6 Hours to the ISS! High speed flight?

Hi all, did a check but found zilch.

The latest Soyus has reached the International Space Station in only 6 hours instead of the 2 days previously.

This is the same timing that supply cargo ships have taken for the last few journeys.

The difference is only 4 orbits are taken instead of the previous 33 to 35 orbits.

Could this help in the planned journey time to Mars?

www.bbc.co.uk...

reply to post by dowot


No, the ISS is only 220 miles from the surface of the Earth.

This seems more about a more efficient quicker way of getting there rather than a faster one.

For example, Apollo 11 took a total of 3 days, 3 hours and 49 minutes to fly to the Moon, the moon is roughly 238,855 miles from the Earth, so this is definitely not about speed.

Originally posted by dowot
Hi all, did a check but found zilch.

The latest Soyus has reached the International Space Station in only 6 hours instead of the 2 days previously.

This is the same timing that supply cargo ships have taken for the last few journeys.

The difference is only 4 orbits are taken instead of the previous 33 to 35 orbits.

Could this help in the planned journey time to Mars?

www.bbc.co.uk...

The ISS is VERY close to the Earth's surface, relatively speaking. The reason it sometimes takes 2 days to get there has nothing to do with with the distance, but has more to do with getting in the proper orbit. This Soyuz is NOT moving faster than other Soyuz or the Space Shuttle.

Remember, chemical rockets spend about 95% of their fuel in just the 1st 8 or 10 minutes of flight after launch. The rockets are not firing for the entire 2 days while getting to the ISS. What is happening is that after 8 or 10 minutes after launch, the spacecraft gets into such an orbit that -- after 2 days -- it will slowly match the orbit of the ISS. Perhaps this particular soyuz and the ISS could match orbits in only 6 hours

Again, it has nothing to do with getting there faster by going faster. The ship that gets to the ISS in 6 hours is moving at the same speed as the one that gets there in 2 days.

The two-day flights to the ISS were done for a couple of reasons:
First, it allowed the freshly-launched crews a couple of days to get used to being in free-fall. Roughly one person it three suffers from more-than-mild "space adaptation syndrome" (SAS). Nearly everyone gets the "full-head" feeling from their blood redistributing itself evenly throughout the body (as opposed to concentrating in the lower-body, as it does in 1G). Added to that, the body's disorientation as it gets used to the idea of "no up" can cause dizziness, nausea and vomiting.

These symptoms manifest more strongly and quickly if the newly-launched astronaut moves around a lot. In the early days, Mercury & Gemini astronauts did not have room in their cramped capsules to move around, so SAS was not significantly observed. Starting with Apollo and continuing with the Shuttle, astronauts could get out of their seats to do work. This brought-on more severe cases of SAS. On the Moon-missions, this was OK because the 3-day trip to the Moon allowed time to adapt. However, on the Apollo 9 test flight of the Lunar Module in Earth orbit (a busy and demanding mission) Rusty Schweikart's SAS caused delays and modifications to the flight plan.

One of the early (and on-going) objectives of the Space Shuttle was to study SAS and ways to alleviate it. Drugs such as "scop-dex" (a mix of scopolomine & dexedrine) helped. As a "common sense" measure, the affected astronauts tried to limit their movements, especially of their heads. Like so many things in space travel, "common sense" turned-out to be wrong. It turned-out that limiting the onset of SAS actually prolonged the adaptation-time. Nowadays, in addition to medication, astronauts have a series of head-movement exercises to help get through the adaptation period more quickly - but it still can take a couple of days. The goal is to have the astronauts ready to move around and get to work as soon as they get to the Space Station.

The other main reason for the two-day flights to the ISS is that it allows more flexibility in the launch window. Anyone who followed the Shuttle program could tell you that the complex beast rarely launched on-time. However, if you're not in a rush to make rendezvous, then you can have several minutes in each ISS-pass in which you can launch. If you're reasonable certain you can launch on-time (which is not terribly difficult with less-complex launch vehicles), you can launch into a closer orbit to your target and thus reduce (and even minimize) rendezvous time.

For the Apollo missions, they wanted the Lunar Module ascent stage taking-off from the Moon to rendezvous as soon as possible with the Command Module that would take them home. From the outset, this is what they practiced. Gemini 6 made the first-ever orbital rendezvous in December, 1965 after four orbits. Its target was the Gemini 7 capsule, already in orbit on a long-duration mission. Three months later, Gemini 8 also did a 4-orbit rendezvous and performed the first docking (with an unmanned "Agena" target vehicle). That summer, Gemini 9 made a 3-orbit rendezvous. Gemini 10 did a modified 3-orbit rendezvous, then undocked, changed orbit and rendezvoused with the old Gemini 8 Agena. Gemini 11 topped them all by rendezvousing with its target on the very first orbit after launch. For the Apollo missions, they originally planned for 3-orbit rendezvous, but with the confidence acquired from the Gemini missions, they were able to use 2-orbit rendezvous on the first lunar landing missions, and then 1-orbit rendezvous on the later missions.

So, in summary: Manned spacecraft are capable of making orbital rendezvous fairly quickly after launch, but for a variety of reasons, they usually take more time.

Hope this helps.