Just because I thought it might be worth considering what an all-solids launcher
might look like using high-performance commercial ATK motors, I found what was a
reasonable booster suitable for the first stage. The following diagram shows the
numeric specifications and compares the solid first stage with an equivalent liquid stage. I’ve darkened out the parameters of the upper stages because those things haven’t changed from my last post.
If you look at the image below, one thing that stands out is that the solid booster is physically shorter (for the same diameter) compared to the liquid booster.
This is due to the solid booster's higher average propellant density, which is almost double that of the liquids that I had selected. In actuality, the liquid booster is lighter by about 200 lbs, but it is physically larger because of the lower propellant density.
A summarization of this Comparison
Now, the main impetus of this design experiment was to look at reasonable performance
solids as examples of upper stage vehicles and, then finally, as a first stage booster.
For amateurs to develop these kinds of vehicles, they would have to try to duplicate
the performance factors of these commercial motors with their own designed and fabricated motors. One good thing from this is that they have a known working example and explicit specifications for trying to develop their own versions of the commercial motors. This will simplify the development task somewhat.
Because I went with off-the-shelf motors, their specifications dictated many of the
requirements for the vehicle (such as stage delta V, thrust and mass ratios). In many ways, I consider these designs to be an upper limit of reasonable size for launching a payload as small as a 1/4 pound (113 grams). Think about it: a payload of 1/4 pound required a launcher with a GLOW of 1914 lbs. This is an effective payload:glow ratio of 0.00013 or 0.013 %. This is pretty poor overall. Nonetheless, with smaller launchers we'll see these kinds of ratio values. But we can do better. To do better means that a fundamental ratio between payload and total rocket takeoff mass will be a higher number. Let's examine how to get to smaller, more manageable rockets in upcoming future posts.