Why can’t we fly a plane into space ?
Why can’t we fly a plane into space what stops it from just flying higher and higher until it in space. well there are several issues but assuming we are in something like a normal jet airliner then one of the main problems is the air or lack of it as we get closer to space. a plane flies because it is propelled forward the wings which shaped to make the air flow faster of the top of them rather than the bottom generate lift as the plane goes faster the wings create more lists when the lift is greater than the weight to the plane it will climb into the air. As our playing climbs higher and higher into the atmosphere the air becomes less and less dense the plane to fly faster to create more iift until eventually it reaches an altitude where the engines either cease to function correctly because of the lack of oxygen or the air is too thin to create enough lift. Just as we need air to breathe then the engine need oxygen to burn to create thrust to propel the plane forward just engines however engines can work at higher altitudes than people. We humans have a limit about 8,000 meters or 26,000 feet above which is what climbers call the “Death Zone”, this is where there is not enough oxygen for humans to survive for sustained period. The summit of Mount Everest is 29,000 feet high in the air density there is about 33% of that at sea level. This means that with each breath you take you’re only getting 33% of the oxygen. If you want to stay at this altitude without additional oxygen you would suffer from a condition called hypoxia were due to a lack of oxygen to the body starts to slow shut down and die. At 12,000 meters or 40,000 feet which is the upper limit for most modern airliners the air density is about 18% of that at sea level. If you were in a plane that had a rapid decompression at 40,000 feet you’ll have about five maybe ten seconds to get your emergency oxygen mask on before you became unconscious. The highest flying jet plane in level flight was the Lockheed SR-71 blackbird with a height of 85,069 feet 42,929 meters and where the a density is just 2% of that sea level. At that height it’s traveling at mach 3.2 or 2190 miles an hour. The SR-71 pilots had to wear a full pressure suit with its own oxygen supply in case of a cockpit decompression or emergency ejection and this was put to the test when you 1966 an SR-71 piloted by Bill Weaver disintegrated that mach 3.1 at an altitude the 78,000 feet as it was performing a test flight to ironically optimizing performance. At that altitude your blood will boil in a similar way to when you open a bottle of fizzy drink as the nitrogen in your blood to the gas in the low-pressure atmosphere. The pressure suit work and Weaver survived the descent from 78,000 feet but tragically the navigator Jim’s Zwayer died of a broken neck resulting from break of the plane. Now while you would think that the SR-71 soft to get into space you need to reach what is called “escape velocity” this is where you are traveling faster than gravity is pulling you back to work and that is 25,020 miles an hour or 40,270 km/h and and if that wasn’t a problem there’s also to recognized altitude at where space starts at 328,000 ft or 100,000 meters well over three times the highest flight of the SR-71. Normal jet engines like those in the SR-71 have a maximum air speed limits for around about Mach 3.5 or 2695 miles now beyond that the air pressure and temperature becomes too high for compresses and the engine to effectively. For hypersonic speeds, experimental unmanned aircraft like NASA X-43 use what is called a scramjet engine. The X-43 is currently the fastest free flying air-breathing aircraft in the world having flown at mach 9.6 or 7310 miles an hour in November of 2004. Scramjets do away with the turbine compressors of the jet engine so they have no moving parts instead they use shock waves in the engine to compress the raise the temperature in the engine to burn fuel and create trust an in theory they can fly up to Mach 20 and possibly beyond. The problem with this is that they won’t work at speeds of less than around Mach 5 so they have to be brought up to speed by rocket engine booster before they can operate, which is how NASA x43 worked. They also won’t work in space because there is no air with oxygen in to combust the fuel So this why space vehicles are launched by Rockets. Rockets can have much more power and can operate from a speed of zero on the launchpad to Mach 33 and beyond which is the escape velocity of Earth. One of the earliest experimental space planes was the North American X-15 which reached a height of 353,000 feet or 107,000 meters 1963 and was powered by a liquid rocket danger but it had to be carried up to 45,000 feet attached to the underside with B-52 bomber before being released. Then of course we’ve had space shuttle the Soviet version of the Space Shuttle the “Buran”, SpaceShipOne and the Boeing X-37, all of which were examples of space planes but we’re really just rocket powered gliders. Rocket differ from Jets because they bring their own oxygen to burn the fuel and don’t rely on the atmospheric oxygen. This means that they can working space equally as well as in the atmosphere. The problem with rockets is that because they need to bring the oxidizer with they makes them very heavily. Look at the space Shuttle for example, the external fuel and the tanks to hold it along with the two solid rocket boosters weighed 1,940 metric tonnes at liftoff and that’s without the space shuttle. All of which has to be carried along with the shuttle to the edge of space where they are they jettisoned. The maximum payload the shuttle could deliver it into a low earth orbit was 27.5 metric tons, which as a payload fraction is just 1.3% of the total take off weight. Rockets however can create huge amount of power, so they can achieve the speed that is need to escape the pull of gravity and go into orbit and Beyond. But what of the future, will we ever get planes that can take off from an aircraft runway, fly into space and then return back to a runway. There are still considerable technical issues to overcome but one design which looks promising is the Skylon. This is an SSTO or Single Stage To Orbit design meaning that unlike a rocket, it stays in one piece rather than having a separate main booster stage which detaches and return to Earth and then a smaller second stage which one goes on to orbit. The key technology makes Skylon work is the SABRE or Synergetic Air Breathing Rocket Engines. Now these are kind of hybrid jet rocket engine which can take off like a normal jet engine, breathe air upto 93,000 feet and at a speed up to Mach 5.4 when then switches to rocket mode and can fly into space for up to 800 kilometers 500 miles above the earth. It would then return to the Earth’s atmosphere and land as normal air-breathing plane to be checked, refueled and ready for launch. Because it uses more efficient engines and the lift of the wings it would use only 20% of the fuel compared to a conventional rocket. It would still need to bring it oxidizer for the rocket portion of the journey but a lot less that will be required for a normal rocket. This allows for a larger payload when compared to the total weight around 5.5% compared to the shuttles 1.3%. Unmanned flight test of the Skylon could be happening by 2025, if all goes well but a potentially large flying in ointment is the recent advances in reusable rockets like SpaceX Falcon f9r and the Blue Origin New Shepherd. These could make the development costs to the Skylon expensive for satellite deployment and supplying the International Space Station. One thing which could come out though, is a rocket less version of the SABRE engine which could make hypersonic air travel more a viable option than using a scramjet. Only time will tell but this is an exciting time for both the future of air and space travel, so we may yet see the plane that can fly to space. So as always thanks for watching and please subscribe, rate and share.