# High altitude stage separation

Normally, at high altitude above Earth's surface, there are stage separation of a rocket. If we consider unmanned rockets, at high altitudes, how does human operators of a rocket who are here on Earth control stage separation?. It is common sense, that human naked eye cannot clearly see the rocket at such high altitude, then how do they exactly control stage separation with precision from Earth itself without seeing anything directly from their naked eye? Do they use some kind of graphical sensors with longitudes and latitudes? Or do they use some kind of camera attached to the rocket?

My another question is, how do human control all the actions of the rocket wirelessly ?(I know this is a funny question, yet I want to understand how it works)? do they use some kind of invisible radiations to communicate with all the minute functional part of the rocket system?

• Separation is not controlled from the ground, so this is not a problem. Commented May 1, 2020 at 11:40
• Recommend closing as containing far too many incorrect assumptions. Commented May 1, 2020 at 11:46
• Stating the incorrect assumptions allows to answer the question and fix the incorrect assumptions. In fact, this is a basic question with good simple answers.
– Pere
Commented May 1, 2020 at 22:22
• Incorrect assumptions are grist for the answer mill. Commented May 1, 2020 at 22:38
• @CarlWitthoft that's not a close reason. There's no rule that a question can only have $n$ incorrect assumptions and those with $n+1$ must be closed and answers prevented. The question is asked in good faith, and is being answered well. What benefit would there be in preventing this?
– uhoh
Commented May 1, 2020 at 22:50

## 4 Answers

For all modern rockets (and as far as I know, for all rockets ever, since at least the V2), the rocket isn't controlled from the ground, but by electronics (computers, for modern rockets) on the rocket itself. The rocket controls its path, stage separation, ullage motor firings, and anything else needed, with few exceptions. This is all pre-programmed. Engineers work out when stage separation should occur and program the computers to control it. For example, the computers might sense that all the engines on the first stage have shut down, wait a few seconds, and then fire the explosives that separate the stages.

The one exception that I know of is that most rockets have a ground controlled destruct mechanism that a range safety operator may use to destroy the rocket. This is used when the rocket may become a danger to those on the ground should it remain intact, such as when its flight path has diverged too far from the plan.

Whether computers or astronauts should fly the launch vehicle was debated early in the manned space program. Those who were in favor of computers doing the flying won out. The Apollo rocket did have a way for the astronauts to take over control of the stack and fly it manually, should the computers fail, but the computers never failed during the Apollo program.

• Regarding that one exception: The Range Safety Officer has two primary functions. Prior to launch, it's the RSO's job to determine whether it's safe to launch due to range concerns. For example, the RSO delays or postpones the launch should a boat or plane moving into the forbidden zone. After launch, it's the RSO's job to determine whether the a bad launch makes the range unsafe. Should the launch vehicle go awry, the RSO sends radio commands to the spacecraft that makes strategically placed explosive devices (aka bombs), typically placed close to a propellant tank, on the spacecraft explode. Commented May 2, 2020 at 8:19
• And even that one exception (the flight termination system) is being / has been automated. See gps.gov/cgsic/meetings/2019/valencia.pdf , for example. Commented May 2, 2020 at 8:19
• Regarding the V1, it's that launch vehicle that made the US realize the need for a Flight Termination System. The US took several V1 rockets (and several German rocket scientists) to the US after WWII. One of those V1 rockets launched from White Sands, New Mexico went astray. It went south and then crashed instead of going north toward a sparsely populated area. It crashed close to Juarez, Mexico, and very close to a munitions dump used by Mexican mining companies to store explosives (read "international incident"). Fortunately, nothing terrible happened. But it was a close call. Commented May 2, 2020 at 8:40
• By the way, the V2 was controlled by electronics too. Of course vacuum tubes electronics, not solid state semiconductor,
– Uwe
Commented Jun 24, 2020 at 13:28

Human operators are generally not involved in separation, that's controlled by on-board computers according to the plan programmed into them. 2 way radio lets human controllers see what is going on and send commands if necessary.

• Human operators are generally not involved, full stop. No human ever (other than the first 3 manned test flights) 'flew' a Space Shuttle. People's job in Flight Control is to say go or no go, that's flippantly about it. Commented May 3, 2020 at 0:34
• "During Space Shuttle mission STS-51-F, a main engine failed during ascent to orbit. Subsequently, indications were received of a second engine beginning to fail, which would have caused a mission abort, possibly including loss of the shuttle. Booster officer Jenny Howard Stein determined that the anomalous readings on the second engine were a sensor error and not an engine problem. At her direction the crew inhibited the sensor, which saved the mission and possibly the crew." - she said, 'Go.' ... just like the ignorable1202 alarms for the moon missions. Commented May 3, 2020 at 0:35
• I hope she got a steely-eyed missileman award for that @Mazura!
– GdD
Commented May 3, 2020 at 8:17

Ground control uses telemetry data transmitted by radio waves from rocket to ground. There is also remote control using radio waves from ground to rocket.

Speed of the rocket and the distance to ground station may be measured using radio waves. If a signal is send to the rocket and relayed back the time delay gives the distance and the frequency shift the speed using the Doppler effect.

Telescopes are used to track the rocket when it is too far for the naked eye.

One of my Japanese friends told me that when launch control saw the malfunction of the first stage of the rocket that launched ASTRO-E, they immediately commanded the second stage to target injection at a lower altitude than planned. They hoped that the third stage might overperform and yield an orbit that they then could raise using thrusters on the payload. If this is true, it's a rare example of real-time commanding of a launch vehicle's trajectory.