why are the noses of rocket, shuttles, planes, missile(…) half spheres instead of spikes?
In: 5557
The “angle of attack” is not always directly ahead, so a needle-bow won’t always be pointed directly into the flow.
If you’re in a ship, trying to cruise due north at 30mph, and you have a 10mph current flowing from west to east, the bow of your ship isn’t going to be pointing north. It’s going to be pointed about 30 degrees west if north. If you trail a kite behind the ship, the kite is going to be directly south of you; you’re going to be headed directly north. The water is going to be hitting the right side of your bow, not straight on the point of the “needle”. The needle won’t be cutting through the water efficiently; it will be pushed through the water sideways.
Aircraft have the same issue. You can see it most clearly during a [crosswind landing](https://www.youtube.com/watch?v=w4EQuM_t8Fo). The aircraft is “crabbing” into the wind, cutting across it sideways rather than head-on. It happens at cruising altitude, too, when the winds aren’t parallel with the direction of travel.
A rounded, bulbous bow is *almost* as efficient as a needle bow when traveling directly forward, but it doesn’t lose that efficiency as the wind is coming in sideways.
Some aircraft do indeed use a needle-like nose. Aircraft designed for sustained supersonic flight have a needle-like nose. ELI5, these planes fly so much faster than the wind can blow that the apparent wind is always nearly directly ahead. (They also manage the supersonic shockwave, but that’s well beyond the scope of your original question.)
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