why do space rockets take off from a upright position instead of taking off of a runway like a plane, reach 40,000 ft and entering space from there.



why do space rockets take off from a upright position instead of taking off of a runway like a plane, reach 40,000 ft and entering space from there.

In: Engineering

It takes a lot of power to get into orbital altitudes, and the best way to reach that amount of power is to just burn a ton of fuel up to get the necessary amount of momentum going in a really short amount of time.

It takes less fuel, which is the most restrictive part of rocket design.

By going straight up the ticket gets above most of the atmosphere, eliminating must of the drag on the rocket. This means that girl is not spent shoving air it if the way, but in accelerating the rocket.

The rockets do turn and start moving sideways fairly soon though, to build up lateral speed. the hard part about teaching orbit isn’t getting the height, it’s getting the sideways speed to circle the earth before it “falls back” to the ground.

A rocket has to go really fast to reach speeds fast enough to orbit, and the atmosphere is thickest close to the ground. So a rocket tries to get out of the thickest part as fast as it can to save fuel, then it turns sideways to get to orbital speeds. Basically it would waste too much fuel going through the atmosphere like a plane.

There are some concepts for high-altitude launches from a plane (Virgin), but the reason that most space programs don’t pursue this is that it adds an extra layer of complexity on top of getting your already-complex engines to fire. With the efficient engines that have been designed recently, it’s really not too wasteful to just keep the traditional vertical launch profile, especially for large rockets that any aircraft just can’t lift.

It’s less energy to go straight up than to go horizontally and angle up. Rockets are already massive things that are almost entirely fuel storage.

It would just be adding steps and complexity that aren’t as efficient as vertical launches. You’ll need wings now, you’ll still need a rocket system at altitude to get to escape velocity, and there would be a lot more time in the atmosphere trying to get to speed which means more heat, more drag, and more energy.

Rockets are huge and heavy, by placing the vehicle in a vertical position all the weight and stress is down the structure of the rocket, if it was horizontal you would need far more support in the structure to prevent it collapsing under its own weight. More support needs a lot more weight and in a rocket the additional weight makes a massive difference.

Excellent question that I believe has been competently answered by others far smarter than me. It made me wonder about the opposite question: why didn’t shuttles land vertically instead of needing to operate like planes that require a runway? These responses infer the answer: atmosphere. Love this question.

Just to add to the other answers something I didn’t see: doing what you’re suggesting would require the rocket to have wings, and wings are essentially dead weight for the main part of the rocket’s flight because it’ll be in atmosphere too thin for them to help. Any extra weight you add to your rocket has a significant fuel cost, which means you have to make the fuel tanks larger and the rocket itself larger, and everything gets very expensive very quickly.

90% of a space vehicle is a compartmentalized fuel tank. The reason for this has been explained already, but briefly, the amount of continuous force needed to reach not only escape velocity from our planet, but to achieve orbit, requires a ludicrous amount of fuel. Rockets were designed the way they were to allow for the fact that these vehicles needed a way to not only carry the necessary amount of fuel required for low earth orbit or moon travel, but also a way to very easily detach those fuel tanks once they are empty, to shed weight as soon as that weight is no longer useful.

The vertical design handles all these factors, where a horizontal design would needlessly increase the difficulty factors by requiring a fundamental change in the rocket design, to factor in aerodynamics in a more significant way, which would require more fuel to handle more weight and a longer flight time before reaching escape velocity.

The key factor for getting away from earth’s gravity isn’t how high you need to get, but how fast you need to go to stay away. For example, to launch to the ISS an orbiter needs to accelerate to at least 17,400mph / 8000m/s.

This is why vast quantities of fuel are needed, not just to lift the orbiter to the required height but impart the energy required to get it up to orbital speeds.

From that perspective, trying to gain height via atmospheric flight (wing lifted) is simply a waste of energy/fuel in a high drag environment.

Consider that when flying at 80,000ft and Mach3+, a supersonic plane generates enough frictional drag that the leading edges have to be titanium to avoid melting. The edge of space is at over four times that altitude (100km/328,000ft) and at some intermediate point wing lift will stop working unless the wings are unbelievably large.

Therefore, the vertical launch profile is a tool to punch through the atmosphere into a low drag environment as quickly as possible so speed can be gained efficiently. HTH.

My geuss is that u need a surface to push off of. Like how it’s easier to jump off of a rigid surface

Two complementary reasons:

1. Rocket engines are not air breathing. That is, they do not and cannot use the atmosphere to generate thrust. In fact, they generate more thrust and are more fuel efficient in a vacuum.

2. Rockets need to accelerate to a speed of ~8 km/s (~17,900 mph, ~Mach 23) to stay in orbit. Doing that inside any substantial amount of atmosphere results in incredible amounts of drag and heat, making it practically impossible to sustain.

Taking these facts together, the best launch trajectory from Earth is to head up, and only start motoring sideways in earnest once above 50-100km altitude.

However, if you can change one of these facts then you can change the launch profile. A spaceplane with air-breathing engines, such as the planned [Skylon](https://en.m.wikipedia.org/wiki/Skylon_(spacecraft)), could make a more lateral ascent through the atmosphere, using wings for lift.

On bodies without thick atmospheres, such as the Moon, rockets can turn sideways to gain speed as soon as sufficient height above the ground is reached (that is, enough height to avoid hitting mountains, etc). [This glorious chart](https://www.christies.com/en/lot/lot-6214825) shows the ascent profile for Apollo 11 from the moon’s surface. Nearby crater ridges are plotted, and it is seen that the ascent module is tilted 60° away from vertical by the time it is just 4 N.Mi. (4.6 mi, 7.4 km) from the ground; and 90° from vertical (i.e. fully horizonal) by the time it is 10 N.Mi (11.5 mi, 18.5 km) from the ground.

How would a rocket fly horizontally? You’d have to add wings to create lift. At that point you’d basically have a rocket powered plane. The great thing about planes is that (due to a good lift-to-drag ratio) they need relatively little forward thrust to stay in the air and gain altitude. Apparently it’s easier/cheaper for a rocket to just increase thrust and launch vertically. There are some rockets which are launched from planes but that’s only really feasible for small rockets and adds complexity for relatively little gain (the great thing about launching a rocket from a plane is actually that you can choose where you launch the rocket, e.g. exactly at the equator, over the ocean, instead of having to build a launch pad there).

For a rocket to reach *orbit* the hard part is gaining enough *horizontal* velocity (about 7.8 km/s (28,080 km/h) for low Earth orbit). To go to space you just have to go up by ≥100km, which is not *that* hard. To quote xkcd: “getting to space is easy. The problem is staying there.” https://what-if.xkcd.com/58/

Lot of good answers here, but one more thing to consider:

To get into orbit, you have to get to a *certain height* and a *certain speed*. Of those two , the *second* is — unintuitively — the dominant hurdle, by a huge margin. Getting to the height is *easy*. Getting to the speed is a *huge* expenditure of energy.

A rocket wants to get as high as possible as quick as possible in order to do its flight in thiner atmosphere with less air resistance then it turns to the side and puts most its effort into sideways movement.

Orbiting a planet is just a high-tech version of the looney toons hitting a baseball around the world and it hitting them in the back, if you throw somthing really really fast then it actually happens as the earth curves away from you faster than you can fall. And if you do this high enough up there’s so little air resistance that whatever you throw will stay up there for years like satellites do.

Air resistance, the biggest enemies to getting to orbit are gravity and drag, you’ve gotta go 10 x faster than any aircraft to get into orbit and your engines don’t have the benefit of using the oxygen in the air as an oxidizer, therefore you want to get above as much of the air as fast as possible so as little as possible of the energy you’re putting in to go fast gets wasted as air resistance. Some small rockers do launch from a carrier aircraft but there’s only so big you can carry on a plane. Another sub category of this is a spaceplane or an ssto (single stage to orbit) aircraft that uses either seperate air breathing and rocket engines it if possible a hybrid that can breath air then turn into a rocket, this is what skylon is attempting and it’s super cheap because no expended hardware, just fuel