The space shuttle vehicle consisted of four main parts: the orbiter, the external tank and two boosters. The boosters would provide the initial thrust for the tank and orbiter to be able to reach orbit. The external tank, which contained 543000l of LOX and 1080000l of liquid hydrogen, had no engine and would be discarded once all the propellants were used [200]. The space shuttle orbiter could lift 29000kg into orbit [204].

The reusable orbiter had three main Space Shuttle Main Engines besides a multitude of smaller manoeuvring engines. The orbiter had a 24m span delta wing, was 37m long, 17m high and had an empty mass of 78000kg[200,206]. The thermal protection system on the space shuttle consisted of, among others, the reinforced carbon-carbon elements at high-temperature locations, such as the nose-tip and the leading edges of the delta wing [200]. The completed underside of the orbiter and part of the side was covered in High-Temperature and Low-Temperature Reusable Surface Insulation. These were in total, 25000-30000 silica tiles, essentially very pure quartz sand,  that protected the space shuttle during the re-entry. 

After re-entry, the space shuttle would autonomously guide itself to one of two possible Space shuttle runways. These were at Edwards Airforce Base and Kennedy Space Center. From the 1990s onwards, after touching down a 12 m reefed braking parachute would be deployed to aid in the deceleration[205].

Six orbiters were made: one test vehicle (Enterprise) and five operational orbiters (Columbia, Challenger, Discovery, Endeavour, Atlantis). All six were named after exploratory vessels [203]. Over its long career, the Space Shuttle deployed the Hubble space telescope and performed its servicing missions. It launched the Galileo orbiter to Jupiter, and Space shuttles also aided in building the International Space Station. The five Space Shuttles performed in total 135 missions and spent a total of 1320 days in orbit. On the 21^st of July 2011, after 30 years in service, the space shuttle program ended when Space Shuttle Atlantis completed STS-135 by touching down at the Kennedy Space Center [201,202].

Atmospheric Entry

The space rider capsule is a lifting body type spacecraft. That means that much like the space shuttle, the capsule generates lift. A lift generating capsule is more complex than a ballistic entry capsule, but the maximum deceleration and thermal loads are lower. Space Rider's ability to perform a gliding entry was tested in the ESA IXV mission, which flew a suborbital trajectory using a Vega launcher in 2015. From the render, one can see that the spacecraft does not have any wings; this is due to the lifting body design, which means that the spacecraft body itself generates sufficient lift to perform a gliding entry. This is unlike the US Space Shuttle or Russian Buran. This also means that the capsule cannot land by itself and requires a parachute system for a safe landing. 

Parachute system

Even though the Space Rider has a lift generating body, it cannot generate sufficient lift for a safe landing. Therefore it requires a parachute system for the final landing. The space rider parachute system consists of two drogue parachutes and a 70 m2parafoil main parachute. The parafoil can be seen below during an X38 test flight. Parafoils are lift-generating parachutes. This means that they work much like the wing of an aircraft. 

The propulsion system of the Dream Chaser is a hybrid propulsion system using HTPB and Nitrous, which is restartable and throttleable. The RCS system uses 800 lbs of ethanol and nitrous as a non-toxic alternative to the RCS system of the HL-20 [184].

The Dream Chaser was initially designed to be launched on the Atlas V. However, as the Atlas is being replaced, it will use ULA's new Vulcan launcher to get into orbit. Its primary purpose is to ferry a crew of 7 or 12000 lbs of cargo to the ISS [184,185]. Because of the lifting-body design, the descent is more "gentle" than a standard capsule return. Due to the L/D ratio of 1.4 during the hypersonic phase and an L/D of 4 during landing, the maximum deceleration of the Dream Chaser is limited to 1.5g [184]. Standard operations are to be run from Kennedy Space Centre, with it landing on the runways used for the space shuttle. However, in an emergency, it can also use regular commercial runways as long as they are at least 7000ft [184].

The first test flight of the Dream Chaser is planned for Q1 2024, which is a demonstration mission to fly to the ISS. If this is successful regular contracted missions can begin [186].

The HL-20, or Personnel launch system (PLS), was a small space plane with a wingspan of 7.2 and a length of 8.8m [178,179]. It had a dry mass of 7863 kg, a landing mass of 9392 kg and a launch mass of 28788 kg [180]. The propulsion system had enough propellant onboard for 335m/s Delta-V, 305m/s for orbital manoeuvring and 30m/s for space station operations. HL-20 had a suspended heat shield attached to the pressure vessel for re-entry. This thick graphite-polyamide honeycomb was the last layer. On top of this, there were thermal tiles for extra thermal shielding.

During the ascent, the HL-20 would monitor the Titan IV for any anomalies and separate if it detected any. As it is a lifting body, it would have the option to fly back to base. If flying back was impossible due to altitude or location, a parachute system would also be onboard. This was a conventional cluster of three 3.6m diameter ringsails. They would be deployed by three mortar-fired conical ribbon pilot chutes [178,180].

Part of the goal for the HL-20 was to make it as safe and cheap as possible. To achieve this, several changes were made with respect to the space shuttle, such as minimizing the amount of parts as much as possible. Also, the HL-20 used the improving state of technology and did away with the heavy hydraulic system and replaced it with an all-electric system to actuate the aerodynamic surfaces [179].

The vehicle would have had a gross mass of 10125kg and be capable of carrying a 450kg payload, including one pilot. It has a height of 14.5m and a 6.3m wingspan [211]. It used a passive cooling system based on water to withstand the heat from re-entry. The X-20s mission profile would have had it perform a flight at 7.5km/s at 98 km altitude right at the edge of space [211,212].

In 1963, it was decided that the X-20 did not have a clear mission, and the program was cancelled as the space bomber mission itself was no longer discussed by the USAF [211,213]. However, the knowledge gathered during the X-20 program would eventually be used for the following space plane programs: Prime, Asset, X-23, and X-24 [211].

The JAXA HOPE-X space plane was a project that aimed to develop an experimental orbital vehicle for testing and validating technologies for future manned spaceflight. The project was started in the 1980s by a partnership between NASDA and NAL, both now part of JAXA. HOPE-X was intended to be one of the main Japanese contributions to the International Space Station, along with the Japanese Experiment Module. However, the project faced several challenges and delays and was eventually cancelled in 2003. One of the reasons for the cancellation was the reduction in scope that occurred in 1997 when it was decided that HOPE-X should be modified into an unmanned cargo vehicle with automated docking systems and a cargo bay. This was believed to be a cheaper and faster way to supply the ISS, which was suffering from problems with the US Space Shuttle program. However, this also meant that HOPE-X would lose its original purpose of being a precursor for a larger manned space plane. The HOPE-X space plane was supposed to be launched on Japan's H-IIA rocket, which had a payload capacity of about 3 metric tons (6,600 lb) to low Earth orbit. This was comparable to the Russian Progress spacecraft's capacity of about 2,500 kilograms (5,500 lb). The HOPE-X space plane had a length of 15.2 m (50 ft), a wingspan of 9.7 m (32 ft), and a mass of 14 t (31,000 lb). It was designed to reenter the atmosphere and land horizontally on a runway.