I. Introduction:
The purpose of this paper is an overview about the current space tourism industry with advanced developments of space vehicles. Until now, seven tourists have ridden Soyuz spacecraft, a Russian spacecraft, to the International Space Station. Capturing the potential demand of space tourism, many private companies began to introduce their new and well-designed spacecraft promising to enable tourist to travel to space. From now to the next couple of years, we are expected to see many launches including testing and commercial flights into suborbital and low Earth orbit. There are also some private companies, who were awarded by NASA for their space programs to carry astronauts to the space station.

II. Virgin Galactic – Scaled Composites (Suborbital):
Virgin Galactic – Scaled Composites founded by Burt Rutan designed a unique type of spacecraft. Using a mothership aircraft, the space plane will be carried to midair and then be released to launch toward the edge of the atmosphere. Using carbon composite construction, the company has introduced two version of the space plane: SpaceShipOne and SpaceShipTwo along with two model of the mothership aircraft: WhiteKnightOne and WhiteKnightTwo. (Ref 1,3) A. Spaceship: a. SpaceshipOne – WhiteKnightOne:
Scaled Composites first launched the SpaceShipOne to the suborbital in 2004 while the first of WhiteKnightOne was in 2002. Overall, the WhiteKnightOne’s features are carriage and launch of payloads up to 7,000lbs; internal fuel capacity up to 6,400lbs; altitude capability above 53,000ft; having large three-place cabin (60” diameter outside, 59” inside); sea level cabin qualified for unlimited altitude; ECS scrubs CO2 for removing humidity and defogging windows; two crew doors with dual seals and dual-pane windows; manual flight controls with three-axis electric trim; avionics including INS-GPS navigator, flight-director, flight test data (recording and T/M), air data; vehicle health monitoring, backup flight instruments, and video system. The White Knight is equipped to flight-qualify all the spacecraft systems, except rocket propulsion. Its design mission is to provide a high-altitude airborne launch of SpaceShipOne, a manned sub-orbital spacecraft. The White Knight’s cockpit, avionics, ECS, pneumatics, trim servos, data system, and electrical system components are identical to those installed on the SpaceShipOne. Using high thrust-to-weight ratio and enormous speed brakes (hydraulic wheel brakes and nose-gear steering; super-effective, pneumatic speed brakes that allows steep descent with L/D <4.5), the White Knight allows the astronauts in training to practice space-flight maneuvers such as boost, approach, and landing with a very realistic environment. Therefore, the SpaceShipOne pilots use the WhiteKnightOne aircraft as a high-fidelity moving-base simulator for training. Besides, the WhiteKnightOne also has other mission capabilities such as: reconnaissance, surveillance, atmospheric research, data relay, telecommunications, imaging and booster launch for micro-satellites. SpaceShipOne has a three-place, high-altitude research rocket, which is designed for sub-orbital flights to 100 km altitude. “The unique configuration allows aircraft-like qualities for boost, glide, and landing. The ship converts (via pneumatic-actuated feather) to a stable, high-drag shape for atmospheric entry. This “care-free” configuration allows a “hands-off” re-entry and greatly reduces aero/thermal loads. Designed for a “shirt-sleeve” environment, the 60” diameter cabin has a space-qualified ECS, as well as dual-pane windows. The ship uses three flight control systems - manual-subsonic, electric-supersonic and cold-gas RCS. SpaceShipOne’s hybrid rocket motor is a non-toxic, liquid nitrous-oxide/rubber-fuel hybrid propulsion system. The avionics onboard provide the pilot with the precise guidance information needed to manually fly SpaceShipOne for boost and re-entry. It also provides guidance for approach and landing and vehicle health monitoring. The unit stores and telemeters flight test data to Mission Control.” (Ref 1) b. SpaceshipTwo – WhiteKnightTwo:
After the success of the first generation of SpaceShipOne and its mothership aircraft WhiteKnightOne, Scaled Composites and Virgin Galactic introduce the WhiteKnightTwo, which has its first flight on December 21, 2008, and the SpaceShipTwo, which is first launched on October 10, 2010. The WhiteKnightTwo is about three times larger than its predecessor in order to perform a captive flight with the larger SpaceShipTwo spacecraft. The WhiteKnightTwo has 140 feet wing-span (only 16 feet less than Boeing 767-300), 78 feet length and 25 feet tail height. It uses highly efficient turbo fan jet engines and is equipped with Quadricycle gear. Also like the WhiteKnightOne, the WhiteKnightTwo will provide preview flights offering several seconds of weightlessness before the suborbital event, and this allows pilots and tourists to practice before the real flight. It is intended to have a service ceiling of about 60,000ft, offering a dark blue sky to passengers. The designs of those two aircrafts are quite different in size, use of tail, engine configuration and placement of cockpits. While the first aircraft uses two T-tails, the second uses two cruciform tails. Moreover, the WhiteKnightTwo has four engines hung underneath the wings on pylons while the White Knight’s pair of engines is on either side of its single fuselage. The WhiteKnightTwo is keeping a record for being the largest carbon composite carrier craft in service. This aircraft has totally 172 flights until now. Similarly, the SpaceShipTwo is a larger version the SpaceShipOne. Although it uses much of the same technology, contruction and design of the first space ship, it is twice larger than the first one. Its design aims for the commercial service rather than only a proof of concept demonstration. The SpaceShipTwo can carry 6 passengers and 2 pilots. It will travel around 68 miles above the boundary between space and Earth’s atmosphere. The SpaceShipTwo has 42 feet wing-span, 60 feet length and 18 feet tail height. Its cabin is 90-inch diameter x 12 feet long and approximately the size of a Falcon 900 executive jet. There are large windows positioned throughout the cabin to afford maximum viewing potential for passengers, and the whole fuselage is also used for passenger cabin. Unlike SpaceShipOne, the second ship uses tricycle gear configuration, 2x wheeled main gear and 1x nose skid. The whole body of SpaceShipTwo is made of 100 percent carbon composite. For its propulsion, hybrid rocket motor is used benign fuel and oxidizer to be more controllable and able to shut down at any time during boost phase of flight. After being released from carrier aircraft, rocket motor is engaged for ascent to space. During re-entry and landing, there is no need for propulsion. This spaceship can achieve a velocity of supersonic within eight seconds of rocket ignition (a maximum velocity of approximately Mach 3.5). According to Virgin Galactic, the SpaceShipTwo has a total independent flight time around 30 minutes, and its flight time with WhiteKnightTwo is around two hours. There are total 55 flights of the SpaceShipTwo. Unfortunately, the latest test flight of SpaceShipTwo on October 31, 2014 encountered an accident, which killed a copilot. The investigators are working to find out the problem. (Ref 3)

B. Launcher-One:
Besides, the company also announced a new launch vehicle called LauncherOne to give satellite operators a better/cheaper option for carrying their small satellites into orbits. It is a two-stage air-launched vehicle using Newton engines, RP-1/LOX liquid rocket. “The second stage will be powered by NewtonOne, a 16 kilonewtons (3,500 lbf) thrust engine. The first stage will be powered by a scaled-up design of the same basic technology as NewtonOne, called NewtonTwo, with 211 kilonewtons (47,500 lbf) of thrust.” [7] The LauncherOne is expected to travel around the Earth at 18,000mph in 90 minutes. Before this vehicle invention, the cost of putting a satellite into space is around $30-$40 million, and with LauncherOne, it will be under $10 million. (Ref 7,8)

III. XCOR Aerospace:
XCOR Aerospace spent many years to develop their commercial reusable launch vehicle, which is called Lynx. It is a two-seat, piloted space transport vehicle that can take human and payloads on a half-hour suborbital fight. The company will begin an initial flight test with Lynx Mark I beginning in 2015. Then XCOR will follow up with several models of production vehicles such as Lynx Mark II and Lynx Mark III in order to address different needs and markets. Like other companies, XCOR is also developing their own rockets such as EZ-Rocket and X-Rocket, which aim for low-cost rocket engines. The Lynx propulsion is compiled with 4 XR-5K18 rocket engines, each producing 12.9 kN (2900 lbf) vacuum thrust with kerosene and liquid oxygen propellants. (Ref 2,4,5)

A. Spaceship: a. Lynx I:
“The Lynx Mark I is the initial flight test vehicle now under development at XCOR’s Mojave, CA facilities. This prototype vehicle will be used to characterize and flight test the various sub-systems of the craft including life support, propulsion, tanks, structure, aero shell, aerodynamics, re-entry heating and other design elements” [5]. The Mark I has a maximum altitude at 62 km (203,000ft), primary internal payload of 120kg (260lb), secondary payload spaces including a small area inside the cockpit behind the pilot or outside the vehicle in two areas in the aft fuselage fairing and 4G re-entry loading. It can achieve Mach 2 speed of ascent (1,522 mph). The Lynx Mark I will be launched for a flight test in 2015. “The flight test program consists of a traditional envelope expansion regime in which is gradually tested to its full flight profile” [5]. Pilots and crew for the Lynx Mark II will use the Lynx Mark I for training purposes. (Ref 5) b. Lynx II:
While keeping the same primary internal payload of 120kg and the same secondary payload as Mark I, the Lynx Mark II can achieve a maximum altitude of 107km (351,000ft). It has non-toxic (non-hydrazine) reaction control system (RCS) thrusters and nonburnite LOX composite tank. Technically, the Mark II will begin its construction and assembly during the Lynx I development program, and Mark II is actually the production version of Lynx I. Mark II is expected to service both the suborbital tourism market and all markets that make use of the Lynx’s internal payload volumes, such as microgravity and biotechnology experiments. The Mark II will have a higher performance than the Mark I due to its lower dry weight while using the same propulsion and avionics systems as the Mark I. Approximately a year or 18 months after the Mark I is launched, the Mark II would go into operation to carry tourist, researchers and scientific payloads across the internationally accepted boundary of outer space, which is beyond 100 kilometers (62 miles) in altitude. (Ref 4,5) c. Lynx III:
After that, the Mark III will be produced to deploy microsatellites or multiple nano-satellites into low-Earth orbit. It will be a highly modified derivative of the Lynx Mark II and be able to carry an external dorsal pod. The total payload capacity for the external dorsal pod is 650kg. Mark III will have an upgraded landing gear, aerodynamics, core structural enhancements, and a more powerful propulsion package as well as other modifications, which are needed to carry the extra weight aloft. (Ref 5)

B. Rocket Engine: EZ-Rocket & X-Racer
XCOR introduced the EZ-Rocket as the first demonstrator rocket-powered vehicle. It is modified from a “Long-EZ” homebuilt airplane by adding twin 400lb thrust regeneratively cooled rocket engines. Then, with both engines running (800lb thrust total) and maximum propellant load, EZ-Rocket can have a takeoff roll of 500m (1650ft) in 20 seconds. “After pulling up, climb is established at constant airspeed at Vy (best climb speed), or 145 knots. Burnout occurs after a maximum of two and one-half minutes, still at 145 knots indicated, which equals Mach 0.4. The maximum altitude that has been attained is 11,500 ft. The maximum climb rate is 31 m/sec (6,000 ft/min)” [9]. The purpose of this program is to design and build a rocket propulsion vehicle that is simple, cost effective, reliable, and above all operable. The target for the EZ-Rocket is to drive costs below $2,000 per flight, and the actual number beat this estimate handily at approximately $900 per flight. After the success of EZ-Rocket, XCOR announces X-Race, which is a logical evolution in the design of EZ. The X-Racer features a larger, simple pump-fed engine with a visually spectacular kerosene exhaust plume. The X-Racer is based on the Velocity SE airframe, a home built aircraft offered by Velocity of Sebastian, Florida. That airframe is modified to carry the XCOR XR-4K14, a 1,500 pound thrust rocket engine, which burns liquid oxygen (LOX) and kerosene. The X-Racer is the first XCOR vehicle to utilize XCOR’s proprietary rocket propellant piston pump, which is a result of 10 years research and development. The pump is the keys system component that allows the elimination of heavy, pressurized fuel tanks as well as heavy, high-pressure gas bottles. (Ref 9,10)

IV. Zero G Corporation:
Rather than introducing a spaceship to travel to the orbit, Zero G Corporation modified a Boeing 727-200 aircraft to allow passengers experience the different states of microgravity. The plane is called G-Force One. Zero G, zero gravity, microgravity or weightlessness is an absence of “weight”, and in fact an absence of stress and strain resulting from externally applied mechanical contact-force, typically normal forces from floors, seats, beds, scales, and the like. Counter-intuitively, a uniform gravitational experiences no g-force acceleration and feels weightless. Zero G Corporation named the company after zero gravity in order to help people experience the weightlessness-stage in the space in order to be ready for space tourism as well as to train pilots to be ready to fly to the outer space. Contracting with NASA, Zero G provides several services in the weightlessness-stage, such as education workshops and even weightlessness-wedding. The current price is $4,950 per passenger. “Using a modified Boeing 727, G-Force One, weightlessness is achieved by doing aerobatic maneuvers known as parabolas. Specially trained pilots perform these aerobatic maneuvers, which are not simulated in any way. Before starting a parabola, G-FORCE ONE flies level to the horizon at an altitude of 24,000 feet. The pilots then begins to pull up, gradually increasing the angle of the aircraft to about 45° to the horizon reaching an altitude of 34,000 feet. During this pull-up, passengers will feel the pull of 1.8 Gs. Next the plane is “pushed over” to create the zero gravity segment of the parabola. For the next 20-30 seconds everything in the plane is weightless. Next a gentle pull-out is started which allows the flyers to stabilize on the aircraft floor. This maneuver is repeated 15 times, and each taking about ten miles of airspace to perform. In addition to achieving zero gravity, G-FORCE ONE also flies a parabola designed to offer Lunar gravity (one sixth your weight) and Martian gravity (one third your weight). This is created by flying a larger arc over the top of the parabola”. (Ref 2, 11)

V. SpaceX:
After the success of the first private spaceship that ever docked to the International Space Station with a robotic Dragon version 1 capsule, SpaceX announced their Dragon Crew Spacecraft version 2 that promises to be 21st – century space taxi for astronauts. With Falcon 9 and Falcon Heavy rockets and 2 versions of spacecraft, SpaceX is ahead of the race of space tourism. (Ref 2, 12) A. Falcon 9:
After spending the company own money to develop Falcon 1 launcher, Falcon 9 was initiated with NASA funding from the Commercial Orbital Transportation Services (COTS) program. Astonishingly, Falcon 9 made history in 2012 when it delivered Dragon capsule into the correct orbit for rendezvous with the International Space Station. Falcon is a two-stage rocket, the first rocket completely developed in the 21st century, and it is designed and manufactured by SpaceX for the reliable and safe transport of satellites and the Dragon spacecraft into orbit. “The interstage is a composite structure that connects the first and second stages and holds the release and separation system. Falcon 9 uses an all-pneumatic stage separation system for low-shock, highly reliable separation that can be tested on the ground, unlike pyrotechnic systems used on most launch vehicles. Falcon 9’s first stage incorporates nine Merlin engines and aluminum-lithium alloy tanks containing liquid oxygen and rocket-grade kerosene (RP-1) propellant. Falcon 9 generates 1.3 million pounds of thrust at sea level (5,885kN) but gets up to 1.5 million pounds of thrust in the vacuum (6,672kN) of space. The first stage burning time is 180 seconds. The second stage, powered by a single Merlin vacuum engine, delivers Falcon 9’s payload to the desired orbit. The second stage engine ignites a few seconds after stage separation, and can be restarted multiple times to place multiple payloads into different orbits. The second stage burning time is 375 seconds with thrust of 801kN. The second Falcon 9 version v1.1 was developed in 2010-2013, and launched for the first time in September 2013.” (Ref 13) B. Falcon Heavy:
Consisting a standard Falcon 9 rocket core and two additional Falcon 9 first stages as strap-on booster, Falcon Heavy (Falcon 9 Heavy) is a variant of the Falcon 9 v1.1. The first launch is expected in 2015. Currently, it is the world’s most powerful rocket with nearly 4 million pounds of thrust at liftoff, and its payload to low earth orbit is 53,000kg (116,850lbs) according to SpaceX. “Three cores make up the first stage of Falcon Heavy. The side cores, or boosters, are connected at the base and at the top of the center core’s liquid oxygen tank. The three cores, with a total of 27 Merlin engines, generate 17,615 kilonewtons (3.969 million pounds) of thrust at liftoff. Shortly after liftoff the center core engines are throttled down. After the side cores separate, the center core engines throttle back up to full thrust. The second-stage Merlin engine, identical to its counterpart on Falcon 9, delivers the rocket’s payload to orbit after the main engines cut off and the first-stage cores separate. The engine can be restarted multiple times to place payloads into a variety of orbits including low Earth, geosynchronous transfer orbit (GTO) and geosynchronous orbit (GSO)” [14]. The Falcon Heavy promises to lift into orbit over 117,000lbs – a mass equivalent to a 737 jetliner loaded with passengers, crew, luggage and fuel. (Ref 14) C. Dragon Spaceship: a. Version 1:
Dragon spaceship is a project designed to deliver both cargo and people to orbiting destinations. It is a partially reusable spacecraft. The first version of Dragon, Dragon V1, was able to deliver cargo to the International Space Station with a Falcon 9 rocket. Dragon V1 has total launch payload mass of around 6,000kg (13,228lbs), total launch payload volume of 25 cubic meter, total return payload mass of 3,000kg and 11 cubic meter total return payload volume. Dragon’s trunk supports the spacecraft during ascent to space, carries unpressurized cargo and houses Dragon’s solar arrays. Inside the spacecraft features 3 configurations to meet a variety of purposes: cargo, crew, and DragonLab. The main purpose of Dragon V1 docking the International Space Station is resupplying the space station such as delivery and return services, and versatile cargo packs such as carrying material like biological samples. b. Version 2:
Lately, on May 29, 2014 SpaceX unveiled Dragon V2, which promises to fly crew as well as to be a human-rated capable of making a terrestrial soft landing on the ground instead of water like Dragon V1. Dragon’s first manned test flight is expected to take place in the next 2-3 years. Unlike the unmanned version of the Dragon, which uses the station's robotic arm to berth to the orbiting outpost, Version 2 will be able to autonomously dock to the space station. Furthermore, according the CEO of SpaceX, Ellon Musk, Dragon V2 can be rapidly reusable as the company’s intention of lowering the cost of spaceflight with affordable, reusable technology since 2002. (Ref 12, 15)

VI. Other NASA CCDev Space Act Agreement:
Besides SpaceX, there are 3 other companies, which are part of NASA Commercial Crew Development (CCDev) program. First of all, Boeing introduced CST-100 Space Taxi, which will have an unmanned test flight in January 2017, and a human test flight will follow around mid 2017 if the first one goes well. The CST-100 is designed to transport up to 7 passengers or a mix of crew and cargo to low-Earth orbit destination such as the International Space Station (ISS) and the Bigelow planned station. Second, Dream Chaser is a reusable, crewed suborbital and orbital lifting-body space-plane being developed by Sierra Nevada Corporation. Similar to CST-100, this vehicle is originally designed to carry up to 7 people to and from low Earth orbit. Dream Chaser originally will be launched vertically on a United Launch Alliance (ULA) Atlas V Launch Vehicle. It also has an exceptional crew safety feature such as non-toxic propulsion system, and on-board propulsion system derived from SpaceShipOne and SpaceShipTwo patented hybrid rocket motor technology. Finally, the last company that will be discussed in this paper is Blue Origin. The company’s status is “we’re working to lower the cost of spaceflight”. This company is developing a fully reusable suborbital vehicle called New Shepard. It is expected to fly 3 or more passengers. New Shepard includes a Crew Capsule and a Propulsion Module. Besides suborbital program, Blue Origin is also developing the orbital spacecraft program, which will technically be based on the same reusable launch vehicle technologies pioneered in the company’s suborbital program. Blue Origin calls the orbital spacecraft Bionic Space Vehicle. (Ref 6,16,17,18)

VII. Conclusion:
Generally, the paper will provide an overall picture of the spacecraft industry. The paper addresses and analyzes potential spaceships and their manufacturers to be able to predict the near future of the space tourism. Although some unexpected accidents show the risks and dangers of the space tourism mission, people should still expect a better outcomes since there are many great ideas and inventions being developed to ensure the safety and low-cost of the space tourism future. For example, SpaceX’s Dragon V2 spaceship with its new landing system promisingly allows human being to step closer to the space future, which is only described in the movie until now.

References

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