As in, not erect it pointing straight up and use who know how much rocket fuel to blast off. Why not just slowly take off like a plane, fly up at an angle and get into space that way?
I am not a rocket scientist but in my limited understanding of space travel I believe they do turn into an angle (relative to the surface of the earth) once the space shuttles speed is high enough until they get in to orbit.
The simple answer is that planes fly because the air moving over their wings creates lift. This air, however, gets thinner and thinner as you go up, and you can never get to space that way.
Saying it is due to lack of lift isn’t an answer. One could, in theory, climb slowly like say a U2 spy plane to the outer reaches of the atmosphere till you could get no lift, then cease to rely on lift only at that point.
The actual answer is to do with atmosphere.
The amount of energy taken to get from down here to up there is an irreducible quantity as far as overcoming gravity is concerned. Whether you spend that energy slowly by going up at a shallow angle, or rapidly by going up at an acute angle makes no odds.
However, what does make a very large difference is atmosphere. If you go up at a shallow angle, you will spend more time bashing through air, which has a high energy cost. If you get up and out quick you will spend less.
Less is good.
What makes me, as knowledgable enough in physics to get myself into trouble, think a couple more times on that question is that air resistance go up with the square of the speed, so going slowly up at a shallow angle might cost less, but even if it does, when there’s not enough air to give you lift, you’ll still be going much slower than orbital speed, so you better have brought with you a huge rocket. And lifting huge rockets would require a whopping huge plane…
Basically the design requirements for a vehicle that can climb slowly through the atmosphere are different to those needed to actually get into space. An obvious problem is the propulsion system. In space you need a rocket with its own onboard supply of oxidiser. Flying for long periods through a sea of air this is hopelessly inefficient as every pound of oxidiser is a pound less payload.
One solution is that used by the X15 and SpaceShip One- use a jet power conventional aircraft to carry your rocket plane above the thickest part of the atmosphere where the problems identified by **Princhester **and **naita **are less. The alternative approach is to design an engine that runs as a jet in atmosphere and them becomes a rocket in space. This is what is proposed for Skylonand the SABRE engine. A recent European Space Agency report has said that there are no insurmountable problems identified with the Skylon/SABRE proposal but that is long way from actually getting it built!
Look at the size of its fuel tank! Does that look like something that can fly horizontally? Those little wings and that huge fuel tank?
Just for comparison, SpaceShip One had a top speed of 1/28th of orbital speed and didn’t even reach the lower bound of what’s considered Low Earth Orbit. The ESA might not see any insurmountable problems, but as you say, we’re still a long way of an implementation.
Even then SpaceShipOne is far from reaching orbit – wiki says it needs 60 times more energy to get to orbital velocity. Maybe you could achieve that with a bigger engine, some boosters, and a lot more fuel (perhaps in an external tank). And now you’ve got a miniature Space Shuttle, without any cargo capacity. SpaceShipOne weights 3.6 tons, scaling up that by 60 increases the mass to almost 200 tons.
Now you have to replace WhiteKnightOne with something that can lift 200 tons to very high altitude… The world’s heaviest cargo plane could lift that much, but it can’t make it anywhere near the 70,000 foot launch altitude currently used by SpaceShipOne.
Or you could just make your engines a little bit bigger, add a bit more fuel, strap on some boosters, and launch from the ground.
To get into space you have to go fast. End of story.
To go fast you need a fuel and an oxidizer but by the time you’re approaching 27,000 km/h there are no air breathing engines capable of acquiring oxidizer from the atmosphere.
Which means you need to drag oxygen along for the ride. Well congratulations, you’ve now built a rocket and if you’re going to drag oxidizer and fuel into space you damn well want to get there as quickly as possible and with as little fuel as possible. Therefore you point your rocket straight up and arc over once you get above the majority of the atmosphere.
I doubt those wings could generate the amount of lift necessary to take flight considering weight of everything. .
True. I’m reading the OP as “Why don’t we have spaceplanes instead of rockets?”
That is probably the most succinct way of restating stating the question, as it is obvious from the design of the STS that it was not intended or capable of horizontal take off (HTO). The answer is twofold; as already elucidated, there is no savings in launching horizontally using pure rocket propulsion, in which the vehicle carries its own oxidizer as well as fuel, as the amount of drag and gravity losses (losses due to having to hold the vehicle up against gravity before achieving orbital velocity) exceed any gains from aerodynamic lift. This is why aircraft use air-breathing engines to provide oxidizer; however, air-breathing engines have limits to how fast they can propel a vehicle and efficiently intake and use air for combustion, as at supersonic speeds the shock wave will choke air coming into the inlet. This is dealt with on supersonic aircraft in one of two ways; the use of special ducting and nacelle design to slow the incoming air to subsonic, or the use of scramjet (supersonic ramjet) propulsion in which the combustion is allowed to occur at supersonic speed down the jet chamber. The latter is challenging because of the rate of combustion relative to the speed of the airflow, requiring a long combustion chamber and typically resulting in incomplete combustion. Scramjet design is also extremely tricky along a wide range of Mach values, as well as demanding sophisticated active cooling measures and/or exotic high temperature materials for the inlet and throat. Although the ESA may have decided that the Skylon (which combines an air-breathing scramjet with on-board oxidizer for atmosphere-to-exoatmospheric flight) the technology has been in development in various forms for over thirty years without a proof-of-concept so far. I wouldn’t hold my breath waiting on the development into a flight vehicle. The use of two-stage vehicles like the t/Space SpaceShipOne and Two configurations or the Soviet Spiral 50/50 separates the air-breather and rocket into different components, but thus far the demonstrated efficiencies do not approach that necessary for orbital flight compared to multi-stage pure rocket boosters.
The other problem with spaceplanes in general, and HTOL vehicles in particular, is that the design that allows for lift (large wings) also substantially complicates thermal protection design for reentry. I’m sure that all readers are aware of the issues with the American STS/Orbiter after the tragic loss of Columbia, but they may not be aware of just how many times the Shuttles have come close to the same degree and type of damage, and how little can be done, even using more recent technology in thermal protection, to enhance the basic design of the Shuttle or other winged orbiter against this type of damage. The best materials for thermal protection are not robust against shock and impact, and the best materials that withstand shock and impact not not generally good insulating materials. For a winged design like the Skylon, this drives the design toward the use of active cooling systems, the Skylon is supposed to use a heat exchanger system in which liquid hydrogen is plumbed through the leading edges to carry away heat, which is a complex and failure-prone method of protection. The better alternative is to go with blunt, rounded shapes for reentry craft that do not create shock-shock wavefronts which amplify local heating. Blunt-arced conical or bell-shaped capsules (Apollo, Gemini, Soyuz) and lifting bodies (the cancelled X-38 CRV) are much easier to design and more reliable during reentry, which is the second most dangerous phase of spaceflight.
There are alternatives to conventional multi-stage rockets and spaceplanes. The Chrysler Aerospace proposal for the STS was a giant blunt-arced reusable single stage to orbit (RSSTO) booster which used rocket propulsion on the way up and aerobraking on reentry, with pop-out air-breathing engines for final descent and soft-landing. (The original winged shuttle proposals also had pop-out engines until it was determined that a pure glide landing mode was adequate.) It was too far afield from the design concepts that were floated as part of the first proposal phases and lacked the required cross range capability (intended for polar orbit launch from VAFB but never used), and would have required the development of aerospace or plug-nozzle engines to obtain the required efficiencies at the range of altitudes, but in many ways was a substantially superior concept that would have provided much greater payload to orbit capability than any proposed spaceplane, and very likely with much higher reliability, less ground processing, and shorter turn-around time.
Stranger
Stranger, thanks for the expert summary!
naita, lazybratsche, I know SpaceShip One and its successors are nowhere near achieving orbit - it was the two craft concept I wanted to illustrate.
Very true! Alan Bond - the chap that came up with the SABRE engine - always seems to keep the concept going but it never quite gets off the ground - figuratively and literally!
This is the answer to the question. The Shuttle is not a plane, it’s a glider, and it can only glide at high speeds when it is nearly empty. It has no way to take off like a plane, nor could its wings generate enough lift for flight when carrying the fuel necessary to reach orbit.
Wasn’t trying to correct you, just furthering your illustration. I.e. here’s an example of a suborbital rocket carried by a plane, what would it take to make it from there to orbit?
Very good summary.
The basic problem is that it takes X% fuel/oxygen (fuel to payload) to put something in orbit, to reach 18,000mph. This is obvious from the size of the tank vs. shuttle; plus 2 expendable boosters. The more stuff you include in “going into orbit” the even bigger your tank. IIRC the typical guess for that ratio is about 90% fuel.
If you try to build wings on a giant tank, you are adding to the weight without increasing fuel capacity so now it has to be even bigger. Ditto for adding pop-out jet engines, or whatever else. Plus, as others mentioned, those huge wings will be heavier because they need to be covered with heat-resistant tiles. (The tiles are very light, but the weight is not insignificant). The joke about the shuttle was that it flew like a brick; it had just enough glide to get down safely. A recent design was the X37(?) which would be a giant lifting body fuel tank, but that was scrapped when it was determined the design was hitting serious technical issues.
There are cheat methods; the shuttle’s strap-on boosters, the multi-stage strategy of most other rockets - whre the big motor and tank does not have to get to orbit, it just has to get the smaller motor half-way there.
The shuttle’s flaw was to hang off the side of the tank, where stuff peeling off the tank would hit the heat tiles. The other flaw was to make the man-carrying reusable spaceship big enough to carry military spy satellite cargo (to get the military on-side with the shuttle program); this ensured the shuttle was too big to stick on top of the tank; and of course, the most important reusable was the giant rocket engine assembly which also could not go on top. Design decisions.
Another problem is that aerodynamic multistage is a tricky design. Most functional designs (X15, Spaceship 1) drop the launch vehicle, since a powered separation can be risky; also, you may get a bit of speed out of the launch, but subsonic (<600mph) does not substantially help when the goal is 18,000mph.
Another alternative is improve the efficiency - get more out of existing fuels. The shape of the rocket motor and it’s efficiency depends on what the surrounding atmosphere and current speed are. IIRC NASA has recently tested the Hyper series that use external combustion which can be more efficient; but those scram jets need to be hypersonic to start working, so you still need a massive normal jet and/or some booster rockets to get flying fast enough to light that up. (the 10-foot long test rockets used boosters to hit the right speed.)
The short answer is that everyone wants SSTo (Single stage to orbit) but technically best case it’s still a long way off.
Thanks Stranger, that was very…detailed! 
One design I read about was a jumbo jet with a small rocket motor in the back; the idea was to get a bit more speed and substantially more height out of the mothership (>60,000 feet) before releasing the rocket. Plus an empty Jumbo had really good lift capacity to carry a very heavy orbiter.