/sci/ - Science & Math

>>9533849
Never going to happen unless it's pure fusion

>>9533849
>travel to other stars
dumb popsci faggot

>>9533849
Might reach 5 or 10% of lightspeed -- and still be able to stop at the far end.
The cost of an H-bomb is mainly in the fission-trigger. Hopefully, we find a more "elegant" method, either continuous controlled fusion or tiny "bomblets" (equivalent to a few kilograms of TNT each) which could be ignited by converging lasers or electron beams.

Probably the most advanced prospect for Manned starships we can think of at present.

impractical

Environmentally destructive. My family's been hardcore anti-nuke activists and we'll be fighting tooth and nail to prevent militarization of space.

>>9533849
We would never risk the rocket exploding upon liftoff and contaminating the whole planet.

Fusion would be fine though.

>>9533912
>anti-nuke activists

>>9533912
You people are genuinely worse than luddites, at least they actually have some points to raise about how fucked modern technology has made things.

All you morons can do is scream and throw tantrums while holding back our entire fucking species.

>>9533969
We're holding the species back from extinction. You're welcome.

Orion isn't fast enough to explore out solar system.

>>9534005
>There is already a hole in the ozone layer.
>Shoot the rocket through the hole.
>Crisis averted.

Congratulations.
You played yourself.

>>9533875

fusion won't be allowed either because it has the word "nuclear" in it.

>>9533849
Well, liftoff is a major no-no.
This 10th of thousand tons device would have to be built in space if you don't want to loose a fucking 1000 km2 worth of land from radiation.

>>9534084
Think of it this way.
>1000 km of REUSABLE rocket land.

>>9534097
Yeah, let's launch people into space from a radioactive area.

>>9534105
>Launching people

Robots and materials.

>>9534005
Delusional/10

>>9533849
https://www.youtube.com/watch?v=RE16UK2o1Yk

>>9533849
>NUKE
>NUKE
>We come in peace
>NUKE
>NUKE
>NUKE

STOP EATING THE BAIT YOU FUCKWITS

>>9533905
Laser sails are a thing, and are more controllable
could turn the sun into a laser projector for interstellar ships

>>9533883
why?

>>9533912
>to prevent militarization of space

>>9534571
They're too far away

>>9534562
A solar-powered laser near the Sun and a monster Fresnel lens out beyond Neptune.
https://www.space.com/22799-interstellar-solar-sails-light-propulsion-infographic.html

Turning the Sun itself into a laser...
I saw that Isaac Arthur video too. Can't fault the man for thinking small, but....

It is the best feasible idea we have for space exploration right now. I saw a presentation by some meme scientists, you know of him, who said it would endanger us to terrorism. I don't see how it would more than nuclear subs, and nuclear subs are probably a lot easier to get at than one of these. Security is of course key, so international development is out, but a joint US military and NASA project makes sense.

>>9534075
It could be. You can get up to meaningful fractions of the speed of light.

>>9534005
You mean well, but the only way we are going to avoid extinction is to collonize space and that is going to require tech at least as dangerous as nukes.

>>9533912
I guarantee that you and your retarded family have absolutely no clue how nuclear technology works nor the power output compared to fossil fuels.
I bet you have an orgone buttplug in your ass as we speak.

>>9534714
>Gather the nuclear arch-wizards.
>Threaten to obliterate the entire planet if we are not allowed get the fuck off of it.
>Leave these plebes behind and come back a few thousand years later to obliterate the planet anyway.

>>9533912
My family, too, hates human progress and tries to stymie it at all levels.

>>9534105
Since they will be traveling on a ship with nuclear bombs firing out the other end, there is no reason why the relatively small amount of radiation would be a problem.

>>9535796
It would be less of a problem with some shielding.

>>9533849
it's the obvious way we're ever going to be able to get to other stars.

1g acceleration trips made possible by the energy density of nuclear fuels

>>9533849
>>9533875
Neither fusion nor fission pulse is a viable interstellar propulsion device. Orion does make for a readily available way to do interplanetary within very acceptable timescales though.

If we're going to the stars it's gonna be by lasersail. Only pure antimatter rockets can even remotely compete but those come with a bunch of obvious... disadvantages.

>>9536715
The effective exhaust velocity of nuclear pulse propulsion is usually estimated at 3000ish seconds. Aka an exhaust velocity of 30kmish/s. Aka the same deltav at mass ratio of e (2.7ish).

That's good for getting to Mars or Jupiter in weeks or months respectively, but going lightyears would still take generations.

>>9533849
Hippies will never allow it nowadays. We could have got away with it in the 60s if Kennedy hadn't been a pussy and kicked the USAF off the project. There are risks sure but they're not as bad as people think.

>>9534084
Air bursts are pretty "clean" and don't give a lot of fallout. What there is rapidly dissipates. You really only have to worry about the launch site and even that would be safe enough to go about shielded after a few hours. Plus the warheads you'd use in atmosphere are small devices, a few kilotons max. You launch in a remote area and head out over unoccupied territory and you'd be fine. Main concern isn't radiation but actually EMP effects from charged particles getting caught in the Earth's magnetic field. These effects can be minimized by launching from the right latitudes into the correct inclination but you're still going to muck things up in certain orbits for a few hours.

>>9533875
what fanciful idea do you have about fusion that makes you think it's so drastically different from fission?
>>9533912
>>9533913
nuclear-powered sea-going vessels just dump their irradiated water into the ocean and your complaining hasn't stopped shit, and it won't fucking stop the nuclear-powered rockets when that time comes.

They've already built and tested nuclear powered rockets, right in our atmosphere, outdoors, at ground level. Your shit didn't stop it then, it won't stop it now, it won't stop it ever. Shut up. Sit down. Take your cancer meds.
>>9535796
we've proven that there are more efficient ways to use nuclear fuel than just tossing nuclear bombs out the back

>>9536730
>nuclear-powered sea-going vessels just dump their irradiated water into the ocean and your complaining hasn't stopped shit, and it won't fucking stop the nuclear-powered rockets when that time comes.
This will only happens if the chinks decide to militarize space. Turns out the Vodkaniggers and Amerimutts were too pussy to actually build orions. There is not much immediate motivation for initial space colonization besides preventing your enemies from getting there first.

>>9536730
>Update

Even without nukes our air is already irradiated.
Our cells die at 1.5 million per second.
EVERYTHING IS ALREADY DEATH REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

At least maybe we will have a fighting chance against the odds in a world where space is just an everyday thing, as it stands now, a single barrage of meteorites and we ALL go bye bye.

>>9536730
>what fanciful idea do you have about fusion that makes you think it's so drastically different from fission?
Pure fusion devices in theory give a better specific impulse for Orion drives and would also result in less fallout for ground launches.

>>9536806
>fusion reactors are fusion bombs we could all die any second now!
>fusion reactors emmit dangerous neutrinos that pass through everything even lead and cause autism!
>fusion reactors generate heat accelerating global warming!
>fusion rockets can be set to hover over populated areas and kill people!
Fusionfags are under the delusion the hippies and whoever decides to make use of their idiocy will let them play with energetic toys. Seems history teaches nothing.

>all the art is for tiny demonstrator versions of nuclear pulse propulsion

The true benefit is that you could build a million ton vehicle, out of steel, single stage to Callisto

>>9533849
using nukes astern to accelerate: fine
using nukes ahead to break: bad idea

>>9533849
>wasting more then 95% of the explotion's energy which is already a small portion of the energy in the fuel
i dont think that shit's gonna happen

also very short bursts of very powerful radiation which means either very heavy shielding or some active shielding (which dosnt protect against everything )

>>9536724

Focus gets too diffuse at interstellar distances.

Try antimatter.

>>9537123
The direction you fire makes no difference. The exhaust still travels "away" from the ship.

>>9537133
Bomb propulsion does indeed waste a great deal of energy and momentum. A controlled fusion rocket would probably be much better.

Project Orion had only one advantage.
We KNOW how to build fission and fusion bombs.
We don't know how to build a fusion motor, and fission motors do even less well than bombs because we have to run them at temperatures which don't destroy the motor. Couple of thousand degrees. Bombs can expel matter at velocities equivalent to millions of degrees because they're intended to self-destruct!

>>9533849
That does not make them any closer.

Travelling to distant stars takes Thousands or even millions years unless (in the frame of the traveller) you're able to do it at relativistic speeds, but this would require impossible amounts of energy and would be actually hazardous, the smallest dust grain being more harmful than an atomic bomb if you hit im at more than 250000 m.s^{-1}

>>9537181
waste is irrelevant anyways, almost all the energy of chemical rockets is "wasted" too

>>9537638
efficiency is very, very important when going interstellar, as the amount of fuel you require is fucking ludicrous under the best circumstances

>>9534005
No, you can thank M.A.D. For that. Can anyone else not fucking stand it when talking about politics and people actually believe we are living in the most peaceful time due to democracy? Instead of you, nuclear fucking weapons?

>>9537640
no its a question of cost, Isp, thrust, etc
Not the amount of fuel or what useful amount of energy you can derive from each ton.

>>9537684
*know
>I’m not phone posting on the shitter. I swear.

>>9537144
The HUGE lense keeps it focused. I forget how big Forward says the lense is, but it's REALLY BIG!

Would we be capable of making a spacecraft that would be capable of accelerating at 1g half way, then decelerating the other half continuously from Earth to Mars? Could a Fusion powered ship do that?

>>9537745
Ever heard the term torchship? Fusion could let us build them.

>>9537757
Would direct thrust be better suited for this? or would using an electric propulsion system be better?

>>9537144
so build a relay highway for this purpose

>>9537778
Direct thrust all the way

>>9539386
>>9537778
If you build the ship for this purpose, you can time the pulses to give a linear acceleration feel to those onboard due to the shocks.

>>9537638
Waste is QUITE relevant.
Chemical rockets are barely up to achieving orbit.
They can't afford unnecessary losses. That's why all boosters nowadays use strap-on solids to minimize that initial "crawl" when thrust barely exceeds the weight of the fully-loaded booster.

But, yes, most of the energy of a rocket is "wasted" until it attains a speed comparable to it's exhaust velocity. Most of the energy in the fuel winds up as heat in the air.
That's why all schemes for rocket-powered cars, locomotives, ships, and (most) airplanes are insane.

>>9537686
The amount of energy you can derive from each ton IS what determines the Isp.
Some fraction of the energy released constitutes the KE of the exhaust.
"Pure" uranium fission (just expelling the fission fragments aft) would give you an exhaust velocity of a little over 4 percent of lightspeed -- an Isp of about 1 million.
To reach 10 percent of c (and stop at the far end) would take a mass-ratio of 110.

Of course, cost and thrust matter too. No point bankrupting the whole world to send a kilogram to another star in a few hundred years. No point in building a craft which could attain 20% lightspeed -- after 100,000 years of operation.

>>9537745
A fusion torchship MIGHT be capable of boosting all the way to Mars at 1 gee.
Image shows a 100 metric tonne (empty fuel tanks) ship going to Mars when the planets are at their closest. The drive is deuterium-tritium fusion and you start with 6 tonnes of fuel.

Total energy used during the flight -- 481 megatons (nearly ten times the Tsar Bomba!)
Energy release is 3.2 kilotons/second
That's Hiroshima every five-and-a-half seconds! You do NOT want to get in the way of the exhaust.
The power is 13.5e12 watts. ASSUME the engine is 99% efficient. Wildly optimistic!!!! That leaves you with 13.5e10 watts inside your own ship, which you have to dispose of by radiation. That's 135,000 megawatts.
For comparison, the Hanford reactor (intended to produce Plutonium) had a thermal output of 250 megawatts (two-tenths of a percent of what we're talking here) and required 30,000 US gallons of cooling water (110,000 L) per minute.
The radiators are going to be large, fragile, and likely to limit the ship to very low accelerations. The Epstein Drive, this isn't!

>>9536724
how do you slow down something that got accelerated by laser sail? assuming it's the first to go where it's going

>>9539545
If you look at the picture in >>9536724 you'll see the sail is ring-shaped with a small detachable center section.
Light from Earth is reflected off the ring. It gets driven to even higher velocities, but the reflected light decelerates the central payload section.

Obviously, this all takes very careful aiming.
And you don't set out until you're confident the people back home with the laser won't lose interest in the project while you're in transit.

>>9534105
only really deadly for the first few weeks

>>9539541
That is interesting, thanks.

>>9539676
You're welcome.
The problem with efficient rockets; i.e. those with good specific impulses and low fuel flow rates (you can see how "thrifty" >>9539541 is) is that momentum varies directly with the exhaust velocity, but the energy in the exhaust varies as the SQUARE of the velocity. The "ultimate" exhaust -- pure light -- carries very little momentum for the amount of energy it takes to create it. That's why flashlights don't recoil.

Larry Niven turned this into "The Kzinti Lesson". The Kzin had some sort of non-rocket space-drive and their ships could run rings around Terran craft. But the exhaust from Terran fusion motors cut the Kzin to ribbons.

>>9539467
>Waste is QUITE relevant.
Of course its relevant, but the optimization is for cost, not for Isp

Thats where all this nut talk about fusion drives comes from. Rather than sane practical ideas of EPP drives

>>9539781
Thats just one of those old sci-fi tropes of "low tech beats high tech" nonsense.

>>9539541
What if you made the propulsion system an open cycle? Meaning, the majority of the heat gets tossed out as the exhaust. Meaning significantly less need for radiators.

>>9539887
how do you dump heat into an exhaust that is millions of degrees

>>9539898
Nein. What I meant was to develop something like a chemical rocket. In that the exhaust IS the waste heat. All of it is being shot out of the rocket. So what I’m saying is, could we use a form of fusion propulsion that uses the same design principle. As in, shooting the plasma n sheit out the ass of the rocket to get rid of heat that way.

>>9533912
god anon, I haven't laughed that hard in a long time

>>9533849
>hey guys what do you think about using nukes

>>9533912
What exactly are you doing on /sci/ then?

A generation ship with nuclear pulse propulsion is probably the only hope we'd have of surviving as a species if we detected a planetary threat.

>>9539861
Mass-ratio (and, therefore, cost) scales VERY rapidly if you change the Isp.

If your required dV is, say, 3 times exhaust velocity you need an R of 20.
If you switch to a less expensive fuel which only has half the exhaust velocity, R goes to 400.

Even if the cheaper fuel is only 10% of the price per lb, it's still not worth it.
It all depends on the mission parameters.
You shouldn't generalize.

>>9539887
When I offered those calculations, I WAS thinking open cycle where the majority of the heat goes out the exhaust. 99% efficient, remember?

Nuclear thermal rockets can't even achieve the temperatures chemical engines do. Burning H2 in O2 releases the heat IN the gas. In a fission reactor, the fuel elements and support structure must be hotter than the gas (often quite a bit hotter!) or there's no heat transfer. And you can't let your engine melt! The advantage of NTRs is the low molecular weight of the hydrogen exhaust. The molecules move much faster at a given temperature. I covered some of this in >>9537181

In a fusion rocket we have to assume the energy goes straight into the KE of the reaction-products, analogous to the way a chemical motor works. You use some sort of magnetic bottle with a deliberate "leak" to keep the gasses from touching the material structure of the engine. But there's nothing you can do about the EM radiation from the reaction, visible light, x-rays, and gammas. Whatever impinges on the engine is going to turn into heat. Even 99% efficiency isn't good enough when dealing with the magnitudes we're talking here.

We don't have controlled fusion, yet, so all current plans for extremely high ISPs (10s of thousands of seconds and up) are ion drives or plasma engines. They take electricity. Converting heat into electricity requires heat exchangers, turbogenerators, condensers, and it's a LOT less than 99% efficient. Typically, half the heat or more is thrown away. Thermodynamics places a strict limit on the heat-to-useful energy efficiency.
So ion drive craft are limited to low accelerations.

>>9539987
KE scales with the square of velocity, while Isp scales linearly with exhaust velocity
The highest possible Isp will never be the optimal choice.

Obviously we can talk about a fictional fusion torch drive, but they aren't a reality yet, nor anywhere close.

So for the foreseable future, even if an interstellar launch took a million tons of plutonium & tritium, thats how you would have to do it.

>>9540034
>And you can't let your engine melt!
Your engine can't melt if the fuel is already a gas.

https://en.wikipedia.org/wiki/Fission-fragment_rocket

>The fission-fragment rocket is a rocket engine design that directly harnesses hot nuclear fission products for thrust, as opposed to using a separate fluid as working mass. The design can, in theory, produce very high specific impulse while still being well within the abilities of current technologies.

>With exhaust velocities of 3% - 5% the speed of light and efficiencies up to 90%, the rocket should be able to achieve over 1,000,000 sec Isp.

https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

>A nuclear salt-water rocket (NSWR) is a theoretical type of nuclear thermal rocket which was designed by Robert Zubrin.

>The fission reaction in an NSWR is dynamic and because the reaction products are exhausted into space it doesn't have a limit on the proportion of fission fuel that reacts. In many ways this makes NSWRs like a hybrid between fission reactors and fission bombs.

>Due to their ability to harness the power of what is essentially a continuous nuclear fission explosion, NSWRs would have both very high thrust and very high exhaust velocity, meaning that the rocket would be able to accelerate quickly as well as be extremely efficient in terms of propellant usage. Such an engine being able to produce both high thrust and high ISP is a very rare trait in the rocket world

>it would be plausible to use another design which would be capable of achieving much higher exhaust velocities (4,700 km/s) and use 2,700 tonnes of highly enriched uranium salts in water to propel a 300 tonne spacecraft up to 3.6% of the speed of light.

>>9540608 allows the fuel to melt, and loosens the temperature limits, but the rest of the engine still has to be cooled. Note "to radiator" caption. Performance is improved, at the cost of losing tremendous amounts of expensive fissionable material -- quite a lot of which has yet to undergo fission. No one ever solved that problem, not even "lightbulb" designs.

>>9540617 is halfway to being an "Orion" and shares some of that concepts advantages and disadvantages. Zubrin's original plan had the reaction just BEHIND the vehicle. Your diagram looks like it's INSIDE, but additional water is injected. Either alternative "dilutes" the thrust, just as Orion does. The NSWR still has excellent performance (though 10,000 sec is "just" 100 km/sec exhaust). See image. With an assumed R of 20, initial acceleration is much less than 1 gee, and a coast period is required. No one at NASA would object to a 5 day trip to Mars! (No one except the accountants!!) Not The Expanse though.

>>9540613 is new to me. The Wikipedia article really doesn't explain how all the desirable characteristics are achieved without overheating the engine (though gamma and neutron absorption, if nothing else.) It also concedes "technical challenges remain". Any additional references?
"Dusty plasma" reminds me of '50s concepts where radioisotopes are thinly plated on a backing sheet and allowed to decay naturally.

>>9540617, if you disagree with my assumptions, suggest a mass-ratio, exhaust velocity, initial acceleration (when the tanks are full), limiting acceleration (engine throttled back to avoid squooshing the crew), and total distance to be covered. I can run, and post, at least a few cases.

>>9540665

>No one at NASA would object to a 5 day trip to Mars!

stop, my penis can only get so erect.jpg

How about alternating or simultaneous fusion and fission?
Is it more possible using "fuishion"?
Is fuishion even theoretically possible?

>>9533912
>My family's been hardcore anti-nuke activists and we'll be fighting tooth and nail to prevent militarization of space.
Good luck with getting visa to China kek

>>9533849
Why do people think we would be capable of developing materials that can withstand a very close nuclear bomb detonation? That deflector plate would be all sorts of cracked and warped before we got out of our solar system. Material science is farther from developing that than we are from building warp drives.

>>9540968
The pusher plate is very large, the bomb is further off than you think it is, and there's no air so the only force on the plate comes from the vaporized bomb casings.

Famous case of an A-bomb set off at the bottom of a shaft. It is only an urban legend that the "manhole cover" was blown clear off the Earth. It probably vaporized from air friction. But high speed movies showed it zipping away, still intact, at several times the speed of sound,

Actual tests have shown materials can survive such blasts. Interestingly, they found a plate whose surface layer had vaporized -- except there was a raised fingerprint on the surface where the material had been left unharmed. The radiation had gone into boiling off the natural oils on someone's skin. So the plan is to "grease" the plate before a shot.

>>9539958
isn't it obvious? He is here to spy on us so we don't get out of line.

>>9540968
Here you go.

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

>>9533912
>to prevent militarization of space.
Implying It's a bad thing.

>>9541582
What use for military would we have in space? Are we fighting Martians? Enforcing the galaxy's immigration laws?

>>9541893
Militarization of space mean more money in space wich is always a good thing.

>>9536724
A generational orion would be a viable interstellar option.

>>9541893
Making Mutually Assured Destruction obsolete. Which in turn. Allows whomever has in space ABM systems (lasers n shiet) invincible to nuclear strike on a strategic level. And well, if you ever wanted to get rid of all of your opponents in the game of life without bad things being inflicted upon you. That would be a good time.

I'm not talking about shitty SDI shit either. Things that were origionally designed for in space solar power, such as using lasers to beam energy back to earth to be used for electricity had the small side effect of being incredibly easy to weaponize into something that could shoot down anything with ease. We're talking 10's of MW to even GW powered fiber optic lasers essentially vaporizing any ICBM and or warheads, and even decoy's. With ease. And the best part. You can send an entire complete satellite with a laser in the range of many MW to GW in one launch. I'm actually surprised /sci/ and /k/ don't talk more about this.

>>9541063
Cassaba Howitzer

>>9542701
The real fun lasers and particle beams would have taken more than one launch. iirc Zenith Star, the closest the US got to a functional laser satellite would have required two. And that was supposed to just be a test rig, full power system would have required multiple launches and/or new boosters. (Rumor has it that the proposed Shuttle-C's payload bay dimensions were set partly with launching such lasers in mind)

The only system that could handle a full strike in "one launch" would be bomb pumped lasers. Essentially you can make a rod in such a way that when you hit it with a shitload of X-rays (Sourced from a nuclear bomb) it focuses the X-rays into a laser. Enough power to kill just about anything. They destroy themselves when fired but a single bomb can power dozens of lasers. They're not that big either. You can send multiple up at once on most launchers. In theory they could have crammed enough of them into a single shuttle launch and invalidated the entire soviet land based ICBM force in one go. Decoys and all.

This thread is already talking about weapons of mass destruction and genocides.

This is why nuclear is wrong - anything it promises inevitably leads to human suffering and environmental destruction.

If you consider yourself intelligent it is a crime against everything not to oppose that evil.

>>9543004
>caring about the people that you are genociding
I don't think you know how to properly genocide people anon.

>>9542701
All the power-from-space concepts I've ever seen use microwave transmission.
Lasers have an inherent thermodynamic efficiency limit. (And the waste heat is difficult to get rid of in a vacuum) So does the conversion-back-to-electricity gizmo on the ground.
Microwaves are superior tor a power system. But they can't be focused into an "instant" death ray.

A power sat would be extremely vulnerable to an inexpensive load of gravel on an intersecting orbit.
And not all warheads need be lobbed in on ballistic trajectories. You may have read
>http://www.newsweek.com/russia-develops-doomsday-nuclear-torpedo-designed-wipe-out-us-coastal-cities-798946
This might very likely be "disinformation"; a deliberate leak to make the US waste resources countering it. But it would be logical if opponents took your fantasies seriously.

I don't think we are particularly far from doing this sorta thing, obviously the generation ship idea is a sham, what you would instead have is a autonomous ship that can grow human eggs in artificial wombs, or indefinately freezing people for travel to another system.

>>9533849
I think its a better use of nukes than using them to bully the only nation which achieved equality which was the ussr

>>9534562
that's not realistic with nowadays technology
the orion drive is totally realistic with nowadays technology

>>9536729
>Air bursts are pretty "clean" and don't give a lot of fallout. What there is rapidly dissipates. You really only have to worry about the launch site and even that would be safe enough to go about shielded after a few hours. Plus the warheads you'd use in atmosphere are small devices, a few kilotons max. You launch in a remote area and head out over unoccupied territory and you'd be fine. Main concern isn't radiation but actually EMP effects from charged particles getting caught in the Earth's magnetic field. These effects can be minimized by launching from the right latitudes into the correct inclination but you're still going to muck things up in certain orbits for a few hours.
just put the fucking thing in orbit with rockets, or build it in orbit all together,

when youre going to other stars, getting to orbit ceases to be "halfway to anywhere" like heinlein said

>>9545119
>just multiply costs and difficulty by 100
>whats the big dealio?

>>9545343
bruh just 3-D print the thing, fag.

>>9545119
You can do that but it slashes your payload.

>>9545343
>>9545050
>>9545119
Some of the people on this board are totally clueless about the scale of the universe.
The planets are a MILLION times further away than the Moon is.
The stars are a MILLION times further away than the planets are.

By the time we're prepared to build starships, students will be asking "back at the dawn of space travel, what the heck was so hard about going into orbit?" or "Why was 'reaching for the Moon' used as an allusion for 'an impossible goal'?"

Look up Project Daedalus! It was a British Interplanetary Society study for an unmanned probe to a nearby star. The goal was to have the trip made within a human lifetime.
That span didn't include the decades of building a massive industrial complex near Jupiter and mining the planet to obtain He3 for the Orion drive ("pulsed" fusion micro-explosions.). That didn't count because the technology and the fuel could then be used to make travel WITHIN the Solar System comparable to taking a mid 20th century ocean liner.

Rocket's don't work in space.

>muh third law

>>9545730
Correction: Jupiter is 'only' about 2000 times as distant as the Moon. And the nearest other star is 'only' about 50,000 times further than Jupiter.

So the nearest other star is a bare 100,000,000 times further than the Moon.
100 MILLION.
Sorry. Got carried away.
I stand by the rest of the comment.

>>9540608
Who says we cant? So long as it resolidifies somewhere else?

>>9540608
Candle Wax Problem.

>>9546094
Candle Wax Solution.

>>9545730
Mining jupiter is not ideal for He3
Saturn is the place to go

>>9546357
Tell the BIS, not me.
https://en.wikipedia.org/wiki/Project_Daedalus

Some flaws have been found in the original concept. A new study is attempting to correct some of these.
https://en.wikipedia.org/wiki/Project_Icarus_(interstellar)
Curiously, THIS link mentions Jupiter and Neptune -- but not Saturn.

somewhat related question. Is the Delta-V required for traveling from LEO to LMO (I took the avg distance between Earth and Mars:) 2,971 Km/s? If I did my math shit right(transit Delta-V=2*sqrt[D*A]), and I wanted a spacecraft capable of not only this kind of Delta-V but to also do it in a transit time of 84.13 hours(I used constant acceleration of 9.81 m/s for the transit Delta-V). What kind of propulsion system would be used? I'm also assuming nuclear power is going to be used, either to power the propulsion device or be the propulsion itself. What would it be /sci/? What would you use?
>Pic unrelated...Or is it?

>>9547146

See >>9539541 for continuous 1 gee boost. That requires AT LEAST a controlled fusion rocket. And probably monster radiators which you didn't include.
Look at the power. That's for a quite small ship (nothing like your monster).

>>9540617 and >>9540617 discuss the nuclear salt water rocket, which is something we MIGHT have been able to pull off if we'd begun in the 80s. It would require more highly enriched Uranium that has ever been produced (even if you count in those countries which probably have fission bombs but swear they haven't) and a LOT more than $24 billion dollars.

>>9547146

See >>9539541 for continuous 1 gee boost. That requires AT LEAST a controlled fusion rocket. And probably monster radiators which you didn't include.
Look at the power. That's for a quite small ship (nothing like your monster).

>>9540617 and >>9540665 discuss the nuclear salt water rocket, which is something we MIGHT have been able to pull off if we'd begun in the 80s. It would require more highly enriched Uranium that has ever been produced (even if you count in those countries which probably have fission bombs but swear they haven't) and a LOT more than $24 billion dollars.

>>9547249
Probs a really stupid question, but. If you increase the flow rate, would that help expend away more heat? Allowing for smaller radiators? Could there be a sweet spot between mass flow rate and fuel needed to do the mission in the first place?

Anyone here actually work at a space company?

>>9547418
You want a certain amount of thrust. Whatever it takes to apply 1 gee to the current mass of the ship.
Assume the motors don't change. Two motors, each identical to the original, will consume twice as much fuel, produce twice as much thrust, and need twice as much heat removed.

On the other hand, suppose you double the flow rate but halve the exhaust velocity. Thrust remains the same, but the energy in the jet (and the energy to be gotten rid of) halves. This solves your problem! Except that the mass-ratio goes up. Your ship is 99.999 percent fuel -- and you need motors the size of Connecticut (figuratively) to produce 1 gee at the start when the tanks are full.
Chemical rockets don't need radiators because chemical fuels lack the energy to produce exhausts faster than about 5 km/sec.
If, as you estimated, the dV is 2971 km/sec, then the mass-ratio for a chemical rocket is 1.15e258. There's not enough matter in the Universe to propel even a single atom to that speed. :)

If MILAB has produced such super-duper spacecraft, why is Kim Jong-un still alive?

>>9547477
mass-ratio is a bitch, that is what I have learned in this entire thread
>If MILAB has produced such super-duper spacecraft, why is Kim Jong-un still alive?
Because he holds the time crystals. Get with it.

>>9541582
this, ever since I was a kid I was waiting until we found aliens to blow up like in Halo or Doom. Obviously that's not happening but I'll take blowing each other up in space as a close second, it could be fun

>>9547484
Yep! The rocket equation is depressing when you apply it to interstellar flight. However, continuous boost is possible within the Solar System, if you're you're willing to settle for a fraction of a gee. Remember, transit time varies as the square-root of the acceleration.
It's 18 days to Pluto at 1 gee, and 180 days at 0.01 gee. Half a year. A little long for a Space Opera, but it took New Horizons 9 years -- and "only" that long because of a gravity assist from Jupiter.
Mars is 18 days off at 0.01 gee at its closest to Earth.

I know what "time crystals" are in IRL.
Are you referencing a videogame or a TV show?

>>9533875
PTBT bans the use of nuclear explosions to fare space desu

Anti gravity explosion maybe a alternative option

>>9547146
If the USA has UFO starship technology then why can't they get their shitty orange rocket off the ground?

>>9547621
Using >>9540665
ship, If we were to position fuel depot's within the asteroid belt or around Mars. Would we be able to significantly reduce travel time for voyages to the outer solar system(gas giants, Oort cloud)?

>>9534630
Lets being them closet then

>>9547787
No.
Required mass-ratio varies as the square of the dV. If it takes, say, an R of 5 to reach so-and-so many km/sec, then it takes a R of 25 to slow down again. If we didn't have to carry the fuel to decelerate there'd be a TREMENDOUS savings. Ships could be smaller, lighter, cheaper, faster. So we carry just enough fuel to reach Mars and rely upon the pre-positioned fuel already orbiting the planet. Right?

Upon reaching Mars, we zip right past the fuel depot (and the planet) at many km/sec. Before we can refuel, we have to match velocities with the station -- which is what we were trying to avoid doing!

Nothing wrong with launching a fuel capsule on an orbit which will be passing Mars (at high speed) just as the ship arrives. Refueling is easy then. The ship can brake -- but the fuel tank goes right on out of the System. It's a one-time deal.

Back in the '40s it was a fairly common SF trope to have "service stations" set up in places where a crippled ship could limp to. You see why that won't work. Relative velocity is just as important as nearness.

I started reading the books The Expanse is based on. A ship gets a distress call. They are the closest craft so they're legally obligated to respond even if it costs them a bundle. Space is not like ships on an ocean. Another ship might be ten times further -- yet able to reach the cripple sooner if their vector is more favorable.
Suspension of disbelief collapsed and I stopped reading. :(

>>9548203
The expanse is based on magic drives with unlimited delta-v & thrust, so it does make sense there... kinda

>>9534571
it's too hard and expensive.
yet pop-sci give the false impression that it's easy.

The probability that our grandsons will live on mars is nearly zero.

>>9548213
I recognized it was all handwavium.
It still takes time to decelerate (the "magic" doesn't include neutralization of inertia, does it?) -- and maybe go back.

If you're willing to overlook the nonsense, I hear it's a decent series.

>>9537181
No. you fly directly into a radioactive orb when you brake wrongly.

>>9549405
>No. you fly directly into a radioactive orb when you brake wrongly.

I have a retarded solution!

We brake using a wire attachment "anchor".

Now, it is a real spaceship.

>>9549425
What is the smallest nuke we can feasibly ride on?

>>9549432
170 meters of steel rope would be necessary to attach the anchor to. The rope itself would probably break unless you perfectly timed two nukes to cancel certain forces along the middle.

>>9549456
Two words.
Blast wings.

>>9549462
This is officially the most retarded spaceship in the world.
I love it.

>>9549405
You don't understand the concept of "inertia", do you?

I'll tell you the Big Secret, but you must promise not to tell anyone else: There is no air in space. No headwind. Stand on the hull and fire a gun in different directions. The bullets all recede at the same velocities. The ones fired "in the direction the ship is moving" don't slow and come back to hit you in the face. Neither does the rocket blast.

>>9549614
You don't understand the concept of "relativity" do you?

That ship is supposedly being slowed after speeding up with many times the energy now being used to slow it down. The mechanism supposedly being an aforementioned nuclear explosion. When the ship encounters the first explosion it will "sink" into the now stagnant cloud of radioactive materials. Congtatualtions you have now irradiated everyone on board the ship.

>>9549432
iirc the smaller Orion designs were slated to use subkiloton devices in atmosphere (Few hundred tons yield), but you could go smaller. They built a proof of concept model that used a couple kgs of C4 for the pulse units and it flew fine. Of course once you get that small you've lost all of your payload.

>>9549360
Well if you accept the handwaving of everything science related, then you could accept the hand waving of "nearness" taking into account relative velocities/trajectories.

>>9549663
You still need a minimum critical mass of plutonium to make the bombs
You can't use a lower amount, I believe its classified, but you could guess its somewhere below 5 kg of Pu

>>9549723
Unless I read that section wrong, "nearness" was measured only in kilometers. Not a word about velocities.
Nothing would have changed if the authors had said "ship which could reach the scene of the disaster in least time must do so."

By NOT doing so, they made it clear they were writing "space opera". The term comes from pulp magazines. Westerns were "horse operas". If you take an "oater" and cross out "horse" every time it appears and write in "spaceship", and substitute "blaster" for "six gun", you can re-sell an old plot in a new market.
Not all space operas are bad. The genre has been re-vitalized in recent years by authors who deal in action set on vast stages of space & time -- but who at least TRY for plausibility and avoid the silliest clichés.

>>9549657
We're talking atomic explosions here.
NOT "stagnant clouds of radioactive material". They are individual particles (roughly the mass of the bomb) expanding at thousands of km/sec, approximately in a hemisphere away from the ship. They may EVENTUALLY (once the ship reaches its own exhaust velocity) be headed in the general direction of Mars, but only in the general direction.

Ship turns over and begins braking. All blasts from this point on will precede the ship. They'll get further and further away. The ship will never run into any of them.

As the ship slows, it will EVENTUALLY be moving slower than the pre-turnover blasts. Since the trajectory is a curve, it's unlikely ANY of the blasts will actually intersect the ship. And even if they did, by that time, each one will be light-minutes (more likely light-hours) across and still expanding away from the flight path. That's not even counting a "coast" period of days or weeks. (Even Orion ships can't boost continuously to Mars or Titan. Most of the trip will still be unpowered.)

It would take an improbably good radiation meter to detect anything. Space is Big. No amount of radiation we release (beyond the trapping effect of the VanAllens) is ever going to "pollute" the System.

>>9549806
So even the explosion will move relatively...
A single pusher plate could do it?
This sounds too good to be true...Too easy.

>>9549806
>>9550514

>Tfw we have been slaughtering ourselves on this planet like cattle when we could have been mining the stars and burning rocks instead of each other and setting up farms and energy center.


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

>>9550514
Don't understand question.
Debris from explosion no different from anything else you might eject from a ship.

There' s a minimum size of a-bombs. (Believe it or not, there was once a design for an atomic hand grenade! A deliberate "fizzle" which wasted expensive uranium. I think sanity prevailed and doubt any were ever built and tested.)
So there's a minimum size for an Orion ship because of the mass of the pusher plate and the shock-absorbers which keep the crew from winding up like NFL players after a few jolts.

>>9550546
It doesn't matter, screw the question I found the answer to it already. I have a new one.
Can you make it spin?

>>9550553
Around the thrust axis?
Sure.
Here's a design with centrifugal gravity.

>>9550557
Larger image

>>9550557
Last one.
Can it be launched through this hole?
*pic related*

>>9541893
Nuking muslims and chinks.

>>9550563
If you wanted to go to the trouble of building a base in Antarctica and hauling all that material down there, why not?
You wouldn't want to launch from Florida and have it putt-putt around the world within the atmosphere before starting to climb. For that matter, you probably wouldn't build it on Earth at all. The fins/landing legs on >>9550557 are silly.

>>9533849
I don't see nuclear pulse drives being used unless they are limited to use in vacuum and even then only after reliable safe methods of transporting warheads are developed.
That said I can see nuclear thermal rockets happening and so it seems does NASA, the ESA and the Russian space agency since all three have announced plans to develop nuclear thermal engines for deep space probes.

>>9551072
NP drives will be limited to vacuum (assuming they're ever built) but they do offer much higher Isps than NT rockets. So there's incentive -- assuming a need to transport large amounts of materials between planets at "reasonable" cost.

Safety in transport isn't a problem. Warheads have been smashed, burned, accidentally dropped from planes -- and nothing happens. It takes a sequence of precisely defined & timed events in the proper order to set off an explosion. You don't want one stolen and you don't want plutonium scattered around, but an inadvertent blast isn't an issue.

I hope that inertial-confinement fusion rockets are developed. That would (mostly) eliminate the need for both "bomb" and NT rockets.

>>9537144
Not with a planet sized lens it doesn't. Look at the diagram again.

>>9539545
Stages. You have a big as mirror sail, part of which you detach and use as a mirror for the slowdown. It's in the fucking diagram.

>>9542651
A generational anything is fishy as fuck. Either you fix aging, or you go relativistic. How would you react to knowing you were born in a tiny fucking tin can and you're never going to see the world you're from or the world you're going to?

>>9537745
>1g
>fusion
not bloody likely, unless you pull some kind of antimatter catalyzed pulse propulsion shit. It takes a LOT of magnets to make fusion happen, and a fuckload of power.

>>9540608
Yeah all we have to do is
>figure out how to contain a high temperature plasma sphere purely by injecting low temperature high pressure gas around it
>figure out how to start a gaseous fission reaction without blowing anything up

Mathfags will call it "excercise for the reader". Engineers will tell you to fuck off.

>>9540608
>>9540617
Not interstellar, orders of magnitude too slow. Literally the only plausible interstellar propulsion devices are antimatter rockets and lasersails.

>>9533849
With a fusion rocket moving at 10% the speed of light it would take 43 years to reach alpha centauri.

Just today Putin announced that Russia developed small size nuclear engines for cruise missile that almost have no range limit.
https://www.youtube.com/watch?v=A2oyIJ6ZHo0

>>9553734
Took the drunkards more than half a century to think of project pluto?

>>9553734
"Overcoming American anti-missile defenses" which never worked very well in the first place. And were never intended to counter Russia.
Near the end of WW2, Congress asked admirals if radar-controlled guns and proximity fuses could defend a ship against a kamikaze attack. No! You shoot down 99% of the enemy forces and you still lose if the one that gets through carries an atomic. This is "fighting the last war" thinking.

Despite Reagan's madness, the USSR had the ability to destroy the US for decades. At the cost of being totally wiped out themselves. Infinite range cruise missiles and torpedoes change nothing.

>>9553755
Project Pluto was abandoned because saner heads prevailed. Once thermonukes shrank to a size which could be carried by an ICBM, Pluto served no purpose. Still doesn't. The Russian superweapon (assuming it's real) is strictly a propaganda and terror weapon. Doesn't change the power-balance.