"Bussard ramjet" for collecting fuels from the atmospheres from suns and planets.

[The Aziz]

We have xenon fuel factories, there's a high chance it's being extracted from the atmosphere. And they are BIG. So Elite Dangerous styled fuel scoop is definitely out of the question. Who knows how other extractors work.

One, because stellar corona is stupidly hot, we're talking in millions Kelvins, so even that tiny amount of collected gas will be H O T. Good luck storing that.

Two, getting low enough to a star to even get any heating effects, at least in KSP, requires a lot of dv. And then you have to climb back. It's far easier, cheaper and safer to head down into a gas giant, probably also made of hydrogen, helium, whatever you need, but much cooler, and as a result, easier to obtain. I suppose there's a reason why the mothership from the trailer launched from station around Jool - plenty of lightweight gasses there.

[Bej Kerman]

No-one has brought up harvesting stuff from the interplanetary/interstellar medium yet which is weird because the post has "Bussard Ramjet" in the name.

[t_v]

1 hour ago, Bej Kerman said:

No-one has brought up harvesting stuff from the interplanetary/interstellar medium yet which is weird because the post has "Bussard Ramjet" in the name.

What’s weird is focusing on interplanetary/interstellar medium when the post also has “for collecting fuels from the atmospheres from suns and planets.” in the name. Drop your fixation on bussard ramjets and think about the actual topic of this thread, or create a new thread on bussard ramjets if you want. As for me, I’m wondering: would you be able to collect regolith from this process? Because, for example, the moon has a lot of dust in its “atmosphere” that has the same composition as the ground. So, not only could your ship fuel up, it could also gain enough metal to make very minor repairs. Or is the percentage of dust too small to be noticeable?

[Bej Kerman]

54 minutes ago, t_v said:

What’s weird is focusing on interplanetary/interstellar medium when the post also has “for collecting fuels from the atmospheres from suns and planets.” in the name.

And as far as I can tell, collecting fuel from larger mediums is a similar technology with far less problems. No, I won't drop the fixation.

[Strawberry]

Bussard ramjets have undoubtedly been already considered by the ksp2 team, anything that is said here wont influence there decisions.

Collecting regolith in the air is definitely possible, however not only is collecting this dust hard (the dust on the moon is very sharp, very fine and very small, it gets into electronics and degrades them), while some dust gets kicked up, most dust sticks near the surface (and even then not "that" much), so its far more practical to just collect the regolith from the surface instead.

[Ember12]

1 hour ago, Strawberry said:

so its far more practical to just collect the regolith from the surface instead.

Earlier in the discussion, I got the impression that you were saying "This wouldn't be useful but it would be fun" about the harvesting of gases from stars.  If this is the case, harvesting airborne regolith would fall into the same category.

[Strawberry]

When I say far more practical I mean in order to collect a noticeable amount of regolith (note not useful, just noticable), you'd need to fly basically right above the surface of a textured moon. The density of regolith is very low, and since moons are small any passes over the surface will be a small distance and at relatively low speeds. Not to mention the developmental issues, for scoops most of the code work would be modifying existing systems, whereas for scoops for regolith you'd need to code a lot more stuff for one feature. Scooping from the sun would have a use (albiet not an efficient use), it would be as a way to slow down using the sun while entering the system all the while collecting some extra fuel, scooping from regolith however wouldnt really have such a use as itd take basically the same amount of delta v to fly right over a moon then to just land on it. 

Edited July 17, 2022 by Strawberry

[t_v]

9 minutes ago, Strawberry said:

When I say far more practical I mean in order to collect a noticeable amount of regolith (note not useful, just noticable), you'd need to fly basically right above the surface of a textured moon. The density of regolith is very low, and since moons are small any passes over the surface will be a small distance and at relatively low speeds. Not to mention the developmental issues, for scoops most of the code work would be modifying existing systems, whereas for scoops for regolith you'd need to code a lot more stuff for one feature. Scooping from the sun would have a use (albiet not an efficient use), it would be as a way to slow down using the sun while entering the system all the while collecting some extra fuel, scooping from regolith however wouldnt really have such a use as itd take basically the same amount of delta v to fly right over a moon then to just land on it. 

A few problems with this:

10 minutes ago, Strawberry said:

you'd need to fly basically right above the surface of a textured moon

Scaling with the size of the body, this is just like passing close to a star. Similar to with stars, the only reason this interaction should really be included is for people to note how little material they are getting. 

11 minutes ago, Strawberry said:

Not to mention the developmental issues, for scoops most of the code work would be modifying existing systems, whereas for scoops for regolith you'd need to code a lot more stuff for one feature.

Not really. If you have a system for extracting resources from passing through an atmosphere, implementing scooping regolith is just as easy as implementing scooping hydrogen. On top of that, you wouldn't have to worry about massive heat flow, making it easier to implement than star resource harvesting.

13 minutes ago, Strawberry said:

scooping from regolith however wouldnt really have such a use as itd take basically the same amount of delta v to fly right over a moon then to just land on it. 

when you say "basically the same," are you counting the delta-v to land and take back off from the moon as negligible? I agree that scooping regolith wouldn't have a use (and I think that scooping from stars has such a low return that it is also useless) but I also think that if the devs have the time to do so, those features should be included to educate people on how dense stars are, or how many trace pieces of dust float around any celestial body. 

[Strawberry]

You cant just implement an atmosphere of regolith on a moon that's designed to not have an atmosphere. Not only would the dust not produce noticeable drag on a spacecraft, the atmospheric system is probably not coded to be able to go that low of a number because why should it, coding it to go that low would slow down everything else. Youd need to code something new instead of just using the air intake system for moons because moons dont have air. The big difference between a moon and a sun is you can land/crash on a moon and you cant do that for a star, and stars are massive when moons are not. Stars aren't dense by any means, but they're still far more dense then regolith, and not only that, but due to stars size, the distance you're going to fly over areas of meaningful density for a sun is far more then the distance youd travel over a moon. 

[Ember12]

I did the math on cooling a starship at the solar surface, and it would not be feasible if I didn't make a mistake.

In this discussion, someone estimated that a starship's radiation shield was 100m in diameter.  The shield was about 1/4 as wide as the conical starship was long (not counting the engine bell) so you'd need a conical fairing 50m in radius and 400m long.  The area of such a cone would be about 70,000 square meters.

Only half of it is facing the sun, so we can divide that by 2 to get 35,000.  Let's imagine we cover it in reflective paint so that only 10% of that gets through, bringing it down to 3,500 effective square meters.

The output of the sun is 64,000,000 watts per square meter at the surface, which is where you are.  This, multiplied by the 3,500 effective square meters, gives a total of 224,000,000,000 watts.

One watt is one joule per second, so you need to remove 224,000,000,000 joules per second.  Hydrogen, the proposed coolant, has a heat capacity of about 14 joules per gram Kelvin (j/gK).  This can be rearranged into 14j=gK.  Assuming the hydrogen starts at 20 Kelvin, and you're okay with your (graphene) starship reaching 4000 Kelvin, K (the change in temperature) is about 4000.  So 14*224,000,000,000=g*4000.  Divide by 4000 and you get 14*224,000,000,000/4000=g, or 784,000 kilograms of coolant hydrogen a second.  This is about three times the weight of an average skyscraper. 

There's just no way to carry that much coolant on a ship of that size.  This would not work at all.

 

[Bej Kerman]

14 minutes ago, Ember12 said:

The output of the sun is 64,000,000 watts per square meter at the surface, which is where you are.

Define surface. Would you really need to get close enough to count as being on the "surface" to collect a useful amount of fuel?

[Strawberry]

That assumes an emissivity of 1, meaning it absorbs all light. Flat graphene has an emissivity of 0.025, getting us only 5,600,000,000 joules transferred. The maximum amount of joules a gram of hydrogen can take can be calculated as the specific heat (14) times the temperature gradient (4000-20 so 3980). Dividing the joules per second by this number gets us only 1407.035 kilograms a second required, a far more manageable amount. 

Just now, Bej Kerman said:

Define surface. Would you really need to get close enough to count as being on the "surface" to collect a useful amount of fuel?

The main difficulty with getting gas from the sun is that the sun gets colder and denser the deeper you go down, and the colder the gas is the easier it is to collect. Collecting gas from the corona is highly impractical due to its insanely high temperature, collecting gas from the photosphere however (the area where visible light gets blocked from going in), is surprisingly far more practical. 

[Bej Kerman]

40 minutes ago, Strawberry said:

The main difficulty with getting gas from the sun is that the sun gets colder and denser the deeper you go down, and the colder the gas is the easier it is to collect. Collecting gas from the corona is highly impractical due to its insanely high temperature, collecting gas from the photosphere however (the area where visible light gets blocked from going in), is surprisingly far more practical. 

You have to get through the corona first. I doubt we will ever build ships that could get anywhere near the photosphere anyway.

[Strawberry]

Getting through the corona isnt hard if youre going at several thousand kilometers a second, and a vehicle could exist in the photosphere (itd be an engineering nightmare mind you, but from a scientific perspective definitely possible.) 

[JadeOfMaar]

On 7/15/2022 at 11:42 PM, Ember12 said:

I don't think this is really feasible.  If a planet had an atmosphere you could make fuel out of, it would probably have combusted already. 

Incorrect. If a planet's atmosphere was full of a fuel and a capable oxidizer, they would have mostly reacted already, without igniting. If it does combust then either something broke physics and kept these gases from igniting under the literally infernal conditions of the planet's protoplanetary phases, or the second gas somehow appeared in bulk after and then never before, but at some point after, lightning finally decided to happen-- the lightning would be quite a spark plug.

If Earth was able to hold onto a lot of Hydrogen, its atmosphere would have a lot more than 1%? water vapor right now. Jupiter has plenty Hydrogen, and trace Water, Methane and Ammonia, but no traces of the other elements that form the hydro-compounds (per the Wikipedia page).

On 7/16/2022 at 12:06 AM, Ember12 said:

I don't understand the "why wouldn't it".  You can't use any gas as a fuel.  There are three main types of engine to consider: 

Combustion, where you burn something like hydrogen with oxygen, or use more exotic fuel mixtures.  Possible fuels: Oxygen, hydrogen, hydrocarbons, or more complex molecules.

Nuclear propulsion, where you heat up a light gas and fire it out the back.  Possible fuels:  Mostly just hydrogen and water

Fusion engines, where you fuse atoms to create energy and thrust.  Possible fuels: isotopes of hydrogen and helium.

If a planet has one of these in its atmosphere, you're in luck, if you can collect enough to offset drag.  But many planets in our own solar system don't have any of these.  Mercury, Venus, Mars, nearly all the moons of Jupiter and Saturn don't have any of these in their air.  Actually refueling a combustion/nuclear rocket would not be something you could rely on. 

Nuclear propulsion (classically: Nuclear thermal) can actually run well on any non-reactive fluid, as long as it's sufficiently thermally conductive (unlike Hydrogen) and you can pump enough of it through the engine's chamber to produce enough mass flow, therefore, thrust, to overcome drag. Users of KSPI-E have the daily routine of feeding seemingly useless ambient gases like Nitrogen and Carbon Dioxide into their Tory-II atomic ramjet or Z-Pinch aerospike. The big deal is how able your gas-diving ship is to save more of its scooped material than it burns while maintaining flight or returning to orbit. If you're flying through an atmo that isn't fusion fuel (such as with a shuttle for crew or payload, visiting Eve's surface) then you only care about having enough fusion fuel to SSTO a few times, and you're infinitely fueled while in the air thanks to the heat source that is your reactor, and the high molar mass of N2 or CO2.

You might be under-informed as well. Fusing pure Hydrogen (also called Proton-Proton or "p-p") is exceptionally difficult. You want the relatively very easy and very safe combination of Deuterium (heavy H2) and Helium-3. Both of these are super rare but always present in stars and gas planets, and they don't casually react like the components of Methane, Ammonia and strong acids like the Sulfides and Chlorides.

A proper gas-diving vessel would use this fusion mix ( D + ³He ) for main power and propulsion, and will likely afterburn with Hydrogen or Water when it needs to trust in thrust.

On 7/16/2022 at 12:22 PM, Strawberry said:

I used the term bussard ramjet in quotation initially due to there not really being a word to describe this (just ramjet we tend to think of for producing thrust instead of collecting gas and scoop is a bit vague).

"Bussard Collector" or "Magnetic scoop" would have done very nicely then. Any magnetic particle scoop is functionally the same kind as the scoop from the Bussard ramjet, but saying "ramjet" unavoidably infers the use of the engine too, and the engine makes no sense in any case other than getting between the stars as fast as possible.

[JadeOfMaar]

Three other things:

1. Everything is wrong with the idea of Sun-diving and trying to protect yourself and collect particles. As others have suggested: the particles would be so incredibly hot, you run into the problem of either metaphorically charging, buck naked, through garden sprays of boiling water ( You will get blazed. It will sting very very badly. Even the slightest amount) or your physical shield would knock the particles out of the way of your scoop, like an open umbrella, making it pointless to try to scoop. (The shield will melt too unless it can be magnetically shielded.)
2. The other day I watched a video by Anton Petrov that suggested that the ISM is much less dense than we imagined, making the Bussard ramjet near or totally impossible to use.
3. If you're going to collect ambient Regolith, consider investing in asteroid processing tech. I'm not feeling the idea of flying a orbital speed over what is likely a Moon-sized or dwarf planet and trying to yoink dirt that way. You're much better off being able to drift alongside and claw a rock that's big enough but not massive enough that you're obviously "orbiting" it.

Edited July 17, 2022 by JadeOfMaar

[Strawberry]

6 minutes ago, JadeOfMaar said:

You might be under-informed as well. Fusing pure Hydrogen (also called Proton-Proton or "p-p") is exceptionally difficult. You want the relatively very easy and very safe combination of Deuterium (heavy H2) and Helium-3. Both of these are super rare but always present in stars and gas planets, and they don't casually react like the components of Methane, Ammonia and strong acids like the Sulfides and Chlorides.

Most of the plasma near the surface of the sun is unionized, not only does this mean they tend to get higher paychecks, they also have higher cross sections, making it slightly easier. Proton proton fusion also produces deuterium. Even assuming that future fusion technology is not efficient enough to get energy out of the proton proton reaction, you can easily use proton proton fusion as the first step to deuterium based fusion (ideally having a tritium kickstarter and using lithium shielding to breed neutrons for a sustainable supply of  tritium from deuterium neutron fusion).

18 minutes ago, JadeOfMaar said:

Three other things:

1. Everything is wrong with the idea of Sun-diving and trying to protect yourself and collect particles. As others have suggested: the particles would be so incredibly hot, you run into the problem of either metaphorically charging, buck naked, through garden sprays of boiling water ( You will get blazed. It will sting very very badly. Even the slightest amount) or your physical shield would knock the particles out of the way of your scoop, like an open umbrella, making it pointless to try to scoop. (The shield will melt too unless it can be magnetically shielded.

While due to corona heating the corona is very hot, its also super super undense. Current day technology's can (and have!) been able to withstand it completely fine with very sensitive electronics on board. Once you get into the photosphere, things get far easier. For red giants collecting star stuff safely would be "trivial", the temperatures are well within what modern materials can handle (around 2k), for our sun it gets trickier, but not impossible. Graphene (which we know will be in game) has insanely high melting points and high emissivity, meaning that assuming you use cooling (which gives you hyperheated gas that you can use for propellant), you can tank the heating effects.

[Strawberry]

I forgot to mention this in the original post, but you should 100% be able to scoop monopropellant out of eves atmosphere

 

Edit: Oops just remembered I already mentioned this in an earlier comment am dumb, though xenon out of jools atmosphere seems like itd enable some whacky stuff which seems good.

Edited July 18, 2022 by Strawberry

[Ember12]

4 hours ago, Strawberry said:

That assumes an emissivity of 1, meaning it absorbs all light. Flat graphene has an emissivity of 0.025, getting us only 5,600,000,000 joules transferred. The maximum amount of joules a gram of hydrogen can take can be calculated as the specific heat (14) times the temperature gradient (4000-20 so 3980). Dividing the joules per second by this number gets us only 1407.035 kilograms a second required, a far more manageable amount. 

I did indeed not consider emissivity, but the process is still not feasible.  Assuming you multiplied my number by 0.025, that means that you would burn through 3 skyscrapers of hydrogen every 40 seconds.  An amount of hydrogen comparable to the mass of your ship every 40 seconds.

And you can't escape by going higher or lower.  That 64,000,000 watts per square meter is still going to affect you anywhere nearby, regardless of the gas density (the denser, cooler gas inside the Sun will impart the same thermal energy as the stuff nearer the surface).

Edited July 18, 2022 by Ember12

[Strawberry]

Just now, Ember12 said:

I did indeed not consider emissivity, but the process is still not feasible.  Assuming you multiplied my number by 0.025, that means that you would burn through 3 skyscrapers of hydrogen every 40 seconds.  An amount of hydrogen comparable to the mass of your ship every 40 seconds.

And you can't escape by going higher.  The Sun's atmosphere might get thinner but that 64,000,000 watts per square meter is still going to affect you even in a vacuum. 

That's why you go fast enough to get out of there in less then 40 seconds. 

[Ember12]

54 minutes ago, Strawberry said:

That's why you go fast enough to get out of there in less then 40 seconds.

Let's assume you take a perfectly straight line, and just graze the solar surface.  Let's also assume that you encounter that amount of heating when within 135,000 miles from the solar surface (not nearly far enough to be outside the corona).  By my calculation, you would need to travel 1003543 miles inside that radius, and to do that in 40 seconds, you would need to move at over 90 million miles an hour, or 13 percent of the speed of light.  At the sun's surface, the 10-meter-diameter spherical fuel tank I mentioned earlier would experience over a billion pounds of drag force.

And this is an optimistic assessment. You would also be heated up during solar approach, and even at this speed, you're dragging along a mass of hydrogen comparable to the mass of your starship, and this isn't even taking into account the cooling of the hydrogen you're taking in.

[Strawberry]

The difference between the corona and the photosphere is like the difference between the density of sea level and the density of the ocean, despite the high temperatures the heating of the corona is "minimal". Also a billion pounds of force spread across a large area is definitely a force a future vehicle can withhold, diamond has an observed compressive strength of 60 GPa (keep in mind the observed, diamond can probably go higher), meaning that it can withstand ~13,500,000,000 pounds of force per square meter with its current highest observed strength.

[Ember12]

2 minutes ago, Strawberry said:

heating of the corona is "minimal".

I would dispute this, because conductive heating is not the only way that your ship can be heated.  As I said before, the sun puts out around 64,000,000 watts per square meter.  This does not depend on atmosphere. That energy is going to affect you even in a vacuum, because it will all be light and radiation. 

6 minutes ago, Strawberry said:

diamond has an observed compressive strength of 60 GPa (keep in mind the observed, diamond can probably go higher), meaning that it can withstand ~13,500,000,000 pounds of force per square meter with its current highest observed strength.

Would you mind walking me through the math you used to get that?  Did you calculate a solid block or a hollow fuel tank?

[kspnerd122]

You can scoop fusion fuels from gas giants, its not combustible but useful for advanced fusion engines

Also, D+He3 fusion is aneutronic, and neutrons are a PAIN to deal with and damage your engine

[Ember12]

Agreed, getting it from gas giants is a far better idea IMO.