Landing on Mars - Revision history

RichardWSmith: /* The Sky Crane */ This was used successfully.

2024-09-18T09:43:06Z

The Sky Crane: This was used successfully.

Michel Lamontagne at 19:00, 26 June 2023

2023-06-26T19:00:12Z

Michel Lamontagne: /* Why Landing On Mars Is Difficult */

2022-03-02T19:04:16Z

Why Landing On Mars Is Difficult

RichardWSmith: Emphasized the difficulties of soft landing on Mars.

2021-05-14T02:34:41Z

Emphasized the difficulties of soft landing on Mars.

Michel Lamontagne at 13:51, 13 May 2021

2021-05-13T13:51:39Z

Michel Lamontagne at 13:46, 13 May 2021

2021-05-13T13:46:58Z

Michel Lamontagne at 13:45, 13 May 2021

2021-05-13T13:45:51Z

Michel Lamontagne: Clarified and updated

2021-05-13T13:39:05Z

Clarified and updated

Michel Lamontagne at 13:24, 13 May 2021

2021-05-13T13:24:50Z

Michel Lamontagne at 13:21, 13 May 2021

2021-05-13T13:21:08Z

@@ Line 40: / Line 40: @@
 ===The Sky Crane===
-the 2009 Mars Science Laboratory (MSL) rover, weighing 775 kilograms (versus MER at 175.4 kilograms each) requires an entirely new landing architecture. Too massive for airbags, the small-car sized rover will use a landing system dubbed the Sky Crane. "Even though some people laugh when they first see it, my personal view is that the Sky Crane is actually the most elegant system we've come up with yet, and the simplest," said Manning. MSL will use a combination of a rocket-guided entry with a heat shield, a parachute, then thrusters to slow the vehicle even more, followed by a crane-like system that lowers the rover on a cable for a soft landing directly on its wheels. Depending on the success of the Sky Crane with MSL, it's likely that this system can be scaled for larger payloads, but probably not the size needed to land humans on Mars.  (See Ref #1)
+the 2009 Mars Science Laboratory (MSL) rover, weighing 775 kilograms (versus MER at 175.4 kilograms each) requires an entirely new landing architecture. Too massive for airbags, the small-car sized rover used successfully a landing system dubbed the Sky Crane. "Even though some people laugh when they first see it, my personal view is that the Sky Crane is actually the most elegant system we've come up with yet, and the simplest," said Manning. MSL used a combination of a rocket-guided entry with a heat shield, a parachute, then thrusters to slow the vehicle even more, followed by a crane-like system that lowers the rover on a cable for a soft landing directly on its wheels. Given the success of the Sky Crane with MSL, it's likely that this system can be scaled for larger payloads, but probably not the size needed to land humans on Mars.  (See Ref #1)
 ===A Sure Way to Land on Mars===

@@ Line 14: / Line 14: @@
 ===Powered landing===
 An entirely powered landing would be possible for a futuristic high thrust vehicle.  This would require a deltaV of about 4.5-to 6 km/s, close to the deltaV required for liftoff from Mars.  Such a powered landing would be a requirement for an airless body such as the Moon.  However, it makes sense to use the Martian atmosphere to help with deceleration and save on propellant, as in the following proposals.
 ===Large diameter parachutes===
@@ Line 41: / Line 52: @@
 For a rough estimate take as a starting point the estimated terminal velocity for the Apollo reentry vehicle.  Estimate that the square of the terminal velocity is directly proportional to mass and the force of gravity and inversely proportional to air density and cross sectional area.  The 10 metric ton vehicle with a 52 meter diameter heat shield should then have a terminal velocity less than 56 meters per second (125 miles per hour) at Mars' surface.  If near the end of this descent a hole is burst through the bottom of the heat shield in the center right under the payload and hinges swing that portion of the heat shield out of the way, then retro rockets can fire at an altitude of 160 meters for 5.1 seconds with an acceleration of 11 meters per second squared and bring the payload to a stop about 17 meters above the heat shield that crashes into Mars.  A few more seconds for horizontal maneuvering and throttling the rocket motor brings the payload safely to Mars on landing legs.  A guesstimate of the required rocket delta V for this maneuver is about 68 meters per second.
 ==References==

@@ Line 8: / Line 8: @@
 == Why Landing On Mars Is Difficult ==
-It is unusually hard to land on Mars, because of its (relatively) large size and its thin atmosphere.  If Mars had a thick atmosphere, it would be straightforward to land with areobreaking, then parachutes.  If Mars had no atmosphere, there would be no concern about surviving the heat of reentry, you could simply use rockets to land.  But the thin atmosphere is thick enough to require managing the heat of reentry, and rockets are needed to land large craft.  Requiring multiple system for a landing, adds complexity, mass, and increases the chances of failure.
+It is hard to land on Mars because of its large size and its thin atmosphere.  If Mars had a thick atmosphere, it would be straightforward to land with aerobraking, then parachutes, as on Earth or Venus.  If Mars had no atmosphere, there would be no concern about surviving the heat of reentry, you could simply use rockets to land.  But the thin atmosphere is thick enough to require managing the heat of reentry, and rockets are needed to land large craft.  The requirement of multiple system for a landing adds complexity, mass, and increases the chances of failure.
 ==Concepts==

← Older revision		Revision as of 02:34, 14 May 2021
Line 6:		Line 6:

	Supersonic retro-propulsion is the proposed landing method for the Spacex [[Starship]]<ref name=":0" />		Supersonic retro-propulsion is the proposed landing method for the Spacex [[Starship]]<ref name=":0" />
		+
		+	== Why Landing On Mars Is Difficult ==
		+	It is unusually hard to land on Mars, because of its (relatively) large size and its thin atmosphere. If Mars had a thick atmosphere, it would be straightforward to land with areobreaking, then parachutes. If Mars had no atmosphere, there would be no concern about surviving the heat of reentry, you could simply use rockets to land. But the thin atmosphere is thick enough to require managing the heat of reentry, and rockets are needed to land large craft. Requiring multiple system for a landing, adds complexity, mass, and increases the chances of failure.
		+
	==Concepts==		==Concepts==

@@ Line 1: / Line 1: @@
-A typical mission to land on Mars consists of atmospheric entry phase using an aeroshell, a parachute descent phase, a terminal descent phase, and ends with the spacecraft touching down somewhere within a predetermined [[Landing Ellipse|landing ellipse]]. The spacecraft can enter the atmosphere either directly from the [[Earth-Mars_Transfer_Trajectory|Earth-Mars transfer orbit]] or it can descend after first being captured into Mars orbit. The parachute descent phase begins in the supersonic flight regime and normally utilizes ring-sail or disk-gap-band supersonic parachute. The terminal descent phase has been achieved with retrorockets and lanyards/skycranes, and spacecraft have been cushioned on touchdown with foam and airbags.
+A typical mission to land on Mars consists of atmospheric entry phase using an aeroshell, a parachute descent phase, a terminal descent phase and ends with the spacecraft touching down somewhere within a predetermined [[Landing Ellipse|landing ellipse]]. The spacecraft can enter the atmosphere either directly from the [[Earth-Mars_Transfer_Trajectory|Earth-Mars transfer orbit]] or it can descend after first being captured into Mars orbit. The parachute descent phase begins in the supersonic flight regime and normally utilizes ring-sail or disk-gap-band supersonic parachute. The terminal descent phase has been achieved with retrorockets and lanyards/skycranes, and spacecraft have been cushioned on touchdown with foam and airbags.
 To date there have been 11 successful soft landings: Mars 3, Vikings 1 and 2, Pathfinder, Beagle 2, MER A and B (Spirit and Opportunity), Phoenix, MSL (Curiosity),  InSight and Perseverance. Mars 3 and Beagle 2 have been declared as successful soft landings though the spacecraft did not operate correctly once on the surface. There have been 4 failed landing attempts: Mars 2, Mars 6, Mars Polar Lander, and the Schiaparelli EDM lander.
@@ Line 8: / Line 8: @@
 ==Concepts==
-=== Powered landing ===
+===Powered landing===
 An entirely powered landing would be possible for a futuristic high thrust vehicle.  This would require a deltaV of about 4.5-to 6 km/s, close to the deltaV required for liftoff from Mars.  Such a powered landing would be a requirement for an airless body such as the Moon.  However, it makes sense to use the Martian atmosphere to help with deceleration and save on propellant, as in the following proposals.
@@ Line 41: / Line 41: @@
 #An initial speed reduction using aerodynamic breaking in the upper Martian atmosphere.
-#Retro propulsion in the supersonic flight regime is used to slow the vehicle during part of the flight path.  This element of the flight path compensates for the low Martian atmospheric density, that otherwise would be insufficient to slow down the vehicle adequately, leading to a high velocity crash on the surface.<ref>Older simulation of the flight path, SpaceX: https://www.youtube.com/watch?v=LQTnWEHl5qU</ref>
+#Retro propulsion in the supersonic flight regime is used to slow the vehicle during part of the flight path.  This element of the flight path compensates for the low Martian atmospheric density, that otherwise would be insufficient to slow down the vehicle adequately, preventing a high velocity crash on the surface.<ref>Older simulation of the flight path, SpaceX: https://www.youtube.com/watch?v=LQTnWEHl5qU</ref>
 #More aerodynamic breaking and conventional retro propulsion is used to land.
-#Precise landing within a few meters of target (rather than km sized approximations) using the capability of very precise landing developed by SpaceX for landing on Earth, that could be transposed to Mars.
+#Precise landing within a few meters of target (rather than a km sized landing ellipse) using the capability of very precise landing developed by SpaceX for landing on Earth that could be transposed to Mars.
-This flight trajectory provides the capability of landing very large payloads on Mars, in the hundreds of tonnes. The required retro propulsive deltaV depends on the entry velocity.  the SpaceX simulations show that the deltaV might be as low as 1% of the entry speed, or 75 m/s.  A tiny fraction of the deltaV required for an entirely powered landing.
+This flight trajectory provides the capability of landing very large payloads on Mars, in the hundreds of tonnes. The required retro propulsive deltaV depends on the entry velocity.  The SpaceX simulations show that the deltaV might be as low as 1% of the entry speed, or 75 m/s, a tiny fraction of the deltaV required for an entirely powered landing.
 ==References==

@@ Line 5: / Line 5: @@
 Wind tunnels, rocket sleds, and drop tests have been used to test equipment for entry, descent, and landing. Work continues on new technology such as supersonic retropropulsion, ballutes, low-density-supersonic-decelerators (and other expandable entry shields), biconic heat shields (and other entry vehicle shapes), and new ablative or non-ablative heat shield materials.
+Supersonic retro-propulsion is the proposed landing method for the Spacex [[Starship]]<ref name=":0" />
 ==Concepts==
@@ Line 35: / Line 35: @@
 ===Supersonic retro-propulsion landing===
-SpaceX and NASA have proposed supersonic retro-propulsive landing as a method to land large payloads on Mars.<ref>https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170008725.pdf</ref>  SpaceX will be using supersonic retro propulsive landing for [[Starship]] and has done simulations of the landing path<ref>https://www.spacex.com/vehicles/starship/</ref>.  This method has been tested and validated on Earth, using SpaceX Falcon 9 first stages in the high atmosphere to simulate Martian conditions.  The flight path is a follows:
+SpaceX and NASA have proposed supersonic retro-propulsive landing as a method to land large payloads on Mars.<ref>https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170008725.pdf</ref>  SpaceX will be using supersonic retro propulsive landing for [[Starship]] and has done simulations of the landing path<ref name=":0">Simulation of the Starship flight path: https://youtu.be/5seefpjMQJI</ref>.  This method has been tested and validated on Earth, using SpaceX Falcon 9 first stages in the high atmosphere to simulate Martian conditions.  The flight path is a follows:
 #An initial speed reduction using aerodynamic breaking in the upper Martian atmosphere.
-#Retro propulsion in the supersonic flight regime is used to support and slow the vehicle during part of the flight path.  This element of the flight path compensates for the low Martian atmospheric density, that otherwise would be insufficient to slow down the vehicle adequately, leading to a high velocity crash on the surface.<ref>Youtube video of Mars landing, SpaceX https://www.youtube.com/watch?v=LQTnWEHl5qU</ref>
+#Retro propulsion in the supersonic flight regime is used to support and slow the vehicle during part of the flight path.  This element of the flight path compensates for the low Martian atmospheric density, that otherwise would be insufficient to slow down the vehicle adequately, leading to a high velocity crash on the surface.<ref>Older simulation of the flight path, SpaceX: https://www.youtube.com/watch?v=LQTnWEHl5qU</ref>
 #More aerodynamic breaking and conventional retro propulsion is used to land.
 #Precise landing within a few meters of target (rather than km sized approximations) using the capability of very precise landing developed by SpaceX for landing on Earth, that could be transposed to Mars.