– could the space shuttle just fly into space like a plane, rather than being propelled vertically by rockets?
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Early designs for the SS actually did intend for it to be Single Stage to Orbit, with a novel dynamic nozzle system. Essentially a rocket nozzle is most efficient at a particular external pressure. Since there is a dramatic difference between the pressure on the ground and the pressure in space, either the system uses multiple rocket stages, or the nozzle diameter is adjusted. However, this proved to be too complicated and it was scrapped in favor of 2 stages.
The other benefit of 2 stages is that you can reduce the weight prior to starting the second stage. A single stage system has to carry all the fuel necessary to get to space, and that’s extra weight in tanks once it gets there.
Rockets generally go straight up initially and then turn horizontal to enter and orbit. You could take off like a plane, but there would be a lot of wasted energy traveling a longer distance through the atmosphere. It would only make sense if you had a plane with an air breathing engine, ie a jet, and then activated the rocket at altitude. With rockets you want to get out of the atmosphere as soon as possible to reduce drag, so you go straight up initially.
The space shuttle never flew in the same way as an aircraft does, the best it could do was fall with style.
It wasn’t a true space plane. It was a reusable rocket that did a rolling landing rather than a space X style vertical one. The only reason it had such large wings was for a military requirement. During development the idea was to put a large spy camera in the cargo bay, launch into a polar orbit over the target, take a picture, and then land back at the launch site 1 orbit later.
The lateral movement required to return to the launch site on re-entry required the larger wings. As the space X starship shows you don’t need large wings for a controlled belly-flop style braking manoeuvre.
This mission profile also set the size of the cargo bay, large enough to hold the standard spy satellite camera system of the day. Commercial and scientific use could have managed with a far smaller shuttle.
By the time the shuttle flew improvements in digital camera technology made this flight profile obsolete and the ability was never used.
The Orbiter (the part of the Space Shuttle that looks sort of like a plane) had it’s own main rocket engines (three of them), but those were not powerful enough on their own to get to orbit, which is why the SS also had the pair of solid rocket boosters at launch. Also even if the shuttle had big enough engines for an orbital launch, it wouldn’t have anywhere near enough capacity to carry the fuel required to get there. That’s why it had the big orange external tank.
Like other replies have said, once you get too high up, there’s not enough oxygen in the atmosphere to power a jet engine, so you have to use rockets. And one of the unfortunate things about rockets is that they need a lot of fuel. Fuel is heavy and bulky, and requires a lot of ‘extra’ volume and weight for your launch vehicle in order to carry the fuel until it’s used. This is why spacecraft pretty much always launch with some sort of rocket assembly that they then separate from before they reach their final altitude. It just doesn’t make sense to bring all of those fuel tanks all the way up with you, it’s too big and heavy and is not useful to the spacecraft once that fuel has been spent.
Another potential solution is to use an larger airplane to get the spacecraft as high up as you can, and then have it separate from the aircraft before using its own rockets to go the rest of the way, but as far as I’m aware none of those built so far have been powerful enough to achieve orbit.
However well-designed your aircraft is, flying will only get you so high, because you need air to give you lift. As the air gets thinner, you run out of lift.
Plus – there’s a trade-off. While there’s air around you to push you up, there’s also air in front of you that you need to push out of the way. And that slows you down. So even if you COULD hit orbital velocity for the height in question, you’d drop back below it very fast if you were to cut your engine. So, basically, no. Eventually you hit a point where the only way to get higher – beyond the noticable atmoshpere – is basically brute force. With current technology, that effectively means rockets.
In principle, IF you could manage to get your aircraft, with an air-breathing engine, screaming horizontally through the atmosphere fast enough, you could just nose-up your ‘plane and let its raw momentum take you up to an orbital height. Unfortunately, “fast enough” is, apparently, about 30 times the speed that anything is capable of today. So, again, no.
As for the actual space shuttle – it was once described as a “flying brick”. It was optimised for a controlled re-entry, not sustained, level atmospheric flight.
The modality you are describing is called SSO, single stage to orbit, and it is the Holy Grail of space launch vehicles. It is the Holy Grail as it is unattainable with current technology. A trip from sea level Earth to low Earth orbit (LEO) has many different mediums that a SSO vehicle would have to adapt for. It is about the first 20 miles (100,000 feet) that is most problematic. It is 60 miles to the Karmin Line, where space officially begins, but the lowest stable LEO is at least 100 miles.
A sea level launch has the thickest atmosphere and a specific engine design/rocket nozzle is required for maximum thrust in that environment (gross oversimplification). As the altitude increases and atmospheric pressures drop, a different nozzle is required to maximize engine performance. When you get to the extremely low atmospheric pressures of LEO, yet a third kind of engine/nozzle is required.
At lower altitudes, attitude control and stability can be achieved through movable control surfaces. These are the wings and fins you see on vehicles that interact with the airflow. Attitude control is also achieved via engine gimbals. At greater altitudes, where the atmosphere is less dense, flight control surfaces no longer work, you need attitude control thrusters. Small rocket engines that can be fired to change the orientation or direction of travel of the vehicle.
These two challenges contribute to the largest challenge, the provision of fuel. Known as the *Rocket Equation* and again a gross oversimplification of it, the larger and heavier your vehicle is, the more fuel you have to carry, which makes your vehicle larger and heavier so you have to carry more fuel…….
The current workable Rocket Equation is 85/15. A MSO, multistage to orbit vehicle, needs 85% of its gross launch weight to be fuel, leaving only 15% for people, cargo and vehicle infrastructure. The only way to change this, other than somehow altering physics, is to create rocket engines with higher specific thrust, so as the alter the Rocket Equation.
In summary, this is what makes MSO’s the best solution right now. You can have different engines for different working environments maximizing the performance of each one. A MSO can carry vast amounts of fuel and it then discards portions of itself when they are no longer needed, lightening the vehicle (read: changing the equation) as it reaches higher altitudes.
Some launch systems get around this by carrying the orbital vehicle to very high altitudes, such as Richard Brandon’s Virgin Galactic, before launch. Research conducted in the 50’s & 60’s with the X-15 project also carried the vehicle to high altitudes before it powered itself the rest of the way.
Until our engine design gets way more sophisticated and efficient, SSO, at least with a meaningful amount of cargo, is out of reach.
No. It literally had no thrust capability apart from orbital maneuvering engines, once it separated from the main external fuel tank.
So, generally the problem is that the shuttle has a LOT of drag and only a little lift. Which is fine when doing re-entry, where the drag helps as the goal is to slow down and glide in. That high drag and small lift does mean it glides rather steeply to a landing where it pulls out a flare up only at the last moment, which is fine. But now let’s say it tried going to orbit doing what you suggest. It’s still going to need all that extra stuff attached to the side, since there’s so little fuel in the actual “airplane” part. It will need the giant “drop tank” that’s bigger than the “airplane” itself, and it will still need the 2 huge solid boosters stuck on the side of that. Now remember how the lift was barely good enough for the empty Shuttle itself to glide? Now it’s having to hold up the giant full tank and full boosters too.
That’s not enough lift to fly like a plane. It’s going to have to be tilted way up just to fly level, and at that point it’s really just flying like a missile rather than a plane anyway. So you may as well embrace the truth that it’s a missile at that point, and fly it like all the other rockets get into orbit.
tl;dr – It only has enough lift to manage a glide when the fuel tank and boosters are gone. When going up to orbit with all that stuff attached, it’s too damned heavy.
All the replies about wings and air are leaving out that jets breath air. There is a point where jet engines would just go out if you fly too high.
BUT the shuttle didn’t have jets, it had rockets. There simply wasn’t enough fuel in the shuttle to make orbit with it’s rockets (even flying like a jet to the upper atmosphere). There was not enough thrust to get off the ground with more fuel without the boosters. Once you add the boosters and external tank, there isn’t enough lifting surface to fly like a plane.
There is a space plane design that switches from atmosphere to onboard oxygen as it goes higher, but it isn’t real yet because it’s a very hard balance to get right and may be impossible.
Technically, you could get into space by maintaining a consistent plane and peeling away from the earth due to the curvature. But losing the lift as the air thins and dissipates means that anything trying to do this would need rockets and wouldn’t achieve it as a plane would from a functional standpoint.
Just to be clear, [this is the space shuttle](https://upload.wikimedia.org/wikipedia/commons/d/d6/STS120LaunchHiRes-edit1.jpg). The whole thing comined, including the plane-looking piece, the big orange tank, and the white side rockets. The plane-looking part is called the *orbiter*, because it’s the only part that actually makes it to orbit.
The orbiter looks like a plane. But it is not a plane. It cannot fly like one.
It might look like it should be able to, since it has wings and three huge rocket engines on the back. Those engines, however, are hooked up to that big orange fuel tank. The whole shuttle assembly uses those engines and that tank to get up to space, but once the orange tank is empty, they throw it away, leaving those big engines out of fuel for the rest of the mission. That is their only purpose.
When the orbiter is ready to land, it is basically out of fuel. It has two tiny little rockets on the back just above the three big ones that you’ve probably never noticed before. They have some fuel, but not enough to fly with. These engines are primarily used to make small orbital corrections once the orbiter has already made it up there. This includes nudging the orbiter out of orbit to make it fall back to Earth so it can land.
The falling part is where the wings come in. I said earlier the orbiter is not a plane. It isn’t. It is, in fact, *a glider!* *A really bad one!* [Here’s a video of a talk given by Bret Copeland](https://youtu.be/Jb4prVsXkZU) describing the landing process. In it, he mentions that the orbiter is lovingly referred to as “a flying brick” and that to prepare the crew to drive this thing they must practice on a modified plane “with its landing gear down and its engines in reverse”. Yeah. The only thing the wings do is steer the near-freefall.
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