14 ms·
Can We Throw Satellites to Space? [video]
- thekalki 4y agoInstead of spin I would be leaning more towards rails on a mountain but this requires more space but should be much more easier on payload
- DiggyJohnson 4y agoJust musing from intuition: but could gravity and magnetic rails come close to the potential energy of a spinning system?
- bee_rider 4y agoIs a centrifuge considered to have potential energy, or kinetic energy?
- Symmetry 4y agoKinetic.
- zasdffaa 4y agoThat was a very interesting question to which you gave a very definite answer, but why do you say kinetic? Maybe I don't understand what potential energy is. from wiki <https://en.wikipedia.org/wiki/Potential_energy https://en.wikipedia.org/wiki/Potential_energy> "In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors" but a spinning disc in a vacuum would maintain energy indefinitely, taken as a whole, and the spinning disc is a stress in itself.
- krisoft 4y agoFrom Wiki: https://en.wikipedia.org/wiki/Kinetic_energy https://en.wikipedia.org/wiki/Kinetic_energy "In physics, the kinetic energy of an object is the energy that it possesses due to its motion." The spinning disc has energy because of its movement. If it stops spinning (moving) it has no more energy. That is what people refer to when they say kinetic energy. > In physics, potential energy is the energy held by an object because of its position relative to other objects That would be when you put the disc on a high shelf and it falls on you. > stresses within itself When you take the disk and you bend it into an S-shape and it is trying to spring back. > a spinning disc in a vacuum would maintain energy indefinitely Assuming frictionless bearings perhaps. But what does that have to do with anything? > spinning disc is a stress in itself. Not in the way physicist think about it. On the other hand, watching a spinning disk is full of stress! Just think of the last scene of Inception.
- wolfram74 4y agoTo desphericalize the cow a bit, the spinning disk would have /some/ potential energy associated with the tension the material experiences to keep itself from flying apart, but yeah, I don't think I'd bother keeping track of it most of the time.
- zasdffaa 4y ago>> a spinning disc in a vacuum would maintain energy indefinitely > Assuming frictionless bearings perhaps. But what does that have to do with anything? Thanks for this, let me elaborate. First, yes, magnetically suspended. That given, take a box containing some quantity E of energy in the form of petrol or TNT, whatever. Chemical energy. Next take a box containing aforementioned disk, spinning with an energy also of E. From the outside there is no observable difference if both they are left sitting on a warehouse floor untouched, however the box with E of chemical energy is potential energy, the box with the spinning disk has kinetic energy, according to your definitions. Yet they are indistinguishable from without. That's my puzzle. (I'm being slowposted so replies may take a while)
- krisoft 4y ago
- bee_rider 4y agoThis is what I thought. My physics is a little rusty so I tried to fit it to a potential energy just based off that comment, haha. Like if we look at the rotating (so, non-inertial) frame of reference, then maybe we could define a potential energy off the centrifugal "force..." but that would be illusionary.
- DiggyJohnson 4y agoSorry, my use of potential was a bit of wordplay on my part. I should have stated my question differently.
- bagels 4y agoIf you have enough mass, and enough change in height, sure. Doesn't mean you have a practical way to use that potential energy though.
- amelius 4y agoWhat if you attach the payload to the projectile with a bungee cord, at exactly the moment it is released?
- blacksmith_tb 4y agoI suspect it'd be hard to find a tether material that could take that kind of force without breaking. There could also be some strange dynamics as the projectile and payload would become like bolas[1]. 1: https://en.wikipedia.org/wiki/Bolas https://en.wikipedia.org/wiki/Bolas
- amelius 4y agoYou're probably right. I would love it if someone could put it in a physics simulator, though.
- thekalki 4y agoYou will loose lot of energy on bungee cord aerodynamics, heat, etc
- amelius 4y agoTrue, but the question is: will the payload suffer less?
- Symmetry 4y agoYeah. With a few kilometers of track you're looking more at a thousand times less acceleration though still more than a human could take. Though emerging from a track kept at a vacuum and slamming into the atmosphere is going to be quite a jerk in any event.
- bodhiandphysics 4y agoYour forgetting the evacuated tube. The issue with rail launch on earth is dealing with the atmosphere
- bagels 4y agoYou'd need an awfully long rail. Where does the energy come from for this idea?
- bagels 4y agoJust for fun, accelerating on a rail to appreciable first stage velocities of 2000 m/s at ~3g (for humans): 60 seconds of acceleration along 60 km of rail
- thekalki 4y agoEarth might be little too thick for this but should work great on Moon, Mars.
- Gravityloss 4y agoIf you don't launch to escape velocity, you launch to an elliptical orbit that intercepts the launch altitude. That's why you basically always need a rocket engine anyway.
- chasil 4y ago...thus the small rocket contained in every spin launch.
- deleted 4y ago[deleted]
- Symmetry 4y agoThe initial velocity just replaces a rocket's booster stage, not a whole rocket.
- ericbarrett 4y agoThe problem is drag and heating. The booster phase of a rocket moves slowest in the thickest part of the atmosphere so it mostly avoids this. Usually at the end of the booster phase a rocket is going 2-4 km/s but it's also at 60 km above sea level. (All these numbers vary somewhat by launch vehicle.) To travel at that speed even at jumbo jet heights, ~15km, would generate insane amounts of heat and drag; the front of the craft would be white-hot and there would be massive loss of energy to friction. And it would still need to have the fuel and engines to accelerate another 5 km/s to stay in orbit. It's physically possible but the engineering is insanely difficult, much more so than a traditional rocket, which is already no cakewalk.
- Symmetry 4y agoOh yes, the casing to let it go through the atmosphere at hypersonic velocity is definetly a significant engineering challenge. But it's a solvable one, unlike trying to get through troposphere at orbital velocities.
- deleted 4y ago[deleted]
- aaron695 4y ago
- martin_a 4y agoRelated: Spinlaunch: BUSTED | https://www.youtube.com/watch?v=9ziGI0i9VbE https://www.youtube.com/watch?v=9ziGI0i9VbE
- dcow 4y agoWhile there may be some valid critique in this video, it’s oozing frankly disgusting amounts of pompous dismissal and consequently I cannot trust its motivations.
- switchbak 4y agoI've tried to listen to this guy in other contexts, and you're right. So much cynicism and arrogance of his supposedly grand intellect. It's just such a turn off.
- chubbnix 4y agoYou’ve got great intuition: https://youtu.be/SpgBkpb7xlU https://youtu.be/SpgBkpb7xlU
- Havoc 4y agoWhat the hell is that & how is it relevant to satellites?
- MichaelCollins 4y ago'He's wrong about feminism so he must be wrong about everything else.' I guess? There's no denying the guy is a blow-hard loudmouth with an obnoxious style and some dumb opinions, but that's no reason to blindly believe the inverse of everything he says. Personally I ignore his videos; not because he's always wrong, but rather because he's always annoying.
- ravenstine 4y agoSomehow I knew it would be Thunderf00t from the title alone. I used to watch this guy religiously (lol) back in the day, and while I still occasionally see what he has to say about certain topics, I find him hard to watch because of what seems to be a lack of humility. Last year I unsubbed. Yeah, some of the stuff he critiques is really stupid (ex. solar roadways), especially when it comes to Kickstarter scams, but his general attitude suggests that no one should ever test insane ideas for the sake of it. I get that reusable rockets have already been achieved, for instance, but Thunderf00t seems to think that's a reason to dismiss the efforts of SpaceX, as if nothing could have possibly been improved upon since the 1990s. He has a real bias towards governmentalized academia, and he's even admitted it more or less in the past, which is why he frequently criticizes commercialization of technology. It's too bad, because he's a really smart guy, and used to make very good points against organized religion. He could be inspiring more people to get into science, but he's now in the business of mocking, which isn't a compelling reason to actually become scientifically literate. The really odd thing about his critiques is that he doesn't actually attack the heart of the problem, which is the media. As long as the mainstream media is scientifically illiterate and is so bereft of ethics that it just wants to sell attention, people will invent cockamamie ideas like the "sky hotel."
- gonzo41 4y agoI think creating cannons along the designs of Gerald Bull would be more promising. Just huck cube sats into orbit. Obviously you'd probably want a cube sat with no moving parts or something that could withstand what I'd assume to be like 10K G's.
- TheLoafOfBread 4y agoEven if something is rated on i.e. 1000G it is rated for a very short time, like a shock or a fall on the ground. Which from my perspective is the problem of whole concept described in the video. In 5:55 minute mark, video is describing force applied on the payload will reach from 1G to 10000G, but how long does this take? 10 minutes? 30 minutes? An hour? Can you have a payload which will be able to withstand 1000G+ for minutes? Contrary to big cannons, like [0] there would be forces of 10000G only for few milliseconds as shells are accelerating only during the time of being in the barrel. [0] https://en.wikipedia.org/wiki/Project_HARP https://en.wikipedia.org/wiki/Project_HARP
- gonzo41 4y agoI would guess you'd do something like try and cast any electrical components in something like a resin so it's just a solid brick that can handle the stresses. But 10k G is a lot.
- TheLoafOfBread 4y agoWell problem is that this concept is supposed to replace 1st stage as it can reach only to 70km. What kind of 2nd stage rocket engine can survive such Gs? Solid booster which you can't control?
- chasil 4y agoThere is lengthy discussion at the end of the video on design changes, primarily for the reaction wheel. They conclude by placing a digital camera in their lab mockup and taking it to 10,000g. This probably would not have worked for a phone, but they seem quite confident.
- deleted 4y ago[deleted]
- gsibble 4y agoThis will definitely work. I can't say how I know, but someone in the intelligence community told me they are banking on it.
- thdxr 4y agoIncredibly well produced video
- synu 4y agoI could be wrong, but I got the sense watching it it was a long form paid advertisement?
- MichaelCollins 4y agoThat seems to generally be the way with space journalism; flatter the companies/personalities to get the best access for filming/interviews.
- jackmott 4y ago
- Havoc 4y agoThink there also a middle ground in this debate that is overlooked. Perhaps it might not work for chucking humans into space. If you can do some with component part of liquid fuel that is in isolation inert that would be a massive win.
- MichaelCollins 4y agoI think you've misunderstood the field of this debate. With regard to manned flight, there is no debate at all; 10,000 Gs isn't compatible with human life. Nobody, not even Spinlaunch, is proposing this for manned flight.
- bagels 4y agoPutting a human on the spinlaunch is how you create human soup. Human tissues cannot withstand those accelerations.
- tromp 4y ago> we ended up doing it for less than a couple of million dollars That's a nice way to make a couple of million dollars sounds less than it is:-)
- TheAceOfHearts 4y agoReal Engineering always does such an amazing job on all their content, although I can't help but fixate on what the release mechanism looks like since it wasn't revealed in this video. This comment was inspired by another commenter saying something about shooting the rocket off the side of a mountain. I'm theory-crafting here without any specialized knowledge on the subject, asking strictly out of a mix of curiosity and fun. Is there an online community where I could pose this question and get a well-informed response about its viability? What if you dug a very deep hole, created a near-vaccuum, and you shot the rocket out like a rail-cannon? Here's a quick and simple sketch [0] of what I have in mind. [0] https://imgur.com/bmHiMdq https://imgur.com/bmHiMdq
- throwoutway 4y agoHow do you produce a near vacuum with a hole on one end?
- picsao 4y ago
- tripa 4y agoBy extending the cannon's end to space.
- TheAceOfHearts 4y agoCan't you do something similar to what the engineers in the rocket throwing video are doing?
- dang 4y agoRelated. Others? Can We Throw Satellites to Space? – SpinLaunch - https://news.ycombinator.com/item?id=32375464 https://news.ycombinator.com/item?id=32375464 - Aug 2022 (5 comments) An Inside Look: SpinLaunch Flight Test #7 - https://news.ycombinator.com/item?id=31098021 https://news.ycombinator.com/item?id=31098021 - April 2022 (4 comments) NASA to Test SpinLaunch, a Giant Slingshot for Launching Satellites into Space - https://news.ycombinator.com/item?id=31010244 https://news.ycombinator.com/item?id=31010244 - April 2022 (1 comment) NASA will test SpinLaunch's ability to fling satellites into orbit - https://news.ycombinator.com/item?id=30996665 https://news.ycombinator.com/item?id=30996665 - April 2022 (199 comments) SpinLaunch completes first test flight with rocket-flinging launch system - https://news.ycombinator.com/item?id=29198589 https://news.ycombinator.com/item?id=29198589 - Nov 2021 (219 comments) Spinlaunch completes suborbital launch without engine - https://news.ycombinator.com/item?id=29175912 https://news.ycombinator.com/item?id=29175912 - Nov 2021 (6 comments) SpinLaunch is building a centrifuge to launch satellites into orbit - https://news.ycombinator.com/item?id=25204660 https://news.ycombinator.com/item?id=25204660 - Nov 2020 (143 comments) SpinLaunch raises $40M to build a machine to catapult objects into space - https://news.ycombinator.com/item?id=17317688 https://news.ycombinator.com/item?id=17317688 - June 2018 (105 comments) Space catapult startup SpinLaunch comes out of stealth - https://news.ycombinator.com/item?id=16439835 https://news.ycombinator.com/item?id=16439835 - Feb 2018 (110 comments)
- quickthrower2 4y agoHacker News is shown as example of naysayers: https://youtu.be/yrc632oilWo?t=2401 https://youtu.be/yrc632oilWo?t=2401 :=)
- remote_phone 4y agoI’ve wondered this about airplanes. Couldn’t we launch an airplane into the air and it spends the rest of the time gliding back down to earth? It would make things a lot simpler and the chance of something going wrong is much less since it’s in a perpetual state of gliding back. Is this even possible?
- ncr100 4y agoI don't know. Gliders are a thing, dragged into the air by a propeller driven plane, untethered they fly for quite some time. https://en.wikipedia.org/wiki/Glider_(sailplane) https://en.wikipedia.org/wiki/Glider_(sailplane) I estimate, speculatively that the energy to bring it to altitude, condensed into an impulse only imparted at launch, would destroy such an aircraft and kill any occupants.
- UberFly 4y agoSure, but no modern airport would be able to accommodate these as the wingspans would have to be huge compared to a propelled jet.
- dharmab 4y agoWhat? Gliders fly out of "modern airports" every day. Not to mention large flying wings like NASA Sunglider, B-2s and wide-winged aircraft like the A380 and An-124. Heck, the Mriya was able to operate at many major airports, although with some disruptive considerations when taxiing.
- naasking 4y ago> Gliders fly out of "modern airports" every day Sure, carrying one or two people. What wingspan would you need to carry 200 people and their luggage? That's what the OP was talking about.
- stdcall83 4y agoWow.
- rep_movsd 4y agoI cant believe anyone with basic physics knowledge can be serious about this. Its the sign of the times where anything thats pitched big tends to be seen as "revolutionary"
- raasdnil 4y agoWe've had many discussions on HN about SpinLaunch, but Brian real goes through and answers several of the questions that were left unanswered, love it.
- jasode 4y agoI think we can assume Brian McManus read over the past HN thread (April 2022) with the skeptical comments about the feasibility because he puts a screen shot of that thread in the video. Deep link to the HN cameo appearance: https://www.youtube.com/watch?v=yrc632oilWo&t=39m48s https://www.youtube.com/watch?v=yrc632oilWo&t=39m48s
- whartung 4y agoI don't know why this system is such a magnet of internet skepticism. Of course the system is extraordinary, but it's an engineering project. An engineering project with a lot of "knowns", vs "known unknowns". It's mostly a materials science project. It's a complicated integration problem with all of the engineering associated with that, but, to be fair, they're not making up a lot of stuff out of whole cloth, they're utilizing known things in new ways. Simply, much of the concept can be simply tested after the napkin math is performed. Tested to the point of either "yea this will work" vs "no way". As far as I know, there's no real government money in this, they don't seem to be running in to a lot of administrative red tape (like, high speed rail is not an engineering problem, it's social and governance problem). So, doesn't seem to be some swamp land boondoggle. Can it fail? Of course it can fail. Is it inevitable? No, I don't think so. I don't think it's a bill of goods sold to investors to fund a few engineers in the middle of the desert.
- marcosdumay 4y agoAny reasonable version of it (what must look very different from the prototype) is an incredibly expensive investment, that must be diluted into what is currently an outrageous number of launches to pay for itself. Besides, there are some very problematic known unknowns involved on submitting things that want to explode to high g. All of it looks patently possible, given enough money and engineer-time. It's the kind of project that may change the relation Humanity has with space, but has huge odds of bankrupting the entity doing it even if it succeeds in reshaping Humanity. So yeah, it's either government built or it won't get built at all.