlikely timing to get it to cross Hubble's orbit and actually hit Hubble at the crossing point, but if it did so at one it should do so at both.)

For it to then hit the ISS, at a far different altitude and inclination is even more problematic.

They got most of the physics right AFAIR, and that was portrayed in a very visually beautiful way. They screwed up stage setup though (like positions of the telescope, ISS and Chinese space station relative to one another) - which is a departure from realism, but not from physics per se.

It wasn't only basic spaceflight. It was basic physics in general. Like when the two protagonists are somehow hanging off the ISS and Clooney has to let go because Bullock can't pull him in. It's a huge important moment plot wise and is really really dumb physics. I still don't even know what the filmmakers mistakenly thought could pull on them in that situation.

According to (IIRC) the film's science adviser, the intent of that scene is that they are still decelerating relative to the station on the chute they are snagged on, and Clooney's charscter believes that the line doesn't hace sufficient strength and may snap with both of them but will hold with just Bullock's character.

If that's not just a post hoc rationalization, the film certainly doesn't seem to convey that effectively, though.

When watching I got an impression that in that scene, they were rotating, so it was inertia that was pulling them apart.

The Expanse is actually relatively accurate except for a couple scenes that were purposefully made inaccurate to aid the narrative, as admitted to and apologized for by the writers themselves on social media.

The 100 will sadly ignore physics, logical consistency, and more, if it can better serve teen drama. Which I guess is a permissible creative decision, just not one I like.

Aside from the bad space physics, which I can put down to a lack of budget, I found the 100 a pleasant surprise.

It's like they told the screen writers "make a teen drama" but then didn't check the script, and the writers get extremely dark in places. The only thing thing they assiduously avoid is rape.

I mean, it's not terrible. I like the premise a lot, and the darkness, and the characters are a bit more 3D than you would expect in this genre. But it's still a teen drama first, and high-concept dark sci-fi-ish story second.

It had a moment there in the AI storyline where it looked like it was going to be a good show. Never panned out.

Totally agree with you.

During the height of my KSP addiction, I wrote a binder for Orbital Transfers.

I can basically lookup the required angle and dV for a transfer from any orbit to another orbit between any two planets and if not in the table, make a good approximation (and then just eyeball it from there)

It's probably my #1 Game that I would have my kids play, if I ever have some, just to teach them what real space physics are.

On the last point, I got giddy with excitement when I read SeveneveS because there were plot points about how orbital mechanics worked.

KSP doesn't have Lagrange points.

I mean, it's understandable, the n-body problem is hard.

It's not hard.

> Principia is a mod for Kerbal Space Program (KSP) which implements N-body and extended body gravitation. Instead of being within the sphere of influence of a single celestial body at any point in time, your vessels are influenced by all the celestials. This makes it possible to implement missions that are more complex and more realistic than in the stock game, especially if used in conjunction with a mod like RealSolarSystem which has real-life celestials.

https://github.com/mockingbirdnest/Principia

Just because someone did it doesn't mean it's not hard.

But it's not hard. Especially since KSP would be a restricted n-body problem (only the spacecraft are affected by gravity from multiple bodies) and the "n" in n-body is about 20 (number of massive bodies in solar system).

It's a game design decision not to include gravitation from multiple sources.

Nice, this might get me back into KSP. Never did like the spheres of influence mechanic.

Let's not go giving The Expanse too much credit, here. That no-thrust gravity slingshot around all of Jupiter's moons in 2 hours was...stretching it.

Well, that (and the shots showing several Jupiter moons simultaneously) was a creative decision - one I strongly disagree with - but otherwise The Expanse is pretty good, and they get lots of minor details right (like engines heating up some metal beams on the exhaust path, or that scene where a PDC round penetrated the Roci and its trail didn't move until they started manoeuvring, etc.).

That and the ships having to flip to slow down burn makes the expanse one of the more realistic portrayals of space flight (minus the epstein drive which is basically magic) in modern tv.

Also, they show decompression way more realistically. Its not like a bomb goes off when a hole opens up in the side of the ship, which is nice.

Burn-flip-burn is nice. It'd be nice to see them performing realistic burns to alter orbits, but that might be too much to ask for.

>minus the epstein drive which is basically magic

It's canonically a fusion rocket, isn't it? So beyond today's means, but hardly "magic".

Any advanced technology... :)

I don't actually recall what the in universe explanation of it was outside of it running off water as its fuel. Either way its specific impulse is crazy.

The authors intentionally made it the one thing they weren't going to try to explain using known physics. It's reactionless and fusion powered.

It's a lot better than people think fusion rockets would be in real life. But the writers actually acknowledged that, in the episode that goes into the drive's history. They had fusion rockets before Epstein, they just weren't near as good before the breakthrough.

And most of the story wouldn't even change if it took longer to go places. The only difference would be that they couldn't show normal gravity inside a spaceship and attribute it to acceleration. It's a slight distortion that saves them money on special effects.

They especially don't show long travel times, but in the books travel is usually counted in weeks or months. Also, in the books they usually travel at ~0.3g for the sake of Martians and the Belters, who are mostly not comfortable with Earth's 1G.

(This is not merely a detail, it's one of the core plot points of The Expanse, as tolerance to gravity is what makes Martians and Belters almost a different species from Earthers; the former can not live on Earth, and so they don't care much about it.)

http://www.projectrho.com/public_html/rocket/torchships.php

assuming an epstein drive is possible yeah it opens up more or less direct brachistochrone trajectories between here and mars. Just wait until the planets align and burn.

There was a scene in the first episode that drove me crazy. They were on the ship hull after a huge explosion had occurred. Tony debris kept flying by in the background at what looked like 30/mph. That broke immersion for me so bad.

yeah, there is a blog post with one of the producers apologizing for it: http://www.danielabraham.com/2017/04/04/guest-post-losing-sc... (minor spoiler alert)

nb. i'm in complete love with the show and that particular scene can be best described as... pretty.

That's a great writeup, and it highlights the fact that sometimes these things happen for purely pragmatic reasons.

I think in the show they are 'flying teakettle' which means flying on steam exhaust. That is to say, there was some thrust.

Reversing to hide behind a moon seems dodgy though.

I think Gravity has a few moments of dodgy orbital mechanics.

Not sure if that was the point!

Yeah, it had some, but it's still a separate league from what came before. I don't expect every movie to be hard sci-fi (wouldn't mind it, though). But they should start getting the very basics right.

2001 space odissey came quite early as well as space 1999

Going from ISS to Tiangong in anything like a real-world spacecraft is, like, super impossible.

It's perfectly possible.

If you land and launch again.

That's a movie stage setup problem though, not a physics issue.

How so? The movie shows them going from A to B, physics says going from A to B takes far more delta-v than the spacecraft would have, therefore it's a physics issue. It would be like a WWII movie showing a bomber taking off from NYC and bombing Berlin.

The Tiangong in the movie isn't a real space station so if the Chinese were to build it they could put it in any orbit they like, even one hypothetically 10m/s of delta-v away from the ISS and there might even be realistic reasons for them want to be energetically close to the ISS. There are reasons not to do it but if there's a good reason like the Chinese want to keep the option of physically linking to the ISS open then there's nothing actually preventing it.

So it isn't two known and far distant locations like New York and Berlin, its more like New York and an unnamed city.

That wouldn't make much sense, but even if we grant that, just switch the complaint to Hubble and ISS. We know where both of those are.

When that movie came out, I was studying a basic astronomy course at the university and we were going through some simple orbital mechanics. We had a long discussion about can the debris of Hubble hit the ISS or not.

The conclusion was probably not, but under perfect storm circumstances (and especially timing) a fragment or two might not be out of the question.

> The Tiangong in the movie isn't a real space station

It's a real space station name. The one they use is much bigger than the real station with the name, but it might be intended to be a future development, or it could be a fictional station with the same name (a city called New York, but with a population of 200 million and located in central France, to borrow your analogy), or they could have just intended the existing station and not bothered to research anything about it besides it's name and nationality.

>It would be like a WWII movie showing a bomber taking off from NYC and bombing Berlin.

NYC to Berlin is well within the originally required flight range of the B-29 (5,333mi at 400mph with a 2k lbs load). It wouldn't be an intelligent thing to do, but it isn't physically impossible.

I was thinking of a round-trip mission, but I always appreciate nitpickery. (And I learned just how much carrying a heavy bomb load affected the range of the B-29!)

You can assume that they just repositioned any three of Hubble, the Russian satellite, ISS, and Tiangong into inaccurate (for the things that are real, like Hubble and ISS, and maybe Tiangong, if it's a further development of the existing station of the same name) or improbable (for those that are fictions, like the Russian satellite or Tiangong, if you assume it's a complete fiction that shares the name of a a real station) orbits, or you can assume they got physics wrong. I don't think the movie provides enough information to make clear where the error is.

If I remember, momentum and orbit matching in Gravity were pretty shady. Still way better than most predecessors, though.

> If you have a kid with even tangential interest in space, get a copy for them.

Not having played KSP, but would do so with my kid, what age do you think would be suitable for them to start playing?

I introduced it to my nephew when he was 12 and he succeded to create pretty efficient flying bombs. A kid can grasp the concepts involved at 10, they can surely have fun before but probably more by exploding rockets and messing around with kerbals.

Thanks. Maybe I'll buy and play first then, looks like we have a few years to go.

I thought the martian was praised for generally being pretty on the money with the science content?

It has a couple problems. Like a windstorm that can tip their spacecraft and knocks a radar dish into the protagonist. But later, the atmosphere is so thin he doesn't need a nose on his rocket.

Also there's no way you can grow that many potatoes on mars with a solar array that size.

> Like a windstorm that can tip their spacecraft and knocks a radar dish into the protagonist.

This is literally one of the two cases in which Andy explicitly said he used artistic license and departed from realism. The other one being super-efficient radiation shielding on Hermes which he didn't in any way explain in the book.

The Martian atmosphere is so thin that you'd be barely be able to feel hurricane-speed winds.

That was one of the two things the author used artistic license on, the other one being unrealistically good radiation shielding on Hermes. The movie took at least one other liberty with science - they explicitly decided to ignore lower martian gravity, as they would make shots much more difficult/expensive, for (in their opinion) little added value.

Except that living in fancy tents or traveling across the surface for weeks/months would result in death by radiation.

Until mars gets a much larger atmosphere and a magnetic field living on the surface is going to require living under ground.

Radiation is a real problem for people on Mars, but death after few weeks or months is overstating it. Increased cancer risk, for sure.

https://img.purch.com/h/1400/aHR0cDovL3d3dy5zcGFjZS5jb20vaW1...

KSP taught me that orbital intercept to rescue Watney was nosense. (The book was slightly more believable here). also the whole swing by Earth and head back at the last minute was wrong. Orbital intercepts between planets requires very precise timing and alignment. A transfer from Mars to Earth is never going to line up with an instant return transfer window back to Mars.

On KSP itself, huge weakness for me in the game is that it is virtually unplayable stock. Absolute minimum you need to install a data providing mod like Kerbal Engineer Redux for both building rockets to quickly assess dVs and TWRs etc and in flight to help with figuring out burns etc. In stock you are reduced to having to use spreadsheets to build rockets and trying to land from visual clues only. The stock game badly needs something like KER. KAC is also helpful to quickly find transfer windows etc.

> A transfer from Mars to Earth is never going to line up with an instant return transfer window back to Mars.

The whole point of the Hermes spacecraft as used in The Martian, though, is that it has a high specific impulse, low thrust ion drive, that runs continually during the entire orbit (using power from a reactor to do so). Andy Weir, the author, is a programmer, and he actually wrote a physics simulator to calculate the required orbit; see here: http://www.galactanet.com/martian/hermes.mp4

So it's definitely not a Hohmann transfer orbit since there is thrust applied throughout, and you are consequently reaching your destination faster than such a transfer would arrive. It ends up being a low thrust brachistochrone orbit.

So anyway, the point is that, since you're continuously applying thrust anyway, you don't need perfect alignment, it just takes you longer if the alignment isn't correct. Andy Weir is a serious hard science fiction nerd, to the point that you can download the data that he simulated for these orbits and verify for yourself that they are in fact correct for the stated specifications of Hermes' ion drive.

Totally agree with you that the Engineer plugin is absolutely essential for playing KSP, though. The game is so frustrating without that because there's so much trial and error with randomly flipping craft thanks to the new aero model if the TWR is off for any of your stages (and it will be until you've played awhile and developed an intuitive sense of what kind of rocket is reasonable -- a proficiency you won't likely reach if you didn't have Engineer from the beginning to help get you there).

Thanks for the link. That was well awesome. I withdraw my criticism.

I had a similar issue with Seveneves recently. I had a strong science-based disagreement with the idea of Izzy always keeping its anchored asteroid facing into the oncoming atmosphere of LEO, which I was sure was impossible because it would be facing the rear as often as it would the front, because objects in space/thin atmospheres don't fly and don't maintain a constant relative orientation just because they're orbiting something. To me it seemed as dumb as a spacecraft that had to constantly have its engines firing behind it just to stay in orbit.

It wasn't until I shared this frustration with a smart friend, and he pointed out that it actually is possible if the space station has a rotational period equal to its orbital period, that I realized I was wrong. The author was indeed being smarter about the science of it than I was, and had done the research. And, forget just the future part of it; the ISS actually currently flies with a specific constant relative orientation through the atmosphere so as to minimize air resistance, using, you guessed it, a rotational period equal to its orbital period, plus occasional corrective actions from gyros and thrusters.

> the ISS actually currently flies with a specific constant relative orientation through the atmosphere so as to minimize air resistance, using, you guessed it, a rotational period equal to its orbital period, plus occasional corrective actions from gyros and thrusters.

And plus solar panels, which get realigned to minimize atmospheric drag when the Sun is behind the Earth.

https://en.wikipedia.org/wiki/Night_Glider_mode

Important to note that night glider mode is dependent on the rotation of the overall space station, so that you can set the orientation of the panels to be edge-on into the wind once and have the overall rotation keep that orientation indefinitely. Without the rotation, you'd have to continuously use the motors to adjust the panels, which would burn them out more quickly, use more power, and since they likely aren't freely rotating, would cause large spikes in air resistance once per orbit when you hit the limit of travel and have to do a large opposite rotation to maintain edge-on orientation.

Tidal influence can keep an object oriented along the local vertical and keep the same face towards the primary. See, for example, Phobos. Or most the moons in our solar system.

This is especially true if an orbiting object has attached to a tether. Gravity gradient stabilization can keep a tether aligned to the local vertical.

Well, if you read his webcomic Casey and Andy, Andy Weir is also a soft science fiction nerd. The box of antimatter never blows up until a solid object goes in, cause that's totes how matter annihilation works.

The reddit did this as a challenge mission, including the Rich Purnell manoeuvre https://www.reddit.com/r/KerbalSpaceProgram/comments/3q4u4a/...

As others have mentioned, The Hermes didn't follow a Hohmann trajectory. It is an ion propelled craft capable of 2 mm/s^2 acceleration. A very weak thrust but powerful in that it can sustain this acceleration for looooong burns.

If just the sun is accounted for, Andy Weir's trajectories are okay (I believe). However putting planets in complicates things. Ion engines really suck at climbing in and out of deep planetary gravity wells.

Neil deGrasse Tyson's trailer for The Martian had Hermes leaving low earth orbit and arriving in Mars orbit 124 days later. Which is nonsense. With 2 mm/s^2 acceleration it would take 40 days to spiral out of earth's gravity well. Not only does this wreck the 124 day trajectory Weir so painstakingly calculated, but most the slow 40 day spiral would be in the Van Allen belts. This astronauts would be killed by radiation.

> finding yourself reading up on actual math to better understand what's happening with your rockets

Never in my life have I ever found myself digging up my old graphics calculator to just play a video game. KSP is honestly my favourite time-waster ever!

I often think good games are criminally under priced.

I must have played Age of Empires a good 1,000+ hours. Possibly even more.

That works out to 6 cents per hour of entertainment.

You can see it as taking risk into account. KSP and StarCraft were both cents-per-hour games for me, but I couldn't have guessed that at the moment I was buying them.

Try NetHack. infinite hours of replayability (the whole game is algorithmically generated and every time you die, every item/tool/weapon/map has a different name and effect) and it's FOSS ;-)

Also it's a pretty hard game on its own. If you're a fan of challenge i'd suggest you try it.

how can you cite gravity as a good example then?

Because regardless of its blunders, it was still an order of magnitude better than Hollywood's standard portrayal of space.

The game also has a horrible habit of turning people into arrogant know-it-all armchair rocket scientists.

>no longer being able to watch most space movies due to frustration caused by the filmmakers not grokking basic orbital physics

Oh boy, this again. Are you not able to watch movies with guns because Rainbow Six taught you how guns work and now you're just too woke to suspend disbelief?

Something about this game causes people to feel the need to signal all their knowledge of science by putting down things for not being pure enough.

Eh, knowledge of a thing means suspension of disbelief is ruined and broken by basic inaccuracies unless the media tries to handwave this away.

Star Trek does lots of this with "inertial dampeners" and their "deflector shield". It's total handwaving, but at least they did it. It helps sell it, like "oh, ok, well... I guess that makes sense?"

Much like most movie and TV "hacking", or even basic programming is totally irritating (to the point it's a trope now). Same deal, different subject.

Exactly. I think you can hand wave most things, and invent your own rules for how the universe works, including magic, aliens, FTL travel, teleportation, resurrection, etc.

But there needs to be at least a cursory hand waving, and the hand waving and the resulting rules must be logical and not contradict each other.

Although hand waved premises can set up the plot (magic exists and there is a school for magic kids) it's not really fun when the plot is advanced by hand waving new things as they are needed, and the hand waving should preferably just be background things like moving from a spaceship to a planet or walking around in space - in a budget friendly way.

I personally have a problem with anti-gravity spaceships, unless the other technology is at least Star Trek-, Star Wars- or preferably even Culture level.

Your attitude is pretty dismissive. I don't think it's crazy to say that once someone understands some principle better, they may become more aware of the excessive artistic freedoms some producers take in twisting reality to make their plotline work. And in general, I don't see what's the point of gratuitously attacking people like this, it's very unpleasant.

Don't be so flippant. It's not exactly controversial to say that trained musicians will suffer more when listening to bad music, so why would it be different for any other skill?

One of the main gameplay mechanics is all about understanding orbital physics, and fiddling around with that for tens if not hundreds of hours will leave anyone with a grasp of it on an intuitive level.

Once the brain is that trained, is it so hard to believe that the process can take on an aesthetic experience? Ant that seeing it done wrong is like a false note in music?

Maybe, but I've got hundreds of hours of KSP under my belt and thought Gravity was fantastic. I'm a proud science and gamer geek, but feel that the urge to nit pick is the scourge of the geek community. I'll happily engage in a conversation about the compromises made in Gravity, it none of them spoiled the movie for me and I'm very glad it exists. If it makes movie goers more interested in Space and feel positively about space research and exploration, that's a wonderful thing.

I think they were saying that Gravity, Interstellar, The Martian and The Expanse are all good examples.

I'm confused about this too. The Martian (at least the book) has good science throughout. But in Gravity, the space shrapnel is moving much faster than the ISS, yet has the same orbit as it. I don't think that's possible, from what KSP has taught me.

It's all a matter of degree. The Martian also has creative decisions that the author semi-apologizes for because they made the plot work. (Such the idea that a windstorm on Mars could blow anything over.)

I don't think it has the same orbit, I think it has a crossing orbit inclined relative to that of the space station. Imagine a belt of debris, much like the rings of Saturn, with the ISS on an orbit that passes through the ring twice on each orbit, on opposite sides of the planet.

...relative to the usual "not even wrong" depictions that Hollywood screenwriters can crank out after barely passing high school physics.

Yes, that's exactly what I meant.

>Ant that seeing it done wrong is like a false note in music?

No, it's not the same because most movies are not meant to be a reproduction of the real thing.

No, but they are (usually) meant to be representative of the real thing, to the degree that it's recognizable. The more that representation diverges from reality, the more suspension of disbelief you'll bust for people that see it. Sometimes it can't be helped, or is one of a few things you are expected to take for granted for the plot, and that's generally okay with most people. Worse is when there's no real reason for it to be wrong except for lack of care. That's when it's really annoying.

Oh please. This is an extremely vapid "stop liking things I don't like"/"not liking things I like" take. And an accusation of "nothing but loser nerds signaling their knowledge in public" is particularly rich coming from someone whose username is a Futurama reference -- a work no less subject to the same (equally vapid) accusation of its appeal being "look at me getting these leet nerd references".

How about art with pretenses towards realism/naturalism (which is not all art, nor should it be) can be more enjoyable for living up to that? And learning something is not a hostile act of self-indulgent performance by the learner, even when that learning might change their perspective on a piece of entertainment media.

Wow, cool, 30 minutes and two comments in and we're already tearing each others' throats out. God, I love the Internet.

There is a line to be walked. Having a gun that never runs out of bullets doesn't fly in most movies, even if they'll fudge exactly how many are fired before a reload. This is due to the general public's level of knowledge on the topic.

It used to be very annoying to watch certain parts of movies when I was younger. Computers and the internet were treated so haphazardly, it was cause for celebration whenever a contemporary computer interface was shown that wasn't entirely bullshit. This isn't relegated to just these topics, I assume there's a wide swath of annoying Hollywood misrepresentations on topics where there's a sizable subculture, and interest enough to sometimes be included in popular media, but with enough obscurity to the general public that Hollywood can basically make up whatever they want about it and most people won't know any better. For example, I imagine a good majority of car chases and slides around turns probably look like crap to stunt and race drivers, professional and amateur.

The effects of this range fro harmless to possibly shifting popular consensus in harmful directions (I could argue that a lot of early fear regarding the internet was misplaced, and the expectations of the public were so off that it may have retarded some basic security awareness for some time).

The annoying part is that all too often it's just a small matter of knowledge that keeps the representation from matching reality, and the only thing that stopped it from happening was a lack of care on the director's part for the subject they were representing. That's what the real shame is, because how hard is it for a director to get someone to sit in and consult on those topics?

> it was cause for celebration whenever a contemporary computer interface was shown that wasn't entirely bullshit.

https://www.youtube.com/watch?v=msX4oAXpvUE

Computer/Hacker Movie inspired GUI: http://geektyper.com/

I remember hackertyper from way back when, but I just spent about 10 minutes with a shit eating grin on my face as I played with the different things on geektyper, it nails the vibe spot on.

With guns, it has already been shifted in a harmful direction.

Suppressors are safety equipment, not badass silencers that let assassins shoot in near total quiet. But because the public only knows the movies, if you want to get a suppressor for your gun you need to pay 200 dollars. Imagine if we made it so you had to pay money to buy a muffler for your car, because Hollywood kept having cars with mufflers running dead quiet.

Or another one is bullet lethality. Handgun bullets make tiny holes in things without a lot of punch, so there is virtually no chance a single bullet from a pistol is going to knock a bad guy down. Maybe if you get very lucky and nail him in the precise right spot in the spine or brain, but otherwise he's still going to be alive and fighting for minutes or even hours. The police aren't putting 15 rounds into a suspect because they're dicks (well, they might be dicks I dunno) but because handgun bullets aren't very good at stopping people. You can only rely on volume of fire and hope you get a good shot to the central nervous system. Heck, even if you annihilate someone's heart the guy's still got about 10 seconds (called the 'dead man's ten') of useful oxygenated blood to work with before he's incapacitated - more then enough time for him to raise his gun and take you with him.

I had a real problem teaching Newtonian Mechanics to students who got most of their Newtonian Mechanics from movies. Their intuition about motion in free-fall was all wrong. Imagine if movies just got this right as a matter of course, and gave even uneducated people correct intuition.

I believe that constantly seeing mega-structures fail incorrectly (e.g. CG buildings falling over) actually contributes to 911 conspiracy theories.

EDIT> It's also a cool feature / talking point. Uneducated person watches a space movie. "Huh, why is the ship pointing backwards, etc." <-- this can serve as a hook for learning.

> I believe that constantly seeing mega-structures fail incorrectly (e.g. CG buildings falling over) actually contributes to 911 conspiracy theories.

The two biggest 911 conspiracy believers that I know are both involved in CGI for their day jobs.

> Are you not able to watch movies with guns because Rainbow Six taught you how guns work and now you're just too woke to suspend disbelief?

The people I know who shoot recreationally do get annoyed gun use in movies. Not "all movies are unwatchable", but OP specifically gave examples of movies he didn't object to. Sit down with a trap shooter and watch American Gangster - they'll probably grimace as the protagonist needlessly racks the gun over and over to make a cool noise.

If the rebuttal is "but that's real, not a game!", I think the point is being missed. Target shooting is not combat, after all. If someone spends hundreds of hours on a recreational version of something, they're that much more likely to be irritated by failures of research or realism.

I agree completely. The only recent movies that I can recall that got firearms handling even remotely correct were the two John Wick movies. Keanu Reeves went out and trained, and got good enough at 3-gun and similar shooting sports that he is actually competitive at the national level.

lol, you say this in a place where any on-screen programming that isn't Mr. Robot is considered buffoonery.

> Oh boy, this again. Are you not able to watch movies with guns because Rainbow Six taught you how guns work and now you're just too woke to suspend disbelief?

A fun game to play in most action movies is count how many shots are fired before the protagonist has to reload. I wish I had one of those magic magazines.

Watch out for those magic magazines though. They have a tendency to disappear in dramatic moments, so you may suddenly find yourself with no magazines and one bullet in your gun at the exact time you need rounds the most.

Why would I want to play a game that turns me into a insufferably pedantic jerk who can't let people just enjoy a damn movie?

That's like saying you shouldn't study statistics and probability because it won't be fun to go to the casino.

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