Difference between revisions of "Space access"

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If colonists are to have access to space, they will need a craft to transport them.
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[[Image:TomsRockets.jpg|thumb|right|300px|A child's fantasy of rockets to Mars and another rocket from Mars to farther space]]
  
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'''Space access''' is the ability for persons to leave a planet's surface. This page is an introduction on basic principles and technology of getting from the Martian surface to an [[orbit]] or into free space.
  
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==Motivation==
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A human [[colony]] on Mars can be established with or without space access. The fight against the gravitational pull requires large amounts of [[energy]]. Since the [[gravity]] of [[Mars]] is smaller than [[Earth]]' and the [[atmosphere]] is thinner, space access is easier. However, the energy resources of such a colony are limited. Using parts of the available energy for space access could be thought to reduce other project's progress.
  
== Requirements ==
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However, space access for a martian settlements also means that there is a way to return the transportation vehicle back to Earth and re-use it.  This will greatly reduce the cost of transportation from Earth to Mars.  This is the [[In-situ resource utilization|In-situ]] ressources paradigm.
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Beyond returning the transportation vehicles back to Earth for re-use, Assuming the colonists went to Mars to stay there and build their own civilization, there still might be some additional tasks to do:
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*Trips to Low Mars Orbit and possible space stations residing there for scientific reasons
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*Trips to [[Phobos]] and [[Deimos]] for scientific and mining reasons.
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*Ferry persons to and from space craft that have arrived from, or are heading for, Earth, or other celestial bodies.  For example, the Mars cycler concept.
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*Possible satellite repair, not a dissimilar task as to what was imagined for the [[space shuttle]] in the 1970's
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==DeltaV and energy==
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The [[w:Delta-v_budget|deltaV]] to orbit for Mars is about 3,8 km/s.  For Earth, taking into account atmospheric friction the deltaV is about 9.3 to 10 km/s. Using the rocket equation Δv=ve*ln(Mo/Mf)  or ''Mo/Mf''= e(Δv/ve) we can see that the mass fraction of propellant to reach orbit is much lower for Mars than for Earth.  For example with Methane and Oxygen propellant, the exhaust velocity (ve) is about 3400m/s, so for Mars the mass ratio is 3, while for Earth it is between 15 and 19.  So it is at least five times easier to leave Mars than it is to leave Earth.
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==Conventional rocket crafts==
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[[File:Starship Mars.jpg|thumb|A SSTO on Mars, the SpaceX Starship is a TSTO on Earth.]]
 
The craft should be:
 
The craft should be:
  
 
*Reusable
 
*Reusable
*Single Stage to [[Orbit]] (SSTA)
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*Single Stage to Orbit (SSTO) ot two stage to orbit (TSTO).
 
*Use propellants that can be obtained from Mars.
 
*Use propellants that can be obtained from Mars.
 
*Able to [[Shared componenting|share components with other machines]]
 
*Able to [[Shared componenting|share components with other machines]]
  
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It has proved very difficult to build an SSTO launcher on Earth, but the lower Martian [[gravity]] would be of assistance to any launching spacecraft. If the craft uses multiple stages, these will all have to be recovered separately, which complicates the process of reuse.  [[SpaceX]] has proposed a combination vehicle that is SSTO on Mars, but TSTO on Earth.  The combination of [[Starship]] and Falcon super heavy, or [[Booster]].
  
== SSTO ==
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Hydrogen, methane and oxygen propellants can be obtained from martian ice. The attitude control thrusters could use gaseous oxygen and methane, kept under pressure.
the craft should have SSTO capability. It has proved very difficult to build an SSTO launcher on Earth, but the lower Martian [[gravity]] would be of assistance to any launching spacecraft. If the craft uses multiple stages, these will all have to be recovered separately, which complicates the process of reuse.
 
 
 
 
 
== Propellant ==
 
Hydrogen and oxygen propellants can be obtained from Martian ice. The attitude control thrusters could use gaseous oxygen and methane, kept under pressure.
 
  
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Early landers will probably be non-reusable or only partially reusable. The descent stages of these landers could be dismantled and reused.
  
== Early landers ==
 
Early landers will probably be non-reusable or only partially reusable. The decent stages of these landers could be dismantled and reused.
 
 
 
== Guidance ==
 
 
The guidance systems on the lander need not be [[hi-tech versus lo-tech|hi-tech]]. The Apollo spacecraft flew to the Moon using less computing power then a pocket calculator. A simple computer, or a [[pneumatics|pneumatic]] system could be used. Although there are advantages with hi-tech systems, lo-tech systems could be included as a backup.
 
The guidance systems on the lander need not be [[hi-tech versus lo-tech|hi-tech]]. The Apollo spacecraft flew to the Moon using less computing power then a pocket calculator. A simple computer, or a [[pneumatics|pneumatic]] system could be used. Although there are advantages with hi-tech systems, lo-tech systems could be included as a backup.
  
== Uses ==
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However, precise landing to a dedicated landing pad would require advanced adaptive control techniques, as otherwise the probable landing area is often measured in tens of km<sup>2</sup>.
Uses for the lander include:
 
Trips to Low Mars Orbit and possible space stations residing there,
 
Trips to Phobos and Deimos
 
Trips to ferry crews to and from space craft that have arrived from, or are headed for, Earth, or other planets.
 
Possible satellite repair, not a dissimilar task as to what was imagined for the space shuttle in the 1970's
 
 
 
==Shuttle==
 
The cost of lifting items from Mars could become considerably less than the cost of lifting them from Earth.  Low Mars orbit, at an altitude of 100 miles, has a velocity of 3440 meters per second, less than half of the velocity needed to orbit Earth at that altitude, more than twice the velocity needed to orbit Luna.  With reusable rockets built on Earth to use liquid methane and liquid oxygen, if the exhaust velocity is 3500 meters per second, there should be 36% of the take-off weight in orbit.  With wings for a [[supersonic in ground effect]] in the 0.1 psi Martian [[atmosphere]], the empty weight should be held to 30% leaving 6% of the take-off weight as cargo. Practicality:
 
 
 
*There seems reason to believe that supersonic in ground effect landing is a significant problem, and that it should yield to the proper effort, resulting in an economic Mars to Low Mars Orbit Shuttle (MTLMOS pronounced metal mos to rhyme with verbose).  Donald Campbell was killed on the 4th of January, 1967 when the "Bluebird K7" racing boat flipped over and disintegrated at a speed greater than 300 mph. <ref> Bluebird K7 article at Wikipedia </ref> The problem seems to have been longitudinal instability when high ground effect lifting forces acted on a center of lift that shifted rapidly with changing attitude. 
 
*This sort of problem is made more difficult by the need to consider the reflection of shock waves in supersonic flight in ground effect.  Such problems were handled successfully when the "Thrust SSC" broke the speed of sound on land during a 15th of October 1997 setting of the world's land speed record.  <ref> http://www.speedace.info/thrust_ssc </ref>  
 
*An ordinary wind tunnel by itself is insufficient for testing craft in supersonic ground effect conditions.  A moving belt of caterpillar like treads on the bottom of the wind tunnel moving as fast as the gas in the wind tunnel could simulate the runway rushing past during landing.  Having a belt of treads that are broad enough and move fast enough for the simulation would be expensive, but not as expensive as doing the testing on Mars.  At least with only 0.1 psi of carbon dioxide needed for a simulation, it would not cost as much as otherwise to fill the wind tunnel with cold carbon dioxide.
 
*Landing at a speed in the neighborhood of 1000 mph (mach 1.9 on Mars) might seem more difficult than the feat accomplished by "Thrust SSC," but moving through only 150th of the gas pressure (100th of the density) more than compensates for the increased speed.  Maintaining lift and orientational stability are the problems for which we have aeronautical engineers, computational aerodynamics, and wind tunnels.
 
  
====Space Elevator====
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==Speculative concepts==
A [[space elevator]] is an interesting alternative both for Luna and Mars. Probably, it allows even more cost reduction.
 
  
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*[[Supersonic in ground effect]] may be used for a winged shuttle even in the thin Martian atmosphere to help reduce costs.
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*A [[space elevator]] is an interesting alternative both for Luna and Mars. Probably, it allows even more cost reduction.  However, Phobos' orbit may intersect the path of a martian space elevator.
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*A [[mass driver]] is powered electrical and requires no chemical propellants. While on Earth this would not work for lifting people to orbit, the conditions of Mars might allow it.  However a mass driver capable of sending payloads into orbit is a large infrastructure.
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*Chemical propellants on Mars will be produced by solar arrays or nuclear reactors, through the electrolysis of water.  So chemical propulsion on Mars is actually electrical in nature.
  
 
==references==  
 
==references==  
<references/>
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<references />
  
[[Category:Transport]]
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[[Category:Settlement Transport Systems]]

Revision as of 20:15, 8 May 2019

A child's fantasy of rockets to Mars and another rocket from Mars to farther space

Space access is the ability for persons to leave a planet's surface. This page is an introduction on basic principles and technology of getting from the Martian surface to an orbit or into free space.

Motivation

A human colony on Mars can be established with or without space access. The fight against the gravitational pull requires large amounts of energy. Since the gravity of Mars is smaller than Earth' and the atmosphere is thinner, space access is easier. However, the energy resources of such a colony are limited. Using parts of the available energy for space access could be thought to reduce other project's progress.

However, space access for a martian settlements also means that there is a way to return the transportation vehicle back to Earth and re-use it. This will greatly reduce the cost of transportation from Earth to Mars. This is the In-situ ressources paradigm.

Beyond returning the transportation vehicles back to Earth for re-use, Assuming the colonists went to Mars to stay there and build their own civilization, there still might be some additional tasks to do:

  • Trips to Low Mars Orbit and possible space stations residing there for scientific reasons
  • Trips to Phobos and Deimos for scientific and mining reasons.
  • Ferry persons to and from space craft that have arrived from, or are heading for, Earth, or other celestial bodies. For example, the Mars cycler concept.
  • Possible satellite repair, not a dissimilar task as to what was imagined for the space shuttle in the 1970's

DeltaV and energy

The deltaV to orbit for Mars is about 3,8 km/s. For Earth, taking into account atmospheric friction the deltaV is about 9.3 to 10 km/s. Using the rocket equation Δv=ve*ln(Mo/Mf) or Mo/Mf= e(Δv/ve) we can see that the mass fraction of propellant to reach orbit is much lower for Mars than for Earth. For example with Methane and Oxygen propellant, the exhaust velocity (ve) is about 3400m/s, so for Mars the mass ratio is 3, while for Earth it is between 15 and 19. So it is at least five times easier to leave Mars than it is to leave Earth.

Conventional rocket crafts

A SSTO on Mars, the SpaceX Starship is a TSTO on Earth.

The craft should be:

It has proved very difficult to build an SSTO launcher on Earth, but the lower Martian gravity would be of assistance to any launching spacecraft. If the craft uses multiple stages, these will all have to be recovered separately, which complicates the process of reuse. SpaceX has proposed a combination vehicle that is SSTO on Mars, but TSTO on Earth. The combination of Starship and Falcon super heavy, or Booster.

Hydrogen, methane and oxygen propellants can be obtained from martian ice. The attitude control thrusters could use gaseous oxygen and methane, kept under pressure.

Early landers will probably be non-reusable or only partially reusable. The descent stages of these landers could be dismantled and reused.

The guidance systems on the lander need not be hi-tech. The Apollo spacecraft flew to the Moon using less computing power then a pocket calculator. A simple computer, or a pneumatic system could be used. Although there are advantages with hi-tech systems, lo-tech systems could be included as a backup.

However, precise landing to a dedicated landing pad would require advanced adaptive control techniques, as otherwise the probable landing area is often measured in tens of km2.

Speculative concepts

  • Supersonic in ground effect may be used for a winged shuttle even in the thin Martian atmosphere to help reduce costs.
  • A space elevator is an interesting alternative both for Luna and Mars. Probably, it allows even more cost reduction. However, Phobos' orbit may intersect the path of a martian space elevator.
  • A mass driver is powered electrical and requires no chemical propellants. While on Earth this would not work for lifting people to orbit, the conditions of Mars might allow it. However a mass driver capable of sending payloads into orbit is a large infrastructure.
  • Chemical propellants on Mars will be produced by solar arrays or nuclear reactors, through the electrolysis of water. So chemical propulsion on Mars is actually electrical in nature.

references