You need three explosive charges, one for each of the retrorockets and a third to use in the combustion chamber. You should still have either the cartridges or powder barrel, so two more must be produced.

The chemistry formula (and Scrupul's information) illustrates an exploding mushroom inside a leak proof globe. As you need two mushrooms, you can optionally buy another leak proof globe at the distributor on the second level.
Catching a mushroom is not that difficult, especially if Ardan is fed a green and yellow compote. The first thing to note is that mushrooms explode pretty quickly after being caught, unless combined with a leak proof globe. To simplify this you should hold a leak proof globe while catching a mushroom so that they can be combined immediately. Watch the mushrooms for a few minutes and note that they tend to drop from the same places. Roughly in the centre, one of the mushrooms first expands, then hovers (albeit for a split second) before dropping. I found this the easiest one to catch, even without the benefit of the compote. Position your cursor as indicated in the graphic and wait for the mushroom to expand, then catch it as it hovers. Be patient, it might take a while before this mushroom is the next one to drop.

Following the formula, insert a purple and red hybrid into the purifier to produce Ptuituuk's crystalline powder. Combine the powder with the spores (mushroom in the leak proof globe) to get Prulmis' explosive mixture. Repeat this process to make a second explosive charge.


Potassium is made by burning either the dead branch, lunar raffia or earth raffia. Use any one of the lave (fire) pools or the adjustable flame (in the shell) to do this.


There are two ways of getting chlorate of potash as well as an alternate substance that can be used as a substitute.
Use a leak proof globe to collect some chlorine gas from the burning smoke on the second level. Make a second lot of potassium and combine it with the chlorine.
Chlorate of potash is one of the items you can request from earth. You need the can opener to open the canister (box) that crashed in the forest, so it must first be repaired with some glue.
There's one last chemistry formula that you haven't found a use for yet.

Process a single purple fruit in the purifier to make Brozlyss concentrate. Use the empty can to get some lumen (third item in the formula) from the machine on the first level and combine these two with a blue fruit to produce Brozludjak's oxygenizing preparation, which can be used as a substitute for chlorate of potash.


If you didn't complete the investigation into the death of Ardan's friends during the trip to the moon, this has to be done before the Supreme Ruler will grant you a level 3 hierarchical key. The Dignitary on the fourth level provides clues, but at a price. If necessary, additional lunars to pay him can be obtained by selling some of the following:
Zubdssik's greasy amalgam (280 lunars)
Yrshnouff's gluance (180 lunars)
Mechanical elbow and hand (40 lunars each
Lunar cotton (80 lunars)
If you haven't found the letter in Barbicane's hat yet then his first clue will be: 'Part of the truth was on the head of your dead friend. To discover it, use a sharp object'. After cutting the hat open with the small knife and finding the letter, or if this was done previously, he tells you to interrogate the only witness in the case, the fourth passenger.
The Dignitary uses the Belbaab conch to speak to you, so perhaps the conch you found would enable you to speak to the rooster. This can be done if the conch is unplugged with some azotic acid. Now that you can speak all languages, go to the shell and talk to the rooster, who completes the investigation for you.


The Supreme Ruler ordered you to return the items you took from the sarcophagus in the necropolis. This only applies to the items taken from the sarcophagus at the far end, near the opening where the earth is visible. The items are the iron bar, lunar tool, Selenite key (level 0 hierarchical key) and leak proof globe. Is the level 0 hierarchical key missing? If so, it can be found on the small shelf next to Scurvy on the third level. Unfortunately he won't let you take it, but the insect spy suggests getting him drunk. Prepare a blue / grape compote and add it to the food supply. The effect of the compote puts Scrurvy in a generous mood and you can retrieve the level 0 hierarchical key.

When you return to the Necropolis at any time during the game, the exit control panel will have some changes.





After completing the investigation and returning the items to the sarcophagus, the Supreme Ruler will grant you a level 3 hierarchical key when you press the request bell.


If you're a stickler for detail, or like leaving things as you found them, use the hydraulic organ again to return the exiles to the crater. Also, the solution to the gilded characters puzzle (first level) can be viewed by inserting the level 2 and 3 hierarchical keys in the slots next to the panels. 


Before blast off back to earth there are a few final preparations. Remove the spent red and blue retrorockets from their slots, fill them with explosive charges and then replace them in the slots. Place the third explosive charge on the large tray in the combustion chamber and activate it by inserting the level 3 hierarchical key in the slot above. Note that the explosive charges are inter-changeable and each can used anywhere. Also, details of how to get the explosive powder from the cartridges or powder barrel are dealt with in the 'Trip to the Moon' section of the walkthrough.
The protective shield must be attached to the bottom porthole, then secured in place by fitting the bolts and tightening them with the monkey wrench.
The device with the bull horns is the firing mechanism for the space cannon. It has a built-in timer, so set the indicator to the extreme right (maximum) by clicking the right-arrow at the bottom. Now pull the lever (trigger) on the right to fire the space cannon. Immediately enter the shell and close the porthole before lift off. Note that the porthole handle is on the left edge of the cover.