# Flying saucer shape rocket vs cylindrical shape rocket

Here's my hypothesis-

Cylinder shaped large rocket is not suitable for vertical landing due to its high center of mass and bulky weight. However an equally weighing saucer shape rocket has more distributed weight and it will ease design of landing gears.

Use a flying saucer shaped like spacecraft and go for slow ascent in the dense atmosphere during lift-off, to overcome disadvantage of it's non-streamline hull shape. In the rarefied atmosphere, it can pick up the needed escape velocity. The re-entry and vertical landing will be comparatively easier due to low center of mass and wider body allows better heat shielding, heat dissipation and deacceleration for a soft landing.

• "Flying saucers" can work, to some degree, as a reentry vehicle but they're not really an optimal shape for a lightweight launch or non-atmosphere vehicle. Commented Mar 26, 2021 at 5:33
• Sounds like your idea is predicated on a super effective propulsion system of the sort that doesn't exist yet. Commented Mar 26, 2021 at 7:35
• So for your question to work, you can't just say saucers are light and cylindrical rockets are heavy. I think you've already given your saucers futuristic propulsion system that doesn't even exist yet, correct? Now you are going to say that they are also lighter? Because they are from the future? In that case the question is not remotely reasonable, and can't have fact-based answers.
– uhoh
Commented Mar 26, 2021 at 16:34
• @seccpur You keep asserting that without anything to back it up. A saucer's wider form factor will take more landing hardware and more structural mass to distribute those loads. Conventional rockets have no trouble supporting several times as much force through the engine mounts. Your saucer will be even heavier and its low center of gravity will make control far more difficult. Commented Mar 26, 2021 at 17:35
• I think you mean "tubular", like a tube. "Tabular" means like a table. Commented Mar 27, 2021 at 0:21

Cylinder shaped large rocket is not suitable for vertical landing due to its high center of mass and bulky weight.

SpaceX seems to have determined that a long cylindrical stage is perfectly suitable for vertical landing.

The center of mass on a rocket stage in the process of landing is quite low. Most of the volume is nearly-empty fuel tanks, which are made of shockingly thin material; the weightiest component is the engines, conveniently located at the bottom of the stage. The mass is distributed like a badminton shuttlecock.

• And a low center of gravity is only beneficial while standing on the ground. Between the decreased moment arm for thrust vectoring, the increased effect of thrust error, malfunctioning engines, and aerodynamic disturbances, and reduced moment of inertia around the horizontal axes, shorter vehicles are more unstable and quicker to topple. They mounted coils of steel on top of Starship prototypes SN5 and SN6 to raise the center of gravity. Control aside, think of the tilt they would have had landing on one off-center engine if they were wider than they were tall... Commented Mar 27, 2021 at 1:50
• Nice answer. +1 for the nearly-empty fuel tank during re-entry. Still such cylindrical shape mega structure will likely crushed the landing gears especially on uneven moon surface. Commented Mar 27, 2021 at 2:02
• @seccpur they've now successfully landed boosters 78 times. It seems a little late to be professing doubt that cylindrical boosters can vertically land. Commented Mar 27, 2021 at 3:45
• My worry is about bigger rockets and on uneven surfaces. Commented Mar 27, 2021 at 7:18
• "tanks, which are made of shockingly thin material". My back-of-the -envelope calculation is that an empty Starship has a lower density than an empty beer can. Commented May 2, 2023 at 21:01

Space rockets design, as we know it, is liquid fuel tanks for the most part. For the fuel tanks, you will choose a sphere or a cylinder. Then, you have multiple stages. Again, the cylindrical shape is a winner.

Now, let's say we have a futuristic antimatter engine that does not require fuel tanks. Would we choose a saucer-shaped design for our spacecraft? Probably not. The saucer shape does not offer particular advantages for a spacecraft.

There is at least one design of Flying Saucer spacecraft that received a US patent in 2005: U.S. Patent 6,960,975