Osmos
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It really IS rocket science
By Sputnik
Some driving instructions for those awkward orbital levels
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How orbits work
Balance of Forces

An object's orbit results from a balance of its forward motion with the downwards force of gravity (there is no sideways 'flinging out' force involved).

So, we'll get the most fuel-efficient control just by changing our mote's forward speed along an orbit (rather than simply firing towards or away from the attractior).

'Pro-burn' means to add forward thrust along an orbital path
'Retro-burn' means add reverse thrust along an orbital path
Going to space the Hard Way

A naive Outward burn

This novice pilot tries to reach a higher orbit just by blasting directly away from the planet.

Undesirable Results:
  • Most of the thrust energy gets used up just shifting the centre of orbit
  • Altitude gain is small, and at right-angles to intended travel
  • Risk of crashing at the perigee (lowest point of orbit)
(Note: While it is possible to get about this way, it's very expensive in fuel).
Playing nice with Gravity
Gaining Altitude

It's better to do forward pro-burn burn at the 'perigee' (orbital low point)

Key Results:
  • A larger elliptical obit extends out from the burn point
  • The craft will always return exactly to the burn point - so no loss of altitude.
  • The craft slows down the further it is from the attractor (an important point later)

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Maintaining Altitude

A longer 'pro-burn' is made at an elliptical orbit's 'apogee' (highest point)

Key Results:
  • Rounds out the ellipse into a large circular obit
  • Again the craft returns to the exact point of the burn
  • Craft's speed becomes constant again
Moving into High Orbit
'Hohmann Transfers' link together the two manoeuvres just covered


Ascending 'Hohmann Transfer'
  • Two pro-burns are used to lift a craft into a high circular orbit.
  • Note these burns are made on opposite sides of the attractor.
  • Cheapest in fuel to achieve high orbit
Dropping down to Low Orbit
The same processes with reversed burn direction to descend

Descending Hohmann Transfer
  • Two retro-burns are used to drop a craft down into a low circular orbit.
  • Again, these burns are made on opposite sides of the attractor.
  • Most economical and safest way to achieve low orbit.
Chasing down a Blob
Orbital rendezvous is always tricky and counter-intuitive.

Wrong
If you're in orbit behind a blob, it seems sensible to power forward to catch it up. But this will actually send you away from it, As seen earlier, a simple pro-burn sends you immediately higher and slower - only distancing your from your target. Gravity is ironic.

Right
One solution is to start with a short retro-burn to reduce your obit - moving you below but closer to your target and moving faster. Then, with good timing, do a longer pro-burn to round out your orbit again to your previous altitude - but now with some increased speed needed to chase down your prey.

Sorry no gif for this.
Orbital Insertion
(work in progress - I'll add some screenshots if there's any real interest)

'Orbital insertion' means leaving orbit around one attractor, to take up orbit around another. Just like the Apollo Program used to do during their moon shots.

En-route in 1969 to recover rare samples of Wensleydale

During the challenging "Epicycles" levels you have several 'moons' to visit. So you'll want to master Orbital Insertion.

Tips for beating 'Epicycles' level

General principles:
  • Move indirectly between the smaller orbiting attractors, by way of making elliptical transfer orbits around the huge central attractor.
  • Make these transfer orbits in reversed direction to the outer orbits
  • Consequently the linked orbits form figure-of-eight patterns. These are cheap on fuel, while avoiding certain insertion approaches that can produce unwanted 'gravitational slingshots'

Walk-through:
  1. Starting out in an anti=clockwise orbit around one of the moon attractors, be sure to gobble up everything circling its gravity well.
  2. Then make a pro-burn when you're at the point in your orbit closest to the central attractor
  3. With luck that will put you in an clockwise elliptical transfer orbit around the huge central attractor.
  4. Relax and complete the low perigee turn through the middle of the map
  5. Then, when you're back out this obit's apogee, there may or may not be another 'moon' to insert yourself in orbit around.
  6. If there is one, make a retro-burn to slow yourself down enough to be captured by that moon's gravity. Your new orbit should be back in the original direction, going with the flow of the moon's cirling motes.
  7. Rinse and repeat
3 Comments
Salgon 6 Jun, 2024 @ 2:42am 
Nice. Thank you. Do you can add some information for Orbital Insertion?
Sputnik  [author] 31 Mar, 2024 @ 3:01am 
Thanks. It was fun to research,
Star Dust 31 Mar, 2024 @ 1:04am 
The real guide here. Thanks (: