NewMarsWiki - User contributions [en]

Twin-stage to orbit

2009-12-10T14:53:29Z

Terraformer:

A twin stage to orbit craft (TSTO), also called two stage to orbit or dual stage to orbit, is a method of spacecraft launch that involves two stages, as opposed to a [[single stage to orbit]] or traditional multi stage rockets, which use 3 or more stages. It has been proposed as a means of creating an RLV ([[Reuasable launch vehicle]]) while avoiding the constraints which have doomed attempts at single stage to orbit spacecraft to date.

=First stage=

The first stage, given that it generates a lower [[delta-V]] and reenters at a much lower velocity, can be built to a lower perfomance than the upper stage, and is much easier to make reusable. Because of this, some ideas propose using a reusable lower stage coupled with an expedeble upper stage. This would be easier to achive on a HOTOL craft, although some designs call for a vertical flight profile instead

Due to the environment the lower stage flies in, and it's requirements, [[Ramjets]] become a practical suggestion. While current Ramjets cannot generate the required speeds to reach orbit, they can get the craft to around Mach 6. Coupled with onboard rocket mototrs, required for boosting the ramjet to start speed regardless of whether they are used later, such a craft may be capable of reaching Mach 10 with a modest [[mass ratio]].

=Upper stage=

The upper stage adds the remaining velocity to the payload to send it into orbit. Depending on the velocity added by the lower stage, the requirements can range from being a near-SSTO to merely existing to circularize the orbit. Due to the lack of air, it must carry all it's fuel and oxidiser onboard. Some have proposed using a [[Nuclear thermal rocket]] to generate the required delta-V, as the extreme altitdue to attenuate any radioactive material which escapes from the exhaust.

=Existing TSTO designs=

The [[DH-1]] - from ''The Rocket Company''
Spacecab and Spacebus - Bristol Spaceplanes
K1 launch vehicle - Rocketplane Kisler

=See also=

[[Single stage to orbit]]
[[Reusable launch vehicle]]

Twin-stage to orbit

2009-12-10T14:52:23Z

Terraformer: New page: A twin stage to orbit craft (TSTO), also called two stage to orbit or dual stage to orbit, is a method of spacecraft launch that involves two stages, as opposed to a [single stage to orbit...

A twin stage to orbit craft (TSTO), also called two stage to orbit or dual stage to orbit, is a method of spacecraft launch that involves two stages, as opposed to a [single stage to orbit] or traditional multi stage rockets, which use 3 or more stages. It has been proposed as a means of creating an RLV ([Reuasable launch vehicle]) while avoiding the constraints which have doomed attempts at single stage to orbit spacecraft to date.

=First stage=

The first stage, given that it generates a lower [delta-V] and reenters at a much lower velocity, can be built to a lower perfomance than the upper stage, and is much easier to make reusable. Because of this, some ideas propose using a reusable lower stage coupled with an expedeble upper stage. This would be easier to achive on a HOTOL craft, although some designs call for a vertical flight profile instead

Due to the environment the lower stage flies in, and it's requirements, [Ramjets] become a practical suggestion. While current Ramjets cannot generate the required speeds to reach orbit, they can get the craft to around Mach 6. Coupled with onboard rocket mototrs, required for boosting the ramjet to start speed regardless of whether they are used later, such a craft may be capable of reaching Mach 10 with a modest [mass ratio].

=Upper stage=

The upper stage adds the remaining velocity to the payload to send it into orbit. Depending on the velocity added by the lower stage, the requirements can range from being a near-SSTO to merely existing to circularize the orbit. Due to the lack of air, it must carry all it's fuel and oxidiser onboard. Some have proposed using a [Nuclear thermal rocket] to generate the required delta-V, as the extreme altitdue to attenuate any radioactive material which escapes from the exhaust.

=Existing TSTO designs=

The [DH-1] - from ''The Rocket Company''
Spacecab and Spacebus - Bristol Spaceplanes
K1 launch vehicle - Rocketplane Kisler

=See also=

[Single stage to orbit]

Airship to Orbit

2009-08-14T12:39:37Z

Terraformer: /* Criticism and Potential Theoretical Limitations */

Airship To Orbit (ATO) is a launch scheme proposed by JP Aerospace. It is a means of employing fuel efficient electric rocket propulsion, rather than conventional rocket propulsion, through use of an airship-derived launch vehicle instead of a missile-derived launch vehicle.

==Component Vehicles==

[[JP Aerospace]]'s Airship to Orbit architecture for orbital launches consists of three steps, each performed by a different vehicle: an airship, an aerostatic platform, and an airship-derived spacecraft.

===The Ascender===

[[Image:Ascender3.jpg|thumbnail]]

This is a photograph of JP Aerospace's Ascender 175 prototype during a float test.

In the first step of the ascent, an Ascender airship carries a payload to mesospheric altitudes, where it docks with an aerostatic platform called a Dark Sky Station (DSS).

===The Dark Sky Station===

[[Image:Dss_block3.jpg|thumbnail]]

This is a CAD drawing of a full-sized Dark Sky Station large enough to support Airship to Orbit operations.

The DSS acts as a transfer point between the Ascender airship and Orbital Ascender, as well as a dock for the OAV. The Ascender cannot be built sufficiently lightweight for an ascent to orbit, and the Orbital Ascender must be too lightly built to survive a descent through the lower atmosphere. Thus, they need to either dock directly or have a service station to meet their needs. JP Aerospace, developing the system incrementally, has opted to create a DSS as a service station for the two, as the DSS can be employed for other purposes before an Orbital Ascender is built. Also, the DSS can serve as a testbed for components and techniques used to build the Orbital Ascender, and is arguably the most convenient place for final assembly of an Orbital Ascender.

The planned final version of the DSS is expected to be on the order of two kilometers across. This is large enough to enable it to carry a massive payload, such as a manned platform, a factory, and/or an entire unassembled Orbital Ascender. The large size of the DSS (greater than the largest balloons launched to date) can be achieved by using a multiple-cell construction and conducting final assembly at altitude. It is possible because of the non-turbulent behavior of upper level winds.

===The Orbital Ascender===

[[Image:Transatmospheric.jpg|thumbnail]]

This is a CAD drawing of a sub-orbital prototype of the Orbital Ascender.

The Orbital Ascender completes the final step of the orbital launch. It is an airship-derived spacecraft. It flies horizontally like an airship, powered by a low thrust reaction drive such as an electric rocket engine. It will employ bouyancy and aerodynamic lift at the beginning of its flight rather than the high vertical thrust of conventional missile-derived launch vehicles. Taking advantage of the rapid variation in atmospheric properties at mesospheric and thermospheric altitudes, it will be able to maintain sufficient horizontal velocity to provide aerodynamic lift all the way up to orbit.

Because of its low density, the Orbital Ascender is capable of relatively smooth re-entry as well, enabling it to act as a re-usable vehicle.

==Criticism and Potential Theoretical Limitations==

There are several legitimate criticisms of the Airship to Orbit scheme which have not yet been satisfactorily answered by JP Aerospace. For example:

The thin air at the Orbital AscenderÃ¢ÂÂs altitude provides little damping of lateral motions, and may make that vehicle subject to damaging chaotic dynamic effects. The vehicles themselves may yet prove impractical to build and operate, being too light to withstand the stresses involved.

Operation of a vehicle which is constructed mainly of plastics promises to be problematic at hypersonic speeds (where aerodynamic energy begins to be transferred into ionizing the incident gases Ã¢ÂÂ and vaporizing plastic). The Orbital AscenderÃ¢ÂÂs heat transfer characteristics will be daunting, if they can be dealt with at all. There may be the possiblity of depositing a thin layer of metal on the skin of the craft, to reduce this, but the metal could ablate as well.

And the low buoyancy available at its intended launch altitude suggests that the Orbital AscenderÃ¢ÂÂs allowed launch weight will be substantially less than that of the proposed DSS. Even if it works, itÃ¢ÂÂs payload to orbit may be too small to make it a profitable system.

All of these issues must be dealt with in order to yield a practical ATO design. However, taken individually, none of them is physically impossible to resolve. The ATO system is still at an early stage of development, and its design is clearly still in a state of flux. Later changes to deal with these issues are highly probable.

JP Aerospace regards their Airship To Orbit designs as trade secrets, and have deliberately tried to obfuscate aspects which they regard as proprietary. This has allowed unsubstantiated claims about their designs to flourish. Elementary engineering errors have been alleged by some critics, and JP Aerospace has not definitively refuted any of these claims beyond simple denial.

Some alleged design errors which JP Aerospace has refused to address even by denial are quite telling, to the point where it is reasonable to speculate that the organizationÃ¢ÂÂs silence on these issues is deliberate. Given the organizationÃ¢ÂÂs otherwise eager attempts at promoting their project, they may have one of two motives. Either the alleged oversights are real, or the answers to the allegations would provide unwanted insight into the nature of their proposed system.

==New Mars Forum Discussions==

[http://www.newmars.com/forums/viewtopic.php?t=1851 Calling our technical experts - Any chance this thing works?]

[http://www.newmars.com/forums/viewtopic.php?t=3509 Dirigibles on Mars - A practical means of transport?] (Related Discussion)

[http://www.newmars.com/forums/viewtopic.php?t=2483 Solar Thermal Ground to Orbit - Solar Thermal Tech to launch] (Related Discussion)

== External Links ==

[http://www.jpaerospace.com/ JP Aerospace Home Page]

[http://en.wikipedia.org/wiki/Orbital_airship Wikipedia 'Orbital Airship' Article]

[http://www.spacefellowship.com/Forum/forum-25.html&sid=584ad19e255deb85b6da70213be20b8d Space Fellowship's JP Aerospace Forum]

[http://www.cruiser.ru/eng/releases.php Proposed Russian ATO Knock-off] (Translated Article)

[http://www.astronautix.com/ Encyclopedia Astronautica]

[[category:Spacecraft and Launch Vehicles]]

Single-stage to orbit

2009-07-19T21:17:50Z

Terraformer: /* Propane/LOX */

[[Image:DC-XA.jpg|thumb|200px|right|DC-XA Test Flight 2]]
A single-stage to orbit vehicle is one that must reach orbit with just one [[Stage (Rocket)|stage]]. Up to this date, no functional vehicle has been built, only technology demonstrators.

The idea behind SSTO was to reduce high costs by building a large reusable vehicle, thus reducing the complexity of the vehicle and its maintenance. But this has a big disadvantage: the vehicle needs to lift its entire structure into space, a problem that multi-staged rockets don't have. But, with the advances in composite materials, building a fully functional SSTO seems feasible.

=Fuel/Oxidiser=

Because of the way it is built, a paradox appears: contrary to most rockets, for a SSTO a dense fuel (kerosene or propane for example) it's more performant than liquid hydrogen. This happens because dense fuels can be stored at room temperature (no need for insulation), and have a higher density. Thus, the mass of the fuel itself might be high enough compared to the mass of the tank and insulation to make it more efficient.

The efficiency of the fuel being critical for a SSTO, it can be further increased by using a better oxidizer, like [[Ozone|ozone]] (O3) or [[Tetraoxygen|tetraoxygen]] (O4).

Hydrogen Peroxide has been proposed as an oxidiser for SSTOs, due to it's storability.

==LH2/LOX==

This is the classic combination suggested for SSTOs, due to it's high [[specific impulse]]. However, it suffers from issues with storage (it is a low temperature cryogen), requiring heavy storage tanks. Compounding this problem is it's low density, meaning the tanks have to be much larger to contain the same mass of fuel as a denser fuel suchj as Kerosene or Propane.

==Methane/LOX==

The lightest of the Hydrocarbons, Methane possesses certain advantages over Hydrogen which make it an attractive fuel choice. It is much denser, meaning tank size (and so weight) can be lower. Due to it's similar boiling point to LOX, it does not need to be as insulated, eliminating the need for a bulkhead between the Methane and Oxygen tanks.

==Propane/LOX==

Propane is a denser fuel than Methane, reducing tank mass further. It's melting point is near to the boiling point of LOX, so they can be stored near the same temperature. This has the advantage of improving the density of the Propane.

==Aluminum/LOX==

Aluminum/LOX monopropellent has been proposed as a potential fuel for an SSTO. While having a low Isp (285s), it has an exceptionally high density, of 1.69g/cc. Due to it being a monopropellent, the operation is simplified, improving safety and reliability.

=Engine=

A problem with a SSTO vehicle is that it needs to use a single engine for all altitudes. The engine must have different bell shapes depending on altitude, otherwise it won't have high efficiency. Multi-staged launch vehicles don't have this problem because the bell shape of the engines on each stage is adapted to the altitude they work in. The current solution to this problem seems to be using an [[Aerospike engine|aerospike engine]].

=Prototypes and demonstrators=

* [[JAXA]]'s on-going experiments with a sub-scale SSTO craft, the Reusable Test Vehicule or [[RVT]]
* [[DC-X|McDonnell Douglas DC-X]] - cancelled
* [[X-33|Lockheed Martin X-33]] - cancelled
* [[Roton]] - cancelled
* ISROs Avatar spaceplane - in development

=SSTO on other planetary bodies=

==Luna==

The Lunar Ascent Module used during the Apollo missions was an expendable SSTO, as it could take off from the Luna surface and reach orbit within a single stage.

==Mars==
For future pioneers of Mars, using a SSTO for orbital access is probably the best design. Such a vehicle would be fully reusable, easy to maintain and operate. Because of the lower Marsian gravity, it should be more efficient than on Earth. Also, because of the much lower atmospheric pressure on Mars, it should be easier to design an efficient bell shape for the engine. It may be possible for an early colony to fabricate an SSTO themselves, although without the payload ratios one imported from Terra would have, but probably still enough for the needs of the colony.

Methane (a denser fuel than hydrogen) could be easily produced by [[Sabatier reaction]].

[[Category:Spacecraft and Launch Vehicles]]

Single-stage to orbit

2009-07-19T21:13:28Z

Terraformer: /* Fuel */

[[Image:DC-XA.jpg|thumb|200px|right|DC-XA Test Flight 2]]
A single-stage to orbit vehicle is one that must reach orbit with just one [[Stage (Rocket)|stage]]. Up to this date, no functional vehicle has been built, only technology demonstrators.

The idea behind SSTO was to reduce high costs by building a large reusable vehicle, thus reducing the complexity of the vehicle and its maintenance. But this has a big disadvantage: the vehicle needs to lift its entire structure into space, a problem that multi-staged rockets don't have. But, with the advances in composite materials, building a fully functional SSTO seems feasible.

=Fuel/Oxidiser=

Because of the way it is built, a paradox appears: contrary to most rockets, for a SSTO a dense fuel (kerosene or propane for example) it's more performant than liquid hydrogen. This happens because dense fuels can be stored at room temperature (no need for insulation), and have a higher density. Thus, the mass of the fuel itself might be high enough compared to the mass of the tank and insulation to make it more efficient.

The efficiency of the fuel being critical for a SSTO, it can be further increased by using a better oxidizer, like [[Ozone|ozone]] (O3) or [[Tetraoxygen|tetraoxygen]] (O4).

Hydrogen Peroxide has been proposed as an oxidiser for SSTOs, due to it's storability.

==LH2/LOX==

This is the classic combination suggested for SSTOs, due to it's high [[specific impulse]]. However, it suffers from issues with storage (it is a low temperature cryogen), requiring heavy storage tanks. Compounding this problem is it's low density, meaning the tanks have to be much larger to contain the same mass of fuel as a denser fuel suchj as Kerosene or Propane.

==Methane/LOX==

The lightest of the Hydrocarbons, Methane possesses certain advantages over Hydrogen which make it an attractive fuel choice. It is much denser, meaning tank size (and so weight) can be lower. Due to it's similar boiling point to LOX, it does not need to be as insulated, eliminating the need for a bulkhead between the Methane and Oxygen tanks.

==Propane/LOX==

Propane is a denser fuel than Methane, reducing tank mass further. It's melting point is near to the boiling point of LOX, so they can be stored near the same temperature. This has the advantage of improving the density of the Propane.

=Engine=

A problem with a SSTO vehicle is that it needs to use a single engine for all altitudes. The engine must have different bell shapes depending on altitude, otherwise it won't have high efficiency. Multi-staged launch vehicles don't have this problem because the bell shape of the engines on each stage is adapted to the altitude they work in. The current solution to this problem seems to be using an [[Aerospike engine|aerospike engine]].

=Prototypes and demonstrators=

* [[JAXA]]'s on-going experiments with a sub-scale SSTO craft, the Reusable Test Vehicule or [[RVT]]
* [[DC-X|McDonnell Douglas DC-X]] - cancelled
* [[X-33|Lockheed Martin X-33]] - cancelled
* [[Roton]] - cancelled
* ISROs Avatar spaceplane - in development

=SSTO on other planetary bodies=

==Luna==

The Lunar Ascent Module used during the Apollo missions was an expendable SSTO, as it could take off from the Luna surface and reach orbit within a single stage.

==Mars==
For future pioneers of Mars, using a SSTO for orbital access is probably the best design. Such a vehicle would be fully reusable, easy to maintain and operate. Because of the lower Marsian gravity, it should be more efficient than on Earth. Also, because of the much lower atmospheric pressure on Mars, it should be easier to design an efficient bell shape for the engine. It may be possible for an early colony to fabricate an SSTO themselves, although without the payload ratios one imported from Terra would have, but probably still enough for the needs of the colony.

Methane (a denser fuel than hydrogen) could be easily produced by [[Sabatier reaction]].

[[Category:Spacecraft and Launch Vehicles]]

Single-stage to orbit

2009-07-19T20:59:52Z

Terraformer: