Building
This is where I'm going to go through planning and building 3 very basic missions sets that can sum up almost everything you can do ingame.
- Satellites
- Landers
- Space Stations
Obviously there are more things you can do and the designs I'm showing are very basic to get the mechanics down and after all, it's a sandbox so you can build, drive, lift, blow up, drill and launch anything you want.
So, the first thing you should ask yourself when presented with a blank build screen is thus.
What am I trying to achieve?
The reason for that is exactly the same reason why we did all the nerdy maths stuff first. Answer the question first, turn your answer into some epic build (henceforth known as a
payload) and then create a suitable rocket (or Launch Vehicle [L/V]) to put it where you need it. You can do L/V first and payload second, especially if you are experienced or have a capable L/V (many of us have a few creations for different purposes and payloads) you've used before, but as a beginner what may happen is your rocket may get off the ground, but the second stage won't have the right TWR/Dv to finish the job and your L/V falls out of the sky and blows up.
To demonstrate the point, I'm going to build from the bottom up, creating the L/V first and then payload.
So, lets throw a hawk and 3 long tanks down with a separator. Then a broadsword and another long tank. And we want to put 20t into orbit, in this case represented by a long tank, some ports and a fairing to cover it all. All up, 118.8t
Ooh, a TWR of .99. That, as we showed earlier, won't fly.
Because we've done it this way, we've been unable to track its TWR until it's completed. The number at the bottom of the screen says that the single hawk engine of stage one isn't sufficient. Easy fix, just put a second one on. Bit over kill, but it works.
But what about stage 2? Because we couldn't check it as we built, it's a mystery until we remove stage one completely
and discover that it has a TWR of 0.74 which is essentially a crash waiting to happen that wouldn't raise its head until you were inflight.
Now, lets try it the other way about and build top down. There is a good ratio for rocket stage sizes that can help when deciding how big everything is going to be, and that is 1:2:4.
That means, for every 1t of payload, you'll need 2t in the stage below, and 4t in the stage below that. Obviously thats just a rough guideline as it doesn't take into account destination etc but if you look at the moon mission from earlier, the weights aren't far off that ratio.
Lets build a payload then. For this first bit, we're going to build a small satellite. Now the design combinations and examples of satellites are damn near endless, depending on what you want to achieve but here we are just going to take a probe, slap a 5t tank on it, some solar panels, docking port, a few RCS and a grasshopper engine so it can adjust its orbit (and de-orbit itself). 10.3t. You'll want this to be far enough up the build area to fit your L/V under it, but with a bit of a gap under the extreme top of the area so you can fit a fairing shroud over it. The TWR of the payload doesn't matter, as it should be in space by the time the engine is fired and it will
always accelerate, regardless of mass (just sometimes, really, really really slowly) because there's no gravity to fight against.
Now the payload is sorted, lets pop an L/V under it.
Since the payload is 10t, then stage 2 is going to be roughly 20t. So, what I do is place an engine down that will lift 20t+10t (in this case, the broadsword) place a separator under the payload engine and then add fuel to the desired weight. In this case, I've put a small and medium basic tank in weighing 15t combined.
Then, I craft a fairing shroud around the payload. Fairings are removable, aerodynamic covers over your payload that mean that drag isn't acting on your wonky, structural part intensive payload and slowing your rate of climb. When building a shroud, figure out the widest part of your payload and place a fairing wide enough to surround it in each side. Then build upwards getting narrower until you put the pointy end on top. Then build downward until the fairing is narrow enough that the little attachment squares is touching the fuel tank on stage 2. You may have to flip the fairing to achieve that.
Your build should look like this so far.
Stage 2 now weighs 19t, a 10t payload on top with an all up mass of 29.3t. With the broadsword and 13.5t of fuel to burn, we've got a good TWR of 1.39 and a Dv of 9.8 x ISP of 281.492 x LN (wet mass 29.3 / dry mass 15.83)
[notice this is stage 2s fuel allocation, not the total fuel on board. We're leaving the satellites fuel out of the equation] = 1701.25 m/s.
Now, we know this won't be enough to hit orbit. We're going to need roughly another 1,100-1,300 m/s to break the atmosphere and another few hundred to get to a decent orbit height.
For stage 1 then, we know we're going to need double again the amount of mass of stage 2. That puts us into the 40 ish ton ball park, with a combined weight of 70+tons and thus need an engine to accommodate this.
The Hawk.
Again, we drop a separator in under the broadsword, put the hawk down and add the balance of weight in fuel tanks and see what we come up with. That equates to an easy 2 long basic tanks at 40 tons, the hawk is 4t plus change for the separator is 44.3t.
Lets run the numbers and see if it is sufficient.
The hawks ISP is 250.741.
The wet mass is the combined totals of stage 1, 2 and payload at 73.63t.
Now even though the L/V is carrying 49.5t of fuel, you're already accounting for that elsewhere. The dry weight of stage one alone is 37.63t as you only have access to the 36t of fuel on that stage.
Thus, stage on D/V is 9.8 x 250.741 x LN (73.63/37.63) = 1649.44 m/s
Combined, that gives you 1701.25 + 1649.44 = 3350.69 m/s of Delta v in your launch vehicle with a satellite payload.
Congratulations, you've just planned and built your first mission.
Now save it, and lets build something else.
