Venus Landers

v0.2 - 25-04-2020

Venus missions

Venus, the second planet from the sun, is a planet that has seen some Russian hardware land on its surface. Some of these missions included a surface lander element. The surface pressure of Venus is about 90 times higher than on Earth. This means that landers slow down significantly due to atmospheric drag. The Russian Venera 9 mission only used a heat shield, which was sufficient to slow down to about 9 m/s ensuring a safe landing. The ring used for deceleration can be seen in the picture on the right. A crushable structure was used to absorb the final kinetic energy of the spacecraft.  


The Vega 1 and 2 missions did use parachutes on Venus. Both missions consisted of a fly-by of Venus, a surface lander and a balloon. The lander and balloon were released after which the entry vehicle would be decelerated by parachute. The entry vehicle broke into the lander and balloon part. The lander had its own parachute system for a safe landing. The balloon inflated during the parachute flight and went its own way. 


mock up of Venera 9

Venera 9

Venera 3

Operator: Soviet Union

Target:   Venus

Landing date:  01-03-1966

Status:  Completed


In 1962, the USSR made two attempts to launch an atmospheric probe to the planet Venus with the 2MV-1 No.1 (Sputnik 19) and 2MV-1 No.2 (Sputnik 20) probes. Both failed to reach a transfer to Venus and re-entered back to Earth.


 It was on the first of March 1966 that Venera-3 became the first probe to enter another planet’s atmosphere. The Venera-3 probe had a parachute on board, in order to decelerate itself during the descent on Venus.  However, all contact with the probe was lost before it entered the Venusian atmosphere. [107]

One week after the launch of Venera-3, another atmospheric probe, 3MV-4 No.6 (Kosmos 96), was launched towards Venus. Due to a propulsion system malfunction, the probe never left Earth’s orbit.


Venera 4

Operator: Soviet Union

Target:   Venus

Landing date:  18-10-1967

Status:  Completed


After the flights of Venera-3 and 3MV-4 No.6, a new Venus probe was launched by the Soviet Union, called Venera-4, which had to transmit data about the planet’s atmosphere and surface. This probe was the first to successfully transmit data from inside the atmosphere of a different planet. Even though it didn’t reach the surface of Venus, it did manage to transmit valuable data from Venus’ atmosphere. It was found that the atmospheric density and pressure at Venus’ surface were much higher than expected, causing the capsule to collapse prematurely. [108]


The Venera-4 vehicle was similar to that of the Venera-3: spherical in shape with a diameter of roughly 1 meter. The high reentry velocities and steep descent profile caused a maximum deceleration of roughly 300 g and the atmosphere in front of the vehicle heated up to temperatures above 11,000 degrees. After the major heating phase has passed, a drogue parachute was deployed to further slow down the capsule, followed by a single main parachute. Both parachutes were made from materials that are able to withstand temperatures of 450°C, in order to deal with the harsh atmospheric conditions on Venus. The parachute had a very unique shape, featuring a circular canopy with rectangular cut-outs.


Mock up of Venera 4

Mock up of Venera 4


The probe’s batteries were designed to only last for 100 minutes after separation from the transfer vehicle, which was thought to be sufficient to take measurements from the atmosphere and surface. Because there was a chance the capsule would land in a liquid, a sugar lock was installed that would  [107][108]


Venera 5 and 6

Operator: Soviet Union

Target:   Venus

Landing date: 16-05-1969 and 17-05-1969

Status:  Completed


The Venera 5 and 6 probes were already well designed by the time that Venera-4 was crushed by the Venusian atmosphere. The engineers made the necessary adjustment to make sure the probes could survive the high pressure, however, a full redesign was not feasible before the launch window. Hence the Venera 5 and 6 probes also became atmospheric probes, while a surface landing had to be postponed to Venera 7. [107]


The capsule and parachute system of Venera 5 and 6 was very similar to that of Venera 4 with several changes to increase the scientific value of the mission. The capsule shell was made stronger, more accurate scientific instruments were carried along, and the parachutes were smaller to allow for a deeper descent until the batteries ran out. Both probes continued transmitting data for more than 50 minutes until reaching an altitude of about 20 km when they were crushed by the dense atmosphere. [107][109]


The parachute of Venera 5 and 6 in the wind tunnel

Parachute of Venera in the wind tunnel

Venera 7

Operator: Soviet Union

Target:   Venus

Landing date: 1970

Status:  Succesful


After Venera 4, 5, and 6 failed to reach the surface, the USSR created Venera 7 with the data gathered from the previous mission to ensure it would reach the surface. So to land Venera 7 on the surface of Venus, they created a 490 kg egg-shaped entry capsule made out of titanium and designed to withstand 540 deg C and 180 bar for at least 90 minutes. Furthermore, to extend the lifetime, they pre-cooled the capsule to -8 Celcius.


The goal of Venera 7 was to reach the surface as fast as possible and gather data from the surface before the lifetime of the probe was at an end. In order to do this, they used the unique circumstances of the Venus atmosphere as a part of their entry system. Venera had only one parachute, which would be reefed. Right after deployment, the parachute would be 1.8 m2 and be limited to fully opened by a line wrapped around the shroud lines. This reefing line had a maximum temperature limit of 200 C, well below the temperature, the probe would encounter. So once the temperatures reached 200 C, the reefing line would fail, and the parachute would increase to its final landing size of 2.5 m2.


However, the actual flight was nothing as smooth as it was designed to be. Six minutes after the reefing cord melted away, the parachute ripped, and a few minutes before landing, it ripped away completely. The capsule hit the surface with 16.5 m/s. After some issues recognising the signal because Venera 7, due to the parachute failure, had landed with an antenna pointing in the wrong direction, returned data back to Earth. With this, Venera 7 became the first human-made object to transmit data from another planet's surface. [111, 113]


Venera7_2
Venera7_2
Venera 7 descent capsule
Venera7_1
Venera7_1
Venera 7 entry vehicle: A. Antenna; B. Parachute; C. Top hatch release bolt; D. Internal heat shield; E. Insulating layers; F. Instrument commutator; G. Pressure shell; H. Shock damper; J. Transmitter; K. Spacecraft adaptor.

The Venera 7 descent capsule

Venera 8

Operator: Soviet Union

Target:   Venus

Landing date: 1972

Status:  Succesful


With the data and flight from Venera 7, NPO Lavochkin could update the design. Venera 8's pressure design limits were decreased from 180 bar to 105 bar as Venera 7 measured a maximum pressure of 92 bar at the surface. This, combined with keeping the same size as the entry vehicle, meant the resulting structure became lighter. That freed-up mass was used to upgrade the parachute system, keeping the same size but increasing the strength and adding a pilot chute. With the remaining available mass extra scientific instruments were added. Also, because Venera 7 landed in the wrong orientation after its parachute failure, a redundant antenna was added which would deploy before landing, creating a good line of sight. [111,112,113]


Venera8_2
Venera8_2
Venera 8 probe diagram: 1. Parachute housing cover; 2. Pilot chute; 3. Main parachute; 4. Deployable radio altimeter antenna; 5. Heat exchanger; 6. Heat accumulator; 7. Internal thermal insulation; 8. Program timing unit; 9. Heat accumulator; 10. Shock absorber; 11. External insulation unit; 12. Transmitter; 13. Pressurised Sphere; 14. Commutation unit; 15. Fan; 16. Cooling unit conduit from carrier; 17. Deployable secondary antenna; 18. Parachute housing; 19. Primary antenna; 20. Electrical umb
Venera8_1
Venera8_1
Depiction of Venera 8 deployed on the surface with the ejected parachute and deployed the second antenna

The Venera 8 descent capsule

Venera 9 and 10

Operator: Soviet Union

Target:   Venus

Landing date: October 1975

Status:  Succesful

Shortly before their arrival at Venus, the landing vehicles separated from their spacecraft. The latter entered orbit around Venus, and were thereby the first satellites to do so. The spherical reentry modules entered the Venusian atmosphere at a velocity of 10.7 km/s and experienced peak deceleration of about 170 g. An ablative thermal protection system handled all the thermal loads associated with the atmospheric entry. At an altitude of 65 km, a 2.8 meter wide drogue chute was deployed with the help of a smaller pilot chute. After sufficient deceleration and removal of the top aeroshell, a so-called ‘drag parachute’ was deployed that further decreased the vehicle’s velocity. This parachute had a diameter of 4.2 meters. When reaching an altitude of 62 km, a cluster of three large parachutes was deployed that allowed for a slow descent through Venus’ cloud layer. These three parachutes each had a surface area of 60 m². Below 50 km, all parachutes were cut loose from the probe to guarantee that it would reach the ground before it would succumb to the harsh environmental conditions. The lander was equipped with a circular metal plate that acted as an aerodynamic decelerator. The combination of the dense atmosphere and a shock-absorbing landing ring allowed for a soft touch-down on the surface, where the probes sent back the first footage from the surface of Venus. For both capsules, it took about 75 minutes to reach the ground after atmospheric entry. [126][127]

The extremely hostile environment of Venus required the engineers at NPO Lavochkin to come up with some very unconventional and unique design choices. Not only was there a need for 6 parachutes, but additionally a very unique thermal control system had to be implemented. Multiple measures were taken to maximize the lander’s survivability in the hot atmosphere: a thick insulation layer, pre-cooling of the capsule, active heat distribution, and a lithium salt heat sink. These measures proved to be sufficient as they allowed the probes to send all the necessary data back to Earth by relaying them via their orbiting satellites. Data reception ceased when the orbiter of each lander moved out of sight after 53 and 65 minutes for Venera 9 and 10 respectively. Therefore it is unknown exactly how long each vehicle survived after landing. [126][127]

Vernera 9 ad 10 EDL sequence
Vernera 9 and 10 in the aeroshell

The Venera probe in it's shell (top) and the Venera 9 and 10 EDL sequence (bottom)


After the successful landing of the previous Venera probes, the engineers at NPO Lavochkin were tasked to design the next generation of Venus landers that would be able of taking more detailed measurements from the surface and even take pictures. The lessons learned from the Soviet Mars program were implemented into the new Venera design, resulting in a 1560 kg heavy, spherical reentry vehicle, containing a 660 kg lander. Two such probes were launched with a Proton rocket from Baikonur on the 8th of June 1975, and on the 14th of June 1975, called Venera 9 (4V1 No.660) and Venera 10 (4V1 No.661) respectively. [127]

Venera 11 and 12

Operator: Soviet Union

Target:   Venus

Landing date: December 1978

Status:  Succesful


Following in the footsteps of the very successful Venera 9 and 10 missions, the Soviets decided to stick with the proven concept and changed little to the lander design. The carrier spacecraft also did not change much, but because the 1978 launch window was less favourable they could not enter orbit at Venus and instead relayed the landers’ signals from a flyby trajectory before continuing on into a heliocentric orbit.

The most notable design flaw in the previous design had been the pyrotechnic lens caps on each lander’s two panoramic cameras. Both Venera 9 and 10 only managed to deploy one of their two lens caps each, and as a result, could only transmit half of the intended 360-degree view. Sadly, the redesigned lens caps on Venera 11 and 12 did not improve matters, and all lens caps failed to separate as a result, leaving the 1978 programme without surface photography.

The EDL system was somewhat simplified with respect to the previous design, with their two supersonic drogues replaced by a single one, and likewise the three main parachutes being replaced by a single one. The mass that this freed up was used for additional science experiments and improvements to the ones already carried.

Apart from the failure of the cameras and some of the surface science experiments, both missions were successful. Venera 9 continued to transmit from the surface for 95 minutes, and Venera 10 was still operational when its carrier spacecraft passed below the horizon 110 minutes after its landing. Both flyby spacecraft continued operating in heliocentric orbits until early 1980. [128]


Pioneer 13

Operator: USA

Target:   Venus

Landing date: 1978

Status:  Succesful


Launched about 2.5 months after the Pioneer Venus 1, the pioneer Venus 2, as opposed to its predecessor, had four probes on board and was not designed to orbit Venus but to enter the Venus atmosphere. The goal was to release these probes and study the Venus atmosphere while the bus would burn up in the atmosphere.

Once the vehicle was 11.1 million kilometres from Venus, it released the largest of the four probes. This spherical probe had a diameter of 79cm and a phenolic conical heat shield which was 1.42 cm in diameter. The total mass of the probe was 316.5 kg. This was also the only probe that had a parachute on board. This was a 3.6 m  diameter parachute. To test it without any cross-wind, it was tested in NASA’s Vertical Assembly Building. Afterwards, the parachute was drop tested at speeds up to Mach 0.8 by dropping it from an F-4. The Final full-scale test was performed by drop testing from a high-level balloon. 

Four days after the large probe separated, the three other probes were released at 9.3 million kilometres from Venus. These probes were named North, Day and Night, after the location where they would land. These probes were identical to each other and had a mass of 93 kg. The scientific instruments were stored in a 46 cm diameter shell and had a conical heat shield, similar to the large probe, only for the small probe which was 0.76 m in diameter. As mentioned before, these probes had no parachute; because of this, the heatshield stayed attached to the probe.

None of the probes was designed to survive contact with the surface of Venus. But they were designed to survive pressures up to 115 bar and a temperature of 495 C. The larger probe was able to resist a 400g deceleration. The smaller probes were capable of withstanding 565 g.

Although they separated days from each other, all probes entered the atmosphere within minutes of each other. The large probe descended through the atmosphere and landed with a velocity of 43 km/hr, at which point, as expected, it stopped transmitting. Although not designed to, of the three smaller probes, 2 survived the impact without a parachute after their approximately 55-minute fall through the Venus atmosphere. The Day probe continued to transmit data for another 67 minutes after impact, at which point the heat, pressure and lack of power also caused it to stop transmitting. [133,134]


Pioneer13
Pioneer13_2
Pioneer13_3

Venera 13 and 14

Operator: Soviet Union

Target:   Venus

Landing date: 1982

Status:  Succesful


Venera 13 and 14 were twinned spacecraft launched to Venus. These spacecraft were launched in 1981, only five days apart. The spacecraft and the landers were similar to each other and the previous Veneras (9-12), especially Venera 11 and 12 [129,130,131,132].

This meant they had a suite of instruments to cover the descent and the limited time they would have on the surface. The entry mass of both vehicles was about 1650 kg, and the final landed mass was 760 kg [129, 132]. The probes entered the Venus atmosphere and started their measurements of the atmosphere until the parachute deployed at approximately 65 km [130]. This lasted until 50 km when the parachute would be cut away, and the lander would continue under its own drag. During the descent, landers were equipped with a microphone to measure the wind velocity. These recordings are the first recordings of another planet [131]. Both landers would land with a velocity of 7.5m/s [131].

Once they arrived at the surface, the landers would transmit data for another 127 and 57 minutes for Venera 13 and 14, respectively, where it made the first colour images of Venus's surface. Venera 13 and 14 both collected two soil samples, one sample from the surface and the other with its onboard drill. Finally, Venera 13 and 14 were equipped with cameras with red/green and blue filters. Which, when combined, would create the first colour images of Venus.


Schematic of Venera 13 and 14

Venera 13 and 14

First color image of Venus taken by Venera

VeGa 1 and 2

Operator: Soviet Union

Target:   Venus

Landing date: June 1985

Status:  Succesful


When Halley’s comet was due back in our neighbourhood of the solar system in 1986, multiple spacecraft were sent. Among which were two spacecraft from the soviet union, VeGa 1 and VeGa 2. In order to get to the comet, these spacecraft were to get a gravity assist from Venus. However, when at Venus, both VeGa spacecraft would also deploy a capsule which would, as multiple Venera’s before it, land and collect data from the surface [169,170]. The entry system also carried a  balloon to be deployed and perform atmospheric measurements [169,170].


In each VeGa entry system, there was one lander and one balloon. These would separate at 65km when the top half of the entry sphere, which contained the balloon, would separate from the bottom half, the half with the lander. The landing sequence of the lander was similar to the Venera landers before it. Deployment of its parachute was at an altitude of 63km, and it would be released at 47km. After which, it would land at its terminal velocity of 8m/s [170].


The landers that touched down on the 11th and 15th of June 1985 were virtually identical to Venera 13 & 14 [169,170]. They had a mass of 716 kg at touchdown, a wide array of measurement equipment for analysing the atmosphere during the descent, and a drill and spectrometer to take and analyse a soil sample [1,2]. Both VeGas had a lifetime of under an hour (56 and 57 minutes) after touchdown on the surface. After which, having completed all their scientific tasks, VeGa 1 and VeGa 2 succumbed to the extreme environment, and contact was lost with the landers.


The balloons, which separated from the lander at 65km, first deployed a 35 m2 parachute to decelerate the system to 8m/s [170]. Once at 55km, the 3.4m diameter balloon would be filled with Helium. Once the balloon was filled, the parachute and filling system would be released at 50km, and the balloon would increase its altitude again until it reached its cruising altitude of 54km [170]. The entire system had a mass of 123 kg at entry and 20kg in its final cruising configuration [170]. On board, it had a temperature and pressure sensor, vertical wind anemometer, light level photometer and a nephelometer for measuring the density and particle size of local aerosols [169,170]. Its battery pack would allow for a lifetime of 46 hours. The data collected would be transmitted directly back to earth [170].


The VeGa landers would mark the end of the Soviet planetary missions to Venus. The Soviets launched, over a 24-year period, 29 missions towards to planet, of which fifteen successfully delivered three entry probes, ten landers, two balloons and four orbiters to Venus [170].

Scematic of the VeGa lander
Scematic of the VeGa lander
The Vega landing sequence
The Vega landing sequence

The VeGa landing and balloon deployment sequence

DAVINCI+

Operator: NASA

Target:   Venus

Landing date:  2029-2030

Status:  Planned


DAVINCI+ is a proposed mission of NASA to study the atmosphere and surface of Venus by descending a probe into the planet’s thick atmosphere. In the past, atmospheric probes and landers have been flown by both the United States (Pioneer program) and more extensively by the Soviet Union (Venera and VeGa programs). Although more recent probes have been studying Venus from orbit, DAVINCI+ will be the first probe to enter Venus’ atmosphere since VeGa did in June 1985. 


DAVINCI+ was a revival of an earlier, similar project proposal with the name DAVINCI, which had a similar mission profile and design. The design of the DAVINCI+ probe has likely not yet been frozen, however early renders indicate that the probe will use two parachutes, featuring a disc-gap-band, to slow down the capsule during its hour-long descent. [42, 43]


DAVINCI+ EDL

Rocket lab Venus Probe

Operator: Rocket lab

Target:   Venus

Landing date:  2023

Status:  Planned


RocketLab plans to launch a privately funded mission to Venus using its Electron launch

vehicle. They are aiming to launch during the 2023 Venus launch window. The mission will use the company’s high energy Photon as a cruise stage and communications relay to bring the atmospheric probe to Venus upon which it will release the probe on a direct entry trajectory. The roughly 20kg probe will not have a parachute or any other deployable of decelerator and will feature an integrated, non-detachable heat shield. The probe will enter through the atmosphere and will take measurements of the cloud layer to determine if it contains substances that are indicative of biological life. Once the probe has passed through the cloud layer it will begin to relay its findings back to the spacecraft in orbit. Due to the lack of any form of method to decelerate the vehicle will impact the surface ballistically and be destroyed. The aim of this mission is to search for signs of life on Venus but also to demonstrate the feasibility of conducting planetary science with small spacecraft.


RocketLabVenus2
RocketLabVenus1

Comparison of Venus Landers

Multiple missions have attempted or have landed on Venus. This overview contains only those missions that reached Venus and started a landing attempt. 

Mission

Nationality

Year

Status

Venera 3

Soviet Union

1965

Failure

Venera 4

Soviet Union

1967

Success - Not designed to work on the surface

Venera 7

Soviet Union

1970

Success - First soft landing on another planet

Venera 8

Soviet Union

1972

Succes

Venera 9

Soviet Union

1975

Succes

Venera 10

Soviet Union

1975

Success

Venera 11

Soviet Union

1978

Success

Venera 12

Soviet Union

1978

Succes

Pioneer Venus 2

USA

1978

Success

Venera 13

Soviet Union

1981

Success

Venera 14

Soviet Union

1983

Success

VeGa 1

Soviet Union

1984

Success

VeGa 2

Soviet Union

1984

Success

v0.2 - 25-04-2020