Europe set for record-breaking space launch

Jun 03, 2013 by Mariette Le Roux
The Arianespace Ariane 5 VA213 stands on the launch pad at Kourou space center, French Guiana, March 11, 2013. The fifth and mightiest generation of Ariane rockets is set to take a whopping 20.2 tonnes into orbit on June 5, 2013, in a cargo craft the size of a double-decker bus and a record for Europe.

Nearly 40 years ago, European countries worried by US and Soviet dominance of space gave the green light to the first Ariane rocket, a wee launcher capable of hoisting a satellite payload of just 1.8 tonnes—the equivalent mass of two small cars.

On Wednesday, the fifth and mightiest generation of Arianes is set to take a whopping 20.2 tonnes into orbit, a the size of a double-decker bus and a record for Europe, proud engineers say.

The payload is the fourth cargo delivery by the European Agency (ESA) to the International Space Station (ISS), bringing food, water, oxygen, and special treats to the orbiting crew.

An ES is scheduled to blast off from ESA's base at Kourou in French Guiana at 6:52 pm (2152 GMT) Wednesday, taking aloft an Automated Transfer Vehicle (ATV), a robot space truck dubbed the .

The cargo craft will carry almost seven tonnes of dry and fluid cargo for its five-month mission.

About an hour after liftoff, somewhere over New Zealand, the ATV, some 10 metres (33 feet) long, will detach from the rocket's upper stage and then deploy its four energy-generating solar panels and navigate autonomously, guided by starlight, to the space station.

It will dock with the ISS on July 15 at an altitude of about 400 kilometres (250 miles) above the planet.

Graphic factfile on the ATV space freighter, the biggest of its kind

"By then it has a velocity of 28,000 kilometres (18,000 miles) per hour, and has to fly to a destination (the docking mechanism) about 60 cm (23 inches) in width," said Bart Reijnen, head of orbital systems at the Astrium space company which built the lifeline craft.

"It has to fly there fully autonomously and dock with this target of 60 cm with a precision of six cm (2.4 inches). That is something that might be difficult to imagine."

The craft has enough fuel to make three docking attempts if something were to go wrong during the final approach, said Jean-Michel Bois, ATV operations manager in Toulouse, France, from where the vessel's flight path will be monitored.

In the case of a failed attempt, the ATV would retreat from the ISS and go into a different orbit, returning two days later to try again.

This has never happened, said Bois, adding: "I cross my fingers."

The Albert Einstein will boast the largest assortment of goods yet delivered to the ISS—a total of 1,400 individual items that include everything from pyjamas and toothbrushes to peanut butter, lasagne and tiramisu for its six astronauts.

Apart from several months' worth of food, the craft carries 4.8 tonnes of fuel needed to dock with the ISS and give it a boost into higher orbit with its onboard engines.

This is necessary because the ISS is in a low Earth orbit and encounters atmospheric resistance which causes it to fall towards our planet at a rate of about 100m (300 feet) per day.

ATVs can also push the ISS out of the way of oncoming space debris.

ESA is contracted to provide five ATVs as its contribution to the ISS, a US-led international collaboration.

The three previous missions have performed flawlessly, muting criticism of the billion-euro ($1.3-billion) development cost.

The Albert Einstein will carry 800 kg (1,760 pounds) of propellant to be pumped into the ISS itself, as well as more than 500 kilos (1,100 pounds) of water and 100 kilos of oxygen, according to Astrium.

And it will bring a scientific experiment designed to test the behaviour of emulsions—a mixture of liquids that do not blend, like mayonnaise—in weightless conditions.

The ATV's pressurised cabin will provide welcome extra space for the ISS crew—Americans Chris Cassidy and Karen Nyberg, Russians Fyodor Yurchikhin, Pavel Vinogradov and Alexander Misurkin, and Italian Luca Parmitano.

After completing its mission, the ATV-4 will undock from the ISS filled with about six tonnes of garbage and human waste, and burn up over the Pacific.

A brief history of Europe's ISS cargo programme

The 's Albert Einstein cargo craft, set for launch on Wednesday, is the fourth and penultimate in a series of hi-tech lifeline vessels bringing supplies and critical altitude boosts to the .

Europe's Automated Transfer Vehicles (ATVs), blasted into space by ESA's Ariane rocket, are the biggest cargo carriers to the ISS since the retirement of the US space shuttle in 2011.

ESA sends an ATV to the orbiting outpost about once every 17 months with around six tonnes of cargo—much of it fuel needed to boost the ISS, which is constantly falling towards Earth due to atmospheric resistance.

Named in honour of the father of relativity theory, the Albert Einstein follows the hi-tech trail of three others since 2008 that also carried the names of science gurus—the Jules Verne, the Johannes Kepler and the Edoardo Amaldi.

It will be followed next year by the last in the ATV series—the George Lamaitre named for the father of the Big Bang theory of the Universe's creation.

At 20.2 tonnes, the ATV-4 is the heaviest yet launched and will bring a record 2.5 tonnes of dry cargo to the six-member space station crew.

ATV-1: Jules Verne (2008)

The first in the series carried a total load of 4.5 tonnes consisting of 3.4 tonnes of fluid and 1.1 tonnes of dry supplies.

The payload heavily favoured propulsion fuel, including enough reserves in case of unforeseen problems with this first-ever ATV docking to the ISS.

The Jules Verne had no late load—that part of the cargo nowadays reserved for last-minute requests and perishables whose packing poses great technical difficulties once the capsule is perched vertically on top of the Ariane rocket that will propel it into space. The loading hatch is right on the vessel's nose—about 10 storeys high.

ATV-2: Johannes Keppler (2011)

This vessel holds the record for the largest boost given to the ISS by an ATV—40 kilometres in a single push.

It also holds the record for the heaviest cargo ever delivered to the outpost—over seven tonnes, though the ATV-4 will have more dry cargo.

The Johannes Keppler took 1.6 tonnes of dry supplies and 5.4 tonnes of fluid cargo, and a big supply of fuel that was used for the special orbital boost.

This was the last ATV not to bring water to the ISS—a task until this point performed by the US space shuttles which had also been responsible for boosting the space station's altitude.

ATV-3: Edoardo Amaldi (2012)

The third ATV carried 4.3 tonnes of fluid cargo and 2.2 tonnes of dry supplies.

As the technology and confidence grew with each successive mission, the ATVs started favouring a balance of more cargo and less backup fuel.

ATV-4: Albert Einstein (2013)

Will carry 4.1 tones of fluid and 2.5 tonnes of dry cargo—6.6 tonnes in total.

It boasts the most complex flight software ever developed by ESA—a million lines of code.

It has the biggest-ever late load, exceeding its nearest rival by more than 218 kg thanks to a new device that can lower an operator deep into the hull to load the holding racks, aided by a mechanical arm that can hold bags weighing as much as 75 kg each.

The Albert Einstein has the largest-ever assortment of goods taken into space, some 1,400 individual items.

The launch of ATV-5, the George Lemaitre, next year, will not mean the end of ESA's ATV programme.

The European agency will supply ATV-derived hardware for NASA's Orion spacecraft being designed to take humans to the Moon and beyond, and scheduled for a test flight in 2017.

This will be the first collaboration between ESA and NASA on a crew transport vehicle.

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Eikka
5 / 5 (1) Jun 03, 2013
100 meters a day is surprisingly much, although it only means 36 km a year. Still, the docking attempts are complicated by the fact that by the time you get to the ISS, it's not quite where it should be.

But the whole thing about hitting a 60 cm target at 28.000 km/h is a bit sensational, because the ISS itself is going about 28.000 km/h in the same direction, so you're only going a few hundred km/h relative to it, which is why it takes the ATV a couple days to catch up with the station. When it gets close enough, it actually has to speed up to match orbits or it would just come in for a turn and fall off again. After the initial approach, the ATV and the station are flying in sync some kilometers apart and have zero speed relative to each other. From there on it's just a matter of inching the rest of the way in practically at walking pace.

antialias_physorg
4 / 5 (4) Jun 03, 2013
s set to take a whopping 20.2 tonnes into orbit, a cargo craft the size of a double-decker bus

I think this really brings it home what kind of power is behind these types of rockets.

So far the ATVs have perfomed really well and I hope all things go smoothly with the Albert Einstein, too.

There hasn't been any news of extending the contract beyond the scheduled 5 modules - which seems kind of a shame. Still, I'm looking forward what the next step in European spacecraft which will undoubtedly be heavily influenced by the ATV series.
Eikka
5 / 5 (1) Jun 03, 2013
Moving in orbit is a bit counterintuitive, because it depends on how long your journey will take. If you're spacewalking near the ISS, things work pretty linearily. You go up to go up, left to go left, back, forward, and so on - but if you fly yourself a kilometer underneath the ISS and stop, and just wait there for an hour, you'll start to drift in the forward direction because your orbit is slightly shorter than of the ISS a kilometer above. But then, because your orbit is probably slightly eccentric as well, about 12 hours later you might just circle around the ISS and find yourself above or in front of it it without doing anything. If you're unlucky, you might even bump into it.

beleg
not rated yet Jun 03, 2013
Does the ISS ammonia leak number the days the ISS is inhabitable?
antialias_physorg
4.2 / 5 (5) Jun 03, 2013
It might seem a lot more complicated than it actually is, since the relative motions/accelerations are small wherever you are relative to the ISS.

Reminds me of an excercise at uni where we had to make a robot follow a figure 8 on the floor. We designed all kinds of complicated closed-loop control functions (throwing everyting we had just previously learned at it), trying to adjust for changes in curvature and whatnot.

In the end one simple function sufficed - just minute linear readjustments as soon as the sensor detected the slightest deviation - to make this thing zip around the floor flawlessly.

And of course: the more complicated your control system the more points of instability it has.
antialias_physorg
3.7 / 5 (3) Jun 03, 2013
Does the ISS ammonia leak number the days the ISS is inhabitable?

Not yet. The station has redundant systems (the leaky system is shut down for the moment).
However, if any more cooling systems fail things can get dicey (cooling is a lot more important than heating in space - go figure).

The ISS will eventually fall apart (like any machine), so technically its days are numbered. At some point the number of repairs needed will not merit the continued operation. There's a couple of things that just accrue over time which affect the overall structure (or large parts of it). Solar panel degradation, micrometeorite damage, corrosion, bacterial/fungal contamination, ...

But hopefully the day when the last astronauts leave ths ISS is still a ways in the future.
Eikka
not rated yet Jun 03, 2013
It might seem a lot more complicated than it actually is, since the relative motions/accelerations are small wherever you are relative to the ISS.


Well, the ISS is drifting down at 4 meters an hour to start with, and if you went spacewalking outside of it, you'd fall at a slightly slower rate because of the different ballistic coefficients, the ISS being less dense and all.

And, the orbital period of a satellite at 399 km circular orbit is 5553 seconds, whereas at 400 km it is 5554 seconds, so you advance one second every revolution, and seeing how you're travelling at 28.000 kph or about 8000 m/s you'd drift 8 kilometers forwards from the ISS in a day, or at a rate of about 300 meters per hour.

So if you're closing in a kilometer below the ISS, you're drifting by about 10 cm/s, which is enough to mess up your approach if you don't take it into account.
antialias_physorg
3.7 / 5 (3) Jun 03, 2013
I agree that you have to take it into account. The thing is - that computation need not be very complicated.

It's only complicated if you have a lot of time between corrective maneouvers because then you have to integrate ovre the entire timespan since your last alteration (and preferrably hav to run a prediction of futur poitions and drifts). Granted: None of which is exceedingly difficult to program for.

The thing is: Making many, smaller corrections will get you quickly into a range where you can just use a linear approximation. This is fast and will give you a very stable/predictable approach - while using the exact same amount of fuel.

Easy solutions are often the best (and most robust) ones.
Eikka
not rated yet Jun 03, 2013
In the end one simple function sufficed - just minute linear readjustments as soon as the sensor detected the slightest deviation - to make this thing zip around the floor flawlessly.


A simple proportional error amplifier is indeed enough if you don't care that the path is never actually on the line, but always a bit to the side. The closer you try to make the thing follow the line, or the faster you make it, the more you risk overshooting due to inertia and getting into an oscillation, where your robot car just can't decide where to go and will shoot off in some random direction. That's when you start to need the ID part of the PID controller and things get slightly more complicated.

Getting a robot to follow a line is easy and simple. Getting it to do so accurately and fast requires finer tuning.
Eikka
not rated yet Jun 03, 2013
It's only complicated if you have a lot of time between corrective maneouvers because then you have to integrate ovre the entire timespan since your last alteration


That's kinda the problem with the ATV's final approach with the ISS, because it's doing it at a snail's pace to lower the risk of what happened to MIR when one of the Soyuz capsules crashed through the solar panels and punched a hole in one module. They're taking it slowly since it's an unmanned vehicle and they have the time to wait.

But they can't keep spending fuel to correct all the drift by force, so they have to predict the trajectory, which is what makes it an impressive feat because knowing exactly where you are in space relative to the ISS and relative to the earth, and how your orbits are, is not a trivial thing to measure down to centimeter accuracy, especially with variables such as atmospheric drag. Any minute error in your prediction tends to accumulate.
Eikka
not rated yet Jun 03, 2013
The thing is that if you're approaching from below, you're going forwards along the orbit relative to the ISS. If you slow down so you would stay still relative to the ISS, you also drop your altitude half a revolution or about 45 minutes later and will actually increase your forward speed relative to the ISS as well as making you fall further away from it if you wait too long, so maintaining "small corrections" as you're making a slow linear approach would use tremendous amounts of fuel just to keep you where you are.

Also, I was wrong earlier. Since the orbital period of the ISS at 400 km is 5554 seconds, you would drift about 5000 meters per hour staying on an orbit a kilometer below the station - not 300 meters.

antialias_physorg
3.7 / 5 (3) Jun 03, 2013
But they can't keep spending fuel to correct all the drift by force, so they have to predict the trajectory

Since we're in space it doesn't matter whether you correct the drift all at once or in small increments. The delta v/needed impulse - and hence the fuel use - is the same for the same period of time.
The only thing that differs is how often you fire the thrusters. But whether you go at it slow or fast makes no difference.

Slow is safer (more abort options). Fast is easier (less complicated meouver calculations)
beleg
not rated yet Jun 03, 2013
Orbital mechanics is free fall. Your approaoch depends on your altitude. - Baumgartner.
j/k. He never said that.
Osiris1
4 / 5 (1) Jun 04, 2013
Nice if solar electric propulsion could be used for this! It already deploys solar panels, and the tech for energy density potential is increasing day by day for this tech. Could also use Dr Chaing Diaz's VASIMR. Pipe down petro shills with the one rates, I can speak too here just as you.
Neinsense99
3 / 5 (8) Jun 05, 2013
No 'Freedom Fries' were harmed in the making of this achievement.
ValeriaT
1 / 5 (1) Jun 05, 2013
is set to take a whopping 20.2 tonnes into orbit
I see, small penis syndrome...;-) The Saturn V rocket was capable to bring 120 tonnes to orbit - in 1967, i.e. before nearly fifty years...