2300 AD: Sung ion drives and light sails, I don't buy it

[Yatima]

I decided to try and develop some background and ship designs for the Sung, so started to read through the sparse published material. It states that the Sung are as technologically advanced as humanity (more so in medical science) but don't have stutterwarp. Fine. Then it states that their system ships make extensive use of Ion drives and light sails – I simply don't buy this.

Why would a civilisation with access to fusion rockets, MHD thrusters and other drive systems subject themselves to in-system travel times in months or years when they have access to faster drive systems? Light sails have barely enough thrust to move the sail, let alone the payload. I can see the Sung using Ion drives in robotic tankers or cargo haulers, for cargos they don't need to get to market for many months, but these drives make no sense whatever for transporting Sung in system.

Ion drives trade off huge fuel efficiency against pathetic thrust, and I bet a Sung's time is as valuable to it as mine is to me, even with its 150 year lifespan.

Thoughts?

 

[rust]

We have not done much research into ion drive concepts,
it may well be that a more advanced technology could de-
velop ion drives which would allow comparatively short in-
terplanetary flight times. Just take a look at the VASIMIR
concept, it is much better than what was considered pos-
sible only a few decades ago:

http://en.wikipedia.org/wiki/VASIMR

 

[Yatima]

Sure, there are advances in Ion engines even now:

http://gizmodo.com/5917866/australia-is-building-a-pee+powered-ion-thruster
http://phys.org/news9786.html

But even so, Ion engines excel at fuel efficiency, they can thrust for ages on low fuel consumption but produce too little thrust. You'd use one if you want to save on fuel mass and don't care how long a journey takes. My point is Sung seem unlikely to use this to travel given almost any viable alternative such as MhD + thrusters, Nuclear-electric engines or the Plasma drives you mention (in 2300AD, the plasma drive listed is an evolution of Vasimir).

Looking at the rule book, we see that:
* Plasma Drive has a fuel consumption of 0.025% a size and cost multiplier of x5 and a max acceleration of 0.1
* Ion drives have a fuel consumption of 0.0025% a size multiplier of x5 and a Max acceleration of 0.01

So Ion drives in 2300AD have one tenth of the fuel consumption of a plasma drive but produce one tenth of the thrust. Why use these for anything except long-duration station keeping or cargos that can get there next year and still sell fine?

 

[Reynard]

The information I'm reading about ion thrusters say the amount of thrust is low because the power sources available *currently* are inefficient. Oh, you mean we don't have compact fusion power plants yet. Current thruster system concepts also assume solar collectors for power. Yeah, how efficient are those today?

http://en.wikipedia.org/wiki/Ion_thruster

Unfortunately, the 2300AD MHD and fusion tables don't show actual power but I believe both are high enough to run an ion engine very well.

As to solar sails, very cheap transport for cargo not time sensitive such as ore shipments that will be arriving continuously.

 

[Yatima]

No, still don't buy it. Looking at Fire Fusion and Steel (TNE version) we see some figures from an earlier version of traveller that shows just how underpowered both these technologies are:

The pressure of sunlight on the sail inside the habitable zone of a star system generates 0.5kg of thrust (or 0.0005 tonnes) per square kilometer of sail. As a square kilometer of solar sail, complete with its rigging, weighs 0.5 tonnes, or 1,000 times as much as the thrust generated, and that is without any payload, it is immediately obvious that the sail generates minute acceleration. (p. 74)

Outside the inner star system, solar sail performance drops drastically.

While adding energy to a rocket exhaust does increase exhaust velocity, the mass of the propellant is a factor too and Ion drives use ionised plasma which is low mass.

I concede Ion drive robotic cargo haulers bringing low-priority bulk cargos to Stark in a continuous stream, but using Solar sails is so inefficient as to be an affectation for any civilisation with a better option. Any better option.

The same goes for passengers, they won't wait the months it takes for an Ion drive ship, compared to the days or weeks other drives make possible. From FF&S again:

The advantages of these [ion] drives are their endurance, low power requirements, and reliability. But the low thrust generated by this sort of drive limits its utility to moving low priority cargos around inside a star system. interplanetary trips by ion drive typically take months rather than days or weeks. (p. 72)

The FF&S details of Ion drives are:

Each cubic meter of Ion drive requires 0.03MW of power from a separate power plant and generates 0.003 tonnes of thrust, consuming 0.0000067 cubic meters of ionizates per hour. (p. 72)

Both these technologies use little or no fuel, but the trade off is tiny acceleration values that make for very long trip times in a star system. Technical advances won't change this enough to matter. The question stands, why would the Sung use these technologies when they have better options?

 

[Epicenter]

It seem the assumption here is that the Sung are using sunlight to propel their light sails.

I've always assumed that the Sung actually used enormous complexes of lasers to push the light sails around the system. Given the Sung appear to have never left their solar system, by the time humanity arrived, the Sung probably had a variety of complexes in the inner and outer solar system -- anywhere that could be developed profitably -- and had large complexes of launching lasers to push their light sail ships around the system. Such a system isn't as flexible as starships, but has its own advantages - their starships would not have devote mass to maneuver drives or thrusters, allowing them to use their sails and maximize mass for cargo. Ships that had to deviate from standard courses used ion thrusters to modify their direction.

Given the large number of very powerful laser complexes, I've always imagined the Sung didn't really have a space fleet - at solar system distances, almost any fleet traveling under lightspeed could be blasted long before they arrived at any base or the Sung homeworld under the principles of the Kzinti Lesson and those "powerful launch laser complexes." The Sung probably hastily armed some of their starships to deal with humanity's naval vessels, but both the launch complexes and their hastily rigged up "navy" had a hard time dealing with ships that could effectively travel faster than the speed of light.

 

[Yatima]

I had considered beamed power, it's certainly an interesting option and does raise some interesting scenarios for the war against humanity over the Xiang. I must look into beamed power, it seems that some quite sophisticated and exceptionally high powered lasers or masers would be required to make this work. Also, as well as using laser pressure on a sail, there's an option to use it to heat or ablate reaction mass, such as ice, creating a rocket exhaust that way.

This also links in to some of the ideas for Sung ship designs that I was kicking around, looking at the ISV venture star from Avatar, which uses beamed power on the outbound course and decelerates at the destination using antimatter engines. I also like that the design puts the engines at the front, pulling a much lighter ship along rather than pushing the ship from the back, which requires more structural integrity of the ship members. Quite clever:

http://www.projectrho.com/public_html/rocket/realdesigns.php

 

[Reynard]

"The question stands, why would the Sung use these technologies when they have better options?"

Just because a science and the subsequent technologies can exist doesn't mean it will be discovered by everyone. For whatever reason, the Sung 'didn't get it'. Maybe the Sung thought the ion thruster and solar sail tech was the height of space travel and FTL was impossible.

 

[Yatima]

Just because a science and the subsequent technologies can exist doesn't mean it will be discovered by everyone. For whatever reason, the Sung 'didn't get it'. Maybe the Sung thought the ion thruster and solar sail tech was the height of space travel and FTL was impossible.

Interesting proposition, Reynard, but I think that if the Sung's technology and science are on a par with humanity (excepting stutterwarp) then they will have the basic principles of rocketry, fission, fusion, magnetohydrodynamics and all of the other concepts they need. This is going to require an economic rationale, a choice they made to use or not use an available technology, so that's the sort of answer I'm searching for, I suppose.

Does that make sense?

 

[CosmicGamer]

Both these technologies use little or no fuel, but the trade off is tiny acceleration values that make for very long trip times in a star system. Technical advances won't change this enough to matter. The question stands, why would the Sung use these technologies when they have better options?

"Better" is relative. You've answered it yourself I believe? "Both these technologies use little or no fuel" While this may not be the best solution in many situations, I can definitely see some situations where saving cost on fuel might be "better" or a ship design that allows operation for a longer distance without refueling is "better".

 

[Yatima]

"Better" is relative. You've answered it yourself I believe? "Both these technologies use little or no fuel" While this may not be the best solution in many situations, I can definitely see some situations where saving cost on fuel might be "better" or a ship design that allows operation for a longer distance without refueling is "better".

I see your point, but there are some absolutes here that we need to recognise. The Better afforded by solar sails is a clear better for humanity today, when getting anywhere in the solar system is an enormous challenge. I wanted to point out that to someone in the Sung's position, Solar Sails are simply not better given the other options available.

Ion drives make sense in one case - non-time sensitive transport of bulk cargos. Beamed power might be a decent post rationalisation of earlier GDW writings on the Sung.

What I'm implying, I suppose, is that the Sung must have fusion/MHD or other forms of in-system transport that are used for transporting persons and for other tasks. The image of the Sung sailing around the system on solar yachts and terribly slow Ion drive ships alone isn't credible to me. So I can try and explain it away as a sort of Retcon, or redefine it, which i presume Colin will have the opportunity to do sooner or later.

Interestingly, Colin mentions Ion engines but not Solar sails in the 2300AD rulebook.

 

[CosmicGamer]

Just because a science and the subsequent technologies can exist doesn't mean it will be discovered by everyone. For whatever reason, the Sung 'didn't get it'. Maybe the Sung thought the ion thruster and solar sail tech was the height of space travel and FTL was impossible.

Interesting proposition, Reynard, but I think that if the Sung's technology and science are on a par with humanity (excepting stutterwarp) then they will have the basic principles of rocketry, fission, fusion, magnetohydrodynamics and all of the other concepts they need. This is going to require an economic rationale, a choice they made to use or not use an available technology, so that's the sort of answer I'm searching for, I suppose.

Does that make sense?

Economic rationale? Since when does one persons economic rational align itself with another? Are there not real world examples of large powerful wealthy corporations and conglomerations suppressing "better" technologies? Government and corporate entities giving out "non economically rational" contracts for personal pocket lining "economic rationale"?

For a less conspiratorial possibility, the government and companies are locked into long term contracts for ship construction and it is not economically viable to pay the penalties to break the contracts and generate new ones for the "better" technology.

Maybe treaties with other governments restricted certain things.

Just because a society has mastered something like nuclear power with safe power plants generating electricity and large military ships on the ocean doesn't mean we automatically have them as a "better" technology in cruise ships or allow the research and testing of nuclear powered airline jets or have mastered reducing it to power automobiles. We have had "battery technology" a long time but battery powered cars are just starting to be viable - where are the battery powered passenger planes and cruise ships? Similarly, even if someone has fusion or a certain level of technology for a power plant doesn't mean it is automatically applicable for space ship propulsion.

I don't know the setting, but I'm sure with imagination there could be many numerous possible reasons that would fit. My presumption is that 2300 does not use some reset dating system and is simply 287 years into the future? I can see a certain group just not "getting it" at the same time as others in this short timespan.

 

[simonh]

"The question stands, why would the Sung use these technologies when they have better options?"

Just because a science and the subsequent technologies can exist doesn't mean it will be discovered by everyone. For whatever reason, the Sung 'didn't get it'. Maybe the Sung thought the ion thruster and solar sail tech was the height of space travel and FTL was impossible.

There's also the Space Shuttle/Buran debacle as a case study. The shuttle was a terrible concept that was misconceived from the start. The Russians couldn't figure out what the Shuttle was for because the design parameters didn't match what NASA and the US government was telling everybody. So assuming the USA had a secret reason for building it*, they decided they should have one too so that when they did figure out the USA's master plan, they'd be able to counter it with equivalent technology. Of course, the USA didn't actually have a secret brilliant master plan because the whole thing was a political football between the Air Force, NASA and Congress that wasn't going anywhere useful, but the Russians didn't know that.

So if you took the last 50 years of space technology development and showed it to aliens, they'd likely tell you to think up something more believable because what you're telling them is so implausible as to just be plain silly. Why would the planet's two major space powers waste an entire generation on dead-end technology like that? It's just too unrealistic.

Simon Hibbs

* I highly recommend the linked article, it's very interesting stuff.

 

[Hopeless]

Just a thought but what if the Sung developed beamed power satellites as both a means of propelling their solar sail fleet but also as a defensive measure?

So rather than having developed fusion rockets and the like they have developed a defensive system that works best using that technology they don't have against the race that uses them?

So these satellites are organised around the system so those solar sails can maximise their movement, they also target anything coming into the system you know like comets or enemy warships and tear them apart with coordinated blasts from enough beamed power satellites to make mincemeat out of them unless they want to mine or recover materials to study or refine...

What was the name of that book series where humanity is absorbed into an alien mercantile empire and one human using maple syrup initially builds the means to defend the solar system as well as buy back all of earth's treasures as the mineral wealth of the asteroid belt is what the aliens' are more interested in.

Another member of the mercantile union eventually ascends into control which is where the beamed power satellite system comes in very necessary... wish I could remember the title of the series!

Ion Engines, whats to stop them having a sort of regular bus or pickup point so these ships would have built up a bit of speed enough to pickup cargo without slowing and then dropping them off to another system that slows the cargo/passenger pod down as the bus heads back on its scheduled run back into the inner system again?

 

[Yatima]

Economic rationale? Since when does one persons economic rational align itself with another? Are there not real world examples of large powerful wealthy corporations and conglomerations suppressing "better" technologies? Government and corporate entities giving out "non economically rational" contracts for personal pocket lining "economic rationale"?

For a less conspiratorial possibility, the government and companies are locked into long term contracts for ship construction and it is not economically viable to pay the penalties to break the contracts and generate new ones for the "better" technology.

All possible, I suppose, but they are essentially hand waving - they seek to explain something in order to support it because it was written into the setting. I don't think that's a solution I can live with, though it'd certainly satisfy many gamers.

I don't know the setting, but I'm sure with imagination there could be many numerous possible reasons that would fit. My presumption is that 2300 does not use some reset dating system and is simply 287 years into the future? I can see a certain group just not "getting it" at the same time as others in this short timespan.

Yes, it's 2300 AD. As I said, I can think of many ways myself to retrospectively justify what the old game material said, I even see some interest in limiting the Sung to some technologies. What interests me is questioning the original materials credibility and coming up with a more plausible reason that isn't simply hand waving – they know of a better engine, they're still arguing over patents, or it's being suppressed by corporate interests. These aren't satisfying explanations because corporate interests will be better served by faster ships. Which are certainly available.

 

[Yatima]

Just a thought but what if the Sung developed beamed power satellites as both a means of propelling their solar sail fleet but also as a defensive measure?

There's certainly mileage in this, Hopeless. A system of solar power satellites, using a Maser to beam power down to Stark, and has the side benefits of being a good transport system and an asteroid deflection system too. Worth considering for sure. I suppose the only quibble is that the contact with the Manchurians was a first contact for the Sung as well as humanity (excluding the Xiang, in their own system), so not sure if they'd put a defensive system as a high priority, maybe just a neat side benefit of orbital lasers/masers.

Ion Engines, whats to stop them having a sort of regular bus or pickup point so these ships would have built up a bit of speed enough to pickup cargo without slowing and then dropping them off to another system that slows the cargo/passenger pod down as the bus heads back on its scheduled run back into the inner system again?

Sure, over time these things can build up huge speed, they just accelerate very slowly. The problem with a cycler system like this is that you need a ship capable of catching up to the cycler to board or unload it, and then it'd have to have the delta V to decelerate itself and the Cycler's cargo to the orbital velocity of the destination. If the only engine is Ion, then this would take as long to rendezvous with the cycler as the cycler took to get up to speed, and as long again to decelerate. In fact, a system of cyclers like this is a great idea but actually requires the Sung have faster drives than Ion drives or solar sails.

Thanks for the contributions, guys, very thought provoking

 

[Reynard]

One thing to remember, the Sung are not human. Their culture, history and mindset are not some parallel to humanity. Why must we assume they would do things as humanity has done?

Steam engines were introduced in the Roman era but waved off as impractical for any but maybe a toy curiosity. European attitudes towards cleanliness set medicine back. What other sciences were ignored or suppressed that may have created a 21st century world in those days? We can't conceive today how anyone would deny the obvious but it happened and may still be happening today.

We can't conceive the Sung not being on par when humans reach them. The Sung want to catch up but who is denying them stutterwarp? The Sung did things their way. That's not 'hand waving', that's the nature of development. There could be another race out there wondering why humanity hasn't grasped their means of interplanetary and/or interstellar travel.

 

[F33D]

Then it states that their system ships make extensive use of Ion drives and light sails – I simply don't buy this.

You can safety throw the solar sail part into the garbage can and chalk it up to carelessness/ignorance of the writer. Unless performance stats are given for the Ion drives, just assume that they are a lot better than what we have now and go with it.

 

[Colin]

The Sung do not use nuclear fission at all, due to several bad experiences with it within the past 100 years. Fusion reactors are significantly more bulky, and not suitable for use as space drives. While Sung technology is largely on par with human technology, it is somewhat higher in medical science, and lower in nuclear power generation and space drives.
They use conventional rockets, laser lift arrays, and air-breathing thrusters, all at approximately TL10, for interface travel.
The Sung have known of the habitable Xiang moon since well before the start of their space-faring period, and it has always been the focus of their efforts. They are not otherwise a major space-faring culture. They do not have asteroid mines, limited orbital infrastructure and industry, and only a limited presence on their planet's moons.
Solar sails are used for cargo, and in the ten years prior to First Contact, laser arrays first started being used for initial boosts. Conventional space flight, for passengers and military vehicles, uses something similar to a VASIMIR drive. Interplanetary flight uses the drive in a low-power mode, but if high-impulse maneuvering is called for, then the drive can manage that as well. Power sources are fuel cells and solar panels, with stand-by MHD turbines for high thrust periods. Advanced cold sleep, courtesy of their medical technology, is common.
During the Slaver War, Manchurian and Canadian forces used drones with kinetic weapons to destroy the Sung orbital laser arrays before taking position over Stark. While the lasers were powerful enough to damage a ship at ranges of several light minutes, Sung gunners had no clue of HOW to hit a stutterwarping starship at those sort of ranges. Since the war, the Sung have not rebuilt the laser arrays, and have been purchasing surplus fusion rocket systems from Manchuria, all the while lobbying to stutterwarp drives, and working furiously in secret to developing them. Half the battle is knowing it can be done...

 

[Yatima]

Hi Colin, thanks for the contribution, really interesting to know your thoughts on the matter.

You included Ion drives in 2300 AD book, and I see that solar sails are covered in High Guard - stating the stowed mass and that they have thrust 0. Do you have plans to expand on this in a future book about the Chinese Arm?