Sunday, 29 March 2015
The Future in Space: Escape Pods, Part I
For me, the introduction to escape pods came via Episode 1 of Star Wars, and the small capsule that R2-D2 and C3PO used to escape from the Tantive IV. Then there were the triangular Sovereign class pods from Star Trek: First Contact, the spherical escape pod from Starship Troopers 3: Marauder, and the flying coffins from Prometheus(yes, I am going to wash my mouth out with soap after mentioning that abomination). Escape pods are an established feature of SF spacecraft, and unlike many other features shown by hollywood as vital, they appear to be a logical addition to any ship. In a more realistic SF 'Verse, however, it seems unlikely that a deep-space craft will be so equipped, for reasons that will be explored later. The type of spacecraft, its mission, and the 'flavour' of the 'Verse all affect the utility of a escape pod, and while they may make sense in the context of Star Wars, they may not apply to many situations in a hard SF world.
Like many kinds of SF tech the escape pod is often confused with other vehicles, and/or misnamed. Quite often there are small spacecraft that serve the same role, such as the Narcissus shuttle from Alien, or the escape craft in which Ripley, Newt, and Hicks escape from the USCSS Nostromo in Alien3(more soap). These two craft do not qualify as escape pods because they have an extended flight capability, enabling in them to make planetfall from beyond orbit, or reach a inhabited system from deal space. As in the case of the Narcissus a 'lifeboat' the craft such as these may in fact be the auxiliary vessel carried as part of normal operation; this is seen in Star Trek(2009) when the USS Kelvin was evacuated with the shuttles.
An escape pod can only be used to reach the surface of a planet from orbit, and possesses only enough DeltaV to deorbit, often combined with atmospheric braking. If used in deep space the pod would simply float until help arrived, as it could if the planet was unsuitable for landing. This is the type seen often in Star Wars, especially the animated Clone Wars, although those are far more sophisticated than might be the case. Unlike a 'lifeboat' craft escape pods are often seems as disposable, having only enough power to make a safe landing and call for help.
Escaping from a dying spaceship just in time to see it exploded in a nuclear fireball moments before the escape pod begins to tear into the atmosphere of the inhabitable, uncharted planet... This is kind of fiction that inspires the inclusion of escape pods in spacecraft designs. Desirable as it might be, however, it is only a fiction. Space is a relatively benign environment; a crippled spaceship will not sink, be torn apart, or explode as an aircraft, ship, or submarine might. And don't forget, in space none can hear you scream, so you will be waiting a long time for help.
Deep space is a different case to a planetary system or orbit itself, so I'll discuss it separately. The most effective way of analysing an escape pod in deep space is to compare it to the lifeboats on a cruse ship. I know, space isn't an ocean, but in this case it is a helpful analogy. If a cruise ship sinks the lifeboats have on job - keep people alive until help arrives, which, given the number of ships in major shipping lanes, should not be too long. It seems safe to assume that a space liner could use escape pods in the same way, but this fails under several criteria. One, the spaceship cannot sink, so there is no danger to staying aboard a spaceship that has been disabled by a failure or meteor strike. Note that NSWR spacecraft are an exception to this, as they can explode if the tanks fail; but even then it would be better to jettison the tanks themselves. The ship will be compartmentalised, so even severe damage should leave heritable sections. Two; the pods cannot carry sufficient life support, food, or power. One a lifeboat in the pacific there is air, sun for solar power, posable fish, etc. to help you survive. In space, any escape pod or 'lifeboat' needs to carry oxygen, filters to scrub CO2, water recycling, etc. This might be doable for the short term, say a few days to a week, but on a Hohmann transfer that is going to do no more than prolong the agony. And if the ships in the 'Verse are fast enough to rescue the survivors, then escape pods are not needed, they could just stay with the ship and its greater supply of food, power, oxygen, etc. So it can be seen that escape pods are infeasible for deep space; dangers like fissioning fuel can be easily dumped, and the pods are going to have fewer resources.
It seems that pods are of the most use when in the vicinity of a planet, which means that Star Trek and Star Wars got something right at least. It also makes them unlikely to be found on spacecraft that spend a long time in transit between destinations, due to the weight penalty. The place they are most lily to be found is on a space station. Stations likely carry far more people aboard than can be evacuated by shuttle alone, have less of a weight limit, and are normally close to planets. Which brings up another constraint; the planet must be habitable, or at the very least, non-hostile. And these may be few and far between in the real world.
The above points can be extrapolated to indicate the type of 'Verse in which escape pods are going to be a commonplace, and where they will be used. Space stations over habitable planets will be the main use, followed by ships that have large crew/passenger numbers and which regularly pass habitable planets. Note that within a solar system this is unlikely, so you are looking at starships. Given the difficulty of interstellar flight, and the time spent in deep space away from any planet, means that only FTL starship really befit from escape pods. This is the case in Star Wars, where hyperspace is used to jump from one habitable planet to another. Usually the starships are close enough to a habitable planet that escape pods are a perfect safety measure. FTL comms also make them more practical, as it allows for a much higher probability of rescue, especially if the starship went down outside normal travel routes.
So you end up with a moderately hard 'Verse. One in which the technology and setting are generally crammed with realistic science, but in which there is FTL travel and communication, a unlikely number of human habitable planets, and starship design that goes in for catastrophic failure(or space battles in orbit, although it is unlikely anyone would survive from the loosing ship, no matter what escape methods they had planned).
Note from Author: to anyone who has been waiting on a new post, sorry for the delays. Blogger decided to eat all the draft posts I had half finished, for some as-yet unidentified reason. Anyway, I should be back on track and posting once a week again now. Upcoming posts will include a look at tactical manoeuvring in a space battle, hydroponics and aquaponics, arcologies, and residential space satations, so stay tuned.