Trade routes will become necessary as humans expand into the Solar System and then beyond. Some places will provide us with metals, others with water and other volatiles, others with minerals needed for life. In other places we might find no water, while in others we will find excellent conditions to grow plants and to produce food. Industrial corporations will also need trade routes. On the other hand, as we keep producing garbage, toxic waste and scrap, we will need to dump or recycle this waste. Finally, there will be tourist attractions that will be worth visiting.
Depending on conditions, each part of the Solar System (and other solar systems) will require different types of transportation.
Space Bases[]
Main article - Space Stations
It would be easier to send one large cargo freighter from Earth to the Jupiter system than to send many small ships towards each of Jupiter's moons. Large ships could be over 1 km long. At that size, a ship would not be able to land on a planet or large moon, the gravity would tear it apart. However, a giant ship could travel without problems in microgravity conditions and could dock with large orbital stations and asteroid bases. From there, cargo could be transferred with smaller ships, able to land on planets and moons.
Mercury - see Mercury Space Station. For Mercury, an orbital station can exist. However, because of the proximity to the Sun, there are strong gravitational perturbations. This is why Mercury has no moon, there are no stable orbits. The Messenger orbiter crashed into Mercury when it ran out of fuel. Therefore, an orbital base around Mercury would need some method of propulsion to keep it in a stable orbit.
Venus - see Venus Space Station. Around Venus, a satellite will be slowly influenced by the Sun and Earth. However, it could remain in orbit for a very long time. Space ships that explored Venus were deliberately deorbited at the end of their mission. An orbital station that circles the planet in around one Earth day would be safe for millennia.
Earth - see Earth Space Station. We have already one International Space Station, but it needs to turn on its engines from time to time to remain at its current orbit. At a higher altitude, the atmospheric drag would be lower still, reducing the need for orbital correction. An orbital station placed at a higher altitude would also be able to service colonies on the Moon.
Mars - see Phobos. Mars has the advantage of two small natural satellites. We could use any of them as a space base. Their orbits will be safe for millennia. Perhaps we could use Phobos as the main logistics base and Deimos as a backup and quarantine station.
Ceres - see Ceres Space Station. As shown by Dawn spacecraft, orbits around Ceres are safe. Dawn itself will remain a perpetual satellite of Ceres. So, it is possible to set an orbital base there too.
Jupiter - see Himalia. The giant planet has many small moons both between the planet and the Galilean moons and outward from them. The inner moons are, however, inside Jupiter's deadly magnetosphere, so these would not be safe for a colony. As for the outer moons, many are retrograde or have high angle orbital planes. From all the outer moons, by far the best candidate for a base is Himalia.
Saturn - see Helene. From all the planets, Saturn has the largest cohort of moons. The inner moons are inside the main rings or other diffuse rings. The outer moons are usually retrograde. Still, there are a few moons that are co-orbitals (Trojans) of some of the larger moons. Their orbits are cleared of dust and other space debris. One of the best candidate for a space base is the moon Helene, a Trojan of Dione.
Uranus - see Perdita. What is interesting is that Uranus has some small inner moons (between the planet and Miranda). The innermost moons are inside the rings, but there is one, Perdita, which could be just perfect for this. The outer moons are usually retrograde, with the exception of Margaret, which has a high orbital angle plane. Perdita and another small moon, Portia, might be suitable for space bases.
Neptune - see Halimede. Compared to other planetary systems, Neptune's is the most complex. The largest moon, Triton, and the only one suitable for terraforming, is retrograde. There are two other moons larger then 100 km, both prograde: Proteus and Nereid. However, Nereid has an extremely elliptical orbit. Navigation between these celestial bodies is extremely difficult. Neptune also has inner moons (prograde, very close to the rings) and outer moons (both prograde and retrograde, with high angle orbital planes and highly elliptic orbits). Building a space station on any of the small, inner or outer moons, would be possible, but not feasible. Since Triton is the largest moon and the most important destination for settlers, it would be better to build an orbital station with a retrograde and circular orbit, sharing the same orbital plane with Triton. However, to make the base functional also for Proteus and Nereid, it would have to be further away from the planet, so that changing the orbital direction does not require as much fuel. An alternative (but not very good) option is to use the outer moon Halimede.
Pluto - see Styx. From all the Kuiper Belt objects, Pluto is the most known and probably the best target for future settlers. Pluto has the advantage of four small moons, that can be used for building an orbital station.
Interstellar Space Station. In one Soviet sci-fi novel, it was proposed that the asteroid 6 Hebe will be used as a spaceport for interstellar flights.
Spaceships[]
Today, on Earth, large ships travel across the oceans for long distances. Then freight is transported by train or by truck from docks to inland areas. Inside a city, freight is moved from railway stations or warehouses close to highways with smaller cars to each place where it's needed. Sending cargo with small vehicles over long distances is not feasible. Still, goods that need to be delivered fast are shipped by airplanes, and from the airport to their destination they are moved by small vehicles. In the same way, depending on costs, passengers are usually transported by air or by train on long distances, then by smaller trains, buses or minibus services for shorter distances. Similar methods might prove feasible for interplanetary and interstellar travel.
Interplanetary cargo freighters. Launch windows don't occur too often (see data below). Freight could wait for even several years for departure and other years would be spent in deep space. Also, it is cheaper to launch a giant ship once then to send many small ships. An interplanetary cargo freighter would have to be very big, measuring over 1 km long. Some models might be even up to 10 km. Such large vehicles would be unable to land on a planet. Instead, they would dock at an orbital space station or a small satellite. At least for the first period of space travel, interplanetary cargo freighters would use the most low-cost trajectories. They would transport cargo, but they might be equipped for passengers as well.
Interplanetary passenger transport. People will not want to wait for the slow, low-cost trajectories used for cargo. Instead, they will prefer faster routes, but not the fastest. Still, with current technology a space voyage will take months or years to complete. A cargo freighter from Earth to Saturn would probably use multiple Mars and Jupiter flybys, but a passenger ship would take the direct route. Even so, launch windows would not occur much more often.
Planetary space transport. There will be smaller spaceships connecting space stations with the planet or with its moons. These ships, designed for freight, for passengers or both, will offer local transport services. Ships that service larger planets and moons will be equipped with thermal reinforced fuselage for aerobraking, with parachutes or wings for landing and also with strong engines for liftoff. Ships that connect bases with asteroids and small moons will be less robust.
Redirect ships. This is a special category of space vehicles. They are small, but with highly efficient engines. They are designed to move asteroids and comets. Redirecting celestial objects is vital to avoid collisions, to bring water and volatiles to terraformed bodies with unstable atmospheres and to bring metal asteroids to metallurgical corporations.
Interplanetary small ships. It makes no sense to send a huge cargo freighter towards a small asteroid or a Kuiper Belt object, where colonies are smaller and the needed amount of goods is small. While mining industrial corporations might still request a huge cargo freighter, small settlements would only need smaller vehicles. However, unlike those used in planetary transport services, these ships would be able to travel long distances.
Personal ships. Probably at a certain point, personal ships would be like personal cars today. At that moment, interplanetary travel would be completely different than in previous ages.
Inner Rocky Planets[]
This includes Mercury, Venus, Earth, Luna and Mars. For all 5, the major problem is the escape velocity a spaceship must achieve in order to detach from their surface. Escape velocities from the rocky planets are measured in kilometres per second. Currently, the only feasible technology to leave a planet is the use of chemical engines, and these require exponentially more fuel the greater the escape velocity is. Landing on the surface would be easier, because after terraforming, all of these planets would have atmospheres that would allow aerobraking. The escape velocity is as follows:
Mercury: 4.3 km/s Venus: 10.3 km/s Earth: 11.2 km/s Moon: 2.4 km/s Mars: 5.0 km/s.
As one can see, Venus and Earth are the most difficult planets to launch from. For Mercury and Mars, the needed amount of fuel would be less than half. For Moon, it would be less than 1/6 of Earth's. This clearly shows that sending goods from Earth into space will be more expensive then sending goods from Mars.
A good way to facilitate space traffic would be to build orbital stations around each planet. For Mars, this would be relatively easier since we could use its two small moons. In this case, large landing ships would regularly connect the planet with the orbital station, facilitating transport of cargo and people. Since bases would be close to the planet, launch windows would occur daily (for an Earth's 24 hours). Also, ships would return daily from the station to the ground base.
Traveling between planets could not be done as frequently. The planets must be aligned in a specific way to allow the cheapest and most effective way to travel. This is called the launch window. Passenger ships would need to travel faster, sometimes using a more expensive route, while cargo ships would use the most low-cost effective route. This might include a number of gravity assists from other planets.
Traveling between Venus, Earth and Mars can be done with highly efficient ion engines. Traveling to Mercury, because it has to break the Sun's immense gravity, would have to use something more powerful, probably including gravity assist from Venus. Sending a ship from Mercury would be more possible with a solar sail.
Good launch windows will occur at the following rate:
Mercury - Venus: 143 Earth days Mercury - Earth: 115 Earth days Mercury - Mars: 101 Earth days Venus - Earth: 584 Earth days (1 year and 219 days) Venus - Mars: 337 Earth days Earth - Mars: 777 Earth days (2 years and 47 days).
These windows are calculated in a simple way, when the planets are aligned. However, many other launch windows exist, depending on what kind of propulsion you use, on gravity assists or on deep space maneuvers.
Note that the bigger the difference between orbits, the more often launch windows occur.
Rocky Planets - Giant Planets[]
The outer giant planets move far more slowly then the inner planets. Whenever an inner planet makes a complete rotation along the Sun, the outer planets move only a little bit. So, if we wait the inner planet to move a bit more, both will be in the right place. Simple calculations show that the launch windows occur at a rate a bit longer then the inner planet's year:
Mercury - Jupiter: 90 Earth days Mercury - Saturn: 89 Earth days Mercury - Uranus: 88 Earth days Mercury - Neptune: 88 Earth days
Venus - Jupiter: 237 Earth days Venus - Saturn: 230 Earth days Venus - Uranus: 227 Earth days Venus - Neptune: 226 Earth days
Earth - Jupiter: 398 Earth days Earth - Saturn: 377 Earth days Earth - Uranus: 369 Earth days Earth - Neptune: 367 Earth days
Mars - Jupiter: 816 Earth days Mars - Saturn: 733 Earth days Mars - Uranus: 702 Earth days Mars - Neptune: 695 Earth days.
As one can see, launch windows sometimes occur more often between inner and outer planets then between inner planets. Spaceships launched from the inner planets could make use of ion engines and solar sails to achieve the desired speed. As they depart from an outer planet, ships would use the advantage of low solar gravity, therefore they can change their orbit more easily. When a ship reaches a gas giant, its gravity could capture the ship more easily. By contrast, as the ship heads for a rocky planet, it would reach its target with great speed. To enter in orbit, the ship could get closer to the atmosphere and use aerobraking.
Between Giant Planets[]
The gas giants move much more slowly. The best launch windows are rare, as seen below:
Jupiter - Saturn: 19.9 Earth years Jupiter - Uranus: 13.8 Earth years Jupiter - Neptune: 12.8 Earth years Saturn - Uranus: 61.8 Earth years Saturn - Neptune: 35.7 Earth years Uranus - Neptune: 174 Earth years.
At this point, it is clear that using the low-cost orbits will not be a good option for the giant planets. Transport companies would like to have a flight at least every 5 Earth years. They would therefore look for any alernative routes. Because of the high distances, ships will need a lot of time to travel.
The delta-v for trade routes between gas giants can also be calculated and assuming the perfect planetary alignments are as follows:
Jupiter - Saturn: 0.50 Jupiter - Uranus: 0.75 Jupiter - Neptune: 0.84 Saturn - Uranus: 0.22 Saturn - Neptune: 0.29 Uranus - Neptune: 0.06
What catches the eye is the incredibly low delta-v budget required to travel between gas giants. Trade routes become possible at almost any alignment with a delta-v budget lower then a Venus - Mars cruise.
Around Gas Giants[]
The systems of moons that orbit all four gas giants offer unique advantages. First of all, the moons have low gravity. Launching a spaceship from their surfaces will require far less cost compared to launching from planets. Please take a look at the following values:
Earth: 11.2 km/s Io: 2.558 km/s Europa: 2.025 km/s Ganymede: 2.741 km/s Callisto: 2.440 km/s Titan: 2.639 km/s Triton: 1.455 km/s.
For other moons, the escape velocity is even slower, usually below 1 km/s.
Launch windows will also be frequent, at intervals of less then 100 Earth days. The trip will also not take too long, about a few days or up to an Earth month. In these conditions, transport companies could offer scheduled service between all colonized moons. Since there are not many stable orbits around the moons, there would not be many orbital stations. However, it should prove highly effective to use a small natural satellite as a station for interplanetary travel.
Asteroids[]
Many industrial corporations and mining facilities will be on asteroids. The main advantage of asteroids is their very low gravity, that makes them excellent targets for spaceships.
Each asteroid has its own launch windows towards other asteroids and planets. However, we can expect more cargo and less passengers at an asteroid. Cargo would be transported when conditions allow the lowest cost, probably as large convoys of ships. Passenger ships will not detach towards all directions, but more often towards a large base of a nearby planet.
A major problem is that asteroids have low gravity. As a result, it is difficult for spaceships to be captured by their gravity. Ship trajectory must be calculated so that the spacecraft will reach the target with nearly the same speed the asteroid is moving. The ship must therefore use an engine to increase or decrease speed in the vicinity of its target. The most efficient way seems to use ion engines, like the one Dawn used to reach Ceres and Vesta.
For the largest asteroid, Ceres, the flight windows are as follows:
Mercury - Ceres: 93 Earth days Venus - Ceres: 260 Earth days Earth - Ceres: 466 Earth days Mars - Ceres: 1161 Earth days Ceres - Jupiter: 7.53 Earth years Ceres - Saturn: 5.42 Earth years Ceres - Uranus: 4.88 Earth years Ceres - Neptune: 4.77 Earth years.
This shows that Ceres and all asteroids will be easily linked to both inner and outer planets.
Kuiper Belt & Oort Cloud[]
The Kuiper Belt and Oort Cloud are extremely far from the Sun, posing a problem for spaceships. They would need to reach high speeds to reach their distant targets in an acceptably short time, but once they arrive they have to decelerate in order to land. Dwarf planets and asteroids have little gravity and cannot capture in orbit a fast moving ship. Also, with current technology, the cruise would take years (for the Kuiper Belt) or decades or centuries (for the Oort Cloud).
It is less plausible that a scheduled service would exist between the small Kuiper Belt colonies and each planet. More probably, there would be flights on demand or scheduled flights connecting one inner planet with an outer planet in the Kuiper Belt. Every 12 Earth years, Jupiter is in the right place for a gravity assist for each Kuiper Belt object. Every 29 Earth years, Saturn is in the right place. And every 59 Earth years, both Jupiter and Saturn can be used for a gravity slingshot. This scheme shows that scheduled transport can exist between the rocky planets and Kuiper Belt.
Flight windows between Pluto and other parts of the Solar System:
Mercury - Pluto: 88 Earth days Venus - Pluto: 225 Earth days Earth - Pluto: 1.01 Earth years or 367 Earth days Mars - Pluto: 1.90 Earth years or 690 Earth days Ceres - Pluto: 4.67 Earth years or 1712 Earth days Jupiter - Pluto: 12.47 Earth years or 4550 Earth days Saturn - Pluto: 33.43 Earth years or 12210 Earth days Uranus - Pluto: 127.0 Earth years or 47410 Earth days Neptune - Pluto: 483 Earth years or 176400 Earth days
As one can see, there are plenty of flight windows between Pluto and the inner planets. However, perfect alignments between Pluto and the outer planets are rare.
Inside Planetary Systems[]
Mercury and Venus don't have moons. Flight windows to their orbital stations will occur very often.
Between Earth and the Moon, flight paths occur nearly every day (the Moon is nearly at the same coordinates in the sky at every 25 hours).
Around Mars, flight windows between Mars and the moons and flight windows between the moons occur daily.
Around Jupiter, perfect alignment between moons occur from time to time:
Almathea: about twice every Earth day
Io - Europa: 3.52 Earth days Io - Ganymede: 2.35 Earth days Io - Callisto: 1.97 Earth days Io - Himalia: 1.78 Earth days
Europa - Ganymede: 7.04 Earth days Europa - Callisto: 4.51 Earth days Europa - Himalia: 3.60 Earth days
Ganymede - Callisto: 12.5 Earth days Ganymede - Himalia: 7.36 Earth days
Callisto - Himalia: 17.9 Earth days.
We can also calculate the needed delta-v for cruises between the moons of Jupiter:
Almathea - Io: 6.948 Almathea - Europa: 7.770 Almathea - Ganymede: 9.035 Almathea - Callisto: 9.393 Almathea - Himalia: 8.387
Io - Europa: 8.327 Io - Ganymede: 5.245 Io - Callisto: 5.377 Io - Himalia: 4.040
Europa - Ganymede: 3.947 Europa - Callisto: 4.027 Europa - Himalia: 2.585
Ganymede - Callisto: 4.033 Ganymede - Himalia: 2.524
Callisto - Himalia: 1.986
For Saturn, there are also many launch windows between moons:
Mimas - Enceladus: 2.95 Earth days Mimas - Tethys: 1.88 Earth days Mimas - Dione: 1.44 Earth days Mimas - Rhea: 1.19 Earth days Mimas - Titan: 1.00 Earth days Mimas - Hyperion: 0.99 Earth days Mimas - Iapetus: 0.95 Earth days Mimas - Phoebe: Earth days
Enceladus - Tethys: 4.79 Earth days Enceladus - Dione: 2.74 Earth days Enceladus - Rhea: 1.97 Earth days Enceladus - Titan: 1.50 Earth days Enceladus - Hyperion: 1.46 Earth days Enceladus - Iapetus: 1.39 Earth days Enceladus - Phoebe: 1.37 Earth days
Tethys - Dione: 5.94 Earth days Tethys - Rhea: 3.24 Earth days Tethys - Titan: 2.14 Earth days Tethys - Hyperion: 2.07 Earth days Tethys - Iapetus: 1.93 Earth days Tethys - Phoebe: 1.88 Earth days
Dione - Rhea: 6.89 Earth days Dione - Titan: 3.30 Earth days Dione - Hyperion: 3.14 Earth days Dione - Iapetus: 2.83 Earth days Dione - Phoebe: 2.72 Earth days
Rhea - Titan: 6.30 Earth days Rhea - Hyperion: 5.74 Earth days Rhea - Iapetus: 4.79 Earth days Rhea - Phoebe: 4.48 Earth days
Titan - Hyperion: 60.1 Earth days Titan - Iapetus: 20.0 Earth days Titan - Phoebe: 15.5 Earth days
Hyperion - Iapetus: 29.1 Earth days Hyperion - Phoebe: 20.4 Earth days
Iapetus - Phoebe: 65.8 Earth days
Around Uranus, many launch windows occur between its moons:
Perdita - Puck: 1.19 Earth days Perdita - Miranda: 0.963 Earth days Perdita - Ariel: 0.832 Earth days Perdita - Umbriel: 0.743 Earth days Perdita - Titania: 0.665 Earth days Perdita - Oberon: 0.657 Earth days Perdita - Sycorax: 0.633 Earth days
Puck - Miranda: 1.28 Earth days Puck - Ariel: 1.06 Earth days Puck - Umbriel: 0.916 Earth days Puck - Titania: 0.800 Earth days Puck - Oberon: 0.790 Earth days Puck - Sycorax: 0.755 Earth days
Miranda - Ariel: 2.92 Earth days Miranda - Umbriel: 2.06 Earth days Miranda - Titania: 1.55 Earth days Miranda - Oberon: 1.51 Earth days Miranda - Sycorax: 1.39 Earth days
Ariel - Umbriel: 5.68 Earth days Ariel - Titania: 2.99 Earth days Ariel - Oberon: 2.86 Earth days Ariel - Sycorax: 2.44 Earth days
Umbriel - Titania: 5.60 Earth days Umbriel - Oberon: 5.15 Earth days Umbriel - Sycorax: 3.92 Earth days
Titania - Oberon: 14.7 Earth days Titania - Sycorax: 7.63 Earth days
Oberon - Sycorax: 10.7 Earth days
Around Neptune, everything is far more complicated. The fact that Triton is retrograde and Nereid has a highly elliptical orbit makes all flight routes very difficult. Flying between a prograde and a retrograde moon requires huge amounts of fuel in order to change direction. Much easier would be to fly to a distant moon at the edge of Neptune's Hill sphere, change direction there (where orbital speed is very low) and then return to the target moon. In order to save fuel, such maneuvers would require multiple flybys around Triton and other moons, to gain or lose momentum.
Around Pluto, a flight between Pluto and Charon can be done at anytime and with the same fuel consumption, since both bodies are tidal locked. Flight paths between Pluto and the outer moons occur at the same frequency as flight paths between Charon and the outer moons.
For Pluto, flight windows exist as follows:
Pluto - Charon: anytime. Pluto - Styx: 9.35 Earth days Pluto - Nix: 8.60 Earth days Pluto - Kerberos: 7.97 Earth days Pluto - Hydra: 7.67 Earth days
Charon - Styx: 9.35 Earth days Charon - Nix: 8.60 Earth days Charon - Kerberos: 7.97 Earth days Charon - Hydra: 7.67 Earth days
Styx - Nix: 93.63 Earth days Styx - Kerberos: 55.51 Earth days Styx - Hydra: 42.62 Earth days
Nix - Kerberos: 70.28 Earth days Nix - Hydra: 70.16 Earth days
Kerberos - Hydra: 167 Earth days.
Interstellar Travel[]
Main article: Interstellar Travel
A zero-generation ship will travel towards a nearby star in more than a human lifetime. We already have the Pioneer and Voyager spacecrafts doing this. Reaching Barnard's Star in 500, 1000 or even 10000 years is not what a space pioneer would dream about. However, it is possible that, at some point, someone will try this. A Soviet sci-fi writer has proposed the use of a comet. There would be a base on the surface of the comet. Settlers would use deuterium (found on the comet) in a nuclear fusion reactor. Energy from the reactor will be used to power a rocket chemical engine, using hydrogen and oxygen from the comet itself. Settlers would travel for almost 1000 years, slowly increasing speed, until there is nothing left from the comet. Then, at the destination, the colony would pass very close to a giant planet and to the star, decreasing their speed via aerobraking and with the help of gravity assists.
First generation cargo and passenger ships would travel at 5 to 10% of the speed of light. This allows settlers to reach the nearby stars within their lifetime. They would be on one-way trips. Each ship must accelerate to the designated speed, then, once it reaches its destination, it must slow down to allow settlers and cargo to land on a planet and terraform it.
Second generation ships would move at a significant percent of the speed of light, 50% or even 80%. This would allow us to colonize the stars that are within 10 or 20 light years away. At this stage, ships could return to Solar System to take other settlers or other cargo.
Can trade routes be imagined at this speed? It is a difficult prospect. What merchant would want to invest in an expensive transport, getting their money back only after 30 years? Communication, even with the speed of light, would take many years to reach Earth. And even then the radio signals would be extremely weak. It would be more efficient to send messages on board the ships, similar to what was done in the Middle Ages. The first settlers would fly blind, towards a star system where they don't know well what could be found. Just imagine what this could mean. Dreaming of a perfect democracy, they might end up sold as slaves at the destination, and nobody would ever know.
Probably, the first and second generation of ships would only transport people and the smallest needed amounts of materials and equipment to build a Terraforming Plant. The trade routes would be paid by states inside the Solar System, willing to extend their domains on other stars.
However, third generation ships would fly above the speed of light. At that point, reaching a nearby star or even distant stars would not be so difficult and might need less than an year. Interstellar trade routes might appear, with regular cargo and passenger ships.
The future[]
All calculations shown above are made based on current technology. However, as colonies will grow and new technologies will be discovered, the time and cost of space flight will gradually decrease.
The first pioneers in America, Australia, the Pacific or African colonies, were used to receiving news from home once every few years. Ocean ships took many months to reach their destinations. In many cases, settlers received no visitors for over 10 years. However, as colonies grew and became independent states and as technology reached new levels, everything changed.
In the beginning, there would be rare and long flights. We might see that scheduled flights occur between the rocky planets first, then there would be regular flights between Earth and the gas giants. Then other scheduled flights would appear between Earth and some asteroids. Soon, inter-satellite transport would develop around the gas giants. Then, by the time scheduled transportation would be needed between gas giants, we would need extra flights between the inner planets. People and cargo would no longer wait up to two years for a flight towards Venus or Mars. Then regular flights would take us to the Kuiper Belt.
When we invent vehicles that will travel at up to 50% of the speed of light (see Interstellar Travel), we would also have improved transportation inside the Solar System. The problem is that humans cannot withstand accelerations above 1G for long periods of time. At an acceleration of 1G, a ship increases in speed by 9.8 meters per second every second. It would reach 35 km/s in an hour and 847 km/s (2.8% of the speed of light) in a day. At this speed, a spaceship would need 6.5 days to reach the orbit of Pluto, plus one day to accelerate and one day to decelerate. A flight from Earth to Venus would only take two days (the time to accelerate and decelerate) and the ship would never achieve 2.8% of the speed of light. It would only accelerate for half of the way and then it will slow down. Until we discover artificial gravity to counter the effect of acceleration, this would set a minimum time limit for interplanetary travel.