Why is it a rocket🚀 is used to go straight up into outer space and not just use an airplane ✈️ ? I’m sure there is a good reason but it seems that the gradual assent would be preferred over the straight up approach.
In: Engineering
Planes don’t carry their own supply of an oxidizer to burn fuel against, since the atmosphere provides oxygen for the engines. They are also designed to propel themselves laterally with engines, using lift generated from the wings to lift the aircraft.
A jet engine requires air to “breather” and generate thrust. Air is pulled in by a turbofan into the combustion chamber at low velocity. Inside the combustion chamber, energy is added by injecting and burning fuel. Part of this energy goes to a compressor which is used to drive the turbo fan, and the rest is ejected at the back of the jet with both a higher velocity, and more mass due to the added fuel. However without air, the jet engine does not work. There is no air in space. A rocket works by combining a fuel and an oxidizer inside the combustion chamber. This is then ejected by the rocket. Breaking it down to the most basic features, a rocket is self sufficient, because it carrier both fuel and oxygen inside it, where as a jet engine only carrier fuel inside it, and pulls air from the atmosphere.
Less fuel is used going straight up. Planes can reach outer space if their engine doesn’t rely on air (i.e. a rocket motor). The X-15 was able to reach space, albeit briefly.
But it’s not just reaching space, it’s also reaching orbit, and for that you need two things, speed and altitude. Going straight up initially then pitching over is the most fuel efficient way of getting large payloads into orbit.
Rockets dont actually fly straight upwards. I remember watching a video of Elon Musk explaining why and how they fly to space and it’s really interesting! He used a penny and a funnel analogy
Several reasons.
The plane is not airtight and pulls in outside air to keep the occupants alive. No air in space, no alive humans on board.
Jet engines require oxygen to burn fuel. Rockets carry their own fuel and oxidizer so they can thrust in an airless atmosphere.
Plane wings require airflow over the wings to generate lift. No air in space, no ability to leave the atmosphere and climb into space.
What everyone is saying is true but another factor is the speed. They don’t go fast enough to escape earth’s gravity. A common plane would need to go 136 times faster.
I believe that there is not air (soft material) to “walk in”. Like an engine of a boat does not have water to “walk in” outside water. Space is basically vacuum. However in another planets there may be atmosphere made of some gas(es). Thus, we can see parachutes of space probes working on mars and if I am not wrong a helicopter robot already flew on Mars (please, anyone correct if I am wrong).
Long story short: airplanes use air as fuel. Rockets have all their fuel built into them. If you fly an airplane high enough it eventually runs out of air and thus fuel and stops working. This is known as the airplane’s ceiling.
Engines require oxygen and the wings require air passing over them to provide lift, in addition height isn’t the problem for orbit it is velocity, rockets don’t go straight up, they just take off vertically shortly after lift off they then lean over and have a lot of horizontal movement https://youtu.be/Zu-Sp3I0c1Q
There are three reasons. In each case I will use the SR-71, one of the fastest aircraft ever built, as the example.
1) The airplane requires air to fly. All aircraft have a service ceiling where the air pressure becomes too low for them to climb further. The SR-71 had a maximum altitude of about 27 km. Below about 120 km air resistance is too great to maintain orbit.
2) The airplane requires air to feed the engines. When you fill an airplane, you are only adding fuel and the air is gathered through the intakes while it flies. No air, no engine. The Falcon 9 uses almost the same fuel as the SR-71 but, since it needs to operate in a vacuum it also needs to carry 2.5 kg of liquid oxygen for each 1 kg of fuel.
3) The airplane can’t carry nearly enough propellant to make orbit. Even with the advantage of being able to harvest more than 2/3 of the propellant in situ, the SR-71 cannot even reach its own full speed or maximum altitude without midair refueling. By comparison, the Falcon 9 is about 90% fuel and the payload takes up a good chunk of the rest.
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