SpaceX Tuesday...
Discussion
Sems they're not going to clean pre-flow rockets as a matter of course now. Just the seams and other areas for inspection purposes.
Source: Post launch press conference:
https://www.youtube.com/watch?v=Aib20nD01WE
Source: Post launch press conference:
https://www.youtube.com/watch?v=Aib20nD01WE
Eric Mc said:
Thanks for the reminder Eric.I still find it very humbling, the mathematical knowledge andcalculations needed to have the vehicles end up alongside each other.
You wait for months for a supply craft and suddenly two turn up in short order!
It's not as daft as it sounds because launches to the ISS from Cape Canaveral and Baikanour are best suited to times when the ISS passes more or less overhead each of those launch sites - and at times that favour launches (usually daylight hours - for safety and recovery reasons if a launch goes wrong).
It's not as daft as it sounds because launches to the ISS from Cape Canaveral and Baikanour are best suited to times when the ISS passes more or less overhead each of those launch sites - and at times that favour launches (usually daylight hours - for safety and recovery reasons if a launch goes wrong).
Eric Mc said:
You wait for months for a supply craft and suddenly two turn up in short order!
It's not as daft as it sounds because launches to the ISS from Cape Canaveral and Baikanour are best suited to times when the ISS passes more or less overhead each of those launch sites - and at times that favour launches (usually daylight hours - for safety and recovery reasons if a launch goes wrong).
How often does the ISS pass overhead?It's not as daft as it sounds because launches to the ISS from Cape Canaveral and Baikanour are best suited to times when the ISS passes more or less overhead each of those launch sites - and at times that favour launches (usually daylight hours - for safety and recovery reasons if a launch goes wrong).
I think it will pass directly overhead the launch sites at least once most days.
However, there are other constraints to favourable launch windows - such as lighting conditions at the launch site or at down range recovery sites (for the manned flights). For example, the Space Shuttle had extremely stringent restrictions on when it could launch because of all sorts of issues - mostly to do with abort procedures and options.
Other restrictions will be based on matters such as, what other launches are scheduled from the launch sites or what other activities are going on in the immediate areas surrounding launch complexes.
Launch controllers and tracking stations have limited capacity to handle launches as well so there has to be gaps between launches so that tracking stations can reconfigure for the next launch.
And finally, after each launch, the pad has to be checked and repaired as launching a rocket invariably causes some damage to the pad and its ancillary equipment. That can take a couple of weeks at least.
However, there are other constraints to favourable launch windows - such as lighting conditions at the launch site or at down range recovery sites (for the manned flights). For example, the Space Shuttle had extremely stringent restrictions on when it could launch because of all sorts of issues - mostly to do with abort procedures and options.
Other restrictions will be based on matters such as, what other launches are scheduled from the launch sites or what other activities are going on in the immediate areas surrounding launch complexes.
Launch controllers and tracking stations have limited capacity to handle launches as well so there has to be gaps between launches so that tracking stations can reconfigure for the next launch.
And finally, after each launch, the pad has to be checked and repaired as launching a rocket invariably causes some damage to the pad and its ancillary equipment. That can take a couple of weeks at least.
Eric Mc said:
I think it will pass directly overhead the launch sites at least once most days.
However, there are other constraints to favourable launch windows - such as lighting conditions at the launch site or at down range recovery sites (for the manned flights). For example, the Space Shuttle had extremely stringent restrictions on when it could launch because of all sorts of issues - mostly to do with abort procedures and options.
Other restrictions will be based on matters such as, what other launches are scheduled from the launch sites or what other activities are going on in the immediate areas surrounding launch complexes.
Launch controllers and tracking stations have limited capacity to handle launches as well so there has to be gaps between launches so that tracking stations can reconfigure for the next launch.
And finally, after each launch, the pad has to be checked and repaired as launching a rocket invariably causes some damage to the pad and its ancillary equipment. That can take a couple of weeks at least.
Many thanks for taking the time to reply Eric. I was aware of weather conditions being a consideration, but all those other factors are not things that I had considered.However, there are other constraints to favourable launch windows - such as lighting conditions at the launch site or at down range recovery sites (for the manned flights). For example, the Space Shuttle had extremely stringent restrictions on when it could launch because of all sorts of issues - mostly to do with abort procedures and options.
Other restrictions will be based on matters such as, what other launches are scheduled from the launch sites or what other activities are going on in the immediate areas surrounding launch complexes.
Launch controllers and tracking stations have limited capacity to handle launches as well so there has to be gaps between launches so that tracking stations can reconfigure for the next launch.
And finally, after each launch, the pad has to be checked and repaired as launching a rocket invariably causes some damage to the pad and its ancillary equipment. That can take a couple of weeks at least.
The Shuttle had many launch restrictions.
It couldn't take off through rain (water damaged the heat resistant tiles)
It had restrictions on upper winds (like most rockets) but was even less tolerant to high level winds due to the asymmetric arrangement of the "stack".
It didn't like the cold (Challenger)
It had limited nose wheel steering and braking so couldn't handle crosswind landings very well. That meant there were launch restrictions based on crosswinds at the Cape's runway (Return to Launch Site Abort) or at the designated trans Atlantic abort site runways (usually in West Africa, Spain or France).
Light levels at the landing runway were not too much of an issue. Quite a few Shuttles landed in the dark. Landing directly into the face of a low level sun was unpleasant but not that much of an issue for the experienced pilots who flew it.
It couldn't take off through rain (water damaged the heat resistant tiles)
It had restrictions on upper winds (like most rockets) but was even less tolerant to high level winds due to the asymmetric arrangement of the "stack".
It didn't like the cold (Challenger)
It had limited nose wheel steering and braking so couldn't handle crosswind landings very well. That meant there were launch restrictions based on crosswinds at the Cape's runway (Return to Launch Site Abort) or at the designated trans Atlantic abort site runways (usually in West Africa, Spain or France).
Light levels at the landing runway were not too much of an issue. Quite a few Shuttles landed in the dark. Landing directly into the face of a low level sun was unpleasant but not that much of an issue for the experienced pilots who flew it.
That's interesting - the most challenging part of a crosswind landing is the landing bit, where you aren't using the nosewheel (landing on the mains, using into-wind aileron to correct; some use a crabbed approach that they "kick straight" at the last minute).
By the time the nosewheel is on the ground you should be pretty slow and in a nosewheel aircraft fairly immune to crosswinds (versus a tailwheel that is always vulnerable). What was the usual nosewheel touchdown speed? I presume so high that crosswinds are still a major threat? I found a reference to the nosewheel coming dowing at 180 knots, which is faster than most aircraft touchdown at let alone de-rotate.
By the time the nosewheel is on the ground you should be pretty slow and in a nosewheel aircraft fairly immune to crosswinds (versus a tailwheel that is always vulnerable). What was the usual nosewheel touchdown speed? I presume so high that crosswinds are still a major threat? I found a reference to the nosewheel coming dowing at 180 knots, which is faster than most aircraft touchdown at let alone de-rotate.
The Shuttle's mainwheels touched down at around 200 knots. So the nosewheel hit at around 150 to 180 knots. Originally the steering was carried out by using differential braking on the mainwheels. That was another limiting factor. There was obviously no reverse thrust available so the split rudder was used as an airbrake. After Challenger, a braking parachute was fitted which helped a lot in getting the run out speed down quickly.
garyhun said:
Eric Mc said:
And the Soyuz launched a few hours ago will arrive alongside early Tuesday.
A veritable bus stop 
The one that went up earlier today is bringing their replacements. And some Christmas presents of course.
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