5 ms·

I flew Orbiter to Mars from earth, docked with the ISS, also made a game of trying to visit each of Jupiter's satellites about 10-15 years ago http://orbit.med

by VLM 11y ago

I flew Orbiter to Mars from earth, docked with the ISS, also made a game of trying to visit each of Jupiter's satellites about 10-15 years ago http://orbit.medphys.ucl.ac.uk/ http://orbit.medphys.ucl.ac.uk/ Its interesting to look at the MFD design for mission planning as an applied version of the linked page. I have not played much KSP, is there anything as realistic as orbiter? From what little I've seen it tended toward comical set of pants, like comparing ChopperLifter to MS flight sim. Orbital docking dynamics are weird. If you undock from the ISS and thrust up a little bit, in half an orbit you'll come right back. Increasing or reducing your speed along the orbit (moving front or back) will eventually affect your altitude. Docking isn't as simple as "if you wanna go forward, thrust forward". All the control mix; like hovering a helicopter but slower. Flying "in formation" can be very expensive in terms of fuel depending on the formation, or it can be free if in a favorable geometry. There is a classic very hard sci fi story along the lines of extorting someone who doesn't know orbital mechanics by literally throwing them off a space station, and the victim panics not knowing he'll be back in half an orbit seeing as escape velocity is a little faster than a human shove! One amusing anecdote is for an inclination change greater than 60 degrees or so, its cheaper to land and take off again or go on a very high orbit into deep space and change your inclination there. The ISS is at a very high inclination and at least energetically, to put the thing into a GTO around inclination 0 or so, it would be cheaper to land and re-launch the thing.

baobabaobab 11y ago
>I have not played much KSP, is there anything as realistic as orbiter? No, it's the most realistic game about spaceflight, but it's not a simulator.
- dragonwriter 11y ago
  It's definitely a simulator, just not primarily an in-cockpit simulator.
  - outworlder 11y ago
    Given enough mods, the in-cockpit experience becomes rather satisfactory. I've flow missions to the moon and back completely in-cockpit
teraflop 11y ago
KSP's physics simulation is much simpler than Orbiter's: it treats the "patched conics" approximation as real, i.e. a craft is only ever affected by one object's gravity at a time. This was a deliberate choice to allow efficient time-warping with large numbers of objects, but it means orbits are unrealistically stable and you can't take advantage of phenomena like Lagrange points. On the other hand, KSP's trajectory planning UI is way, way more intuitive than anything I've seen for Orbiter, albeit not quite as automated or flexible.
- exDM69 11y ago
  The term "patched conics" is actually a bit of a misnomer in the KSP community. A more "scientific" term would be two body dynamics. Patched conics techniques are mission planning methods that provide semi-analytical solution to lunar and interplanetary trajectories and help searching for launch windows and planning outbound maneuvers. It's a rather crude approximation for real world use, but it gives good initial values to be used for more sophisticated (and computationally expensive) methods. This mission planning utility for KSP implements the patched conic algorithms: http://ksp.olex.biz/ http://ksp.olex.biz/ Once you find a launch window, you can use that as a starting point for a more fancy method such as this: https://alexmoon.github.io/ksp/ https://alexmoon.github.io/ksp/ (this implements "pork chop plots" or solves the two body boundary value problem, also known as the Lambert or Gauss problem) For real life (or Orbiter) use, the next step would be to numerically integrate the entire trajectory in a restricted n-body setup. For more information, see: Carlson, K. M. "An Analytical Solution to Patched Conic Trajectories Satisfying Initial and Final Boundary Conditions" http://ntrs.nasa.gov/search.jsp?R=19710007291&qs=Ns=Loaded-Date|0&N=4294795459 http://ntrs.nasa.gov/search.jsp?R=19710007291&qs=Ns=Loaded-D... (NASA has made this NTRS paper available again, I tried real hard to find it a few years ago because it was temporarily but intentionally offline)
archon 11y ago
> I have not played much KSP, is there anything as realistic as orbiter? From what little I've seen it tended toward comical set of pants, like comparing ChopperLifter to MS flight sim. By default, yes, it's pretty comical. But that's where mods come in. The modding community for KSP is huge, and there's a large set of mods that aim for higher realism (for example: overhauling the atmospheric flight model to add realism; adding the need for life support; adding the need for a satellite network to enable communication with Kerbin). There's a pack of mods called Realism Overhaul that does those things and a lot more.
exDM69 11y ago
As others have mentioned, Kerbal Space Program uses two-body mechanics, ie. only one celestial body has gravitational influence on the spacecraft. And every gravitational field has perfect spherical symmetry. In Orbiter, you can get restricted n-body dynamics and non-spherical gravitational fields so things such as Lagrangian points or Molnya orbits can be simulated. The solar system of KSP is a lot smaller in scale, the home planet is just 600 km and the atmosphere is 70 km thick. Liftoff to orbit takes just a few minutes (instead of 8-10 min) and a full orbit is about 30 min (instead of 90 min for LEO). KSP mods can add a level of realism and add more "scientific" tools to the game. "Kerbal Engineer" is a must-have addon because it adds some numeric data about the orbit that the game developers have intentionally left out (a decision I disagree with). MechJeb is a popular addon that adds all sorts of automation, similar to some Orbiter MFD modes. There are also mods to use the real solar system (in real scale) instead of the fictional universe. But no, overall, KSP is not nearly as realistic as Orbiter is. However, making any comparisons is pretty useless - they are both really fun games with a different emphasis and I play them both regularly.
- Animats 11y ago
  Kerbal's two-body mechanics thing is the worst limitation. Getting into orbit around Mun looks weird, as you suddenly snap from one gravitational system to another. Slightly non-spherical gravitational fields don't matter too much unless you're doing a lot of orbits.
  - exDM69 11y ago
    > Slightly non-spherical gravitational fields don't matter too much unless you're doing a lot of orbits. Actually the effects of non spherical gravity is one or two orders of magnitude greater than the influence of all the other bodies in the solar system combined for low earth orbit satellite operations. It has a huge effect, causing a rotation of the orbital plane several degrees per day (up to 10 or so). The effect isn't as great for lunar or interplanetary trajectories, though.
- MichaelGG 11y ago
  Is the 2-body mechanics just a question of simulation speed? Or why wouldn't they compute based on the top N nearest-biggest objects?
outworlder 11y ago
It's much simpler than Orbiter. But don't let the comical characters fool you: the only thing truly lacking is N-body simulation. > Orbital docking dynamics are weird This is simulated well enough. > One amusing anecdote is for an inclination change greater than 60 degrees or so, its cheaper to land and take off again or go on a very high orbit into deep space and change your inclination there. Yeap. KSP players are well acquainted with that. Also, it can be cheaper to use the moon to perform inclination change maneuvers. It was even done in real life: http://www.nytimes.com/1998/04/30/us/trying-to-save-satellite-company-is-sending-it-to-moon.html http://www.nytimes.com/1998/04/30/us/trying-to-save-satellit... That maneuver is, oddly enough, patented.
yourapostasy 11y ago
If you like docking maneuvers and want to play with them on iOS, then I found the Mission Orion app [1] pretty fun, leaning strongly towards the simulator side of the spectrum. [1] https://itunes.apple.com/us/app/mission-orion/id879837704?mt=8 https://itunes.apple.com/us/app/mission-orion/id879837704?mt...
rzzzt 11y ago
Shuttle by Vektor Grafix felt quite realistic back in its time (1992), although I don't know how much of the experience can be attributed to proper orbital mechanics calculations. https://en.wikipedia.org/wiki/Shuttle_(video_game) https://en.wikipedia.org/wiki/Shuttle_(video_game)
munchbunny 11y ago
KSP isn't nearly as realistic as Orbiter, but I personally see it as a good thing because it makes the right simplifications to give even a 10-year old a reasonable chance at developing an intuitive understanding of orbital dynamics. Said 10-year old won't be able to plot a real trajectory for a rocket/satellite, but giving a 10-year old an intuitive understanding of inclination changes, gravity slingshots, Hohmann transfers, etc. is an amazing feat by itself.

by VLM 11y ago

baobabaobab 11y ago

>I have not played much KSP, is there anything as realistic as orbiter? No, it's the most realistic game about spaceflight, but it's not a simulator.

dragonwriter 11y ago
It's definitely a simulator, just not primarily an in-cockpit simulator.
- outworlder 11y ago
  Given enough mods, the in-cockpit experience becomes rather satisfactory. I've flow missions to the moon and back completely in-cockpit

teraflop 11y ago

KSP's physics simulation is much simpler than Orbiter's: it treats the "patched conics" approximation as real, i.e. a craft is only ever affected by one object's gravity at a time. This was a deliberate choice to allow efficient time-warping with large numbers of objects, but it means orbits are unrealistically stable and you can't take advantage of phenomena like Lagrange points. On the other hand, KSP's trajectory planning UI is way, way more intuitive than anything I've seen for Orbiter, albeit not quite as automated or flexible.

exDM69 11y ago
The term "patched conics" is actually a bit of a misnomer in the KSP community. A more "scientific" term would be two body dynamics. Patched conics techniques are mission planning methods that provide semi-analytical solution to lunar and interplanetary trajectories and help searching for launch windows and planning outbound maneuvers. It's a rather crude approximation for real world use, but it gives good initial values to be used for more sophisticated (and computationally expensive) methods. This mission planning utility for KSP implements the patched conic algorithms: http://ksp.olex.biz/ http://ksp.olex.biz/ Once you find a launch window, you can use that as a starting point for a more fancy method such as this: https://alexmoon.github.io/ksp/ https://alexmoon.github.io/ksp/ (this implements "pork chop plots" or solves the two body boundary value problem, also known as the Lambert or Gauss problem) For real life (or Orbiter) use, the next step would be to numerically integrate the entire trajectory in a restricted n-body setup. For more information, see: Carlson, K. M. "An Analytical Solution to Patched Conic Trajectories Satisfying Initial and Final Boundary Conditions" http://ntrs.nasa.gov/search.jsp?R=19710007291&qs=Ns=Loaded-Date|0&N=4294795459 http://ntrs.nasa.gov/search.jsp?R=19710007291&qs=Ns=Loaded-D... (NASA has made this NTRS paper available again, I tried real hard to find it a few years ago because it was temporarily but intentionally offline)

archon 11y ago

> I have not played much KSP, is there anything as realistic as orbiter? From what little I've seen it tended toward comical set of pants, like comparing ChopperLifter to MS flight sim. By default, yes, it's pretty comical. But that's where mods come in. The modding community for KSP is huge, and there's a large set of mods that aim for higher realism (for example: overhauling the atmospheric flight model to add realism; adding the need for life support; adding the need for a satellite network to enable communication with Kerbin). There's a pack of mods called Realism Overhaul that does those things and a lot more.

exDM69 11y ago

As others have mentioned, Kerbal Space Program uses two-body mechanics, ie. only one celestial body has gravitational influence on the spacecraft. And every gravitational field has perfect spherical symmetry. In Orbiter, you can get restricted n-body dynamics and non-spherical gravitational fields so things such as Lagrangian points or Molnya orbits can be simulated. The solar system of KSP is a lot smaller in scale, the home planet is just 600 km and the atmosphere is 70 km thick. Liftoff to orbit takes just a few minutes (instead of 8-10 min) and a full orbit is about 30 min (instead of 90 min for LEO). KSP mods can add a level of realism and add more "scientific" tools to the game. "Kerbal Engineer" is a must-have addon because it adds some numeric data about the orbit that the game developers have intentionally left out (a decision I disagree with). MechJeb is a popular addon that adds all sorts of automation, similar to some Orbiter MFD modes. There are also mods to use the real solar system (in real scale) instead of the fictional universe. But no, overall, KSP is not nearly as realistic as Orbiter is. However, making any comparisons is pretty useless - they are both really fun games with a different emphasis and I play them both regularly.

Animats 11y ago
Kerbal's two-body mechanics thing is the worst limitation. Getting into orbit around Mun looks weird, as you suddenly snap from one gravitational system to another. Slightly non-spherical gravitational fields don't matter too much unless you're doing a lot of orbits.
- exDM69 11y ago
  > Slightly non-spherical gravitational fields don't matter too much unless you're doing a lot of orbits. Actually the effects of non spherical gravity is one or two orders of magnitude greater than the influence of all the other bodies in the solar system combined for low earth orbit satellite operations. It has a huge effect, causing a rotation of the orbital plane several degrees per day (up to 10 or so). The effect isn't as great for lunar or interplanetary trajectories, though.
MichaelGG 11y ago
Is the 2-body mechanics just a question of simulation speed? Or why wouldn't they compute based on the top N nearest-biggest objects?

outworlder 11y ago

It's much simpler than Orbiter. But don't let the comical characters fool you: the only thing truly lacking is N-body simulation. > Orbital docking dynamics are weird This is simulated well enough. > One amusing anecdote is for an inclination change greater than 60 degrees or so, its cheaper to land and take off again or go on a very high orbit into deep space and change your inclination there. Yeap. KSP players are well acquainted with that. Also, it can be cheaper to use the moon to perform inclination change maneuvers. It was even done in real life: http://www.nytimes.com/1998/04/30/us/trying-to-save-satellite-company-is-sending-it-to-moon.html http://www.nytimes.com/1998/04/30/us/trying-to-save-satellit... That maneuver is, oddly enough, patented.

yourapostasy 11y ago

If you like docking maneuvers and want to play with them on iOS, then I found the Mission Orion app [1] pretty fun, leaning strongly towards the simulator side of the spectrum. [1] https://itunes.apple.com/us/app/mission-orion/id879837704?mt=8 https://itunes.apple.com/us/app/mission-orion/id879837704?mt...

rzzzt 11y ago

Shuttle by Vektor Grafix felt quite realistic back in its time (1992), although I don't know how much of the experience can be attributed to proper orbital mechanics calculations. https://en.wikipedia.org/wiki/Shuttle_(video_game) https://en.wikipedia.org/wiki/Shuttle_(video_game)

munchbunny 11y ago

KSP isn't nearly as realistic as Orbiter, but I personally see it as a good thing because it makes the right simplifications to give even a 10-year old a reasonable chance at developing an intuitive understanding of orbital dynamics. Said 10-year old won't be able to plot a real trajectory for a rocket/satellite, but giving a 10-year old an intuitive understanding of inclination changes, gravity slingshots, Hohmann transfers, etc. is an amazing feat by itself.