Spaceships

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Lazarus Lazarus's picture
Spaceships

While I am assuming that you probably want to follow a similar model to how spaceships were presented in the first edition (not drilling down into the science of specific impulse and thrust to weight ratios of motors) it seems like some of the language could be cleaned up to be more accurate.

As an example, metallic hydrogen reads "Due to the great amount of thrust produced," This should probably be changed to "Due to the high thrust to weight ratio," as any form of propulsion can produce large amounts of thrust given a large enough motor (even things such as VASIMIR engines can produce 'large amounts of thrust'. They would simply require engines so enormous that while they are producing millions of Newtons of thrust the acceleration is very low).

This would be useful as it would prevent people from arguing as to whether something that was written was just 'shorthand' and shouldn't be taken literally or if it is suppose to be taken literally.

I would propose the following edits.

Hydrogen-Oxygen Rocket (HO): Though optimized with improved engine design and light-weight materials, these are essentially the same primitive rockets that humanity used to first reach the moon in the 20th century. While their high thrust to weight ratio offers excellent acceleration their fuel hungry nature severe limits to their top speeds. As a result they These are rarely used and only common with groups too poor or primitive to safely manufacture metallic hydrogen.

Metallic Hydrogen Rocket (MH): Metallic hydrogen is a solid form of hydrogen created using exceedingly high pressures. Although naturally unstable, it can be stabilized in tanks with carefully controlled electrical and magnetic fields. By selectively reducing these fields near the exhaust nozzle, small amounts of metallic hydrogen can be made to swiftly and explosively revert to conventional hydrogen gas, propelling the rocket with great force in an easily controlled fashion. Due to the great amount of thrust produced Due to the high thrust to weight ratio, metallic hydrogen engines are necessary to escape the gravity well of most planets, so are common in planetary landers and short range vehicles.

Plasma Rocket (P): This drive heats hydrogen into plasma and accelerates it using a powerful electrical field. This results in a very low thrust to weight ratio but is much more efficient in its hydrogen consumption than a metallic hydrogen motor. As a result plasma rockets typically reach much higher speeds during most trips. This type of rocket was very common in the mid 21st century, but has been superseded by fusion rockets and is only used in older and more primitive spacecraft, notably scum swarms.

Fusion Rocket (F): Similar to a plasma rockets, fusion rockets require significantly higher temperatures and pressures, and the rocket also produces large amounts of power for the spacecraft resulting in extremely efficient use of hydrogen. The low thrust to weight is noticeably improved over plasma rockets though it is still typically too low to allow for unassisted launching from the surface of most solar bodies. Fusion rockets are now the most common form of propulsion for spacecraft designed for long-distance voyages.

Anti-Matter Rocket (AM): Anti-matter rockets mix small amounts of anti-matter into the hydrogen fuel, producing enormous amounts of energy relative to the hydrogen consumed and an exceptionally fast and powerful exhaust. While these rockets lack the high thrust to weight ratio of metallic hydrogen they still have a higher thrust to weight ratio than fusion rockets and are the most efficient of all engines. These rockets typically carry a heavily shielded magnetically contained anti-matter storage vessel. Though safe, the vast energy release possible if there was an accident means that anti-matter rockets are forbidden from coming closer than 25,000 km from any inhabited planet or moon. Likewise, very few habitats will allow an anti-matter rocket to dock with them, and instead require the spacecraft to remain at least 10,000 km away and for all cargo and passengers to be transferred using a small craft like a small LOTV. Anti-matter is exceedingly expensive to produce and so anti-matter rockets are only used in military vessels and in fast couriers designed to carry critical cargoes across the solar system in short periods of time.

With those changes in place I would then make a modification to the spacecraft chart on pg. 54 and insert two additional columns to show the acceleration capabilities of the ship as well as the maximum delta-v (though I would quite likely list it as 'Maximum Velocity' even though that's not truly accurate) with a note warning that a spaceship travelling should only reach about 45% of its maximum velocity so it has enough energy to slow back down when it reaches its destination.

e.g.:

For the Bulk Carrier after the movement type of 'Fusion' there would be an acceleration column that says '.01g' and a Maximum Velocity column that says '100 km/s' (assuming that about 10% of a bulk carrier is used to store hydrogen and that the bulk carrier uses much smaller fusion engines than the transport).

Those modifications should make it a lot easier for people to come up with reasonable estimates as to how long it would take to move between two bodies without people being required to use the Tsiolkovsky rocket equation while preventing confusion as one person assumes that people riding in a fast courier are going to be pasted to their seats while another person recognizes that they won't be. Additionally it would leave things in a place that are more 'accurate' and which are less likely to be completely countermanded by any future material concerning spaceships.

My artificially intelligent spaceship is psychic. Your argument it invalid.