Nexus: The Jupiter Incident science Q's

[Mazryonh]

Hi, this game had a chapter that focussed around harder sci-fi than is normally found in gaming (minus the unrealistically short engagement ranges for the weaponry involved and the Star-Wars-style asteroid fields).

My questions centre around the transit times mentioned in the various mission briefings, and what possible performance standards this could imply for the ships ingame. For one thing, the 6th ingame mission involves a trip from Jupiter to Pluto. The CO giving the briefing claims that "with our current drive technology, the journey would take almost 4 years . . . however, if we use the (fusion-engine-equipped) alien ship, it would take only a few weeks." The exact start- and end-dates of the journey are May 19, 2112, and June 1, 2112.

The exact questions I would like answered are:

[*]Is the virtual solar system depicted ingame accurate for the dates specified?
[*]What kind of performance level for the Angelwing's fusion engine is implied by the transit time?
[*]How does that performance level stack up against proposed real-life fusion drives?

There's also another long trip right at the beginning of the game, from Low Earth Orbit to orbit around Jupiter's moon Europa, taking from September 3rd, 2111 (with a stop-over in orbit around Earth's moon to pick up two cargo ships on September 5th) to April 28th, 2112. This time the less-advanced ships are using "chemical engines." Is such a transit time realistic, and what kind of performance level for those engines does that imply? Also, is it better to have just one rotating section for artificial gravity on a combat spaceship like the ISA and Spacetech ships do in the first chapter of the game, or two contra-rotating sections like the Kissaki Syndicate combat spaceships do for artificial gravity?

[Eternal_Freedom]

Actually, I as under the impression that the Angelwing used it's IP drive to reach Pluto, not it's fusion engine. After all, "almost four years" is 200 weeks (for the sake of argument) and "a few weeks" might mean anytihng up to five or six. So if the fusion engine was used it woudl have to be 40 times more effective, and we don't see that borne out by the ship's in missions.

As for the solar system being accurate for those dates I have no idea, but I see no reason why it wouldn't be since "real solar system dynamics" was a selling point for the game.

[Terralthra]

It's worth pointing out that the relative orbital points of Jupiter and Pluto to each other is highly relevant in calculating this. In the best-case/worst-case scenario (ie, a scenario that most favors the alien technology over existing human technology), the orbits could be lined up such that the Stiletto, under IP-drive, can do a nearly-direct orbit transfer by simply speeding up from Jovian orbit and slide almost perfectly into Plutonian orbit with little turnover or vectoring orbital velocity, as the two orbits are near their closest approach, with Pluto slightly "behind" Jupiter.

Remember that per Keplerian orbital mechanics, an orbiting body moves faster nearer perihelion than at apihelion, so if the orbits lined up such that both planets were near perihelion at a close approach to one another, their relative orbital velocity would be at its minimum, and increases once Pluto passes Jupiter. In such case, as your ship's overall dv/dt is lower, the transit distance increases as a function of time taken. The longer transit distance means you have to aim further ahead (or even behind), which means the transit increases more than naïve calculations based solely on velocity would imply. It wouldn't actually take a 40-fold increase in drive delta-v to equal a 40-fold decrease in transit time, because of this.

Without looking up the relative positions of the planets in 2112, I can't tell you how closely the actual movement of the planets matches up with the outlined best-case/worst-case, but it's possible that such a scenario exists, without a 40-fold increase in delta-v required.

[Eternal_Freedom]

The game map and dialogue specifically state the orbits of Jupiter and PLuto were almost exactly opposite at that time, meaning a flight of 44 AU.

[Me2005]

I am not a rocket scientist, but it looks like, according to Atomic Rockets, making the first mission (Earth-Jupiter) with chemical powered ships is not possible. Chemical rockets cannot provide enough DV to use a Hohmann orbit - the lowest DV option- and it would only occur every 13 months and take ~33 months to complete. You'd need a brachistochrone trajectory to make that time, and enough DV to provide constant acceleration of less than 0.01g for the whole trip. 0.01g would get you there in about 3.5 months.

The Jupiter-Pluto Hohmann mission's DV actually lower than the Earth-Jupiter one, according to the charts provided. You can get that with a relatively low-tech Orion drive (drop atomic bombs behind your ship and set them off), but unfortunately, the sync period is only once every 12 years, and the trip would take 52 years. Using a 0.01g brachistochrone orbit for the whole trip, you'd probably be taking 10 months to a year. It looks like just about any fusion drive could make the trip at 0.1 g easy enough though, and that'd get you into your 'few weeks' time period.

As a note, the delta-V available involves the ship's engine preformance and the ratio of fuel to non-fuel mass onboard any ship. The 0.1g number above would mean you're flying a ship of up to 60% fuel mass.

And to your rotation question; having one rotation section means you need to fire thrusters to counter the rotation. But you have fewer moving parts (especially vacuum sealed hubs) than a counter-rotation setup, so it's most likely a wash.

[Mazryonh]

I am not a rocket scientist, but it looks like, according to Atomic Rockets, making the first mission (Earth-Jupiter) with chemical powered ships is not possible.

Well, in Nexus: TJI's first chapter, space travel appears to be routine as air travel, so it's reasonable that the megacorporations mentioned in the introduction (the ISA, representing the Terran government, has control only over Earth and the moon) left propellant depots in the path of high-traffic routes to allow for the space-borne equivalent of inflight refueling. Then again, Nexus: TJI isn't the strictest with its scientific accuracy when it comes to spaceship/starship drives. Like Babylon 5, several smaller ships of the Noah colony faction are ostensibly equipped with what are called ion drives, yet these still manage periods of high thrust, just like certain Babylon 5 ships manufactured by the Terrans and Narns in that series.

The Jupiter-Pluto Hohmann mission's DV actually lower than the Earth-Jupiter one, according to the charts provided. You can get that with a relatively low-tech Orion drive (drop atomic bombs behind your ship and set them off), but unfortunately, the sync period is only once every 12 years, and the trip would take 52 years. Using a 0.01g brachistochrone orbit for the whole trip, you'd probably be taking 10 months to a year. It looks like just about any fusion drive could make the trip at 0.1 g easy enough though, and that'd get you into your 'few weeks' time period.

Thanks, though I wonder just which of those would be suitable for a "combat" drive that requires sustainably high thrust to jink and maneuver in a timely fashion. The Angelwing is some 800 meters long (its "dry" mass is unmentioned), which should be longer than almost any of Trek's Enterprises.

The IP (InterPlanetary) drive in Nexus: TJI is something of a conundrum. The ingame description describes it as a way to travel at high speed, safely submerging the ship in subspace, but never mentions whether it is FTL or STL. The fourth episode's introduction cutscene implies that it is FTL (able to transit between planets in a trivial amount of time, something that could take minutes to hours even at a significant percentage of light speed), but even if it is, it is clearly not up to even Trek standards, because all factions in the game require pre-existing wormholes for the majority of their interstellar travel. The "Wormhole Cataclysm" mentioned in the game's backstory is caused when the existing wormhole network realigns and redirects or closes off many existing routes, so they can't go dashing from star system to star system at will with their IP drives. Oh well, at least the developers had the foresight to make it so that IP-jamming/interdiction technology exists, so "the map still matters" in the words of Atomic Rockets.

And to your rotation question; having one rotation section means you need to fire thrusters to counter the rotation. But you have fewer moving parts (especially vacuum sealed hubs) than a counter-rotation setup, so it's most likely a wash.

From a section I've read on Atomic Rockets but can't remember the exact page for, a single spinning gravdeck (without some internal means of compensating for the torque generated) just means that your maneuvering thrusters have to be programmed to compensate for the gyroscopic motion of the gravdeck, something to the tune of "if you want the bow to pitch downward while your single gravdeck is spinning, your thrusters just have to be programmed so that the yaw-left thruster fires instead." Still, I've been wondering whether a spinning gravdeck could be used as a method of reactionless orientation-changing (due to gyroscopic forces), or if it would require more than one. Don't real-life space stations use gyroscopes to change their orientation without needing to expend reaction mass?

[Eternal_Freedom]

My understanding of the IP drive was that it's "translight" not "superlight." So, It an take you up to 0.8c-3 or 4c, which is speedy enough to move around a solar system easily, but of no real use in interstellar travel.

As for the "Ion drives" bit, they are actually called "Ionstream" engines, which does not automatically equate to ion drives as we think of them. Clearly they can't be ion engines because of the observed capabilities. I suspect they are an earlier/older version of the "Plasmastream" engines you get later.

[Me2005]

Well, in Nexus: TJI's first chapter, space travel appears to be routine as air travel, so it's reasonable that the megacorporations mentioned in the introduction (the ISA, representing the Terran government, has control only over Earth and the moon) left propellant depots in the path of high-traffic routes to allow for the space-borne equivalent of inflight refueling.

I'd neglected fuel depots, which would make the journey more feasible with any drive. Every time you can add fuel that you didn't carry, you increase your DV, so it's certainly possible to do it with fuel drops. [/off topic] I'd read a really interesting article somewhere on using ion-drives to put fuel dumps into specific orbits, exactly for this purpose. It'd take a few years to get set up, but once it was running, crewed missions could use chemical drives and shorten all their missions tremendously.[/off topic]

Thanks, though I wonder just which of those would be suitable for a "combat" drive that requires sustainably high thrust to jink and maneuver in a timely fashion. The Angelwing is some 800 meters long (its "dry" mass is unmentioned), which should be longer than almost any of Trek's Enterprises.

Some of the fusion drives produce quite a bit of thrust, but you could take a look through Atomic Rockets' engine list. Adding a high-thrust fission or chemical drive for maneuvers wouldn't be an extraordinary thing to do, and many of the fusion engines and fission engines could share fuel.

The IP (InterPlanetary) drive in Nexus: TJI is something of a conundrum. The ingame description describes it as a way to travel at high speed, safely submerging the ship in subspace, but never mentions whether it is FTL or STL.

I think this is your answer - it's definitely a non-real drive since we don't know anything about using 'subspace'.

From a section I've read on Atomic Rockets but can't remember the exact page for, a single spinning gravdeck (without some internal means of compensating for the torque generated) just means that your maneuvering thrusters have to be programmed to compensate for the gyroscopic motion of the gravdeck, something to the tune of "if you want the bow to pitch downward while your single gravdeck is spinning, your thrusters just have to be programmed so that the yaw-left thruster fires instead." Still, I've been wondering whether a spinning gravdeck could be used as a method of reactionless orientation-changing (due to gyroscopic forces), or if it would require more than one. Don't real-life space stations use gyroscopes to change their orientation without needing to expend reaction mass?

Yes, you get a gyro effect from a spinning deck, so two would counter that out. It's not really a big deal though, mounting your RCS differently and programming it to work shouldn't be hard.

I think you could try to use a grav-deck as a reaction-less RCS, but you'd have to keep in mind that you'd be dealing with a huge mass that probably has people in it. So just slamming the brakes on it to reposition your ship won't do the people inside any favors, and you're just as likely to start spinning your whole ship around. From what I understand of the real-life positioning gyros, they aren't that big, they are counter-oriented, and they are mounted differently than a huge spinning habitat would be.

My understanding of the IP drive was that it's "translight" not "superlight." So, It an take you up to 0.8c-3 or 4c, which is speedy enough to move around a solar system easily, but of no real use in interstellar travel.

This is actually a pretty cool idea, a sci-fi magic drive that just gets you up to very high sub-light speeds. Does it also take you out of real-space, as the "submerging the ship in subspace" comment would indicate (disengagement of the drive drops you back to normal speeds, and you can't crash with it enabled)? That would alleviate issues with rouge captains using their ships to annihilate planets.

[Eternal_Freedom]

THere is some freaky blue wavey/tunnely effect when the drive is used, and when the drive shuts down you get yanked back to normal space at the same speed you were in when the drive activated, which is why IP blockers work. However, as several cutscenes show, while using your IP drive you can still see other ships and planets. We know the drive can't be an FTL engine since we can see that tunnely effect I mentioned moving away when ships jump at distinctly STL speeds.

I suspect that it does some freaky subspace relativity-no-longer-applies stuff combined with a mass-ligthening thing to get your ships up to really high speed. I'm rather fond of the translight idea though. It's enough to be physics-breaking (in a settgin with traversable wormholes that's not hard) but still limited to within a solar system.

[Mazryonh]

I think you could try to use a grav-deck as a reaction-less RCS, but you'd have to keep in mind that you'd be dealing with a huge mass that probably has people in it. So just slamming the brakes on it to reposition your ship won't do the people inside any favors, and you're just as likely to start spinning your whole ship around. From what I understand of the real-life positioning gyros, they aren't that big, they are counter-oriented, and they are mounted differently than a huge spinning habitat would be.

I'd still like to know how a single gravdeck (evacuated and sealed for "combat conditions") could be used for changing a spaceship's orientation, though, and how it would be different from using a contra-rotating gravdeck setup to do the same. For the latter, instead of braking a gravdeck's motion, couldn't you just spin on faster to than the other to produce a useful gyroscopic force? How many axes would the two different setups allow turning in? Or would you need two spinning habitats mounted at perpendicular angles to allow turns in all 3 axes? How much fuel would this help to save?

This is actually a pretty cool idea, a sci-fi magic drive that just gets you up to very high sub-light speeds. Does it also take you out of real-space, as the "submerging the ship in subspace" comment would indicate (disengagement of the drive drops you back to normal speeds, and you can't crash with it enabled)? That would alleviate issues with rouge captains using their ships to annihilate planets.

With the way the game depicts it, you can't interact with normal space so as long as your ship is fully submerged in subspace (though there are certain rare devices that can force ships out of that mode, and IP blockers seem to be common enough that they can prevent surprise assaults). In the "Titan" mission where Marcus and his Angelwing crew prematurely exit subspace before the rest of their battle fleet arrives, and the Gorg Titan station activates its IP-blocker, preventing the rest of Marcus' fleet from returning to normal space before they are able to disable the IP-blocker. This would imply that ships in IP-drive mode are unable to affect realspace in any way, and indeed the game always portrays ships as exiting IP-drive mode "at rest" with respect to the chosen battlefield, possibly making it a form of Alcubierre Drive limited to "transluminal" velocities instead of "supraluminal" velocities seen in Star Trek and Star Wars.

Another thing I'd like to know is how bad the rocket equation would work out to be if, as originally planned, the Angelwing's trip from Pluto to Jupiter was a round-trip (the mission briefing implies that they were originally slated to return to Jupiter with scientific "articles of interest"), rather than being forced through the Solar-System/Noah wormhole as circumstances dictated (the game calls this the "Alpha Gate"). I take it that it isn't likely that the Angelwing could carry enough fusion-engine fuel to make that round trip (the game implies that the transit was only possible with the IP-drive's aid, which for some reason the Jupiter base's scientists couldn't unlock while the Kissaki scientists could), but there is the possibility of "in-situ resource gathering." Could the Angelwing land on Pluto/Charon and then start gathering fusion fuel for the return trip? I don't think the gravity would be a problem to escape from, though I'm not sure many fusion reactors could efficiently use raw hydrogen disassociated from methane or water ice from Pluto/Charon, never mind how long it might take to gather such fuel.

Then again, the Angelwing is implied to have artificial gravity of the Trek/Star Wars level, given Commander Sweetwater's quip about "changing the pastel-pink sheets in my cabin"--you don't use bedsheets, you use sleeping bags in ships without artificial gravity or when the gravity is apt to be turned off or fail at short/no notice, so perhaps they have mass-lightening technologies as well to make the Angelwing (or perhaps just its fuel) more mass-efficient.

[Eternal_Freedom]

I'm certain the "only a few weeks" trip involves the IP drive, especially since the Mechanoid disables your IP drive with its first or second shot, prompting your flag lieuteant to point out "We can't escape!" The IP drive being some form of translight Alcubierre drive seems the most likely, especially when considering the actions of the IP blocker in tthe Titan mission.

But then again, the Raptors used an IP blocker to pull your convoy into realspace. Maybe the Gorg and Vardrag blockers work differently.

[Me2005]

I think you could try to use a grav-deck as a reaction-less RCS...

I'd still like to know how a single gravdeck (evacuated and sealed for "combat conditions") could be used for changing a spaceship's orientation, though, and how it would be different from using a contra-rotating gravdeck setup to do the same. For the latter, instead of braking a gravdeck's motion, couldn't you just spin on faster to than the other to produce a useful gyroscopic force? How many axes would the two different setups allow turning in? Or would you need two spinning habitats mounted at perpendicular angles to allow turns in all 3 axes? How much fuel would this help to save?

This I do not fully understand. I know it has to do with energy stored as rotation; similar to a flywheel, but I do not know exactly how it would allow you to maneuver. I imagine that stopping the rotation in one direction would move you in that direction, and spinning up the other; but other than that I don't know. As to fuel savings; there'd be none - your reactor is producing the energy used to spin the ship anyway. Now Propellant savings...

Probably not much energy savings either way, and the effects on your crew won't be ideal. The situation where such a system would be useful would be one of a very-long duration craft, which does not stop to refuel often and is involved in high-RCS situations frequently, but has loads of extra energy production.

With the way the game depicts it, you can't interact with normal space so as long as your ship is fully submerged in subspace (though there are certain rare devices that can force ships out of that mode, and IP blockers seem to be common enough that they can prevent surprise assaults). In the "Titan" mission where Marcus and his Angelwing crew prematurely exit subspace before the rest of their battle fleet arrives, and the Gorg Titan station activates its IP-blocker, preventing the rest of Marcus' fleet from returning to normal space before they are able to disable the IP-blocker. This would imply that ships in IP-drive mode are unable to affect realspace in any way, and indeed the game always portrays ships as exiting IP-drive mode "at rest" with respect to the chosen battlefield, possibly making it a form of Alcubierre Drive limited to "transluminal" velocities instead of "supraluminal" velocities seen in Star Trek and Star Wars.

That sounds like it adds some really good strategic mechanics to the universe.

Another thing I'd like to know is how bad the rocket equation would work out to be if, as originally planned, the Angelwing's trip from Pluto to Jupiter was a round-trip (the mission briefing implies that they were originally slated to return to Jupiter with scientific "articles of interest"), rather than being forced through the Solar-System/Noah wormhole as circumstances dictated (the game calls this the "Alpha Gate"). I take it that it isn't likely that the Angelwing could carry enough fusion-engine fuel to make that round trip (the game implies that the transit was only possible with the IP-drive's aid, which for some reason the Jupiter base's scientists couldn't unlock while the Kissaki scientists could), but there is the possibility of "in-situ resource gathering." Could the Angelwing land on Pluto/Charon and then start gathering fusion fuel for the return trip? I don't think the gravity would be a problem to escape from, though I'm not sure many fusion reactors could efficiently use raw hydrogen disassociated from methane or water ice from Pluto/Charon, never mind how long it might take to gather such fuel. [/qutoe]

It'd depend on the propellant and engine used, but carrying enough with a fusion drive for a two-way trip really shouldn't be a problem. Gathering propellant on both ends probably also wouldn't be a problem; most propellants should be readily available in a sci-fi universe where travel is frequent. It helps that many propellants are hydrogen in one form or another. But the game's issues could be explained (hand-waved) away by saying that the ships' mass-ratios are only worthwhile if they are less than what would be easy for the trip; due to the way weapons work, or armor requirements, or crew rations, or whatever.

Then again, the Angelwing is implied to have artificial gravity of the Trek/Star Wars level, given Commander Sweetwater's quip about "changing the pastel-pink sheets in my cabin"--you don't use bedsheets, you use sleeping bags in ships without artificial gravity or when the gravity is apt to be turned off or fail at short/no notice, so perhaps they have mass-lightening technologies as well to make the Angelwing (or perhaps just its fuel) more mass-efficient.

If it's using a spun-gravity section, that's not really gravity control, but that does imply that they don't use their spun-sections as gyro-RCS.