Was it ever explained why Space Station V, used as a transfer point from Earth orbit to the moon and other planets, was in a low Earth orbit rather than a higher orbit, which would have been more efficient for transfers to other locations in space?


Low Earth orbit is the most efficient place to locate a transfer station. The energy required to reach low Earth orbit is the most efficient place to locate a transfer station. The greatest difficulty in launching spacecraft is getting them into stable orbits around the Earth. The reason for this is that the energy required to reach the initial low Earth orbit needs to be imparted all at once, starting from launch. In contrast, once a body has reached orbit, it is comparatively straightforward to launch it further out into space.

The is seen historically in the NASA program. The first two manned spacecraft programs (Mercury and Gemini) were entirely based on low Earth orbit operations. The Apollo spacecraft headed to the much larger elevation of the moon operated by essentially blasting into a trajectory that would lead to a low Earth orbit, then following that up with another burn that carried them on a free return trajectory around the moon. The first stage of the ascent was, by far, the most demanding, due to the Earth's huge gravitational field that had to be overcome.

The same kind of situation applies in a hard science fiction context as well. Once systems are in orbit, they can be assembled to make a further craft at leisure.

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    I will have to disagree with you on your statement "once a body has reached orbit, it is comparatively straightforward to launch it further out into space." As I understand what is called the Delta-v budget (en.wikipedia.org/wiki/Delta-v_budget) it indicates that launching from LEO to deep space requires 23 times more energy than from the Earth-Moon Lagrange Point 1 to deep space. A transfer station in LEO does not make sense in terms of energy expenditure. – Bob516 Dec 29 '18 at 23:59
  • The $Delta v$ budget is not a very useful comparison on its own, because with staged rockets the amount of mass you are accelerating decreased at each stage, meaning that a given impulse contributes more $Delta v$ at each stage. – Buzz Dec 30 '18 at 0:26
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    @Bob516 I'm not sure where you're getting the factor of 23 from. Launching from LEO to Earth escape is about 3.22 km/s of Delta V, whereas launching from LEO to EML-1 is 3.77 km/s just to get there and stay there (and an additional 0.14 km/s to then go to Earth escape). I think what you're missing here is the impact of the Oberth effect. – Kyle Dec 30 '18 at 1:03
  • @Kyle I misread the table the wiki page. – Bob516 Dec 30 '18 at 2:19
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    @Bob516: to go further from LEO takes launching propellant from Earth, but a propellant-delivering spacecraft can launch the most propellant when its delivering to LEO. The available payload mass is at a maximum for launches to LEO, making LEO the most efficient location to consolidate equipment, supplies, propellant, etc. – Christopher James Huff Jan 5 at 3:12

Space Station V hosted a range of facilities including an orbital Hilton Hotel. It was used as a transfer point, sure, but the majority of people on board seem to tourists (who are presumably traveling from Earth to the station, then returning to Earth) which means that a nice close Low Earth Orbit would be a far more efficient location than a high orbit in the middle of nowhere.

The name "V" (five) also suggests that there were at least four other stations, possibly in different orbital positions depending on the need for various transfer windows. Floyd simply traveled to the nearest station that had an available shuttle.

No matter how many times you left Earth, Dr. Heywood Floyd told himself, the excitement never really palled. He had been to Mars once, to the Moon three times, and to the various space stations more often than he could remember. Yet as the moment of takeoff approached, he was conscious of a rising tension, a feeling of wonder and awe - yes; and of nervousness - which put him on the same level as any Earthlubber about to receive his first baptism of space.

2001: A Space Odyssey - Arthur C. Clarke

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    The name "V" (five) also suggests that there were other stations, possibly in different orbital positions depending on the need for various transfer windows. The first three stations were destroyed in wars, and the fourth disappeared mysteriously within 24 hours of coming online... ;) – Lexible Dec 29 '18 at 23:22
  • @Lexible Is this from the novel? It has been a very long time since I read it. – Bob516 Dec 29 '18 at 23:25
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    @Bob516 That's a joke and a reference to the series Babylon V. ;) – Sava Dec 29 '18 at 23:27
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    @Bob516 - I was basing it on the prominent placement of the Hilton Hotel booth in the centre of the concourse and the wide range of facilities available in the novel ("The lounge had been redecorated since his last visit, and had acquired several new facilities. Besides the usual chairs, small tables, restaurant, and post office there were now a barber shop, drugstore, movie theater and a souvenir shop selling photographs and slides of lunar and planetary landscapes, guaranteed genuine pieces of Luniks, Rangers, and Surveyors, all neatly mounted in plastic, and exorbitantly priced.") – Valorum Dec 29 '18 at 23:59
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    German tank problem suggests there are 10 with no other info given – William Grobman Dec 30 '18 at 1:45

The transportation model in "2001" consisted of reusable winged shuttles from ground to a Low Earth Orbit (LEO) station, then transferring to LEO-to-lunar-surface shuttles.

This kind of model was prevalent in mid-century sf; sometimes a Lunar orbit station and moon-to-low-lunar-orbit rocket shuttles were added (Heinlein favored this system).

This thinking was based on the plans of von Braun and others. It was thought more efficient to use specialized craft for each leg of the journey rather than one multi-purpose ship.

  • I absolutely agree it is more efficient to use specialized craft leaving from a transfer station. It is the location at LEO that seems odd based on Delta-v requirements to get to the Moon or the planets. I was hoping it was explained somewhere why the station was located at LEO – Bob516 Dec 30 '18 at 0:02
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    As Heinlein said, "Once you get to earth orbit, you're halfway to anywhere in the solar system." – Christopher James Huff Jan 5 at 3:18

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