[jebus]

Good Evening.

Can anyone answer a question i have about amateur rockets. Iv seen many videos on you tube and they all seem to be at around 120,000 ft max altitude with the horizon at eye level. my question is why cant amateur rockets go any higher? and if they could go higher at what point to globe earthers believe the horizon will start to fall and the horizon look curved?

Any help with this question much appreciated. i did try to look online for maximum altitude for amateur rockets but can not find an answer as to why they are unable to go any higher.

Regards..

J

[nickrulercreator]

Rockets don't go a max of 120,000 ft. It's extremely hard to send rockets even 10,000 feet. But 120,000 is something else. At that point it barely even qualifies as "amateur." People can and have gone higher, but the highest REAL amateur rocket has gone to 73.07 miles in 2014: https://en.wikipedia.org/wiki/Civilian_Space_eXploration_Team#Space_Shot_2014_"GoFast"_Rocket, or 385,810 feet, more than 3 times higher than just 120K feet. Before that, the same team sent one rocket 72 miles in 2004. They have a history of doing that, though they are HUGE projects.

Videos don't show the horizon to eye level. It'd be really difficult to even measure this, since the rocket spins, turns, etc. This means the horizon is constantly moving throughout the frame. A better way to determine this is a weather balloon. Much more stable, though it will not go nearly as high. In these videos you can see the horizon drop.

[JohnAdams1145]

To explain why it's so hard to build rockets that go really high, you need to take a look at the https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation. The point is the more time you spend fighting gravity (trying to go higher, since amateur rockets don't enter orbit), the more delta-v you need (proportional to g and t). Delta-v is exponentially related to the mass fraction (the launch mass of the whole rocket to your payload mass).  This means that if you want to go twice as high at the same thrust (and therefore the same acceleration), you need 7 times the mass fraction (7 times bigger rocket). The reason why rocket launches are so expensive is because NASA is right at the limits of modern engineering in terms of trying to minimize weight to save some of that exponential amount of fuel.

What you say about the "horizon rising to eye level" is completely false; this is a result of cognitive biases such as confirmation bias and the fact that the dropping is such a small effect. It's just not true for a rocket at 120kfeet; you can see it slightly dips. If you actually fly that high, you may see some curvature if you look carefully enough; of course, a camera is no substitute because the lens can cause substantially more distortion if manipulated correctly.