Everyday Space Drives

[regex]

Not sure if this belongs in The Lounge or not? Anyway, I've been daydreaming for the past couple of days, playing around with COADE and reading too much Atomic Rockets (probably), and I got to thinking about how people would get around the solar system in the future. I'm not talking about potential future research/project spaceships created by large government/corporate entities, I'm talking about the most realistically feasible "rocketpunk" propulsion systems we might see; those in commercial and individual hands in a future where the solar system has been populated to some extent. Things like a drive with a reactor + shadow shield and some tankage on a pole with a Bigelow on the other end, or whatever. Those little ships of the solar system.

My thoughts are:

Early on ion, MPD, and other electrics if fission reactor energy density is high enough with closed-cycle NTRs for high-thrust tasks. We'd probably always see "lower-tech" electrics in the inner system, and even out to the asteroid belt. After that, maybe nothing unless fusion drives become possible. MPDs given enough power can achieve some amazing stats but by the time you're pumping that much power into them you're either paying too much for reactor mass or you might as well use the reactor byproducts for an exhaust. I'm not keen on FFRs, NSWRs, or Orion/Medusa drives for the average schmoe; that makes zero sense to me. Maybe in a military/large government sort of project. I also tend to shy away from specialized fuel systems like lithium fusion liners, for instance; I don't think that's accessible to the "everyperson" and would trend towards things like PJMIF instead (although energy density is always a concern).

Anyway, I'm interested in your thoughts. Is specialized fuel not a huge concern? Would we see an incredible diversity of propulsion systems for different tasks? Is some sort of fusion drive going to overwhelm everything else?

Edited September 28, 2017 by regex

[tater]

Solar thermal? 

[Nibb31]

I don't think we will ever get to a point where people have individual spacecraft.

The amount of energy required to accelerate a couple of tons to orbital speeds is just huge. Even if you find a way to contain that energy in a compact and safe enough package, that sort of energy would be way too destructive to have people keep in their garage or fly around risking collisions or putting it into malevolent hands.

 

Edited September 28, 2017 by Nibb31

[Canopus]

Engines using only the most readily available resources as propellant. Things like Electrothermal and solar thermal rockets using water as a propellant. Maybe even solarsails. I don't think Nuclear reactors will be too widespread in Spacecraft seeing as they rely on a rarer resources and thus might be confined to places that can't always rely on solar power, like surface installations. 

Also cool to see someone still playing COADE around these parts. I just got the Gold Achievement yesterday 

Edited September 28, 2017 by Canopus

[regex]

1 minute ago, tater said:

Solar thermal? 

Wow, I've never heard of that, thanks! Learn something new every day. Looks like you'd have similar isps to closed-cycle NTRs and they'd be much simpler, for the most part. Methane would be my propellant of choice for the simplicity of tanking it.

1 minute ago, Canopus said:

Also cool to see someone still playing COADE around these parts. I just got the Gold Achievement yesterday 

I don't really play the campaign, game turned out to be nothing like what I expected (was hoping for some kind of fleet management but it's all scenario-based). Regardless, it's awesome for playing around with the designer, well worth the cash.

[tater]

Here's some pics for people of solar thermal:

 

 

Note the Rocketdyne test exhaust velocity...

that's an I_sp of 805.

[tater]

A 150 ton (wet) Mars transit vehicle could have a dry mass of 40 tons, and over 10,000 m/s of dv. 

That's enough for a Mars return. 40 tons is 2 B330s. Perhaps a lander could be sent ahead to dock in LMO.

[regex]

10 minutes ago, tater said:

A 150 ton (wet) Mars transit vehicle could have a dry mass of 40 tons, and over 10,000 m/s of dv. 

That's enough for a Mars return. 40 tons is 2 B330s. Perhaps a lander could be sent ahead to dock in LMO.

Oh sure, and if you assume, as I am, that there are propellant depots and all the general amenities one would expect from a multi-planetary society then that 10km/s goes a lot farther or includes even more payload. Combine that with some argon and a PIT on solar power (you've already got some enormous collectors) and you'll get some fantastic Mars transit times. What might also be interesting is a "boost service" where a solar/laser-thermal tug frees the electric-drive craft from the confines of planetary orbit relatively quickly in order to increase transit times. Although that still leaves the problem of braking at the destination, but it might be nice for trips to the asteroid belt.

[tater]

I was basing mass on the needs for the Mars DRM 5, lol. So yeah, totally different for your scenario. 

[sevenperforce]

If we assume that we have a bunch of space stations and orbiting colonies and propellant depots and transatmospheric ferries (i.e., commercial transport services to get passengers, cargo, or both down to the surface of a body and back again), then sailing from body to body might be a realizable leisure activity.

Might even have some pretty nifty designs...like, a high-thrust engine for initial transfer injection, a high-impulse engine to provide constant low acceleration to decrease transit times, and a heat shield for aerocapture at the destination. Sporty.

[Zeiss Ikon]

"Family car" might be something equivalent to what the Stone family bought (used) when they decided to leave Luna (The Rolling Stones, Robert A. Heinlein).  Heinlein apparently believed (well, everyone did in the 1950s when this was written) that NTR was the only way to go to the Moon or further -- then he decided stabilized monatomic hydrogen (he called it "Single-H") was the best reaction mass (never mind density/tank mass concerns -- the Rolling Stone would have resembled a party balloon more than a 1950s Ley/Bonestell rocket ship).

Still, a fission reactor has most of the advantages Heinlein called out -- long working life, low moving part count (control rods, and a pump), and doesn't require any really exotic materials, especially if you use water instead of Single-H for reactant.  Safety might be improved by taking a page from Rocket Ship Galileo and building these as thorium breeders rather than uranium/plutonium cycle.

Of course, there'll be yacht clubs, and they'll race and pleasure-sail from planet to planet, set "classes" by sail area and control method, and complain to each other than a yacht is a hole in space you throw money into.  A fairly modest solar sail can beat a NASA launch from Earth to Mars, and the further you're going, the bigger the advantage the sail has.  Let someone invent some sort of suspended animation, and you'll see these guys sailing all the way out to Neptune and there'll probably be a few who disappear trying to "single hand" to Proxima.

[regex]

In the inner system, with solar power being so abundant, I see no reason why smaller craft would have reactors, but out past the asteroid belt? Would we expect government regulation or licensing in order to operate them? It's basically adding a whole new level of complexity to the craft, you may not see the carefree electric sailing of the inner system out by Jupiter, or they'd have massive collectors that may not be as accessible to everyone. Craft with reactors might be purely the domain of business interests or rich families.

But then, who knows what we'll be using for power by the time we are able to indulge in a rocketpunk future. I can't see that happening for at least ... 7~800 years, at a bare minimum. Of course even at that time fusion power may be 30 years away and Falcon Heavy will still be three months in the future.

Side note: Although living in space will require discipline from birth to the grave no matter where you are, I feel like the outer system requires even more from the individual and group, so the government regulations may be a moot point

Edited September 29, 2017 by regex

[ChrisSpace]

Well, from what I have lying around the house, and from a bit of internetting, here are some options I have found:

 

Solid chemical rockets (model rocket motors are already easy to acquire, but the exhaust velocity is really low)

Liquid chemical rockets (much harder to build, higher exhaust velocity)

Solar thermal rockets (similar to solar sails but more expensive and produces more thrust)

Laser sails/Laser thermal rockets (similar to their "Solar" counterparts, however they'd need a powerful laser and the most powerful civilian-made one I know of had an output of 200W from 1kW of input energy)

Some kind of "Orion" using conventional explsives? (I have no idea what the thrust or exhaust velocity for this would be)

 

Personally I think a combination of methods would be most practical. Liquid chemical rockets to boost into orbit (helped by Solid chemical rockets that detach during ascent STS- or SLS-style), then one of the more efficient low-thrust options to travel between planets. I might do some math on this later.

 

Edit: Okay, after looking around on the internet, here's some links that should help give a rough idea of what kinds of propulsion systems should be available through various means of aquisition:

http://www.watzlavick.com/robert/rocket/regenChamber/index.html

http://www.watzlavick.com/robert/rocket/regenChamber3/index.html

http://aeroconsystems.com/cart/liquid-motors/rocketdyne-lr64-rocket-motor/

http://pages.total.net/~launch/ss67b3.htm

http://www.maxentropy.net/rocketry/liquidproject/design/design.htm

http://www.dailymail.co.uk/sciencetech/article-2068224/Up-sale-online-A-NASA-rocket-engine-used-build-missiles.html

http://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/Monopropellant Data Sheets.pdf

http://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/Bipropellant Data Sheets.pdf

http://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/GPIM AF-M315E Propulsion System.pdf

http://aeroconsystems.com/cart/liquid-motors/rocketdyne-lr101-bipropellant-rocket-motor/

 

As an example, if one of the types of 1000lbf engines is used and they're arranged in the same way as the engines on the bottom stage of the ITS, that should provide 186.8kN of thrust. If we give the main vessel's chemical propulsion an initial TWR requirement of 1.0, that gives it a mass of 19048kg.

Edited November 9, 2017 by ChrisSpace

[cfds]

2 hours ago, ChrisSpace said:

Some kind of "Orion" using conventional explsives? (I have no idea what the thrust of exhaust velocity for this would be)

You already listed them as "Solid chemical rockets".

[kerbiloid]

Laser propulsion...

Spoiler

... with payment cards.
Out of money = out of energy.
Banned by the administration = out of energy.

12 hours ago, Nibb31 said:

I don't think we will ever get to a point where people have individual spacecraft.

The amount of energy required to accelerate a couple of tons to orbital speeds is just huge. Even if you find a way to contain that energy in a compact and safe enough package, that sort of energy would be way too destructive to have people keep in their garage or fly around risking collisions or putting it into malevolent hands.

To orbit.

Spoiler

In orbit.

Spoiler

 

8 hours ago, Zeiss Ikon said:

A fairly modest solar sail can beat a NASA launch from Earth to Mars

For those who don't hurry.
Also, the slower is the ship - the heavier should be life support and habitat. (Supplies, protection, artificial gravity, etc)

[YNM]

Actually, I have a bigger question :

 

What would our travel be for ?

How many of us will be traveling ?

Who are we travelling somewhere so far ?

This matter a lot. A simple tweak results in different answers to what kind of mode will be suitable.

Ex :

- "Bussiness visit, few, exec" : you get your luxury spaceship.

- "Holliday, few, commoners" : Either "No" or you get a "bus".

- "Working, lots, common workers" : Move there, so probably something big and cheap and single use.

That's what I have been thinking so far. This applies for Earth-based travels too.

[ChrisSpace]

4 minutes ago, YNM said:

What would our travel be for ?

I'm aiming to see if I can get something that can hypothetically reach the lunar surface using avaiable resources with a budget of just a few million dollars.

5 minutes ago, YNM said:

How many of us will be traveling ?

I'm aiming for... 6, maybe? First I'll see if it's possible for 1.

[wumpus]

14 hours ago, Zeiss Ikon said:

Of course, there'll be yacht clubs, and they'll race and pleasure-sail from planet to planet, set "classes" by sail area and control method, and complain to each other than a yacht is a hole in space you throw money into.  A fairly modest solar sail can beat a NASA launch from Earth to Mars, and the further you're going, the bigger the advantage the sail has.  Let someone invent some sort of suspended animation, and you'll see these guys sailing all the way out to Neptune and there'll probably be a few who disappear trying to "single hand" to Proxima.

"Beating a NASA launch from Earth to Mars" isn't hard (for equal launch windows) but requires an extreme amount of energy&reaction mass to do so.

As far as solar thermal, any word on [real] transparent aluminum, or other transparent materials with high melting points?  I'm assuming things like quartz and flint crystal would make a good combustion chamber (unlike NTR, you can heat the reaction mass higher than the melting point of the combustion chamber).  Don't expect to go much further than the asteroid belt, but the belt is probably the only place in space with a positive return on financial investment.

And once again I should point out that you can transport chemical fuels via high-Isp and gravity "cheats" as efficiently as you need, and then let humans get where they need to go in a hurry (ideally re-fueling after each burn or escape/capture pair).  Getting fuel from LEO to beyond the Van Allen belts is an issue, which is why you don't hear it suggested in going to Mars, but if you had some easier space access to rocket chemicals it should work well.

A "conventional Orion" is likely to only make sense as an air-breather to orbit (I might be wrong, but I think the Isp of nitrogen-based oxidation is pretty bad).  There has been some work on the idea, but it doesn't seem to go anywhere.  In practice, expect something more like a "pulse-jet" engine that detonates instead of combusts.  This gives a higher Ve, but it also tends to destroy the engine.  It is also one of the loudest noises ever, possibly worse than supersonic propellers. 

[regex]

5 hours ago, YNM said:

Actually, I have a bigger question :

 

What would our travel be for ?

How many of us will be traveling ?

Who are we travelling somewhere so far ?

This matter a lot. A simple tweak results in different answers to what kind of mode will be suitable.

Anything and everything that random people do in whatever quantities of crew are required. This is a "rocketpunk" future. Your question here pretty much presumes a wide variety of space drives for all sorts of purposes. NTRs for slow-haul bulk cargo, gigawatt plasma drives for long duration research vessels, a hall-effect thruster some kid turned out in their school's milling machine, the family Winnebago, there could be all sorts of things.

For me it really boils down to the complexity of the drive and systems around it. A small inner-system craft is relatively simple from an overall POV (despite being a technological marvel) being composed of a hab, storm shelter (most likely), solar panels or collectors, some batteries, reaction mass, and the drive. You might not even need a huge hab if your populace has some sort of direct neural interface but then, one wonders why they haven't retreated to a simulation (that's a social question beyond the scope of this, the same as "why are we in space in the first place?", the answer being "for because"). Anyway, for me a big concern is the simplicity of the drive system. I doubt we'd see PJMIF or some other form of fusion drives in the hands of small or medium business concerns or enthusiastic kids not only because they're fairly complex but also because of the power needs and, in certain cases, the special fuels. The same goes for chemical rockets due to their complexity and often short lifespans. NTRs are an odd one where I can see medium-sized business concerns perhaps using them but the complexities surrounding operation of the engine keep them out of smaller hands, which is one of the reasons I found the solar/laser thermal engines so attractive; they're simpler and safer despite having their own drawbacks. Electrics would be pretty huge in the inner system, IMO.

Which brings us beyond the inner system, past the asteroid belt, where solar power is much scarcer. Is fusion power always thirty years into the future? Are we still using fission reactors? Life is much different the further you go out, at least in orbit, because the craft are more technical and the need to specialize is greater, crews are larger and life more regimented.

The inner system is more of a playground because you can get around with a few solar panels and a tank of argon. What does the outer system, in orbit, look like? Engines and powerplants? Are my assumptions wrong?

[kerbiloid]

2 hours ago, regex said:

a hab, storm shelter (most likely)

 

2 hours ago, regex said:

if your populace has some sort of direct neural interface but then, one wonders why they haven't retreated to a simulation

A typical near-future habitat for amateur spaceships. (Internal view)
Usually placed inside a cylindric protective hull.
All-in-one: hab, shelter, command center, fitness room.
Virtual reality helmets and voice interface.

Spoiler

(While one of crew members sleeps, another one makes exercises for health, generates electricity and creates artificial gravity for the first one.
Every 6 hours they switch.

Edited September 29, 2017 by kerbiloid

[regex]

2 minutes ago, kerbiloid said:

A typical near-future habitat for amateur spaceships. (Internal view)
Usually placed inside a cylindric protective hull.
All-in-one: hab, shelter, command center, fitness room.

E: Wasn't there a tangent in another thread about lofting subs into space? Yeah...

Edited September 29, 2017 by regex

[DDE]

@regex Another COADE player, back when they first released tapered radiators, I did a thing.

 

I think not having any reaction mass in the reactor, and a versatile electric powerplant at your disposal would be two huge plusses for the Far Belters.

[raxo2222]

What about beam network powered personal spaceships? You can try to build one of these in KSPI Extended mod.

You wouldn't need dangerous fission reactors and expensive fusion reactors on your ship.

Of course you would need specialized spaceports, where microwave/infrared laser beam would power your ship.

 

Edited September 29, 2017 by raxo2222

[regex]

Ugh... Water's isp is hideous, lol.

21 minutes ago, DDE said:

I think not having any reaction mass in the reactor, and a versatile electric powerplant at your disposal would be two huge plusses for the Far Belters.

Oh man, you totally reminded me of SAFE-400. IIRC it's a relatively simple mechanism, quite light, and puts out about 100kW of usable electricity. That's plenty for a small electric or two and for the mass it's worth it to carry a few for extra power or in backup (obviously the size and output would vary but I always like real world examples). Stopping at the fuel depot could also involve swapping out your reactor for a fresh one.

And you're totally right about the coolant flush, "solid state" reactors like RTGs or heat-pipe power systems would probably be favored by the outer-system. Hell, you could scavenge a lot of waste heat into an exchanger.

28 minutes ago, raxo2222 said:

What about beam network powered personal spaceships? You can try to build one of these in KSPI Extended mod.

See posts above, although KSPI is a bit beyond what I think is technically feasible for the smaller entity to operate on a regular basis, besides being incredibly optimistic.

[YNM]

6 hours ago, regex said:

Anything and everything that random people do in whatever quantities of crew are required. This is a "rocketpunk" future. Your question here pretty much presumes a wide variety of space drives for all sorts of purposes. NTRs for slow-haul bulk cargo, gigawatt plasma drives for long duration research vessels, a hall-effect thruster some kid turned out in their school's milling machine, the family Winnebago, there could be all sorts of things.

Ah, I see.

In that case, I believe the limiting point will be efficiency (mass-wise) and energy source. We probably would still see solar panels, but our propellant will be something that's abundant everywhere (so no hydrocarbon) and mayhaps only needs electricity or heat from the Sun to operate. I elect Ion or VASIMR (magnetohydrodynamic) - type propulsions.

EDIT : Also, I question planet-based colonies. I think all of them will be in space, so everyone have their space hubs.

Edited September 29, 2017 by YNM