Author Topic: Taking Off With Orbiter  (Read 8351 times)

Offline Noldi400

  • Jupiter
  • ***
  • Posts: 627
Taking Off With Orbiter
« on: August 19, 2012, 02:45:50 PM »
Well, here we go...

I just downloaded and started learning Orbiter. That ought to occupy my time for the last year or so.
"The sane understand that human beings are incapable of sustaining conspiracies on a grand scale, because some of our most defining qualities as a species are... a tendency to panic, and an inability to keep our mouths shut." - Dean Koontz

Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Taking Off With Orbiter
« Reply #1 on: August 19, 2012, 04:37:28 PM »
Let me know how it goes. It's one of the very few interesting programs that runs only on Windows, an OS I refuse to run except under very extreme duress.

Offline Noldi400

  • Jupiter
  • ***
  • Posts: 627
Re: Taking Off With Orbiter
« Reply #2 on: August 19, 2012, 07:45:03 PM »
Well, for someone with no flight or flight sim experience, and no more understanding of orbital mechanics or physics than the average reasonably intelligent space-nut, it's going OK.

If we can agree that "OK" can be defined as tumbling in three axes in space, or searching helplessly for that runway I just departed.  More computer and more screen would be a big help.
"The sane understand that human beings are incapable of sustaining conspiracies on a grand scale, because some of our most defining qualities as a species are... a tendency to panic, and an inability to keep our mouths shut." - Dean Koontz

Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Taking Off With Orbiter
« Reply #3 on: August 20, 2012, 04:02:20 AM »
Well, to learn orbital mechanics I can think of a couple of fairly basic maneuvers:

Raising and lowering the opposite side of an orbit with an in-plane burn.
Changing an orbital plane with an out-of-plane burn. Do the burn at the equator to change the inclination only.
Burn from a low circular orbit into a hyperbolic escape trajectory.
Do a burn along the local vertical for an equal-period separation from a space station.
Compare escape burns from apogee and perigee of an elliptical orbit (demonstration of Oberth effect).
Compare inclination-changing burns from apogee and perigee of an elliptical orbit.

That should get you started.

Offline Noldi400

  • Jupiter
  • ***
  • Posts: 627
Re: Taking Off With Orbiter
« Reply #4 on: August 20, 2012, 10:29:10 AM »
Those are certainly on my list, and in fact the first one is closely related to getting into orbit in the first place. There's a very handy computer display that shows your current orbital data - when you get sufficient altitude, you make a prograde burn until your projected perigee is a nice comfortable positive number.  Where I'm having trouble is in more basic control areas - spatial awareness has never been my strong suit and it definitely shows.

One minor problem is that all readouts are metric - altitude is in km, velocity is in m/s, etc. It's going to take me a while to convert my thinking.

As I said, I have basically no experience even in a flight sim. I think what I'm going to do is download something the equivalent of a Piper Cub and fly around in atmosphere until I get a feel for the program itself.
"The sane understand that human beings are incapable of sustaining conspiracies on a grand scale, because some of our most defining qualities as a species are... a tendency to panic, and an inability to keep our mouths shut." - Dean Koontz

Offline Kiwi

  • Mars
  • ***
  • Posts: 471
Re: Taking Off With Orbiter
« Reply #5 on: August 20, 2012, 11:08:23 AM »
D'ya think Chuck'n'Norris could learn a thing or two about space travel from this program?

I see that some members have commented about the lack of replies from them, but perhaps they are very nice, busy people like others here.

Maybe Chuck is away doctoring the maimed, drunk and disordered in the Intensive Care Unit in some hospital, or checking out bugs in computer programs for Chinese radar installations. Perhaps Norris is adding some intriguing new finds to an interesting collection of socks, or they could even be just spending quality time together playing chess, or something like that.
Don't criticize what you can't understand. — Bob Dylan, “The Times They Are A-Changin'” (1963)
Some people think they are thinking when they are really rearranging their prejudices and superstitions. — Edward R. Murrow (1908–65)

Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Taking Off With Orbiter
« Reply #6 on: August 20, 2012, 02:23:20 PM »
One minor problem is that all readouts are metric - altitude is in km, velocity is in m/s, etc.
What's wrong with that? Metric is the only way to go.
Quote
As I said, I have basically no experience even in a flight sim. I think what I'm going to do is download something the equivalent of a Piper Cub and fly around in atmosphere until I get a feel for the program itself.
If you want to learn how to fly a spacecraft you might actually be better off not knowing an airplane. Many of the rendezvous maneuvers are highly counterintuitive to pilots. In the early days of the Gemini program, before they understood the orbital mechanics, they had a very hard time doing it. They'd point to their targets and go, and the next thing they knew they were moving away from it.

Offline Noldi400

  • Jupiter
  • ***
  • Posts: 627
Re: Taking Off With Orbiter
« Reply #7 on: August 20, 2012, 08:14:50 PM »
Quote
What's wrong with that? Metric is the only way to go.
Nothing wrong with it, it's just gonna take me a while to get used to it. Although in atmospheric flight, k/h would be more intuitive (for me anyway) than m/s. I just don't have a feel yet for how fast 100 m/s is in real-world terms; easy enough if I have a second to think, but you don't always.

Quote
In the early days of the Gemini program, before they understood the orbital mechanics, they had a very hard time doing it. They'd point to their targets and go, and the next thing they knew they were moving away from it.
Well, "apply thrust to slow down" doesn't make much sense at first glance.  You may be right though - thinking in terms of aerodynamics certainly trips up enough HBs.

"The sane understand that human beings are incapable of sustaining conspiracies on a grand scale, because some of our most defining qualities as a species are... a tendency to panic, and an inability to keep our mouths shut." - Dean Koontz

Offline cjameshuff

  • Mars
  • ***
  • Posts: 372
Re: Taking Off With Orbiter
« Reply #8 on: August 20, 2012, 08:48:44 PM »
Nothing wrong with it, it's just gonna take me a while to get used to it. Although in atmospheric flight, k/h would be more intuitive (for me anyway) than m/s. I just don't have a feel yet for how fast 100 m/s is in real-world terms; easy enough if I have a second to think, but you don't always.

It's not particularly useful to relate orbital distances and speeds to planetary ones anyway. Your points of comparison are the distances and orbital velocities of various objects, and those are generally given and worked with in metric. The moon orbits Earth at an average of 1.022 km/s, that's 22 m/s more than an even 1 km/s...no tricky conversion factors. Earth orbits the sun at just under 30 km/s, earth surface escape velocity is a bit over 11 km/s, a circular orbit 400 km above the ground takes ~7.7 km/s. Just 1 km/s is 3 times the sea level speed of sound...the moon travels 2.2 times the circumference of the Earth along its orbit each day. There's little point in even trying to relate the speeds involved in spaceflight to anything that takes place in the atmosphere.

As ka9q said, metric is the only way to go. There's just no point in trying to use Imperial units in space, and trying to do so will only cause headaches.

Offline Noldi400

  • Jupiter
  • ***
  • Posts: 627
Re: Taking Off With Orbiter
« Reply #9 on: August 20, 2012, 09:15:47 PM »
Quote
It's not particularly useful to relate orbital distances and speeds to planetary ones anyway. Your points of comparison are the distances and orbital velocities of various objects, and those are generally given and worked with in metric.
Very true, and probably not much of a problem in real world spacecraft. But Orbiter's "training" vehicle takes off like an airplane, which puts you in atmospheric flight for the first part of the flight, so it's not all maneuvering in space.

The only problem is my learning curve - I'll get there, it's just going to take time. It's like calling up the "Orbital Elements" display and picking out what I need to know at the moment from:

SMa
SMi
PeR
ApR
Rad
Ecc
T
PeT
ApT
Vel
Inc
LAN
LPe
AgP
TrA
TrL
MnA
MnL

Which I have to remember stand for:
Semi-major axis
Semi-minor axis
Periapsis distance
Apoapsis distance
Radial distance
Eccentricity
Orbit period
Time to periapsis passage
Time to apoapsis passage
Velocity
Inclination
Longitude of ascending node
Longitude of periapsis
Argument of periapsis
True anomaly
True longitude
Mean anomaly
Mean longitude

Now, these terms may be familiar and intuitive to you guys, but I'm having to learn from scratch. So, hey, not more than a year to get up to speed, right?








"The sane understand that human beings are incapable of sustaining conspiracies on a grand scale, because some of our most defining qualities as a species are... a tendency to panic, and an inability to keep our mouths shut." - Dean Koontz

Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Taking Off With Orbiter
« Reply #10 on: August 20, 2012, 10:34:31 PM »
I see one missing: RAAN, the right ascension of the ascending node. Sometimes longitude is used instead, but right ascension makes it clear that you're measuring it in an inertial frame, not a rotating earth frame.

Another parameter often used is C3, twice the specific orbital energy. It's used more often in escape trajectories but is valid for any orbit. It's twice the sum of the potential energy per unit mass plus the kinetic energy per unit mass, a constant for any 2-body orbit not experiencing drag or thrust. It's defined as zero for an exactly parabolic escape trajectory, so it's negative for a closed orbit and positive for a hyperbolic escape trajectory. This convention makes the math far easier in the N-body problem.

Can it display Cartesian coordinates, aka state vectors? That might be somewhat more intuitive, or at least show the same data in a complementary way.

While metric/SI is the way to go for spacecraft engineering, another set of units you should probably know about are "canonical" units. They are normalized for a given planet so that its gravitational parameter is 1. The canonical unit of distance is a (usually equatorial) planetary radius, canonical velocity is the velocity of a surface-skimming satellite, and a canonical time period is the time it takes to go 1 radian around on a surface-skimming orbit (i.e., one canonical distance unit along the orbital track). Many tracking programs use these units internally to minimize roundoff problems and then convert to SI on output.
« Last Edit: August 20, 2012, 10:42:12 PM by ka9q »

Offline Noldi400

  • Jupiter
  • ***
  • Posts: 627
Re: Taking Off With Orbiter
« Reply #11 on: August 20, 2012, 11:17:15 PM »
I'll have to get back to you on that/those. It has a lot of options in the display - that was just the list from the 'default' orbital elements screen. I'm still plowing through a host of unfamiliar terms.
"The sane understand that human beings are incapable of sustaining conspiracies on a grand scale, because some of our most defining qualities as a species are... a tendency to panic, and an inability to keep our mouths shut." - Dean Koontz

Offline scooter

  • Venus
  • **
  • Posts: 72
Re: Taking Off With Orbiter
« Reply #12 on: September 14, 2012, 09:56:56 PM »
Orbiter has been on my computer in it's various versions for many years. I can take the Delta Glider to geostationary , or the CSM in the Saturn V...though I'm certainly not particularly efficient.
It is a great way to learn the basics though...whatever you do prograde increases your orbit's energy, retrograde the opposite. Inclination changes are most efficient at/near equator crossing. Lower orbits are "faster" (groundspeed wise) than higher orbits.

It sure gives you a feel for just how smart these real rocket scientists here really are! There are a number of tutorials available on the site.

And in the Shuttle days, they would upload orbital parameters so you could duplicate mission activities, which was quite amazing...I recollect loading a Shuttle mission post-undocking, and with the hi-res Earth graphics on the computer screen and the NASA channel live camera views of Earth on the TV...the match of the two passing scenes was startling!!

Orbiter does "rock", even on Windows ;)

Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Taking Off With Orbiter
« Reply #13 on: September 15, 2012, 08:39:38 AM »
"Startling", eh? Obviously that's how it's all faked! How did NASA let that ever get out! Somebody's head must have rolled for that breach of hoax security...

 :)

Does Orbiter let you fly multiple spacecraft? I would think so, as many people would want to do the ISS and Shuttle or Soyuz at the same time and perform rendezvous and docking.

If so, try some maneuvers relative to another spacecraft that stays "put" in its initial orbit. Try small maneuvers in each direction: prograde, retrograde, zenith, nadir, crossplane. The latter three should be interesting because they won't change the orbital energy and you should come right back to your starting point every half orbit later.


Offline scooter

  • Venus
  • **
  • Posts: 72
Re: Taking Off With Orbiter
« Reply #14 on: September 15, 2012, 02:33:46 PM »
It does come with a "docked to ISS" scenario in the ISS fleet pack. There is a much improved Shuttle and ISS pack addon that gets incredibly involved with a terrfifically detailed model, numerous custom MFDs, controllable RMS (all of the joints) for both Shuttle and the ISS arm...etc.
The latest verson has a SpaceX Dragon add-on...took that to and from the ISS a few times. It's great stuff.