Near Future Saucer

[Dave Angel]

I’m a fan of the Near-Future and interstellar mods, and while reading about the proposed second generation EMdrives, my thoughts turned to a re-usable craft, taking advantage of existing and emerging technologies. With KSP, you are effectively limited to rockets and spaceplanes, although, should certain techs evolve, then there is a strong argument for a saucer.

The saucer shape accommodates a centrifuge quite nicely in a SSTO form factor, and whilst our Kerbals don’t care about the long-term effects of zero-g, it would surely be a concern of any future astronauts.

I’ve started to conceptualise then a craft that would utilise emerging technologies to see what the art of the soon to be feasible is and pugged them together into a build. These technologies should mature over the next few decades, justifying the use of optimistic values.

As KSP doesn’t model saucers well, this will probably end up as a more or less prebuilt craft, with maybe a few connections for things like docking ports, a hanger space and surface mount equipment.

I will share the .blend file if anyone wants to have their own take on this or move it forward.

Propulsion

Primary Propulsion System

Four second generation EMDrives housed in gimbled mounts provides the primary thrust for the craft. Shawyer claims the second-generation drive, using super conducting microwave cavities should be able to produce 30kN/kW, or 1KW of power would produce 3 tonnes of thrust.

Assuming the flyer weighs around 100 tonnes, 70Kw of power would be ample to accelerate the craft at around twice gravity. If 25KW was provided to each gimbled mount

Direct Nuclear Turbojet

The basic principle of the nuclear turbojet is that intake air is taken in, and instead of being mixed with fuel and ignited, its simply superheated by a nuclear reaction, excited and exhausted out the back of the craft. Our craft uses a fusion reactor, who’s operating temperature is north of 100 million degrees Celsius, giving us the opportunity for some cheap thrust where its most needed; with the atmosphere.

RCS

Without traditional control surfaces, RCS will be needed for all phases of the mission. The gimbled main drives will of course provide a lot of the manoeuvrability needed.

Gravity Wheel

Extended missions in zero gravity lead to muscle and bone wastage, along with a host of other health issues, so providing simulated gravity in any craft designed for prolonged endurance is advantageous. As real gravity would require so much mass that the TWR would be somewhat adversely affected, other than constant acceleration the only current option available is a centrifuge. The saucer shape is to accommodate a 10M radius torus, which contains the main quarters of the craft which can not only rotate around the centre at a steady 9RPM to simulate 1g, but can also be stopped and rotated by 90 degrees in the transverse access to that when operating in normal gravities the crew can walk around normally.

The gravity wheel will use magnetic suspension to reduce friction and in turn the power and heat generation as a result of rotating the cabins.

Reactor

A small Nuclear Fusion Tokamak reactor producing around 500MWh will provide power to the craft,

Essentially, there are two competing designs for fusion generators; Stellerators and Tokamaks. Whether Stellerators or Tokamaks become the preferred mechanism for fusion, the process and output will be similar. Tokamaks require super conducting magnets, and as we are banking on that technology for our primary propulsion system, we will plump for this option.

Current achievements in fusion use two isotopes of hydrogen; Deuterium; a naturally occurring isotope found in 0.0115% of natural hydrogen and tritium, which is virtually non-existent in the natural world because it is unstable and decays with a half-life of 12.3 years. Whilst Tritium can be created from lithium, for this process we will assume that advances are made and Deuterium- Deuterium fusion is achievable within our reactor. Per Kilogram, Deuterium produces 8.42 × 10¹⁴ joules considering the efficiency of the reactor, the consumption rates specified by the team working on the ITEL Tokamak reactor, running at 500KWh would take around 125Kgs of fuel a year.

Thermal Systems

Thermal control systems are one of the more challenging aspects of the craft. Cooling is not just required for running the propulsion systems and reactor; both of which requiring lower temperatures associated with super conductivity, but also if maximum reuse is to be desired, ablation is not a suitable mechanism for re-entry heat control.

Current active cooling systems pump ammonia around conditioned systems and utilizing radiators to dump the heat into space. Essentially, other than refinements such as piezoelectric pumps, and designs to reduce re-entry thermal effects are only paths currently open to us.

Oxygen Scrubbers

To create oxygen from carbon dioxide you need photosynthesis which needs trees, however its often said that while the last 50 years have been the period of progress for computing and electronics, the next 50 will be for genetic engineering. Craig Ventnor has proposed genetically engineering bacteria to be super-efficient at this process, and given the proposed timeline of the flyer it would be fair to assume that, along with other duration extending systems like water purification, this technology would be incorporated into the design – with used air being pumped through tanks of algae-like genetically engineered protozoa, and producing nice clean breathable.

Mission Profile

The following mission profiles would fit our craft.

·       Transportation

The movement of people and materials to and between bodies

·       Resource Gathering

Collection of rare and desirable resources from Space or from other astral bodies

·       Exploration

Travel to distant bodies, and utilizing scientific equipment or launching probes to this effect.

All essentially require the use of a cargo bay, so we will incorporate one into the centre of our craft, which could contain raw materials, a rover for surface ISRU\G or other payload.

WIP

So I've started the model, with the saucer shape and nacelles for the EMDrives and shock cone at the top for the turbojet, leaving a large area underneath for the rover hanger.

Image here...

https://ibb.co/je0JLv

[DDE]

Expect hate. I'm about to start.

25 minutes ago, Dave Angel said:

second generation EMDrives

Shawyer DOESN'T KNOW A FLYING **** about how his own "drive" works, or spacecraft engineering. It's the same person who thinks that a propulsion system with TWR in the nanodigits would allow flying cars, and that it's inherently stealthy - despite requiring ginormous amounts of electricity and rejecting most of the energy input as heat.

You might as well use a Kuat Drive Yards motor from a Star Destroyer.

25 minutes ago, Dave Angel said:

A small Nuclear Fusion Tokamak

Called it.

Add millions of square meters of high-performance radiators, along with, say, a couple thousand tons of shielding for the high-energy neutrons. Not to mention that practical energy generation systems for fusion reactors have not been developed, and would likely add another ten thousand tons.

Edited June 6, 2017 by DDE

[Steel]

34 minutes ago, Dave Angel said:

Gravity Wheel

Extended missions in zero gravity lead to muscle and bone wastage, along with a host of other health issues, so providing simulated gravity in any craft designed for prolonged endurance is advantageous. As real gravity would require so much mass that the TWR would be somewhat adversely affected, other than constant acceleration the only current option available is a centrifuge. The saucer shape is to accommodate a 10M radius torus, which contains the main quarters of the craft which can not only rotate around the centre at a steady 9RPM to simulate 1g, but can also be stopped and rotated by 90 degrees in the transverse access to that when operating in normal gravities the crew can walk around normally.

The gravity wheel will use magnetic suspension to reduce friction and in turn the power and heat generation as a result of rotating the cabins.

 

I can't remember the exact figures, but you (regrettably) cannot make a centrifuge that small and spin it up to 1g without ill effects for anyone in it. You end up with considerably stronger forces on your feet than on your head and subsequently endure nasty side effects when your blood doesn't go where it's needed. From what I remember, for a 1g centrifuge you need something about an order of magnitude larger, or you could just spin up a smaller one to maybe 0.1 or 0.2 g.

Also for an SSTO, a saucer doesn't have a huge number of favourable aerodynamic properties...

Edited June 6, 2017 by Steel

[DerekL1963]

Yeah, what DDE said.  Your proposal isn't science, or even science fiction - it's fantasy.
 

35 minutes ago, Dave Angel said:

So I've started the model

If you've started a model before running the numbers, you're far down the wrong path.

[DDE]

2 minutes ago, DerekL1963 said:

Yeah, what DDE said.  Your proposal isn't science, or even science fiction - it's fantasy.

TBH it's only about as bad as Interstellar. Those guys too had two Tokomaks in a tiny SSTO with no rad shielding in sight.

@Dave Angel, due to radiation issues, you simply can't beat the classic tailsitter rocket. But instead of using a tiny radiation shadow shield (see image), you decided to wrap your habitat around the reactor, ballooning your shielding mass a hundredfold at least, with no benefit at all.

And that's assuming an atmospheric-capable craft would be taken out of LEO and thus need a-grav.

[Steel]

@Dave Angel please don't take any comments here personally, it's just that you've posted this in the "Science and Spaceflight" subforum that for the most part believes that EM drives are pretty far removed from both science and spaceflight (and also doesn't want to spend another thread arguing about them)

[Green Baron]

Blowing in the same horn. I'd be happy if we could at least pretend to keep a science background. Or rename the forum :-)

 

There isn't even a first generation emdrive and there is no reliable proof that the thing works. Nobody can explain what was measured, if something was measured at all.

The saucer shape is from fun pictures of the second third of the last century (maybe older) :-)

 A fusion reactor is far from a working example. All the coils and magnets to contain a plasma of a few grams are heavy.

I mean, that all is fun as an add-on for computer game, but that is all imo.

 

[sevenperforce]

Ditto on what everyone else said about emdrives and fusion reactors.

If you're going to go the saucer route, you should spin up the whole ship rather than wasting time with a separate rotating segment.

A saucer shape is decent if you have rotating engine nacelles, because you can land and lift off vertically but then transition to lift-assisted forward flight. It also is nice and draggy with a good blunt shape for aerobraking.

[Dave Angel]

OK, should have expected that, but i did say future technologies...

Some good points though that will send me back to the drawing board.

Quote

I can't remember the exact figures, but you (regrettably) cannot make a centrifuge that small and spin it up to 1g without ill effects for anyone in it. You end up with considerably stronger forces on your feet than on your head and subsequently endure nasty side effects when your blood doesn't go where it's needed. From what I remember, for a 1g centrifuge you need something about an order of magnitude larger, or you could just spin up a smaller one to maybe 0.1 or 0.2 g.

..Yes your right, looked this up, and your right, Looks like 2RPM is 'safe', so thats a 200M ring. Guess 0.2g will have to do!

[DDE]

3 hours ago, Dave Angel said:

but i did say future technologies...

That's not an excuse for magic.

It's borderline-impossible to produce an SSTO without resorting to fission or fusion power. Once you go there, it becomes very difficult to create a swiveling engine nacelle because of the stupendous amounts of rad shielding involved. And having a separate hover engine is a death sentence for an aircraft, let alone a spacecraft.

Basically, flying saucers suck. There is no way they are more useful than more conventional alternatives.

Consider the classic rocketship. Main engines used for hovering. Can do with a very narrow radiation shield. And you don't need a ring to get artificial gravity.

 

Edited June 6, 2017 by DDE

[mikegarrison]

With gravity by rotation, the key is to have a large radius and a small rotation rate. The rotation itself gives you all sorts of undesired side effects, so you want the rotation rate to be as small as possible. This paper found that patients lying down in a rotating bed were able to adapt over a few days to tilting their head without getting sick at up to 23 rpm. But most people assume that to have a functional environment in which you can walk around and do work and such, it would be better for the rotation to be kept to only 2 or 3 rpm.

[Green Baron]

Some people actually do pay money to have a ride on fast rotating devices at fun fairs.

But this probably a European phenomenon. Might be connected to the age old habit of self castigation or something :-))

[YNM]

British Railways beats you by almost half a decade.

With patents !

[sevenperforce]

The only reason to do a flying saucer design is if you have a handwavium gravity rail device or something like that.

[For the uninitiated, a gravity rail is a fictional device which permits a vehicle to be "locked" at a single point in a gravitational gradient, allowing it to hover without expending propellant. It is one of the few types of antigravity which doesn't violate conservation of energy or momentum.]

[K^2]

19 hours ago, mikegarrison said:

With gravity by rotation, the key is to have a large radius and a small rotation rate. The rotation itself gives you all sorts of undesired side effects, so you want the rotation rate to be as small as possible. This paper found that patients lying down in a rotating bed were able to adapt over a few days to tilting their head without getting sick at up to 23 rpm. But most people assume that to have a functional environment in which you can walk around and do work and such, it would be better for the rotation to be kept to only 2 or 3 rpm.

2 RPM is the most commonly cited figure for "comfortable for everyone". Unfortunately, 1g at 2 RPM means a 250m radius. If you plan to build that as a ring, we are talking about a station half a kilometer in diameter. Nearly five times larger than end-to-end length of ISS. Hopefully, we'll see structures like that in the future, but it's not something you want to start with for interplanetary flight. Maybe when you get to the stage of needing cycler ships.

Kerbals might be a lot tougher, of course, and maybe they are fine with lower gravity and higher RPM. But at that point you aren't really going for realism anymore.

[shynung]

4 hours ago, K^2 said:

1g at 2 RPM means a 250m radius. If you plan to build that as a ring, we are talking about a station half a kilometer in diameter.

Not necessarily.

If we can, for example, build a tail-heavy long ship (CoM as near the tail as possible), we can make a ship that's less than 500m long. Still much longer than the ISS, but at least it's a bit simpler to build.

[Green Baron]

Uneven mass distribution ... wouldn't that be forced into a bound rotation soon ? And wouldn't the momentum change then cause that thing to rotate around the longitudinal axis ? Not sure, a question ....

If so, don't look out of the window :-)

[sevenperforce]

39 minutes ago, Green Baron said:

Uneven mass distribution ... wouldn't that be forced into a bound rotation soon ? And wouldn't the momentum change then cause that thing to rotate around the longitudinal axis ? Not sure, a question ....

If so, don't look out of the window :-)

Bound rotation?

The concept is a tumbling penguin rotation, nose over tail. Gravitational vector is, unfortunately, opposite the vector at play during the acceleration phase. This is not a problem if you do an Apollo-style cabin flip before you spin up for the outward journey. 

More on that concept....

[Steel]

2 hours ago, shynung said:

Not necessarily.

If we can, for example, build a tail-heavy long ship (CoM as near the tail as possible), we can make a ship that's less than 500m long. Still much longer than the ISS, but at least it's a bit simpler to build.

Doesn't really satisfy the OP's idea for a saucer-type spacecraft though

[magnemoe]

5 hours ago, Green Baron said:

Uneven mass distribution ... wouldn't that be forced into a bound rotation soon ? And wouldn't the momentum change then cause that thing to rotate around the longitudinal axis ? Not sure, a question ....

If so, don't look out of the window :-)

Not a problem, have you seen the centrifuges they use for high g training? they have an heavy counterweight close to the axis. Interesting for the long boom type spacecraft who uses an nuclear engine in the rear. You would have fuel tanks next, then payload and crew quarters on top. Added bonus is that g load on payload will be low. You could probably even extend to boom, perhaps even use an cable. 
Only downside is that trust and rotation gravity would be opposite, yes the trust g is low and don't last too long but still an issue.
 

[K^2]

7 hours ago, shynung said:

Not necessarily.

If we can, for example, build a tail-heavy long ship (CoM as near the tail as possible), we can make a ship that's less than 500m long. Still much longer than the ISS, but at least it's a bit simpler to build.

 

12 hours ago, K^2 said:

If you plan to build that as a ring, we are talking about a station half a kilometer in diameter.

I added emphasis to point out the contradiction.

[Bill Phil]

A lot of the literature and studies about rotation tolerance are not very complete. Most of the scenarios rotate about an axis that isn't particularly far from the person. And some even point to the possibility that people could adapt to 4 rpm at the least. Potentially 6. We need more experiments. Almost none so far have been in free fall, if any.

[shynung]

2 hours ago, K^2 said:

I added emphasis to point out the contradiction.

I understand. I simply put forward another method of getting 1G via rotation that's far less mass/resource-intensive, which I think is more appropriate for a ship. For stations, rings are more acceptable, but as you say, we run into the size problem.

Edited June 8, 2017 by shynung

[Dave Angel]

Quote

A lot of the literature and studies about rotation tolerance are not very complete. Most of the scenarios rotate about an axis that isn't particularly far from the person. And some even point to the possibility that people could adapt to 4 rpm at the least. Potentially 6. We need more exp

I think there was a plan to add a rotating module to the ISS called the Nautilus-X, but it got canned - as most of the experiments planned relied on zero-g conditions it was seen as an expensive option.

[K^2]

6 hours ago, shynung said:

I understand. I simply put forward another method of getting 1G via rotation that's far less mass/resource-intensive, which I think is more appropriate for a ship. For stations, rings are more acceptable, but as you say, we run into the size problem.

If you aren't going for a ring station, I think tethers are the way to go. Once you're at a cruising trajectory, simply extend you engines/reactors/whatever on a long tether and give the system a gentle spin. I honestly don't see us making regular round trip flights to Mars until we learn to do something like that with our ships.