ATV fuel consumption

A while back, a reader asked for fuel consumption figures for our favourite space freighter via the blog’s feedback form:

“I would like to have some detailed info on the consumed fuel in kg during the rendezvous phase of ATV towards the International Space Station, split for attitude and orbit manoeuvres. In detail I am looking for data on fuel consumption evolution to maintain the ATV with the wished attitude possibly for each phase (Yaw Steering, Target Pointing).”

Then we have the all important Flight Dynamics Team without whom we would not be anywhere near the ISS. Credit: ESA

Members of the flight dynamics team at ATV-CC. Credit: ESA

A quick email to ESA's Laurent Arzel working on the Flight Dynamics team at ATV Control Centre in Toulouse gives all the answers we could need.

Laurent writes: “Between launch and docking, ATV burns fuel for the phasing period as the spacecraft raises its altitude to the first checkpoint (S-1/2), which is 5 km below and 39 km behind the International Space Station. In addition, it burns fuel to keep pointing in the right direction.”

“After the S-1/2 point, until docking, ATV continues to burn fuel for its flight and specific attitude control to the Space Station.”

The numbers

ATV-5 approaching Station in August. Credits: Roscosmos-O. Artemyev

ATV-5 firing its thrusters on Station approach in 2014. Credits: Roscosmos-O. Artemyev

The rough-average figures are 800 kg of propellant used for the phasing period, assuming the Space Station is flying at around 415 km altitude.

If the phasing lasts five days, an ATV requires 60 kg of propellant for yaw steering to constantly keep the solar panels basking in the light of the Sun. The amount of propellant used in this period for yaw-steering attitude control is a linear function, so adding a day for phasing would require 1/5 more propellant (so 12 kg more each extra day).

Another consideration is the slew manoeuvres that set ATV on the correct track before and after each orbital manoeuvre. This is a linear function depending on the number of manoeuvres. During an average 5-day rendezvous and docking period, the propellant consumed for slew is 10 kg.

Once ATV pass the S-1/2 point, a normal rendezvous requires around 300 kg of propellant.

ATV-3 fueling. Credits: ESA/CNES/Arianespace/Optique Video du CSG–S. Martin

ATV-3 fueling. Credits: ESA/CNES/Arianespace/Optique Video du CSG–S. Martin

How much does your fuel weigh?

Whereas on Earth we often speak in litres of fuel (or gallons of course), in space flight fuel is not always liquid. To make matters more complicated, most fuel uses oxygen to burn – the oxidiser. For vehicles that travel on the surface of our planet, oxygen is quite easy to find, just stick an air intake valve on an engine and you are done. Spacecraft (and submarines) however have to pack their own oxidisers.

Mix the fuel and the oxidiser together and you have what is called propellant. In your car, the fuel is petrol or diesel while the oxidiser is the same air you breathe. ATVs use MMH (MonoMethyHydrazine) as fuel and mix it with the oxidiser MON (Mixed Oxides of Nitrogen) in a ratio of 1.65 oxidizer-to-fuel.

Fuel consumption figures (extra-urban)

MMH molecule. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Methylhydrazine-3D-balls.png#mediaviewer/File:Methylhydrazine-3D-balls.png

One of the molecules that pushes ATV to the Station: MMH Credits: Public Domain via Wikimedia Commons

So once at its cruising speed of 28 800 km/h (thank you, Ariane 5), an ATV needs 1170 kg of propellant, of which 441 is MMH and 729 is MON.

Considering MMH density is 0.875 kg/l, we would need 504 litres of the stuff. Using a MON density of 1.114 kg/l we would need 654 litres of MON to dock an ATV.

Combining these gives a total of 654+504=1160 litres of propellant to dock an ATV, once in orbit.

Docking generally takes five days, so during that time period an ATV will travel: 24 hours in a day X 5 days X 28 800 km/h = 3.456 million km travelled on 1160 litres of propellant which translates to a 'fuel consumption' of just 0.03 litres per 100 km!

Disclaimer: These calculations show fuel consumption for educative purposes and may not reflect real driving results, your mileage may vary. We did have fun working this out, keep your questions coming…

ATV-3 in Kourou showing fuel tanks. Credits: ESA/CNES/Arianespace/Optique Video du CSG

ATV-3 in Kourou showing fuel tanks. Credits: ESA/CNES/Arianespace/Optique Video du CSG

Posted in Flight dynamics, Free flight, Fun stuff | Tagged , , , , | 8 Comments

Arms that never tire: Robots in space! 28 Jan

Join us for a hangout with ESA Astronaut Tim Peake & Rosetta Project Scientist Dr Matt Taylor as they discuss robotics in space missions. #RobotsInSpace

Date: Wednesday 28 January 2015 || Time: 17:00 GMT 18:00 CET 11:00 Houston ||

Access via http://goo.gl/nfxg0g

#RobotsInSpace

#RobotsInSpace

#RobotsInSpace

Presented by ESA in cooperation with the UK Science and Innovation Network and the UK Space Agency.

 

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Something rare in the air

A quick update this morning from our ATV-5 Mission Manager, Massimo Cislaghi.

On Friday evening, 17 January, the ISS crew noticed a bad smell inside the ATV cabin. The crew 'closed the door' (shut the ATV hatch, which normally remains open) as one would do at home, waiting for instructions from ground. It is virtually certain that the source of the odour is some trash cargo.

Yesterday, it was decided that an inspection will be carried out today to try and identify the stinking cargo bag and eliminate the smell.

The only (modest) effect on attached phase operations is that the water transfer planned for today has been postponed.

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ATV-5 mission report #37

The folks at ATV Control Centre in Toulouse supplied another mission report on ATV Georges Lemaître, three weeks before its undocking. Unloading of water, fuel and air is either finished or almost. With engineering precision the update lists cargo unloading as only 98% finished. The remaining 2% refers to the reentry recorders that will document ATV-5's demise on 27 February (more about this in future posts)

During last weeks (false) alarm on the International Space Station, ATV Control Centre turned off ATV-5's fans and Inter Module Ventilation, but they have returned to normal operations. Before that water was transferred to the Stationa in exchange for liquid waste.

The numbers:

  • Dry cargo : transferred 2647kg (98%) (all dry cargo transferred to ISS, reentry recorders left in ATV)
  • Water : transferred 633 liters (75%)
  • Oxygen: all O2 transferred, and 73% of air
  • Refuelling propellant : 860kg.  transfer done
  • Accepted trash : 1398kg
  • Accepted liquid trash : 231 liters
Posted in ATV-5, ATV-CC, Operations | Tagged , | 1 Comment

Got questions? We have answers

We saw a question yesterday in Twitter from someone, and now we can't find the tweet. :-( But we did note down the query:

.@esaoperations why won't there be more ATVs? 
What will replace their capabilities? Thanks.

Regardless of their source, they're good questions!

ATV-5 Mission Manager Massimo Cislaghi replies to the second point:

There no 1:1 replacement to the ATV, but rather there will be a redistribution of its capabilities among the rest of the ISS servicing fleet, i.e. Dragon, Cygnus (when back in operation), HTV and – of course – Progress, this last vehicle being to my knowledge the only one capable of performing ISS reboost and refuelling.

ESA's Head of the Space Transportation Department Nico Dettmann replies to the first point:

The five ATVs have paid ESA's obligations in the ISS programme until 2017. It has been decided to discontinue ATV, but to develop the MPCV-ESM (European Service Module) for NASA to compensate for ESA's ISS obligations until 2020. This decision provides a  European exploration perspective beyond low-Earth orbit, while building on ATV heritage.

Posted in ATV-5, European Service Module, ISS Partners, News and updates, Orion, Technology & engineering, Video | Tagged , , | 1 Comment

Mission update 9 January

Today marks just 34 days before ATV-5 undocking from the ISS and 47 days until re-entry.

ATV5 Georges Lemaître - At the very back end of the International Space Station

ATV5 Georges Lemaître - At the very back end of the International Space Station

The mission is doing extremely well, and, as mentioned recently by our mission manager, Massimo Cislaghi, in an email: Georges Lemaître’s performance continues to be 'EXCELLENT'.

With the spacecraft in good shape, cargo off-loading and trash loading continue according to plans, while teams at ATV-CC are very busy preparing for undocking, a two-week free-flight phase, phasing for re-entry and finally, on 27 February, re-entry itself, which is shaping up to be a spectacular show (we’ll report on these upcoming activities in future posts here in the blog – Ed.).

As last week ended, on 9 January, ISS crew were busy in ATV installing adapter plates. ESA’s Samantha Cristoforetti and NASA’s Barry Wilmore installed adapter plates on several ATV rack fronts.

Sam & Butch

The function of the plates (which are not installed everywhere) is to attach additional bags in front of the racks, protruding inside the ATV central corridor; thus cargo bags can be strapped to the adapter plates allowing for additional cargo to be stowed outside the rack volume.

Also as of 9 January, Jean-Michel Bois, head of the ESA operations team at ATV-CC in Toulouse, sent a status update, reporting that everything is nominal with the vessel and the ground segment: 2647kg (98%) of ATV-5’s dry cargo (2695kg) has been transferred to the ISS (click on the ‘Continue reading’ link for details).

Finally, to end off today’s post, here are some records/’firsts’ gathered by Massimo:

  • ATV-5 has been the heaviest vehicle ever lifted by an Ariane rocket (20,245 kg)
  • ATV-5 has uploaded and delivered to the ISS the largest quantity of dry cargo launched in one European satellite
  • ATV-5 has loaded the largest quantity of late cargo just three weeks before launch (1,234 kg)
  • ATV-5 has uploaded the largest quantity of potable water to the ISS (843 kg)
  • ATV-5 has uploaded and delivered the largest quantity of Russian fuel to the ISS (860 kg)
  • ATV-5 has performed the first ISS PDAM

Continue reading

Posted in ATV-5, Cargo, Mission updates, Operations, Technology & engineering | Tagged , , , | 1 Comment

ATV-5 Mission Manager 2/3 mission report – reentry plans

ATV-5 seen during ISS flyunder on 8 August. Credit: ESA/NASA

ATV-5 seen during ISS flyunder on 8 August. Credit: ESA/NASA

ATV-5 mission manager Massimo Cislaghi sent us this informative update on ATV-5's planned reentry that will take place next month:

As promised with my previous mid-mission report of 7 November I come back to you for a short update, this time focusing on the preparation of the end of the mission, which also means (sigh ...) the end of the entire ATV Programme.

Lidar view of ISS. Credits: Jena-Optronik

LIRIS Lidar view of ISS. Credits: Jena-Optronik

A novelty introduced for ATV-5’s docking was the LIRIS demonstration including a special ISS "fly-under". With that finished we are now concentrating our efforts towards the implementation of another totally new operation during Georges Lemaître’s reentry, which deserves few words of background.

Mir. Credits: NASA

Mir. Credits: NASA

When the International Space Station reaches its end of life, the big orbital complex will have to be de-orbited, similarly to what was done with space station Mir in 2001. The amount of energy required to brake more than 400 tonnes of hardware to have it captured by Earth’s gravity, is not and will not be stored onboard at that time. This means that the Space Station’s speed will be reduced slowly so its atmospheric reentry is expected to occur in a path that is not as steep as one would like ideally. We call it a "shallow reentry". The operational and safety implications of such a manoeuvre are enormous. It will be necessary to predict when and how the International Space Station will start its fragmentation, whether explosions will occur and how fragments will behave. Will all the fragments be captured by Earth's gravity or will some remain in orbit? How will their shape affect their trajectory as they hit denser and denser atmosphere? Which fragments will burn during reentry and which ones could touch Earth’s surface, and where?

Continue reading

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ATV-5: Europe’s heaviest-ever payload

Looks like our favourite spaceship, ATV-5, weighed in as Europe's heaviest-ever payload! The vessel was launched on 29 July 2014 at 23:44 GMT, with a mass of just over 20,245 kilograms. Thanks, Arianespace!

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Pumping up the ISS

Station repressurisation complete! Next planned ATV-5 activity set for 23 December: water transfer.

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Seeing ISS through a computer’s eye

Infrared view of ISS. Credits: Sodern

Infrared view of ISS. Credits: Sodern

This week the first images from the LIRIS technology demonstration were published on the ESA website. LIRIS is demonstrating technology that could be used for docking with uncooperative targets by scanning space objects in infrared and lidar. For its first outing in space it was place on ATV-5 to scan the International Space Station. The results are some incredible views of the weightless research centre.

Some people on Twitter were asking why the resolution of the images are so low. We asked Olivier Mongrard, project engineer for LIRIS at ESA to explain:

The image resolution should be put in the context of a demonstration for Guidance Navigation and Control. The sensors were selected for navigating spacecraft and not for Public Relations!

Lidar view of ISS. Credits: Jena-Optronik

Lidar view of ISS. Credits: Jena-Optronik

Infrared detectors typically deliver smaller resolution images than found on normal camera cell phones today, but for vision-based navigation, the resolution on the Space Station image is sufficient at 70 m distance to navigate adequately.

As we get closer to the target, the resolution is enough to make out even small features and the accuracy reached based on these images will only increase as we start exploiting the data LIRIS has returned.

Keep in mind that we want to extract navigation-relevant information on spacecraft autonomously, using the spacecraft's onboard computers. One of the challenges of vision-based navigation is to extract data without demanding too much in terms of computing power. So for our purposes too much resolution can be detrimental as it would require more computers.

For some of the vision-based navigation that Rosetta is performing around comet 67P, analysis of the images is done on Earth with powerful machines, for LIRIS the objective is that the spacecraft itself do all computations in real-time...

 

 

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