Any discussion of black holes and similar always reminds me of Terry Pratchett's observation that it's hard to discuss physics using a language designed to tell other monkeys where the ripe fruit is ;)
My method for shielding is distance. I live on the East Coast and my radioactive in-laws on the West Coast. I don't recommend it though, as no matter how far away they are their going to send me to an early grave.
The difference between radiation requirements for LEO vs GEO (and above) is night and day. A LEO capable FPGA is $5, a GEO capable FPGA is $15,000. Redundancy means nothing if the part latches up and burns out.
Neutron stars can also go flying on exciting trips through the universe as a result of the dynamics of their birth. That presents the possibility of a neutron star being an extrasolar capture or even temporary visitor.
One thing I always wondered, why not shield the sleeping bags? Lead lined sleeping bags, plastics for cabin shielding etc... You don't wear it all day but but it could cut a nice chunk out of the daily exposure.
12:50 Short answer should be: Yes, except that things get atomized and redishifted to the maximum, so they can't be seen. But otherwise (ignoring a couple of physical effects) they would indeed appear as frozen images on the back hole's surface.
Hmm. Ultra high density polyethylene is pretty tough stuff, used for body armor panels & such. I’ve no idea how hard it would be to manufacture in the appropriate sizes, but maybe it could be used as a structural skin for at least parts of the crew areas on interplanetary ships. It would probably make decent micro-meteor protection too.
From the vantage point of a distant outside observer, an object falling towards a BH and very near the event horizon would not only be gravitationally redshifted and frozen in time but also smeared and scrambled over the whole surface of the event horizon.
The best space related channel out there. There.are so many channels but many alas say too much superficial stuff with no deep insight. But I guess every level of analysis has its audience. Here is the place for the more in depth kind of viewer lol
@@viestursgfl6178 Yed you are right I am subscribed to his channel. You are right I forgot him. I was thinking about those who use catch phrases like click bait etc.
Scott is exactly the perfect middleman between the "hard science" side of things and the "space is cool" discourse. For someone who doesn't need to understand the maths of it all, but wants to be in the know about what goes on in space research and technology, he's a truly fantastic resource.
PBS Space Time has in depth stuff and usually tackle Black Hole phenomenons without fussing around. Another good channel is Sabine Hossenfelder, also no fuss, but not focused on space alone but rather physics and what else is on. Both those channels are being moderated by publishing phD physicists with teams behind them, so should meet the high levels you set.
Fairings: I wonder if the JWST program would have cost less if they had decided to spend the money to develop an enlarged fairing for Ariane 5, rather than all the mechanisms to fold the mirror and such. I know that the thermal blankets and instrument systems were a major deal, but maybe some of it would have been simpler if an oversized (7m?) hammerhead fairing had been developed, even as a one-off.
I think that some of the reasoning for the folding mirrors was to allow them to adjust the focus to address manufacturing flaws, since the JWST is too far away for a practical service mission like the one that was performed on the Hubble Space Telescope.
The JWST is massive. A plus-sized fairing might have made things a little easier, but there still would have been a lot of origami required. Plus, even if payload volume wasn’t an issue, I think a lot of the JWST just isn’t able to handle launch forces in the deployed state. Can you imagine that multi-layered sun shield or the secondary mirror arm in that situation?
HI Scott, Active radiation shielding was my actual thesis idea on MSc, But it was in 2019 and I learned someone else came up with the idea first. Still very interested in the tech. Thanks for the video! Orbit safe!
Not sure Elon plans much in that area. In his fantasies about "colonising Mars" are much bigger questions than radiation to answer. Getting there (reliably) is only the first massive and expensive challenge. I would not even trust my car or bike to work for 15+ months without show stopping issues.
Scott, could you talk about the difficulties of try propellant engines. The source of all knowledge, Wikipedia, talks about the Rocketdyne test and the RD-701 but is quite short.
I've heard of theoretical proposals for a lithium-fluorine-hydrogen engine, apparently it's hard to keep the lithium molten hot while having the others be cryogenically cold, I'd imagine the fluorine alone is hard enough as-is
You already know the solution to rampant air-sickness (motion sickness)… pilots have learned that keeping their heads as still as possible mitigates the inner-ear fluid from sloshing too much and makes it more difficult to be incapacitated because of motion sickness. I know fighter pilots love to make riders sick, so I’m sure ‘keeping your head still’ probably is only so effective; I’m sure there’s limits to how well it allows someone to cope with 5-9G’s and rapid changes in direction. But I (coming from a family of 5 pilots) would even take a back-seat ride in a fighter over anything in space, besides maybe doing an orbital run in a space shuttle type spacecraft that lands on a runway. That would be the only thing that would appeal to me more. Just going up and then floating down wouldn’t do much for me. The launch would be cool but so would it be on an F-18 (or better yet, an F-15) and the landing would be awesome and you have such a better view of your surroundings when the pilot inevitably does tons of aileron and barrel rolls, and there’s constant changing of directions, so it seems cooler and more complex of an experience than a virtual launch and floating back to earth on a parachute INSIDE a pod without very good visibility. Aside from the power of the initial rocket launch, and the view from its apogee, everything else is sub-par to every other aspect to a ride in a supersonic and highly maneuverable fighter plane. I can see the “prestige” playing a factor in some people’s decision making, but aside from some ego trip of saying you’re among the very few to have been to space, the actual experience is probably not as comprehensively enjoyable. But let’s be real; either of those would be fucking incredible to do. I’m old enough to have been a cockpit during a commercial airplane landing, and it was utterly incredible and thrilling. Couldn’t imagine a hyper-maneuverable aircraft.
About the notion of a black hole appearing to be covered with frozen objects near the event horizon--in Misner, Thorne and Wheeler's text there's a section where they talk about this and point out that the objects wouldn't just appear to slow down, they'd also get redder and dimmer, and for typical black holes the time of emergence of the last visible photon would be fairly short. So you wouldn't be able to see a voracious black hole's event horizon covered with old frozen debris; if you could get a clear look, it'd just look like a black hole.
These days, tungsten powder mixed into Ultra High density polyethylene is preferred instead of lead. Lead can neutron activate and become uranium. Secondly polyethylene works well to slow down neutrons which if it hits aluminum can spallate.
Ever since seeing the advancement of rockets that can launch, controlled land, refuel then launch again. It's really made my imagination want to see a refilling station on the Moon. So our missions can have tons more propellant then our current situation that takes most of the fuel to escape Earth's gravity, leaving little fuel left for the rest of the actual missions goals.
I love the idea of things falling into a black hole slowing down for the outside observer. Imagine a story where a starship is flying by a black hole and they realize there's something odd falling into it. The do math and determine it started to fall in millions of years ago. Its so red-shifted they can't tell what it is clearly. Is it just a weird asteroid? Is it evidence of an alien civilization? They only have a few days/weeks to figure it out since their ship doesn't have the Delta V to stop in orbit if they want to make it to their destination. Do they decide the discovery is important enough to stop anyway and ask for a rescue afterward?
Lead blocks gamma rays but is fairly neutron transparent. The Russians used lead as the coolant in the reactor of Alfa class submarines. For blocking neutrons you want hafnium as it is the beginning of a long chain of high neutron cross section elements. You also want to be about 3 meters away from your aluminium radiation shield to protect against the very short lived secondary particles resulting from stuff hitting the aluminium. Kerosene is not the most efficient rocket fuel particularly for deep space operations but it is easy to store and a good rad shield.
Neutrons are harder to attenuate than gammas. Trick is to use poly shielding due to their high hydrogen content which scatters the neutrons, followed by a dense material such as lead. Water and diesel fuel also work great as a scattering agent, and do a decent job of absorbing gammas.
My impression of why hydrogen is useful is that cosmic radiation splits into two groups, atomic and protons (or helium radicals), while you can repel charged nuclei with a magnetic field you need to dissipate the momentum of atoms. If an atom strikes another heavy nucleus, like uranium, most of the energy is going to go back into the atom (though probably shearing off electrons). If an atom hits a hydrogen, either elemental or aqueous because it is of equal mass it imparts a large amount of energy on the atom, with the hydrogen being torn from the molecule dissipating energy on the surroundings. The slowing of cosmic radiation creates a shower of energetic particles that require several more collisions. The aqueous version of a shield needs to be something like 2 meters thick except the part of the shield facing the sun, it might be useful also have other solutes such as borate and dissolved heavy metals.
On the subject of black holes, the best theory I've heard of to date is that they're Fuzzballs (made of strings). There's a very good PBS Spacetime video explaining this. In fact, this is the one and only theory I know of that actually makes sense as it doesn't result in any paradoxes. Basically, in this theory, there is nothing beyond the event horizon. Spacetime ends there so there is no inside of a black hole/fuzzball.
Im sure the lady from vintage space said the gemini design was actually started later than Apolo when they realised they needed to try stuff out and some of the systems were more advanced. It was more of a pilots space craft.
Scott, if you decide to do a deeper dive on that idea of a star shielding its own planet from a nearby neutron star, there's another angle to consider. You discussed the possibility of the neutron star going supernova and affecting the nearby system, potentially disrupting the planet's orbit. But what if that star system didn't exist prior to the supernova? A nebula near the supernova, disrupted by the shock wave, collapsing to form a new system within the radiation danger zone of the neutron star. There's no reason that the planet and its host star would ever have to survive the actual event of the supernova.
I've looked around online a bit, have not found anyone else to ask or answer this question: How would Apollo 13 have turned out if it had been a J-Class mission intended for longer time on the Moon? Obviously the LM would still need to become the lifeboat, but would the additional power and other resources in it offset some of the issues they faced? I realize just how close it was to get them back, a testament to the planning, skills, training and creativity from all parties involved.
There seems to be this idea that we'll live on Mars but does the lower gravity not make this impossible or at least not without severe health problems?
We simply don't know. We have huge amounts of data on living at 1G, lots on living in microgravity. In between that, we have exactly 12 sets of data, ranging from a few hours to about 2.5 days, contaminated by extended periods of microgravity on each side, of living at lunar (1/6th) gravity. This SHOULD have been a primary mission of the ISS, but...
2 года назад
We don't actually know. We have about 3 million years of experience living an entire lifespan at 1g and about 35 years of experience living a couple of months at 0g, but we have practically no experience with anything between 0g and 1g. (We have very limited experience living for a couple of days at 1/6g from the Apollo program.) So, the answer is: we have no idea what the effects are of living an entire life in 1/6g on the Moon or 1/3g on Mars. We don't even have any data from long-term experiments of say, living at 1/3g for a couple of weeks that we could extrapolate.
there's always been a human cost when exploring new frontiers, and I don't get why some people can get so hung up about it. people made ocean voyages to their near certain death all the time back in the old days, and tried to fly on paper glued to twigs. it ain't no big deal. you just have to go find out!
bubble wrap? I like the idea - service the missing tiles on arrival and do the condom or wrap - I mean how hard would it be to send a bot around the ship - ablative saran wrap an asbestos sock ? humm bubble balloon a starship cozy. Build an ice shield during the flight - made of human pee and burn it off on the way down. Yuck yea maybe a forward facing shield for the initial orbit and eject it, coming in on the standard star shield. Humm You were thinking on the way out but it is shedding the velocity pre landing that is the hard part. I like the wrapper bots - for the space dock, starship storage, supplemental radiation shielding. Hold that thought.
black holes appear to be something we can’t explain probably because they are unexplainable, the way they interact with our universe has me to believe they are part of the 4th dimension.
Scott, could you do a video explaining why Falcon 9 1st stage does an entry burn? Watching a return to cape landing versus a barge landing for the first stage, you notice a dramatic difference in velocities. On the most recent return to the cape flight the first stage (as reported on the video) had a velocity of 4400 kph and after the burn it was 2700 kph. On many barge landings the entry burn begins at around 8000 kph and decelerates to 5600 kph. We are told that the entry burn is to reduce the velocity so the first stage doesn't burn up in the atmosphere so why the large differences in the barge versus return to cape velocities?
Timestamps: 0:00 Start 0:12 What is currently state-of-the-art in radiation shielding for deep-space missions? 4:22 What about sending long-term missions to Jupiter? 6:20 Can a planet be shielded from a neutron star's radiation by a yellow/blue/similar star, and what would the sky look like from that planet? 9:34 Would you rather fly on New Shepard or be a passenger in an FA-18 for 30 minutes? 10:19 What about "Big Gemini"? 12:37 Explain how objects falling into a black hole appear to slow down and freeze -- and why don't they stay recorded as a frozen image on the surface? 15:54 Why don't rocket companies have a wider range of fairing sizes? 17:33 Are spaceplanes just hard to develop, or do they offer no advantage over capsules? 19:27 Can the fuel stored in Starship keep it cool as it enters into the atmosphere?
The more you think about it, (Event Horizons, AdS/CFT and i-reflection), overall, the more you are compelled to return to e-Pi-i logarithmic time-timing Fluxion-Integral sync-duration in the holographic Black-body of Zero-infinity (Kelvin), Eternity-now Imagery Interval.
The Apollo uys all reported difficulties with sleeping due to visible particles showing up in their retinas. They called them Z rays for some reason then.
The solution you describe is only for ambient radiation and allow people to live, but long term exposures have of course never been studied. It is likely all occupants of such a craft would die of Leukemia, or worse, during a mission to any planet. Coronal Mass Ejections and other completely normal radiation events outside of our earth's magnetosphere would immediately ruin everyone's day.
Hello Scott, First of all a big thanks for all your amazing video, I find them so interesting and informative. You must but so much work it to them. I do have one question about something I saw on the BBC that SpinLaunch I would imagine you would have to have a very strong satellite to stand up to the G forces, But looking at it is it not doing like Virgin are doing ie taking a rocket up high the letting go from there? Keep well, keep safe and enjoy life.
Since Jupiter's main moons are tidally locked to the planet, I'd have thought that radiation protection would simply be a case of picking the right location so that the moon itself shielded you? (Assuming the other trivial problems, like traveling a billion miles or whatever the transfer distance is, could be overcome!)
Sorry if im just exceedingly stupid tonight but im not sure I follow. At 6:04 are you saying that because the gravity is low enough, that the water pressure should be low enough that diving is possible once you get through the ice? Or did I miss something? Thanks for the video!
About electron density and it being the reason lead is good at blocking gammas and such -- I wonder if, using an array of electron beam generators, you could create a protected region where they all converged? Obviously, lead is easier and it would take a lot of power, but it might be a great deal lighter, especially if the region you wanted to protect was pretty small. Also scaleable. Beam power could be made very high.
2:10 yes lead is good at blocking gamma because it contains a high density of e-, but no lead is NOT a good shield for neutrons. Neutrons are obviously not sensitive to electrons. You can block neutrons more efficiently with less material using hydrogen rich materials like water or some plastic like PET, because energy transfer is more efficient with neutron - light nucleus (like proton) collisions, compared to neutron-heavy nucleus (like lead) collisions : it's like a billiard ball transfering most of it's energy to another billiard ball, compared to a billiard ball just bouncing against a heavy canon ball without loosing energy
Somehow the idea of high energy particles barreling through a poop barrier and hitting the astronauts is disturbing. Do they put air fresheners on the capsules?
F/A-18 Blue Angels! They pull up to 7.5G. New shepherd pulls less (I’m assuming less than the 3G of the shuttle) You know, if given the choice, I’d have to go with the F-18 ride. They give you control of the aircraft for a bit. With New Shepherd, it’s a short ride and you’re a complete passenger with no controls or ability to control. If only the space shuttle were still active, it combines both my interests (aviation, spaceflight) into one. And, you actually got to land it.
but if a black hole slows time, wouldn't that "slow" gravity as well, i guess it wouldt cancel it out but should have some effect no? or does it make it even worse maybe?
Watched an interview with one of the scientists from NASA working on the Mara missions. And their answer was to get there as fast as possible and have medications to deal with it post exposure. I found that kinda disturbing lol.
There was one or two studies out of jpl last year which said that i would be possible to survive a round trip to Mars with shielding and the dose of radiation would be 1,2-1,5 sieverts. This was done with data from mars 2020 sensors.
Nice discussion of black hole time warping. If it should be impossible to see inside a black hole, then we should, in theory, never be able to see a black hole. We can only see the event horizon on the outside of the hole itself. Which begs the question, how do we know it's a hole if we can't ever see inside it?
Hi Scott, I have always wondered if water exists on Mars or inside the Moons craters, wouldn't that water be radioactive for the future astronauts? Scientist talking about using Mars resource (soil & water) to grow plants but is that really possible? Thanks
Maybe a commenter can answer: If you unequivocally want to see if there is life in soil or water what do you do? You either make a slide and put it under a microscope or you make a petri dish with some agar and then visually inspect after a few days. So my question is: Why did NASA go with the labeled release experiment rather than an experiment that could give less ambiguous answers about the presence of bacterial life on mars? Why are there no microscopes on mars?
would have appreciated a bit more detail (numbers!) on the radiation levels on Mars transits - "go during the Solar maximum and take 10cm of Aluminum plating with you and it'll be fine" is a bit low on detail
But does that mean that black holes can't exist? Because there is no way for them to form, as everything stays outside of event horizon (though infinitely close to it). Does that mean that there is no actually singularity, but instead sphere surface with [almost, but not exactly] infinite density?
