Soyuz TMA Re-Entry

Today's trivia dives into the detail of how Astronauts return from space.

On March 1st 2016 Scott Kelly (NASA) and Mikhail Korniyenko (RSC) returned to Earth in the Soyuz-TMA spacecraft. How does an astronaut return from orbit in this spacecraft?

Soyuz TMA spacecraft

The Soyuz TMA-M (transport, modified, anthropometric) is the latest in a very slow evolution of Russian human-rated spacecraft.

Soyuz TMA-17 before docking

Primary Functions

• Carry up to 3 crew into a variety of orbits
• Orbital transit
• Docking
• De-orbit and re-entry
• Soft landing

Its design philosophy is based around automation. Most of the main tasks required for re-entry are automatic. It can also be fully controlled from ground control stations. Crew can override as required, for example if they encounter an emergency. A lot of its design is focused around many levels of redundancy. Automated systems have usually two backup systems and include some kind of reasonable contingency if all were to fail.

Artistic image of the 17 July 1975 Apollo Soyuz Test Program (ASTP) the first docking of a Russian and American spacecraft showing comparable scale of the Apollo and Soyuz spacecraft

The first Soyuz was developed at the same time as the American Apollo program as part of a secretive Soviet lunar mission which was eventually halted due to a number of reasons. This same craft has undergone three main design evolutions to spacecraft used today.

Its use as a crew transportation and return spacecraft for space stations was first proposed by the Russians as the Automatic Crew Return Vehicle for both the joint NASA/RSC project on the Mir space station and the International Stance Station. If the station was damaged by space debris or a medical evacuation was required, the Soyuz would be used for these tasks. With its 110+ manned launches it has an extensive track record.

Undock

Soyuz TMA-03M spacecraft (left) eases toward its docking with the Russian-built Mini-Research Module 1

Once the crew are onboard and suited up in their pressure suits, they will go through various checklists to prepare for the flight. This takes in excess of three hours, which may include time verifying there are no drops in pressure within Soyuz.

View from the on board computer system pilots view with information overlay

Once released from the station, springs inside the docking ring push the craft away from the station. The Soyuz is only able to use its reaction control thrusters once it is far enough (20m) away from the station to prevent covering the station in liquid propellant.

De-Orbit burn

The de-orbit burn is also automatic. Once the spacecraft position is accurately known, the computer calculates the angle and duration of burn to get the required landing trajectory to a pre-determined landing site.

This burn is critical as it determines the angle of descent into the atmosphere:

• Too shallow and it will bounce off the atmosphere without showing down, resulting in overheating.
• Too steep and the crew will experience too much deceleration force (in excess of 10g) which may be fatal for the crew.

Soyuz is made up of three modules, at the front is the Orbital Module, in the middle is the Descent Module and at the back is the Service Module which includes the solar panels

Once the de-orbit burn is complete, the Orbital and Service modules are jettisoned. Explosive bolts fire which push the jettisoned modules away from the descent module. They will burn up on the atmosphere on reentry. If for some reason the modules do not separate correctly, the Soyuz is designed so aerodynamic forces will break the modules apart in any case.

30 minutes later the spacecraft will cross the Kármán line at 100km and come into contact with enough atmosphere to start re-entry.

Re-Entry

Seen from the International Space Station, the Soyuz TMA-05M descent module begins to re-enter the Earth's atmosphere, leaving a plasma trail as the Expedition 33 crew streaks toward a pre-dawn landing on the steppe of Kazakhstan.

During re-entry the capsule will decelerate from orbital velocity (17,000mph) down to speeds where the parachutes can be deployed. This deceleration is the result of the capsule crashing into the atmosphere. The heat shield of Soyuz is rated to withstand the incredible temperatures of re-entry, however the shape is also crucial as well:

"If the reentry vehicle is made blunt, air cannot "get out of the way" quickly enough, and acts as an air cushion to push the shock wave and heated shock layer forward away from the vehicle. Since most of the hot gases are no longer in direct contact with the vehicle, the heat energy would stay in the shocked gas and simply move around the vehicle to later dissipate into the atmosphere." - Wikipedia

The re-entry is also completely automatic. The computer will use reaction control thrusters to create a steering effect, enough to keep it aligned with its target landing site. Should the computer fail, or an emergency arise such as depressurisation, the backup re-entry process will start a ballistic re-entry. This re-entry is faster because it is steeper but induces up to 8g of force on the crew.

Re-Entry as seen from the inside window of Soyuz Buzz Feed

Landing

Once the descent has slowed enough, the parachutes can be deployed. First two drogue chutes, followed by a main chute. This slows the capsule down to the required landing speed.

Around the same time the heat shield, and external window covers are jettisoned.

Just before landing 6 soft landing solid rockets fire to improve the landing which an astronaut still describe as "feeling like you are being hit by a truck".

During the early Soviet missions the landing site was less predictable. The cosmonaut would expect to be greeted by team parachuted in to assist. Now days helicopters and ground support vehicles arrive at the predetermined landing site and are in constant communication with the capsule as it lands.

Soyuz TMA-01M spacecraft shortly after the capsule landed

References:

• NASA Overview
• Detail on Soyuz
• PDF on Re-entry Detail
• YouTube - ESA Landing Sequence for crew training
• YouTube - Roscosmos State Corporation
• YouTube - Re-Entry Footage from Apollo 11 1969
• YouTube - Re-Entry Footage from Orion 2015

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Luna-9

Today's trivia hopes to cover a slightly less well known Moon landing; from the Soviet Union space program.

The year is 1966, the Soviet Union had had mixed success with landings on the Moon. Since the start of their mission to land on the Moon in 1958, they had launched 20 missions. Only two missions, both in 1959, had succeeded. Luna-2 successfully (intentionally) crashed into the surface of the Moon, Luna-3 provided the first photos of the far side of the Moon.

However they were learning hugely from their space program and had refined the launch vehicle which would take the next mission, Luna-9 to the first soft body landing on the Moon.

Launch and Approach

The launch vehicle was the Molniya-M (a design derived from an earlier ICBM design, last used 2010) which operated as a four stage rocket. Was considerably more reliable than previous rockets and provided enough lift to get the 1.5 ton lander into orbit, set it into a gentle spin and provide the final velocity to get it into a trajectory towards the Moon.

A helpful simulation of the entire launch, approach and landing

This journey lasted 4 days and included a crucial course correction where the lander pivoted over so its rockets were directed at the Moon which allowed it to start its descent towards the surface.

The Luna-9 Lander; the body contained the flight control systems, the front contained the probe payload to deploy to the lunar surface

The lander was equipped with radar altimeter which allowed it to determine how high it was from the surface:

• At 25km from the surface the retro-rockets fired to slow descent
• At 250 meters the retro-rocket cut out and 4 stabilising rockets fired
• At 5 meters a contact sensor fires, and the probe is jettisoned from the top

The probe then bounced on an inflated air cushion before coming to rest on the lunar surface. Once stationary, the air cushion is jettisoned off.

A reconstruction of lander deployed the probe safely to the surface

The probe itself as comparatively quite simple. It consisted of a hermetically sealed container in which was held:

• radio equipment
• program timer
• heat control system
• geiger counter
• television system

Images Received

Approximately 250 seconds after the probe came to a halt the probe sprang open its four petal shaped panels and began a photographic survey of the lunar environment.

Model of the Luna-9 probe with 'petals' and radio masts deployed

The probe for the mission was equipped with a simple imaging system (by modern standards). It consisted of a television camera which pointed upwards and a mirror which was angled out towards the lunar surface. The mirror was rotated by a motor at a constant rate.

It would start recording images and broadcasting them via radio transmission back to Earth to be received by Soviet Union radio telescopes.

This also allowed the Jodrell Bank Lovell radio telescope to receive the same images.

Lovell Radio Telescope

It was quickly realised that the received signals were encoded in Radiofax, an internationally agreed standard for sending images between newspaper companies around the world.

"A Muirhead facsimile convertor and receiver were rushed out to Jodrell Bank from the Daily Express newspaper offices in Manchester. When the signals received the next afternoon were played through the machine, out scrolled, line by line, the first ever picture of the lunar surface taken from the surface." -- quote Professor Tim O'Brien

Perhaps to the Soviets dismay, the Express published the first image ever taken from the surface of the Moon before they did.

First photograph taken from the surface of the Moon in February 1966 by the Soviet lander Luna-9

Successes

The mission achieved a number of firsts:

• First soft body landing demonstrating the kind of flight control systems which would be required to land people on the Moon
• First images transmitted from the surface of another body in space
• Confirmation that the Moon's surface could support a foreign object; theories at the time predicted things might simply sink into the surface
• First recordings of radiation from the surface of the Moon (30 millirads per day)

A panoramic image captured by the probe full Size.

Last contact with the spacecraft was at 22:55 UT on 6 February 1966, after which its onboard batteries expired.

Warp Speed

Today's trivia takes us hurling through the currently understood theory of warp travel.

Warp travel is probably one of the largest achievements in the science fiction adventures of the Star Trek and other universes. Warp travel allows spaceships to travel faster than the speed of light to overcome the seemingly mind boggling distances involved in interstellar travel.

Astronomical Perspective

• Distance between Earth and Sun = 1 AU (Astronomical Unit)
• AU ~= 150 million km
• Voyager is the highest energy spacecraft launched (nuclear powered)
• Cruising at 3.6AU, in 33 years Voyager has travelled ~116AU
• Nearest Star: Proxima Centauri 4.3 light years
• 1 light-year = 63,240 AU
• Voyager has ~75,000 years remaining

There have been various research proposals on how to travel through these vast distances in faster time, perhaps fast enough for a human life span. Those are interesting, but not the main subject for todays trivia.

General Relativity

Before we can dive head long into possible warp drives, we need to brush up a little on our theroy of general relativity. Well... we need a couple of useful concepts.

We understand that the speed of light in a vacuum is constant and represents a theoretical maximum.

This leads us to the idea that the fastest way to travel between two given points in space at the speed of light is simply the distance divided by the speed of light.

However, there is a situation where it is possible to travel faster than the speed of light. This is when the universe is expanding or contracting.

If we were to attempt the same thought experiment of travelling between two points I the universe whilst the universe was collapsing we can see that we would travel faster than the speed of light. (Perhaps the same effect of needing to go to toilet; the closer you get the greater the urge?)

That is as far as I need to go into the theory of general relativity.

Warp Drive

In 1994, Miguel Alcubierre published a paper which details how a theoretical warp drive could work.

It centres around this principle of expanding or collapsing the space-time of the universe.

Alcubierre states in his paper that if the region of space time in front of the ship was collapsed, it would bring the distant star close to the ship. If the region behind the ship was expanded it would move the ship further away from its starting point.

This would allow the ship to travel though space time without having to actually travel. The crew inside the 'warp bubble' would not feel any acceleration, and time would pass normally for them.

This warp bubble would have forward motion though space-time and allows the ship to travel considerably faster than the speed of light.

To take us back to the previous thought experiment. If a ship wishes to travel to some distant star:

• travel on conventional propulsion until it was clear of its home planet (will be explained shortly)
• Align with the distant star
• Engage its warp drive
• Halfway along the journey it would then need to reverse the direction of its warp drive to begin decelerating
• Arrive some distance from its destination (also explained later)
• Travel on conventional propulsion the rest of the way

Expanding Space-Time

One of the interesting side effects of the this concept is that it needs Negative Energy to produce the space-time warping effect.

Negative energy is a theoretical concept at the very edge of our current understanding. It is included in the explanations of certain fields including gravitational fields and a number of quantum fields.

Negative energy has some very strange properties:

• Accelerating in the direction opposite to applied force
• Causes normal positive matter to self accelerate infinitely
• Has a negative gravity effect

Current research indicates it is possible to detect the presence of negative energy.

Side Effects

As you might imagine, such a system has some unusual side effects.

Risks to Ship

• If the warp bubble destabilized, it would distort the ship horribly
• Recent research indicates superluminal velocities would generate so much Hawking radiation that it would destroy the ship inside the bubble

Risks to Surrounding Space

• Destroys space in front of it, creates space behind it.
• Would destroy anything that comes into contact with warp bubble
• Any particles collected infront of the bubble would be released in an energetic explosion akin to a sonic boom shockwave directly infront of the ship

Risks to the entire Galaxy

• Something the size of Jupiter in negative energy required

Conclusion

This is a fascinating and growing area of research. Calculations are being changed and revised all the time. The energy requirements of a theoretical warp drive are being refined to the point NASA have commissioned research and a new rendering of what a warp drive capable ship might look like.

References

Warp Field Mechanics 101

The warp drive: hyper-fast travel within general relativity

How to Explore the Universe