Hello and welcome back to this Orbiter
2016 video series. I'm Tex and this is
episode 4 of Journey to Saturn. In the
previous episode we covered the Jupiter
slingshot as well as the first major
mid-course correction on our way out to
Saturn. In this episode we will conduct a
few minor mid-course corrections, go
ahead and encounter Saturn, as well as
complete the capture burn at Saturn. Now
we won't make it to Titan in this
episode because it did just prove to be
a little too much to cover, so in the
next episode we'll encounter Titan as
well as rendezvous with MAV in Titan
orbit, so some exciting times to come
indeed. Before we begin I'd just like to
quickly mention that I recently released
a new type of video for me. It is a
documentary-style video, of course about
Saturn and it was inspired from this
video series we're making here.
The original idea was to create a short
sequence to place in the middle of this
episode where we sort of talk about
Saturn and what we know about it.
I mean it makes sense to talk about
the planet we're actually traveling to right?
But as I did research in the
project grew I quickly began to realize
that it deserved to be a
standalone video instead of sandwiched
in between an episode here where fewer
people would have an opportunity to see it.
So I assume if you're here watching
this video series you've probably
already seen it, but just in case you
haven't I'll put a card up at the top of
the video that you can click on where
you can go and watch that Saturn
documentary. Please do check
that out when you get a moment I would
love to hear what you guys think seeing
as this is a new type of video for me to make.
And if you enjoyed it also share it
on the internet I would love for other
people to have an opportunity to see it
and maybe fall in love with space as
much as we do. I mean the more people we
can get interested in space can only be
a good thing right? But as it turned out
I really enjoyed making the video. It was
a lot of fun researching it and learning
new things that didn't already know and
putting the whole video together was
just quite enjoyable. So, I was thinking
maybe I would make some more videos like that, perhaps about the moons of Saturn
as we travel to them throughout this
video series could be interesting, but
maybe I'll branch out and make other
types of videos like that about other
planets in the solar system space or
spaceflight in general could also be fun.
Let me know what you guys think of course and if you have any ideas of your own
about documentary type of videos space related that you'd like to see, post in the
comments below or hit me up on social media, I'd love to hear from you
and I always appreciate your
feedback. So, I apologize for the rather
long intro now, but without further ado,
let's go ahead and get started with this episode!
All right so we are here on our way to
Saturn
PeT has about halved since we last set up
the course correction burn and we had
talked about getting the orbital period
or getting our time to periapsis
to be a multiple of titans orbital period, and we did that in the last episode.
Then we talked
about waiting until the time to
periapsis basically halved and then we
would repeat the same process again, so
that's what we're doing. The PeT number has halved, so first thing we're going to do
is adjust our periapsis by bringing it
down to 3,000 km (3.000 M).
That does fluctuate quite a lot this far out
from Saturn.
You see the G contribution for Saturn is
actually only at 0.01 at the moment, so
we're still a long ways out, but
nonetheless we will go ahead and make
sure PeA is back down to 3,000 km and also just as important we want to make
sure that line of nodes is sitting directly over our periapsis.
Once we do that we'll bring up
the protractor again double-check the
angle with Titan and just make sure that
our PeT is in fact a multiple of a Titan's orbital period.
Okay so our periapsis looks good and line of nodes looks good.
Just zooming out; we're going to
target Titan here...
just make sure we know where Titan is located.
So I've opened the protractor let's
go ahead and move the protractor
directly over the center of Saturn so
sort of like this we want the bottom
middle part of the protractor be in the
center of Saturn and we're going to
rotate it around so it lays over that
line of nodes and our periapsis.
Again making sure that zero degrees is at our periapsis so we're going to move our
mouse up to where Titan is and we can
see that it's not quite 111.6 degrees,
so let's move our mouse up to where it is 111.6 degrees, or as close as we can get it.
Some where like that, and let's time accelerate until Titan gets directly over that point.
OK, that's good. Now we can close the
protractor and let's just figure out the
orbital period here.
So if we open the calculator and we take our current
PeT: 17.92 and divide that by Titan's orbital period: 1.378
that is 13 exactly, so that is a multiple of Titan's orbital period. Fantastic!
That means we need no
course corrections at this point in time
other than adjusting the periapsis and
the line of nodes as we have already done.
So, we can go ahead and time
accelerate again
and we'll wait until PeT basically halves from where it is now.
OK, I've cut forward in time,
and you can see PeT is about half of what
what it was before and of course once
again the first thing I'm going to do is adjust our periapsis, bring that
back down to 3,000km and put the line of nodes directly over our periapsis.
Then we're just going to make sure that Titan is about where it should be. I don't think I'm going to
open the protractor again for this
because I know about where Titan should be,
close enough for the angle of 111.6 degrees.
Actually a good reference in this
case it worked out that the line going
through the center of Saturn, the
straight line going through the center
of Saturn that represents Saturn's orbit
around the Sun and Titan should be
pretty close to that line. I don't think
it was right over it, but it was pretty
close to it, so that's going to be a
close enough reference for us I think we
won't need to open the protractor again. But of course if you wanted to be super
accurate you could do that every time.
So, Titan is actually not at that angle
just yet so what I'm going to do is just
time accelerate. Titan's basically on the
other side of Saturn from where it needs
to be, so we're just going to time
accelerate until Titan moves over to the
angle that we calculated which was again
111.6 degrees off from our periapsis.
So you can see Titan is about there now...
Somewhere...
right about there. That was according
to protractor where 111.6 was, so now
that Titan is at that angle let's again
use the calculator to double-check that
PeT is a multiple of Titan's orbital
period. So, 8.263 divided by
1.378... and that gives us 5.996
So, it's a little bit off we could go ahead
and correct that. So, rounding up to 6
Take 6 times Titan's orbital period
gives us 8.268,
so technically our PeT right now should
be 8.268. That means
we should probably slow down a little
bit. It's probably close enough we don't
need to adjust it, but we'll go ahead and
mess around with this for a minute.
Now while I'm doing that I just wanted
to highlight a comment that a user by the
name of MontBlanc left on my video
episode zero.
It was really a good comment that explained why it is important for us to have that line of
nodes at periapsis and the importance of
how that affects our encounter at titan
So basically what he said is an
important step in the process is to make
sure that prior to arrival at Saturn you
rotate your orbital plane with respect
to Saturn, so that the line of apsides
of your approach orbit more or less
coincides with a line of nodes of Titan's
orbital plane, with relation to your
orbital plan. So, this means that you
will execute the the capture burn at
your periapsis by Saturn as you pass
through the line of nodes and after that
burn we will not be in plane with Titan,
but if we get the timing right we'll
reach our apoapsis as we pass through
the line of nodes and thus have an
encounter with Titan. And he goes on to
say that the this plane rotation
maneuver is best carried out some
distance from Saturn, really just to keep
the manoeuvre costs low -- and we did do
that. We're still a long ways from Saturn,
but his explanation was was more technical than mine probably
and I think that it really highlights what's going on here and the importance of
swinging that line of nodes over periapsis, as well as the importance
of getting the timing right as we're
doing right now once again because by
making sure that our PeT is a multiple
Titan's orbital period, that ensures that
we get that timing right. So all of these
things really have to come together to
ensure that we minimize how much Delta V
we're going to need to both get
captured by Saturn and encounter Titan
you know all all sort of together if you will.
So I thought that was a really good
explanation so I just wanted to to
highlight his comment, but basically
we're continuing with our course
corrections here. I'm making another adjustment to PeT just trying to get it
as close to a multiple as we can. Quite frankly I believe that everything so far
has been close enough to a multiple... everything's pretty much
rounded up to a multiple anyways and
we're not talking about a small rock
here like maybe Phobos or something, so
I'm sure that it was close enough that
we would have still had an encounter
with Titan. But I'm probably just trying
to split atoms here by getting you know
the the PeT exactly at a multiple of
Titan's orbital period each time. I'm not
sure how many more times I will do that
but we will certainly continue forward. As PeT comes down, we'll continue
adjusting our periapsis altitude because
we want to make sure that that
definitely is at 3,000km in
altitude and also that that line of
nodes sits right on periapsis So, we're
just continuing to time accelerate here.
Our PeT is coming down. You can see Titan is coming back around to our angle.
We may check a PeT again just to make sure, but I don't think it's
gonna be worth making any more
adjustments. We'll just double check.
So, Titan is getting to our angle 111.6 there; let's just double check PeT.
divided by Titan's orbital period. So, 2.750 for our PeT divided by one 1.378
That's 1.995, again it rounds up to 2.
That's close enough. I'm not going to
adjust that again, so just zooming in
let's go ahead and adjust our periapsis
once again. It's a not quite at 3,000km,
so we're just going to keep doing this until we fall within
Saturn's strong SOI and our periapsis
should not be fluctuating as much anymore.
So we won't have to be making these adjustments anymore.
So far at this point after the initial course correction, all  of these adjustments have been very minor
using just a little bit of linear RCS.
Honestly that looks fine right
there we're going to continue time
accelerating forward and probably get
within Saturn's
strong SOI here...
And there it is. You can
see we have fallen within Saturn's
strong SOI. The G contribution on the
orbit MFD is at 0.50, so
our periapsis still looks good at 3,000km above the surface and we're
basically encountering Saturn at
this point. Why don't we go ahead and
open up BurnTime MFD and let's just put in
our Delta V remaining here, 72,435 m/s.
I'm gonna put that in right here after MCC 3. So, we used 185 m/s
since our original course
correction burn. We will put in Delta V
at encounter once we get closer to
Saturn and then also notice that I
changed the last two lines to the Titan
moon orbital insertion and MAV
rendezvous that just made more sense for
our particular situation. So yeah, we'll
come back and enter in those Delta
velocity figures whenever we get to
those points in the flight. I
think at this time...this is definitely a
major highlight of the flight as we
cruise down to Saturn. We are on course
there's really not much else we need to
do we might just make a few minor
corrections to our periapsis as we coast
down, just to make sure it stays around
3,000km, but let's take some time and just
enjoy the cinematic views of our
encounter here at Saturn. We'll come
back when it's time to set up the
capture burn, so I'll see you guys in just a bit!
[Music sequence]
Wow!! That is always just a stunning view. Saturn truly is the crown jewel of the
solar system. I hope you guys
enjoyed that cinematic sequence. That was
really fun to make, but yeah it's a time
to get down to business here and get our
capture burn out of the way. So let's put
in our Delta V here at encounter.
72, 341 m/s remaining -- we used
a little bit adjusting periapsis
coasting down but not much at all.
So I'm gonna open up Interplanetary MFD, but first let me just
start a little bit of rotation in here.
We're gonna of course turn retrograde,
but we'll get a better view of Saturn
too. So I'm gonna open
Interplanetary MFD and you probably guessed it...the DeltaVelocity program.
There we go, now what I'm going to do for time to
ejection is put in roughly our time to
periapsis. So let's just set that at 2,900
seconds. Hit projection and let's go to
dVf and for this. We're going to get that
from our spreadsheet where we calculated
the to burn solution. So if we look at
the first burn at planet periapsis,
that's 3,215 m/s,
so that's what we're gonna put in for our capture burn here
at Saturn periapsis. So we'll set that at of course -3,215 m/s.
Now that gives us a preliminary
solution that we can use to tweak it.
Now before I go any further we're just gonna zoom in a little bit. Let's go back to TeJ
and I want to move those two blue
lines between periapsis at Saturn. So, the
first blue line is where the burn begins...
the first blue line on the left that is
and the blue line on the right is where
the burn ends. We want to split the
that burn up so half of the burn is done
before periapsis and the other half after.
Now on the right side, I'm going to share
the left side with the right. With the Map
program, I'm targeting Titan and pressing SEL so that we can see our periapsis
and relative inclination at Titan. We'll
turn on sphere of influence and the plan.
So, you can see with the plan on
that we're actually lowering our
apoapsis too much...it's coming down below the altitude of titans orbit around Saturn.
I think what we'll need
to do for now anyways is take some of
that dVf out that we put in. So we would
go plus on the dVf and you'll see that
our ApA is raising up over on
the Map program on the right side.
That looks better. It's roughly around
Titan's orbit, but we can look at the
periapsis number at Titan as well. We
want to shoot for somewhere around 600km
above the surface of Titan because it's out of Titan's atmosphere,
but also more importantly, that's about the altitude that MAV is orbiting at
which we need to rendezvous with once we get to Titan.
So, what we're gonna do is
just play around with the variables.
We're not going to adjust the date very
much, we'll just fine-tune it just a
little bit, trying to keep it right in
between periapsis like that, but we'll
use the other variables;
probably Delta velocity forward and
maybe the inward here. I want to just
play around with these until I can get
that periapsis down to about 600km above Titans surface, but I
also want to make sure that we're coming
in pro-grade. So that means our relative
inclination needs to be under 90 degrees.
As I time accelerate here get a
little closer to the burn, we're about
2400 seconds from the burn and one thing
that you might notice is I'm not
changing anything, yet the periapsis at
Titan is changing on its own... so is the
relative inclination. Both Dimitris and
I were really scratching our heads on
this. We couldn't figure out why that was
happening. He was saying that it really
shouldn't be happening like that and it
didn't matter if we use the Delta
velocity program or the target intercept
program. Either way, it was
constantly changing, so that makes
setting up a solution obviously pretty
difficult because the whole idea behind
this is we find a solution with a periapsis
at our target and do the burn. As you
know it usually comes out pretty
accurate but for whatever reason here at
Saturn -- we tried it in both Orbiter 2016
and 2010 -- we had the same problem. So, in any case what I'm gonna have to do here
is just try to play around with the
variables and get the periapsis where I
want it, but probably what we'll have to
do is get a little closer to the burn
and maybe overshoot where where we want the periapsis, anticipating that it will
fall down to 600km during the
time that we conduct the burn. Now it's
really just going to be sort of Buck
Rogers using IMFD in a sense because
I just don't know a better way to do it unfortunately.
But I think this is still going to be
the best way to minimize our dV
expenditure so that we can conduct the
Saturn capture burn and also get our
encounter set up over at Titan. You
can see actually the periapsis at
Titan is about 880km and it's
climbing while I'm not changing anything,
so it's pretty close to where we want it,
but like I said it's changing on its own.
We're about a little over 1,000 seconds
from the burn, so let's just time
accelerate here and maybe just get
oriented roughly in the right direction
before we get too far ahead.
Just change our view so we can watch Saturn as we coast down to the night side, but yeah, let me just
tweak dVf to bring periapsis back down. OK, so we're coming in pro-grade and
overshooting periapsis a little bit...
there's 1,500km and it's falling
on its own toward our target at 600km,
but it's going to get there long before we
reach the burn.
We're still 932 seconds
from the burn and just putting in some
more dV inward here, just trying to
really guess how much overshoot this.
I think probably what we're gonna have to do is just get
it set as good as we can probably time
accelerate here in a minute get a little
closer to the burn because we're still
quite a ways out here.
So periapsis is looking good we're just
watching it come down now on its own.
I wonder if I target the equator and reference Titan...okay so we can
see our periapsis with the plan up at
Titan and it's still changing on its own,
so that didn't make a difference. I
thought maybe if I reference Titan
instead of targeting Titan on the map
program that maybe I would get something
more accurate but that didn't work out,
so we'll go back to referencing Saturn
and targeting Titan. I mean
unfortunately I just don't know a better
way to do this. I mean...periapsis... every
time we get it close to where we want it
look how quickly it changes! It's changing
like insanely fast there, so let's just
go ahead and time accelerate and get
much closer to the burn and I guess
we'll just have to get it set up as
close as we can.
Overshooting it like I said, just make sure we're oriented
pretty much for the burn. OK, so it's
close enough...
we're 150 seconds from the burn, so
let's just toy around with the
periapsis here... okay so we we were
retrograde we went through Titan coming
out on the other side and now we're
pro-grade. Periapsis is at 1600km
and falling on its own and it's getting down too close
to 600km, too quickly based on
our time to the burn. Yeah that really
sucks, so overshooting it again there's
2,200km, we are still pro-grade,
relative inclination looks good.
OK so periapsis is at 2,000km
right now and falling... I'm just
going to go with that. I don't think
that's going to be good enough though.
You can see periapsis is falling quickly.
Again, we wanted it to be at
600km, but we're still just
50 seconds from the burn. I'm time
accelerating and we've hit Auto burn so
we're just gonna let IMFD do its thing
here because otherwise I'm gonna sit
here just guessing at this all day long. We'll just see how bad this is.
I'm quite sure that we're gonna have to
clean up the burn ourselves here, so I
turned off the plan we'll see things in
real time over on the right side, on the
map program as IMFD conducts the
auto burn here. We should be able to see
once were captured by Saturn the display
on the map program will change....
there it goes!
We are now captured by Saturn and
you can see our apoapsis quickly coming down.
OK, so that's looking good. The auto
burn is still working at 10 times
acceleration here. OK, now we're at
normal time just about one second...
less than a second left for the burn and I
can already tell you it's not going to
be enough. Alright look how high our periapsis is that Titan. It was 115,000km
above the surface of Titan, so
let's continue burning and bring
periapsis down. So we can just go ahead and set it here.
IMFD didn't burn long enough... So we're retrograde...
let's keep burning and go through Titan...
okay we went through the center of Titan
we've come out the other side using
linear RCS and... there we go.
Periapsis is at 603km
above the surface of Titan and our
relative inclination is 41.2 degrees, so we're coming in pro-grade and
altitude above Titan looks fine. So, I've unshared the MFD on the left side,
I'm gonna use the map program with
Titan targeted, but on the right side I'm
actually going to reference Titan and
I've got the equator targeted. So we're
gonna use the right side actually to do
a course correction, but I guess we're
not actually going to cover that in this
episode because it was just getting too long.
Let's open burn time though
and we have 69,106 m/s remaining
So we're gonna pop that in right here after the capture burn at Saturn. We used 3,235 m/s...
and what do we calculate? 3,215 m/s, so what we
used 20 m/s more. Yeah I
guess in the grand scheme of things
maybe that's not so bad considering that
was a little bit of Buck Rogers solution
set up there, but there we go. I mean we're
captured by Saturn and we have a nice
close encounter over at Titan, so not bad.
If anybody happens to know why
that's occurring, please do leave
comments below. Like I said both Dimitris
and I were scratching our heads on that
trying to figure out why that was happening.
In any case we're on our way. We're on
the night side of Saturn and that looks
spectacular! You can see the rings of
Saturn illuminated by the Sun even
though we're over
here on the night side it's still
providing us with some views, so that's
just always awesome to see. I believe
as of recording this video Cassini died
just a couple of days ago, so rest in
peace Cassini, we will definitely all
miss you. A big thanks and congratulations
to all of the people that
worked on that mission so hard over the
years. It's sort of poetic -- maybe
ironic -- I don't know, that we are now here
at Saturn picking up the torch so to
speak. On our manned mission to Saturn...very cool as Saturn comes into view
here. Gosh, that is just always so awesome
to look at. I'm just going to rotate over
a little bit so that we're looking sort
of right at Saturn as we coast out away
from it and just enjoy the views. This is
just spectacular. I'm just gonna do a quick
save for you guys here if you want to
pick up from this point in my scenario
pack, but um yeah, that's going
to wrap up this episode as we drift away
a little bit from Saturn here. In the
next episode we're going to do a course
correction for Titan and then of course
we need to conduct the orbital insertion
burn at Titan, but more importantly we
need to rendezvous with MAV, so some
interesting things that we will be doing
in the next episode. Listen guys, I
really appreciate you following the
series. It's been a lot of fun!
Be sure and like the video, leave me
comments, and subscribe for updates if
you're interested in my videos. I hope you guys are all doing really well and
once again thanks for watching. Take
care, and until the next episode,
we'll see you then!
