With FTL technology is it possible to leave after another and yet arrive before it?

Question

There's a plot point in my script that has been bothering me for a while. My story has faster-than-light travel thanks to distortion engines, which re-purpose the artificial gravity inside the ships to use for acceleration (near neutron star intensity when warping). The ships need to make a trip from earth to an alien planet. The thing is, there's one ship that leaves after the fleet but somehow arrives before them at the destination. The problem is that the ships are of identical design, so there's no tech advantage tipping the scales in favour of the tardy ship.

Perhaps a specific trajectory would allow the tardy ship to cut the line? I am uncertain, please educate me.

Answer 1

Famous historical example

... of one fleet leaving after another but arriving at the destination earlier, although both fleets had the same kind of ships.

The year is 1798. The French fleet rules unopposed on the Mediterranean Sea. The British send an expeditionary fleet in the Mediterranean with the goal of intercepting and engaging the French fleet.

On 19 June 1798 the French fleet commanded by Vice Admiral François-Paul Brueys d'Aigalliers left the freshly conquered Malta heading for Alexandria in Egypt, carrying an invasion force intending to conquer Egypt and the other Ottoman possessions in the Levant, with a view of opening a French-controlled route to India.

On 22 June, the British fleet, which was at that time was near the southernmost point of Sicily, got word (from a Genoese merchantman out of Ragusa) that the French had sailed for Alexandria. Rear Admiral Sir Horatio Nelson ordered the fleet to Alexandria at top speed, hoping to catch the French while they were still disembarking the troops.

The British fleet arrived at Alexandria on 28 June. The French were not there, and nobody had even heard of any invasion force.

Nelson spent the next month searching for the French fleet around the Anatolian coast, around the Greek coast, and around Sicily; finally, on 28 July the British fleet (which was then somewhere near the Peloponnese) received a notification (from the Ottoman governor of Crete) the the French fleet had been seen at the end of June sailing south of Crete towards Alexandria.

Nelson odered the British fleet to sail to Alexandria again, and again at top speed. On 1 August they sighted the French fleet at anchor in the Bay of Aboukir and the rest is history.

What had happened was that:

1. The British fleet was sailing much faster than the French fleet. They had the same kind of ships, but by and large British naval officers were much better at coordinating fleet movements, with the effect that British fleets could (and did) move faster than French fleets.

2. The British fleet had overtaken the French fleet on 22 June; at dusk, they had seen the sails of four unknown ships. During the night, the British fleet continued sailing at speed, while the French reduced sail because of course that's what one does when it's dark outside and one needs to be cautious against potential navigation hazards which may have been lurking in the eastern Mediterranean undiscovered for three thousand years despite of continuous and intense navigation. (OK, there was some fog too.)

   In the morning, the British looked around for strange ships but saw nothing, because by that time the French were dozens of miles behind.

3. Upon arriving at Alexandria on 28 June, Nelson made his enquiries, got his answer that nobody knew anything about any French fleet, and left promptly on the next day. Unknown to him, the French, instead of sailing directly from Malta to Alexandria, had taken a sight-seeing tour around Crete (with the express intention of not sailing directly to Alexandria, to make any enemy scout doubtful about their true intentions) and arrived two days after the British fleet had left.

Key points to remember:

1. Fleets do not normally move at top speed. They generally move at the best economical speed, which provides a good compromise between speed and endurance.

2. Even when a fleet moves at top speed, its top speed is the top speed of the slowest ship in the fleet.

3. Fleets need to maintain cohesion and order. The top speed of a fleet is lower than the top speed of an individual ship, because the fleet needs to coordinate ship movements, take corrective actions when one or more ships get displaced, send scouts to look around and come back and so on.

4. Very often it happens that a fleet will avoid sailing on a direct course to the destination, with the intention of making it harder for the enemy to guess where the fleet is going.

(Read all the entracing details on Wikipedia.)

Answer 2

Your typical navigational computers may alter travel paths to avoid areas of unstable gravity variations or massive objects, such as planets or even a random gas cloud. There may be significant levels of caution programmed into the NAVI computer to ensure, to a magnitude of 4-5 standard deviations that there is no impact on the ship while flying this course.

The "tardy ship" could have reasons to override such safety precautions to reduce travel times. They can allow probabilities of detrimental effects to well below recommended levels to cut corners and save time. Instead of steering clear of an object by billions of km, this pilot could skirt to within 100 million km and cut minutes off per maneuver. If dozens of such risky maneuvers are done over the trip, it could cut hours off the travel time, although an increased risk to the ship. but with the absurdly cautious NAVI, these risks are worth it.

Answer 3

Human endeavors require coordination and synchronization. The more people and machinery that are involved in any endeavor, the higher the probability that something gets screwed up or breaks at an inopportune moment. (This isn't fiction; even just skimming military history shows a cornucopia of examples where something going wrong at just the wrong moment changed the course of battles and even entire wars and those are just the incidents notable enough to be recorded.)

Therefore, when travelling great distances, a battle fleet designates a series of rendezvous points along the path where all ships arrive and check in to say that everything is okay before proceeding to the next rendezvous point. Any repairs that needs to be made or cargo/personnel that needs to be transferred between ships (e.g. Captain So-and-so got severe space-food poisoning and needs to be transferred to a hospital ship or one ship didn't have the backup AE-35 unit they normally carry because the supply corps couldn't find one before they left and their main one, of course, chose this time to burn out) occurs at these rendezvous points. The commanders and crews handle this crisply and professionally but it still takes a small but significant amount of time for each rendezvous.

A single ship, not having to coordinate with anyone else, can take a direct route to the destination.

Answer 4

Let me DWKraus you up a nice list!

1. Rogue pilot hacked the ship. The ships were of identical design. No longer. Your captain (actually captain's Aspergery wingman) has modified their ship. It is faster. Other new attributes of the ship may be less welcome.

2. Shortcut. Space is curved. Your pilot takes advantage of local space distortions near supermassive objects (and one which is the reverse of that) to get there faster.

3. Fleet is slow because it is a fleet. The fields interfere with one another and so en masse the fleet is slightly slower.

4. Ship actually left early. Fake ship / fake crew was left at origin.

Answer 5

A Few Thoughts:

Here's a few ideas I have on that:

• Interference: Multiple gravity wells by multiple ships SHOULD, in theory, give your warp engines more FTL power than a single engine. But in practice, each ship is tuned to use their own gravity well most efficiently. The fleet together is slightly slower than an individual ship since the gravity wells disrupt each other. This can be standard (everyone knows it will happen) or accidental (one ship is out of harmony, and throws off all the rest)
• A fleet is as slow as the slowest ship: Although all the ships involved are the same make, slight variations in maintenance mean that if one ship is 0.01% slower, the whole fleet is slower. Say all the ships are on a harmonizing schedule. If your individual ship was delayed because, say, they were in the middle of harmonizing their engine and would have been the slowest ship, then once the engines are harmonized, they end up being the FASTEST ship, with the most up-to-date harmonizing.
• Spin-up: Your ships take time to accelerate to FTL speed, and their gravity wells take time to build up to neutron-star levels. Stars are constantly moving relative to each other, and your second ship passed close to a rogue neutron star shortly after it left. While navigation systems are smart enough to avoid threats like this, they can't compensate for unexpected opportunities. The fleet didn't know about the neutron star, so they couldn't take advantage of the initial acceleration boost it could give.
• Coordinating arrival: Fleets are unable to coordinate their arrival times in a star system over long distances. fleet protocol says you arrive at the same time to support each other in an engagement. Even if no engagement is planned, fleets always stop short of their destination, wait till all ships are together, then make the final leg in together. Your rogue ship doesn't do this, so they arrive first.
• Power surge: Your ship was delayed while they fixed the engines. Even after repairs, the engines malfunctioned, pumping the engines with 110% normal power. It's riskier to stop, and since emergency use allows up to 120% with reasonable safety, they decided additional repairs could wait until after they arrived.
• The fleet encountered a navigational hazard: The fleet was unexpectedly delayed when it needed to course correct after passing near a rogue black hole. The follow up ship thought it would arrive after, but instead it arrives before.

PS No one out-DWKraus's DWKraus.

Answer 6

The Mechanics and Limitations of Gravity Drives

When your fleet leaves it can not just have all the ships turn on thier gravity drives to 100% and expect everything to be okay. Gravity acceleration is always a balancing act between maximizing acceleration and minimizing gravitational sheer.

If your gravity source is a neutron star density mass with a 1 meter radius just in front of your 100m long ship, then the front of your ship will be accelerating at ~279560000 m/s^2 but at 100m behind this gravity well you will experience only ~2796 m/s^2 This massive difference creates what is called gravitational sheer which in your case would not only kill everyone on board but rip your ship into a cloud of debris. The way you compensate for sheer is to project your gravitational focal point far in front of your ship. So, if you were to instead move that focal point ahead 1km in front of your ship, then the front of your ship only experiences 27m/s^2 acceleration and your rear experiences 23m/s^2. This would create a very survivable gravitational sheer, but take you a VERY long time to get up to FTL speeds

So in order to reduce the sheer enough to not kill the humans on board, and achieve an acceleration of ~279560000 m/s^2 like the surface of your neutron star, you'd have to move the gravity focal point ~ a million km ahead of your ship ... but this also means any ship within a million km of you will also feel this same pull... personally, I would suggest you start off with a modest acceleration to try to make your gravity wells smaller and have your ships spend most of their time just moving out of the star system so they don't throw planets out of orbit. Then as they get out into deep space, you slowly ramp up to these higher accelerations.

Why this Makes a Fleet Slower than a Lone Ship

Whatever actual acceleration and focal distance you go for, it will still mean creating a huge gravitational field. So even with ships flying far apart, thier gravity drives will still affect one another. The guys at the back will drag the guys at the front backwards as the guys in the front drag the back guys forward; so, to keep your whole fleet from instantly accreting into one big ball of ships, all ships will have to set various powers and vectors away from each other with only the lead ship being at 100% in the direction it is going, and that lead ship will be slowed down by all the gravity drives going behind it. This means a fleet can not move nearly as fast as a lone ship; so, even if the lone ship has to go around the fleet, it will achieve a much greater acceleration without any other gravity drives holding it back.

While it would be possible for a fleet to spread out enough to have negligible drag on one another, the whole point of operating as a fleet is Concentration of Force. If your ships fly so far apart that they can not support each other, then they are each as vulnerable as a lone ship.

Answer 7

A fleet of interstellar starships is big, and the space around a planet can hold nasty surprises

The planet has a bit of a cluttered environment, with a bunch of moons (both big and small) in orbits with various inclinations, and a thick ring system inside that. You do not want to warp into these or come out of warp in their vicinity.

Since a large fleet needs a considerable amount of separation between ships to keep their gravity drives from interfering from each other and reduce the possibility of ultrarelativistic collisions if a ship goes out of control in cruise, and there are a lot of ships in the fleet, it takes up quite a lot of space in space.

The fleet, being spread out over a volume of space comparable to that of the planet itself (or maybe even more), has to come out of warp and slow to approach speed well away from the planet, so that the individual ships of the fleet can use their onboard radar to navigate down into the safe zone below the lowest rings - the fleet's cruise formation is far too large for them to be able to simply warp directly into the safe zone without crashing quite a few big, expensive ships into the inner moons, the rings, or the planet itself.

The lone ship, though, being vastly smaller than the fleet in cruise formation, can safely warp straight down into the safe zone, saving quite a bit of time.

Answer 8

Flank speed

Any engine has an optimal performance rating, a maximum safe load, and a maximum running speed:

• The optimal performance rating is the speed you want to run the system at whenever possible, it is the point of maximum input-to-output ratio. This is where you get the most bang for your buck.
• The maximum safe load is a different story that's the point of maximum output without unduly altering your maintenance schedule, i.e. as fast as you can go without your engine burning out too early on you.
• Maximum running speed is the just short, for a while, of engine component failure. This is how fast you run the system when you're in dire straits already and the risk of blowing up is worth it. Maximum running speed is not a pace you can maintain because you are causing massive wear on the system every second and one or more components will weaken to the point where the current speed exceeds their point of failure eventually. This is Flank Speed and it should never be used lightly.

On an interstellar trip the fleet should be running at optimum so they get the most out of every gram of fuel for a ship to break away they can burn their reserve to crank the drive up to maximum safe load maybe even flank if they're more desperate than cautious.

Answer 9

With FTL technology is it possible to leave after another and yet arrive before it?

FTL is Time Travel, unless you take the proper precautions. ref.

If needed, you can have the second fleet arrive before they even left. Star-Trek does it sometimes when the plot needs.

Answer 10

Space isn't static - with bodies constantly moving, and spacetime bends. Even in 'in system' launches, there's certain periods where, taking travel time into account, there's shorter routes. The same way the distance between planets in a system changes as they move, the second ship might have left at a time that resulted in a shorter route.

Its also worth considering/thinking both in terms of "3d" for distances, that space time bends, and there might be more 'risky'/faster routes. Assuming FTL here is "punching" through space, there might be longer routes that are lower risk, and shorter routes that are high risk, and routes might not be a straight line, point to point route.

Answer 11

A fleet with a hundred vessels has just multiplied the possiblity of a FTL drive breaking down by a factor one hundred. Fleets travel together, so if one ship breaks down everyone may have to wait for it to fix it self before continuing. The more ships you have, the more chances for any one ship to fail.