On 2021-12-25 15:48, Snidely wrote:
> The easy part of the flight (flight!) has been successful!
So I looked up the L2 orbit for JWST at
and of course, I have some questions.
Is reaching L2 considered requiring escape velocity? Close to it, or not
even close? (1.5 million kilometres is pretty far from Earth).
The site above says Arianne will get JWST on a direct route to L2
without first orbiting Earth.
Does Ariane first stage fall straight down back to Earth? Does it's
second stage do the same?
Some of the NASA animations seem to depict a trajectory that is almost
straight up, as opposed to what one traditionally sees for ships going
Has wnyone got a link (or short explanation) of the orbital mechaniscs
involved in _reaching_ that point? (I have seen explanations of why it
stays there once there).
At L2, with orbital period shorter than it should for that altitude, is
JWST in danger of wandering out into space if it strays too far from the
L2 sweet spot? (aka: more energy than needed to stay in orbit around sun
at that altitude)?
Or can one shoot straight up and avoid the pesky issue of Earth's orbit
because its gravity becomes too small at that altitude and it only adds
a bit to the Sun's which is why you need orbital speed that is higher
than if the Earth weren't between you and sun ? (hence 365.25 orbital
period around sun when at that altitude it would be greater)
Does the Earth provide a "gravity" assist to accelerate JWST
horizontally as it climbs up? or does JWST get all the energy needed
from its own engines to travel a greater distance than the Earth does
in 365.25 days?
(I was under the impression it would be a Mars-like transfer with JWSt
accelerating forward, increasing altitude in sun orbit, which would
cause it to lag behind Earth, but once at 1.5m km altitude higher, would
nudge isrtelf forward to catch up with Earth and "snap into L2" once at
the right place, but apparently that isn't the case).
Once at L2, if it strays too far from the sweet spot, would JWST go
wander into space, hoping to be found by advanced civilization who would
build a great ship around it, and program it to return to Earth with a
mission to seek its Creator?
Another question with regards to the circular motion of JWST in a plane
perpendicular to radial line going to the sun with no mass in the middle
of that plane). Is this "required" because L2 sweet spot keeps moving,
or is that "orbit" unnecessary and all within L2 sweet spot, and done to
keep JWST "above the Earth's horizon" so its solar panels are not in
Last question: I understand urgency of deploying solar panels and
antenna. But is there a reason they popped everything open before
arriving at L2? Wouldn't you want your fragile bits protected while
engines are still doing firings?
Wikipedia says it has 159 litres of hydrazine and 79.5l of oxydizer.
That may make it the world's most fuel efficient vehicle if it can climb
a hill 1.5m killometres long with only 159 litres of gasoline :-) (and
that includes fiueld for station keeping for roughly 10 years, so that
is pretty amazing).