Jump Point

Jump Points refer to any point at which a JumpShip may initiate or resolve a "jump" through interstellar space. Traditionally, there are two jump points in a system - the zenith and the nadir of a star's gravity well (normally above and below the star's planetary system elliptic). There exist other points, called "pirate points", that a JumpShip can use, but recharging the Kearny-Fuchida Drive is more difficult and dangerous from these points.

Standard Jump Points

A JumpShip must operate in zone where gravity levels are below a certain minimum. These zones are generally referred to as "jump points." The typical jump point is found at a minimum distance from the local star known as the "proximity limit," which is where gravity drops below the critical level for the hyperspace field of the Kearny-Fuchida drive to form properly. This zone is determined almost exclusively by the star of a system, which is far and away the largest gravity well in a star system (often by a factor of hundreds or thousands).

The proximity limit is a sphere (but for small planetary distortions) typically several astronomical units (AU) in radius around the star, though stars larger than Sol may have proximity limits many hundreds of AU in radius. Sol's proximity limit is about 10.2 AU. (For comparison, the proximity limits of planets outside their star's proximity limit is typically a few million kilometers, or a few percent of an AU.) That distance is determined by the type of star and can range anywhere from 75 million kilometers (for a low-energy M9 star) to over 347 billion kilometers (for a high-energy B0 star).

Beyond a proximity limit, all of space is a valid jump "point." It is quite possible for a JumpShip to jump into deep space light-years from any star system. Indeed, when imagining jump points, it might be best to consider most of space one giant, valid jump point but for tiny bubbles near stars and even more microscopic bubbles near planets.

However, there's rarely anything of interest in deep space worth jumping to, and the risk of a drive failure and difficulty in recharging without sunlight means few captains are willing to take their JumpShips into deep space. In fact, few will even visit the millions of uninhabited stars in the Inner Sphere, instead huddling close to the couple thousand inhabited systems of the Inner Sphere. After all, JumpShips usually only have radios to call for help if they breakdown, and radio signals will take years to reach the next inhabitable system - which may not be listening for such faint signals.

And since the destinations of interest are habitable planets anyway, which are exclusively inside the proximity limits of stars, most JumpShip captains will select a point reasonably close to the planet. Such a jump point would be resting on the proximity limit of the star system, a "proximity point."

The closest proximity point to a planet would be on a direct line drawn between the star, the destination planet, and reaching to the proximity limit. However, such points are deep in the planetary plane of the system, the "plane of the ecliptic," where most planets, asteroids, and debris are found. Besides the damage risk, the multitude of small gravitational effects make navigation to such points difficult to calculate. As a result, they are little used but for military ships looking to shave a few hours off the transit to the planets (which typically requires days of travel at 1G, about 9 days in the case of Terra.)

There are, however, proximity points that avoid all the mess of the ecliptic by being directly above and below the north and south poles of the star. These points are only slightly further from the inhabitable planet and are the furthest possible points on the proximity limit from the interference of the ecliptic. These two locations simplify navigation so much that they were used in the early 2100s by the Deimos Project for test jumps before mankind made interstellar jumps, and have remained the standard jump points for travel by Kearny-Fuchida drive ever since - hence, they are called the "Standard Jump Points." They are also often referred to as "zenith" and "nadir" jump points because of their locations above (zenith) and below (nadir) the star, with respect to the layout of the star system.

These jump points minimize the influence of planetary gravity on jump calculations . Indeed, jump calculations made from a zenith or nadir point are usually satisfactory for up to six months before planetary movement necessitates their recalculation.

While JumpShips have fairly capable fusion rockets that would allow 0.1G of steady acceleration (vastly better than any real world rocket), they are generally left at the jump point. Instead, DropShips, giant shuttles that ride on the exterior of JumpShips and "drop" free at the destination, handle the multi-day flights to and from the destination planet. The fusion rockets of DropShips are so efficient that they can sustain 1G of flight for days and weeks on end. DropShips normally utilize this capability to accelerate at 1G toward the destination for half the flight, followed by a 180-degree rotation and braking at 1G for the remainder of the flight. Such a half-and-half allows DropShips to provide passengers with near-continuous Terra-normal gravity while covering vast distances in days. The 10.2 AU flight from Terra to its jump points would take 2-3 years by the fastest chemical-fueled probes of the 20th Century, but only 9 days for 1G DropShip (or about 28 days for 0.1G JumpShip).

The energy output from the star (also based upon its type) determines how long a JumpShip can recharge its drive and can range anywhere from 151 hours (for a B0 star type) to 210 hours (for an M9 star type). The actual time required between jumps must also include the Jump Sail deployment and recovery times, typically about 100 minutes for deployment and 150-200 minutes for recovery. If the Jump Sail is damaged or cannot be deployed, the JumpShip's power plant can be used to recharge the fusion drive.

With any power supply, the JumpShip's crew must take care to not charge the drive too rapidly. In most cases, charging the drive faster than 175 hours risks damaging the drive, with the risk increasing exponentially as time is decreased. A JumpShip's fusion engine or a recharge station can recharge the KF Drive in 24 hours, but that almost guarantees the KF drive will be damaged beyond operability. Because of the frequent use of fusion engines to "quick charge" the KF drive, it is sometimes not understood that fusion engines can recharge the KF drive safely. However, fusion engines can offer a safe charge if they take more than 176 hours to do so.

Pirate Jump Points

There are some non-standard jump points that will allow a JumpShip to enter a system much closer to the destination planet than the star's zenith or nadir jump points will. They are commonly used in high-risk military operations where surprise is vital to the operation's success. Jumping into a pirate point poses several risks, which is why most traditional merchants and even military units will not use them. Because of potential solar system instability, it is possible that the JumpShip could appear too close to a system body, which could destroy the vessel and its passengers. Another issue is that the JumpShip must recharge its K-F drive using its engine rather than the Jump Sail. This could potentially damage the fragile drive and render the JumpShip inoperable.

Recharge Stations

Some systems (particularly Successor State or regional capitals) provide recharge stations at one or possibly both jump points. These stations are capable of beaming stored energy directly at a JumpShip's JumpSail and reduces the recharge time to 150 hours in most cases.