The Dismal Feasibility of Solar Corona Breaking & Corona launch

About a week ago I wrote a bunch of fun math in a (mathematica) notebook mostly as idle daydream entertainment... but all I tried to be accurate with all the math. 

So imagine you've built a star ship bigger than an oil supertanker and sent it out toward a habbital world.  And to ruin the fun, imagine you have to use real physics, and it's going to take multiple generations to get there and your propulsion is powered by onboard hydrogen reactors - a "just 30 years away" technology that might be ready in two hundred years.  And lets imagine a reactor and relativistic thrusters that "burned" hydrogen fuel into helium and spit out the helium waste at very close to the speed of light, so that said ship's thrusters can use and push with the relativistic momentium equations (p= MoV / (1-v^2/c^2)^0.5). 

Part of the "anti-fun" in going somewhere with Einstein's physics in space is that your gas petal and break are exactly the same thing.  Your fuel filled spaceship is sort of like a full can of soda, about 394grams full and 15 grams empty... so the closer you get to your target, the more sporty your ship is going to handle - so long as your thrusters stay the same.  In such a spaceship, Full engine thrust that started at doggish 1/26th of earths gravity by trips end (with empty fuel tanks) would feel a bit stronger than gravity we get here on earth.  (reality check, good luck even hitting 1/26th of a g from the thrusters even at the end of the ride.  Thrust would likely be far lower.)

This of course presumes most of the ship is going to be fuel... which only seems to be a requirement of impatient sorts like... well... most of humanity.  As the fuel to cargo ratio changes, the ship takes hundreds more years to get to destination, largely because it spends more time "breaking" and you have to carry more fuel to carry the fuel you carry in cargo in a unproductive loop.  Breaking here means the ship has to slow down by pointing it's thrusters at the very thing it wants to get to and blasting away so that it doesn't blow right into.

So this got me thinking, could a ship do solar corona breaking?  The corona is plasma, has inertial mass and plasma resists magnetic fields.  So just generate a huge magenetic field and crash into the solar plasma at whatever force you'd like as you can in theory vary the magnetic field size impacting the plasma.  Reality check - slowing down means magnetic coils get heated by a large fraction of the change in kinetic energy - speedy thing go in, molten thing come out - just from the helfire magnetic antenna wave absorbing bellyflop never mind that the sun is hot.  So it isn't hard to imagine a ship that could get close to the sun and fuel scoop or plasma/aerobreak, although survival with current tech is problematic.  If the breaking arch through the corona was 1% the sun's radius at 43700 kilometers, and said ship & crew could tolerate 5 times earths gravity while breaking through the corona in a peircing arch, that break manuver would take 944 seconds.  And in 944 seconds at 5g the hellfire plasma corona breaking manuver nets a 46270 meters per second speed reduction.

46 kilometers per second sounds fast.  It's about what it takes to get out of our solar system if you start near the sun.  And yet, even if you exit our solar system at that velocity expect to wait 34 thousand years before you reach the next star.  My hope is a 'Hypothetical popcan space ship' would be able to do it in less time... and if it could, why bother with a dangerous scortch mark breaking maneuvors?  

Even if the solar corona breaking manuveur covered a nice 1/4 arch around the sun the breaking only subtracts 231km per second in speed and increases "bake time" to about 78 minutes, provided the break acceleration stays at a survivable 5 times earths gravity.  I argue that most humans could survive 5g, the crush of 4 people stacked atop them for 78 minutes, with a respirator floating in a shallow pool.  The padi dive tables seem to indicate so, but still given the pressure gradients, with some risk of stroke, lung embolism and alveoli rupture.   

Corona bellyflops only makes sense if popcan space ship launches with near empty tanks - cannon style - with 1/25th fuel and then ends with a coronal belly flop that somehow earned a refuel.  A minimum fuel strategy... might be viable.  But is hard to do with real physics and real materials, so hard it might be nearly impossible to do bellyflop refuel leaving compression heated fusing star plasma in a "tokamak reactor shaped mega sized fuel tank that is just about hot enough to undergo fusion and blow the tokamak apart.  Hmm... maybe if the bellyflop fuel collection intentionally detonated collected fuel ram-jet retro rocket style it would work out.  But that's a bit beyond my math play.  

And that brings us back to a dismal future where fast spaceships with low fuel to ship crew and cargo ratios are painfully impractical.  Magnetic Plasma Bellyflops with less fuel are not likely to be a thing, not because stars are too hot, but because strong magnetic fields that could slow a ship need so much energy to run and unfortunately effectively convert some percentage of decades worth of reactor output (reactor energy->kinetic energy=speed) into electromagnetic coil heat in just a few minutes with predictable 'so hot they explode' results.  

And so the reality of space travel is slow.  Unless you can send ultra-low mass ships with a crew of cells that grow into humans on arrival, expect multiple generations worth of travel time.  Still, maybe my grankid's grankid's could leave sol and set sail someday.

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