Port of Gtk+ Place your satellite
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Description: Understanding effect of mass and distance on orbital velocity.

Goal: Make sure the satellite does not crash or fly away

A satellite revolves around the Earth because of the force between them. Orbital velocity of a satellite of Earth is directly proportional to the square root of the mass of Earth and inversely proportional to the square root of the distance from the center of Earth to the satellite.

In this activity, play with the speed of the satellite and mass of Earth to see what happens to the satellite. If the speed of the satellite is slower than the required orbital speed then the force applied by the Earth on the satellite is too much and thus the satellite gets pulled towards the Earth and burns in it's atmosphere. If the speed of the satellite is more than the required orbital speed then the Earth's force is not enough to keep it in orbit and thus the satellite flies away due to it's own inertia.


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bcoudoin created this task.Feb 6 2016, 10:34 PM

There is an close to be released version of it done by JB Butet in the branch djibb-place-your-satellite2. It needs some cleanup and review before being integrated.

rkaur claimed this task.Feb 29 2016, 8:28 PM
rkaur added a subscriber: rkaur.
nitish added a subscriber: nitish.Jun 20 2016, 8:22 PM

Hi , if this task is open can I work on this Activity??

In T1528#40104, @nitish wrote:

Hi , if this task is open can I work on this Activity??

Yes, to my knowledge nobody is on it. Have you tested the JB Butet version?

No , I have not tested the JB Butet version. According to you should I create an activity from scratch or some modifications in JB Butet version ??

rkaur removed rkaur as the assignee of this task.Jun 29 2016, 6:30 AM

I would like to write this activity on QtQuick from scratch. Is anyone else working on this port?

Utkarsh Tiwari

jjazeix added a subscriber: jjazeix.EditedFeb 25 2017, 1:52 PM

first pass of things to clean:
activity itself:

  • remove blinking text.
  • the resizing is not handled (images/texts too big, overriding of the satellite by the planets, texts overriding, the text in the button does not fit...)
  • there are too much elements in the screen. I guess we can add levels (for the planets for example).
  • if you hover the planets, some of them become very small (there is a zoom for the Sun)
  • putting an intro could help win some space.
  • resizing the screen makes the satellite to start.
  • it would be nice to use the hint button to show a preview of the trajectory.
  • once you have chosen a direction, you can't change it.
  • user interface can be improve, it's not easy with the sliders.
  • the zoom slider can be improved: if you zoom completely on left, you can't see anymore the planet/satellite. I would add a min/max zoom value. The planet radius is not readable if zoom is big.
  • I got these 2 warnings on the console:

file:///.../Qt5.5.1/5.5/gcc_64/qml/QtQuick/Controls/Styles/Base/SliderStyle.qml:202:13: QML Loader: Binding loop detected for property "y"
qrc:/gcompris/src/activities/place-your-satellite/PlaceYourSatellite.qml:330: TypeError: Cannot read property 'length' of undefined

For the first one, it may be Qt related but the second one is to fix.

  • remove blinking text, I don't like it :).


  • headers missing
  • qsTr() missing
  • would be better to have svg (and a README if images not taken from the Gtk+ version)
  • indentation/code style

You also need to think that when we resize, all the elements are still well displayed.

jjazeix moved this task from Backlog to WIP on the GCompris: Activities board.Feb 25 2017, 6:06 PM
iamutkarshtiwari removed iamutkarshtiwari as the assignee of this task.May 5 2017, 8:04 PM
jjazeix moved this task from WIP to Backlog on the GCompris: Activities board.May 12 2017, 6:28 PM

anyone working on this ?

@jjazeix I want to add this activity as task to complete in GSoC period ?
Can I know what more is left to be completed ?

@dekumar there is a list above, feel free to test the activity and see what is still left to do. Then, feel free to add any improvements that can be useful for the children to learn about

Actually I'm not even sure this is a good activity concept, as it has the same flaws as the "intro gravity" activity we have. That is:
-increasing the size of something doesn't directly means increasing its mass (if you stretch something, it will take more space but have the same mass), that can lead to bad misconception for kids.
-increasing the size of a planet sounds very weird to me, as it's not realistic at all.

I was already thinking since some time that we need to change the "intro gravity" activity to fix those problems, so adding another activity with same problems doesn't sound good to me.