The Medusa Spaceship Drive

[Music] the Medusa Starship Drive offers us the chance to sail between the Stars propelled by nuclear [Music] bombs the amount of energy released from a kilogram of an atomic bomb dwarfs what an equal amount of chemical fuel would release by a factor of around a million and fusion bombs even more so thus it's no surprise we have contemplated nuclear energy methods for running spaceship sh but sometimes it can surprise folks that we've considered running those ships on actual atom bombs rather than say a nuclear reactor and an ion drive nonetheless the nature of high- powerered

proportion is that it tends to be decidedly explosive and you would be safer standing near several hundred lb of explosives going off at once than next to your typical rocket Flame the other problem is that nuclear reactor is a heavy thing compared to a bomb and converts its energy into Bo in water to toward a turbine and produce electricity and then run some form of electric propulsion like an ion drive and tends to lose a lot of that compactness and low mass advantage that c off a bomb has what's more while we have fision bombs

and fusion reactors we don't have Fusion reactors just the bombs and fusion is more compact than fision for this reason we have spaceship designs that see to run on nukes the best known is the Orion Drive which which use an immense Pusher plate on a spring behind a ship to absorb repeated blast and translate them into a steadier thrust for the ship allowing relatively fast interplanetary travel and indeed even Interstellar speeds of a few per of light speed but this is not the only design and today we'll be looking at another the Medusa drive this

one is principally different on the surface as it use an immense parachute in front of the ship rather than a plate from behind to absorb the blast with the sail and drag the ship forward by tethers connecting them this has many potential advantages over the classic Rion Drive which we'll look at today but I fig we should start by answering the first two questions that usually come up with this method which is first why isn't the sail being torn to Smither by the repeated blast and second why aren't those tethers being shredded that are connecting

the shoot or sail to the ship ironically the ladder tends to be the one folks bring up most and it is actually the easier part I think folks are assuming the tethers run through the blast zone and are fragile but they aren't coming much close to the blast in the sail is as they detached to its Outer Edge and they would be thicker than the sail in practice I think you would place the sail much further from the ship than the blast were from it and have a long tether since this minimizes how much forward

shielding your ship needs and it already needs a fair amount anyway to handle radiation and collisions at High speed I always view it as a parachute in Reverse where it drags you forward rather than slowing you backward or down in some ways though it's a bit more like a jellyfish and indeed that's how John de Sol's 1991 Los Alamos report had it where he wrote one can visualize the motion of the spacecraft by comparing it to a jellyfish the repeated explosions will cause the canopy to psate Ripple and throb the teos will be stretching and

relaxing the concept needed a name its Dynamics suggested Medusa so a space jellyfish plus the snake-headed monster lady procus fat in Greek mythology and that's the origin for the name for those who were wondering interestingly I didn't know till I started outline the script even though it's mentioned in the article I forc heard of it from a 2012 write up on it from Paul gilst at centuri dreams which if I haven't plugged recently remains one of the best places to find out what's new and groundbreaking and deep space exploration besides here of course and also

of course don't forget to hit the like And subscribe buttons another surprising thing I'd forgotten about that was in the article was that the basic idea probably goes to Freeman Dyson who is probably the most referenced scientist on this channel and something of a personal icon to me I say probably because he is listed as the author of a 1958 memo called the bolo and the squid that is still classified and Dyson was heavily involved involved in the early project Orion work part of which involved trying to get around that giant Pusher plate which included

options like reeling out cables with plates on the end of them which could absorb that momentum instead an elastic tether is a good way to distribute a blast too stretching it out and letting it drag your ship forward as opposed to Big Pusher plate and spring approach that notion is also what I tend to have in mind when I suggest using a packed up solar or laser sail as your pusher plate that's one alternative use of the big sail too as a solar sail or laser sail your size is dictated by how big of blast

you're using and how sturdy your seal is to that type of radiation which by default is plasma and gamma rays and x-rays those cannot be reflected at least not by current technology so your sail is entirely absorptive when it comes to momentum transfer when two objects Collide be it two cars or a ball bouncing off a wall or a photon on hitting a giant sail the most momentum that can be transferred is twice what the incoming object has because it can bounce backwards at the speed it came in at thus losing that forward momentum and

gaining the same amount backward which means whatever it hit by conservation momentum just gain double that momentum itself and in the other direction if it can't bounce or reflect just get absorbed like a gamma ray or high energy particle then the most you can impart is the momentum it has when it strikes and mges into the object it hit and it can do less too much like shooting a piece of paper with a bullet if the impact is too powerful for that absorbing object it will just get punched through with only some of the momentum

absorbed so your sail can't be too fragile and indeed you want it thin enough to be low mass and just barely able to handle the blast you can recycle and repair bits of it during the journey too indeed it will probably also be taking some damage from the front as collisions with it will occur and fairly often as it's a lot wider than your spaceship probably is in terms of collision cross-section of course a big O'Neal cylinder size Colony Ark ship might only have a saale no wider than it is and just detonate thousands of

nukes a day but a shield in front of you is not necessarily a bad thing either as an impact on that sale likely won't damage it much but is likely to cause fragmentation to whatever was hit by there's also going to be some continuous pressure back on that sale which you might spin along its Central axis to keep it spread out but you could also give shoves with a ship laser to keep forward of the ship if it drifted back or off to a side you could send replacement Sails this way or patches too so

that's the two big advantages it has over the Orion drive already with Medusa that the forward sail can be a light sail to gain extra free speed and can act as a collision shield now potentially you can pack a bomb around with material that will absorb all that gamma and super heat and release photons red shifted to some wavelength we can bounce the question is if you could do that with less extra material than simply including other bomb wood but in an ultimate sense if you get away to bounce gamma rays then your maximum speed

for an identical ship goes up by the square root of two or 41.4% higher so what's the actual process and pieces well first the sail or shoot as I've been calling it more formly is is known as a spinor and it's a bit of an obscure sailing term for a sail designed to capture wind when sailing down wind the spinal curved shape allows it to fill with wind providing significant proportion by maximizing surface area exposed to the wind this sail is used primarily for high-speed sailing when the boat is moving in the same direction as

the wind and it requires careful handling to maintain balance and to avoid collapsing or tangling the same analogy applies to our Medusa sale as we want to maximize the surface area exposed to the blast which is also spherical at least in its own inertial reference frame so a sail shaped like a spherical cap works best the name is mysterious and probably irrelevant the best guess I found is that the first ship that used the sale design in the 19th century was called the Sphinx and it got mispronounced a hemispherical blast sail is probably even more

accurate but I think an actual Medusa s would be set up to change its geometry by tightening or loosening the tethers holding it to the ship or the main tether back to the ship they probably join into also by rotating the sail or having cables in it that you could tighten or that ran from the outer rim to the center or you could alter the sail between flat disc and even a cone and you might do that if you are blowing a lot of Plasma on your detonations for the same reason we do with rocket

nozzle designs or to pull power out for the ship by absorbing energy moving more or less perpendicular to the direction of motion which can provide no thrust for you but you could use that to generate electricity for life support and ship operations so too you might twist the sail or uncover one side to provide a shove off AIS left right up down to turn the ship I find it easier to think of the Medusa as a version of a parachute or an umbrella curing you into the wind merry Poppin style but whatever works for you

and that analogy has resulted in me picturing Mary Poppins as having snakes for her hair so maybe not the best visualization I think the parachute works better for me because I tend to assume you are using it to slow down at a destination and it would be shoved up by a laser sale to leave so it is a parachute slowing you down in that case so to rather than have to carry all your fuel thousands of nukes someone could be firing them off from a cannon to go off in front of you potentially even from

relay stations out in deep space conceptually anyway more likely they'd resupply by having a device that had an overrun speed on you that you could Harpoon with a magnet on a tether and drag over to your ship for detonation at your own time of choosing or even firing over the raw materials for making nukes but you might prefer the trajectory and detonation of a nuke to be solely under your control not that of whoever was running that ship that way if they went crazy they not only don't have a huge nuclear Arsenal at their disposal

while entering your space but you already have nukes targeted their way you can nudge onto a lethal course only ships entering an uninhabited system need to have their own nukes on board and you could wait to give them their slowdown nukes till they were in deep space and moving at high speed away from your system now we often imagine the tether only being a few kilometers long we tend to assume we are using small nukes and that as the sail absorbs them again as a hemisphere or smaller spherical cap that blast goes off in what

would be the center of the sphere if that sail weree a complete sphere so every bit of the sail is gain the same shove and this then pushes it forward and puts those tethers under tension which results in the ship being pulled forward and the sail yanked backwards but a net shift forward for both while the debris of the bomb is moving backwards or the reflected particle bouncing out the sail also gets that net momentum backwards same as most proportion systems overall momentum is conserved as much forward as back and the propellant carries that backward

momentum away the suggested bomb was a 25 ton nuke not 25 kilotons or megatons just 25 tons that mass 25 kg itself this is why you will see specific impulse listed for it as low as a few thousand seconds which is still 10 times better than chemical fuels of course but it's simply a very low powered bomb with a low yield to mass ratio bigger bombs with more yield per mass of bomb do much better and you'll see it cited as high as 100,000 seconds of specific impulse I think you could do better by using

a very large design and high year Fusion bombs probably not a shocking Viewpoint from someone whose unofficial Channel motto is that if Brute Force isn't working you're not using enough of it and of course I'd also couple it with pushing beams to get underway as a reminder specific impulse is essentially the time an engine could hover in place on Earth Earth's surface gravity of 1G times that impulse will get you the effective exhaust velocity too and for 100,000 seconds of specific impulse you're getting a speed of 490 to 980 km/ Second the lower value is

if you want to slow down at your destination which a flyby prob of course would not that's a huge speed but it's only a six or a third of of 1% of light speed solum designed it in the 1990s before graphine was on the radar so his basic design C for high strength polyethylene for the canopy of the sail itself 500 m in radius or a kilometer across or about 3,300 ft across and something like 10,000 individual tethers he also considered qu M myar as the canopy I should note that while Interstellar applications are always

brought up with the Orion and Medusa drives most the analysis is done around them being interplanetary ships so something using little 25 ton bombs weighing 25 kg or one ton yield a kilogram getting you 10 times the specific impulse of chemical rocket would is very nice that munition incidentally is basically the DV Crockett or w54 nuclear warhead that was designed for Frontline use by infantry you can do at least 40 times better than that which translates to 40 times higher specific or 40 times higher speed needless to say this would also work with more sophisticated

bombs like antimatter catalyze Fusion which would also be more Compact and probably ideal antimatter by itself would do even better but there's easier ways to harness that as a rocket fuel but if you're applying to tow and O'Neal cylinder to another solar system I think you can't justify using even nukes in the 10 Megaton region as your fuel and propellant that means a much bigger sale or a stronger one probably both but graphine might be ideal for that role that also let you contemplate teos hundreds of kilometers long maybe even longer you might wonder why

and in this case it brings up a thir Advantage the Medusa has over an Orion in that the explosion can not only be further from the ship but also further from whatever the ship is leaving a ship in orbit of Earth that starts blowing nukes off to leave is likely to find itself shot down but if it had a th000 km long tether between it and the Medusa sail it could be detonating nukes way up there instead and smaller ones in particular would be rather harmless that far up I think you'd unfur that and have

a beam pushing system shove you out past CIS luno space it saves Fuel and also means you could pass them off their packet of nukes only as they left CIS luno space you also be using that sail as a parachute against solar wind and sunlight as you enter your destination system or dragging the ism interstellar medium as you approach both of which are more effective the faster you are going so you use a laser sail to help you get to speed and you use the parachute approach on the ism to slow you from highest speed

and the nuk to finish slowing from higher speeds and then solo Sals for helping you as you get slower and enter the brighter regions of a star system possibly deploying some smaller solar power beaming system at this point just ahead of you to further help you slow or to help slow other ships following your wake why send a big Colony ship when a colony Fleet might work better as with many of our spaceship designs it tends to do best when used in tandem with other systems though as always there's a cost to trying to employ

and maintain multiple Drive systems this would tend to use the same material same repair Crews and same onboard Manu facturing and recycling so it works well together it's awesome because it allows Interstellar travel without any new technology much like the Orion as opposed to options like gravitic propulsion that we discussed later this month on December 15th but I thought we'd finish up today by talking about its interplanetary version and for use out beyond the inal system where sunlight is getting a bit thin to use for power or propulsion and keeping a tight beam on a

ship generated from the inner system might be impractical needless to say if you're trying to leave an asteroid base or a comet you can't be setting off a nuke right next to it so you rather need traditional thrusters which are very wasteful or some sort of launch assist from them which requires significant infrastructure on their end or you can employ the Medusa to detonate the bomb a ways away and yank you clear so we use the Solem 1990s design specifically being mindful it could be upgraded in many ways those 25 5 ton bombs don't need

to be very far off to be safe that is a huge explosion but we have conventional explosives of that scale like the Moab 11 tons or the bigger Russian foab 44 tons respectfully short for the mother and father of our bombs and both still a thousand times weaker than those nukes used at the end of World War II still big but not doing damage miles away it might seem surprising that the design calls for a tether almost 5 mil or 8 km long especially when the spinor is just a kilm wide but that's less about

protecting the ship than giving the tethers a lot of stretch you are essentially storing the blast energy into them they could stretch quickly and relax more slowly Distributing the pool and this case a tether that long for a blast that big will keep your pool to about 1 G and of course it's teos plural and a lot of them too they are about a millimeter wide myar tether one amusing limitation on Tether and why it's handy to have many skinny ones is they will warm up from stretching and relaxing and that heat has to radiate

away a million teers with the same cross-section as a single big one a thousand times wider will have a thousand times more surface area to radiate with in this version you will be detonating bombs rather quickly too on order of about 20 to 25 a minute you are practically machine gunning them out and that makes them a produce a ship a pretty terrifying Target if one pulls up to your planet to engage in trade and a dispute rises though presumably you have far more weapons on your own orbital defense platforms obviously you can go slower

with your detonation rate but there's no advantage to detonating your bombs at a slower rate than your ship can handle mass of the tethers bombs and canopy probably are around half or more of your ship for the same reasons they always are under the tyranny of the rocket equip more fuel in engine higher speed but you could go quite small in your drive and fuel Mass with one of these and still pull off respectable speeds the core design is something that could get you to Ms in say a month in the basic design it assumes

10 tons of canopy and 50 tons of Space Capsule for the crew and cargo it all depends on your fuel ratio and how energetic that is per mass of fuel as a loose calculation it would generally exceed whatever an Orion Drive can do as the Orion drive's flat plate does not absorb as large a percentage of the blast as the hemispherical Medusa and you'll see aan Drive estimates as high as 5% of light speed higher than that too but on more dubious footing and the Medusa would beat that out as its sail weighs less and

it uses more of whatever bomb you're using for the Orion now as noted you can build much higher yield to mass ratio bombs than what I'll just nickname the D Crockett Medusa and this was hardly lost on the developers of the idea the concern is if your teos can handle a bigger bomb stretching them and again we didn't have graphine or Nano tues when this was proposed and from a practical perspective we still do not but another workaround was proposed the servo winch to get around the bungee jumping aspect of the tethers that stretches them

out and could get impractically long for even hyp strong materials an appealing alternative is to use a winch system upon detonation a motor generator powered winch would release the line to the spinor at a pre-programmed rate ensuring constant acceleration for the Space Capsule during this phase the motor generator generates electrical power which can be efficiently stored once the capsule reaches the sple speed the winch would then reel in the line at a controlled rate again maintaining constant acceleration this retraction phase would produce less acceleration than the release phase resulting in a net gain of electrical

energy conceptually you can think of this as throwing out your Sail on a fishing line playing out as the bomb shoves it forward and reeling yourself back in more slowly behind it it also gives you a good way to convert some of that blast into a reasonably steady Electric Supply though in no circumstances are you detonating bombs the entire trip unless maybe you're a speedy yard not traveling between two moons of a planet you'd run out of fuel and would do better to accelerate faster a nuclear reactor RTG hardly seems a concern for a steady

power supply when the ship is carrying a massive Arsenal with it anyway that's a good point to close on because the idea of a ship powered by nukes obviously brings up misuse I have no easy answer for that just some solutions like keeping the fuel packages at secure sights in orbit of Earth that could toss them into the ship once it was leaving syis Space by other means or by launching nukes at ships entering inhabited systems rather than having them carry their own slowdown nukes but we always need to be mindful of the reality of

spaceships and another common say on this show is that there's no such thing as an unarmed spaceship it takes nuclear power to get a ship to high speeds because it's all that's energetic enough and that ship even if it's pushed up to speed by sunlight or some magic War ho drive with no onboard fuel still has a terrifying amount of energy moving at 1% of light speed it not only could Ram someone but it could simply shoot a 2 kg slug off at something to Ram it instead striking with 9 trillion Jews of energy just

over 2 kilotons of damage and so seven of those would strike an object with the power of the little boy atomic bomb used in 1945 no special weapon needed they could have checked a handful of garbage out their airl lock this does not mean nukes are safe just any spaceship traveling at these kinds of speeds is incredibly dangerous for my part I think that means embracing nuclear propulsion as it simply does so much better than methods currently employed but your mileage may vary we talked about more nuclear systems in detail in our episode the nuclear

option and of course more advanced spaceship drives from the mundane to the highly theoretical in our advanced spaceship Drive compendium and as mentioned we'll be deep diving gravitic propulsion Concepts in a couple weeks but for now let me know what you think of the Medusa drive and its cousins leave a comment in the episode description below or join in the chat on any of our Forums on Facebook Reddit or Discord and don't forget to hit those like And subscribe buttons we've been talking about Advanced spaceship drives today and a lot of our audience would like

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so we talked about inell spaceships able to take us to new worlds today and next week we'll ask how technology might permit more Off the Grid living in the future like allowing remote settlements on new Wards or habitats in the spaceships that Carri us there after that we'll explore another far more theoretical spaceship Des design as we see what science has to say about gravitic spaceship proportion then we'll return to something a little more grounded in the here and now as we look at Giant space elevator tethers attached to the ground and the improvements and

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