The Carbon Footprint of a Satellite

Sometimes in life you are being asked a unique question and you can but wonder; why did I not think of this earlier. This is one of these times: in August this year I was approached by a good friend who is currently building a constellation for earth observation. He was wondering for all the good they were doing, what would be their impact on the environment. I had no clue which made this question even more interesting. Let's have a look!

TL:DR ~57 ton CO2e for a typical ESA satellite (including Ariane 6 launch), <15t CO2e for a satellite built in a factory and launched with a re-usable rocket.

Introduction

It should be at the back of our minds, the humanity, our current way of living is not sustainable. If we want to avert the climate catastrophe we need to de-carbonize our industry. Satellites are usually seen as good tools to to understand and then take actions to mitigate climate effects but with the increasing numbers of satellites we should also think about what is our part and what we can do to lessen our effects. So when Thomas a friend from a company that wants to build an earth observation constellation asked me for me to help him assess the carbon footprint of his own constellations I was all ear.

Dear Tom,

?

I have a question that may sound a bit unusual to you. We are trying to evaluate the carbon footprint of our future constellation.

Best Regards

Thomas

Dear Thomas,

that's an interesting idea. Something along the lines, "This is our (CO2) impact and this is what we do." Not sure about actual numbers though. Let me think about it :)

Kind Regards

Tom

So we wrote a few emails back and forth and this is a compilation of the ideas and viewpoints that we came up with. If you have your own research or know somebody who already did this, I would be glad to hear about it!

What contributes to your carbon footprint?

In the following we will look into what contributes to the carbon footprint of a satellite, starting from the rocket launch to the actual satellite manufacturing.

Rockets

Most people would first think of rockets when it comes to CO2 production. They burn they smoke, easy but is it? Well mostly yes, rockets that burn carbon based fuel produce CO2, however there is at least one rocket whose stages combustion all are based on LOX and H2 consequently producing water not CO2. This is the Delta 4 Heavy.

If the carbon footprint would only be rocket exhausts then we should all fly with this rocket. However, to use an analogy if you had the choice to either use an emission less electric car which you throw away after each journey or a gasoline guzzler like an old Humvee which makes 4-8 miles to the gallon which you keep for multiple trips then this calculation gets more complicated.

Example Calculation:

With these assumptions let's get down to business. In this example I will look at Falcon 9 since I found these numbers most easily and also due to its attractive cost its one that will be used often for small satellites.

Exhaust

A falcon 9 launch create 500 ton CO2 per launch and has 16.8 ton to LEO capacity when landing and re-using the rocket. Lets assume the actual payload capacity due to launch adapters, ESPA rings and launch separation systems is 10t (100 satellites with 100kg). Then we are talking ~5t per satellite for the fuel of the launch.

Note: Falcon 9 Block 5, around 500t fuel, LOx & Kerosine 2:1 (mass ratio). 166t Kerosine at 3kg CO2 per kg Kerosine = 500t CO2e per launch?

Raw Materials

In addition to that you have the build (and operation) that generates CO2. With SpaceX reusing their rockets up to 100x (currently 10x proven) that should be a fairly low number per rocket.

Re-usable rockets reduce the CO2 footprint

For a single launch and assuming 19 ton Steel (1.8-3.6kg CO2e * 2-3x due to machining -> ~200 ton CO2e)?and 1 ton electronics (100kg COe /kg -> 100t CO2e) for Electronics for the dry mass of the rocket (20t). Then the CO2e to make per rocket would be around 300t CO2e. Or around 3t per satellite.?

Development

What this ignores is the many many many person years that go into the development of a rocket. A quick estimation shows that this will be around 50-350kg CO2e per satellite for Falcon 9 and 0.5-1t CO2e per satellite for a Ariane 6 At the higher end of the range stand rockets that are many years overdue and a large team.

The massive delays of Ariane 6 don't make for a green rocket.

Note: I have not found good data for falcon 9 development cost. I have seen anything from $300M to $1.6b. Assuming $200K per year that would be between 1500-8000 person years. At 1000kW/h per person & year at 0.42 kg CO2e per KW/h that would lead to 630 ton CO2e to 3,300 ton CO2e or 6.3 ton to 33 ton CO2e per rocket assuming to split the NRE over 100 rockets. Consequently 63-330 kg CO2e per satellite for a Falcon 9.

Note: Arianespace 9000 people in total - 25% to be fired after Ariane 6 development done; so thats probably the design overhead, development fro, 2014-2022 -> 8 years @ 2300 people). Ariane 6 will launch maybe 100x (Ariane 5 had 105) then, thats 2,300,000 kWh * 0.42 * 8 / 100 =?77t CO2e per rocket (for R&D). The Ariane 64 has the same SSO capacity as Falcon 9 block 5 so lets assume 100 satellites of 100kg max. So around 770kg CO2e per small satellite of 100kg.

Note: second data point 3.6 billion EUR in development cost at assumed 150kEUR/(person*year) over 8 years = 3000 persons, so my assumption of 2300 people seems to be in the right order of magnitude.

Satellites

Satellites itself contribute significantly to their carbon footprint by ways of materials as well as personnel. While the influence on the materials is limited we will see that especially the personnel makes a significant difference.

70-80% of the CO2e in an ESA mission comes from the long development cycles. To optimize here would be good for the environment (and save cost).

In total the CO2e for the material is around 5-10 ton but the CO2e for the team can be much higher! For example if you need a 25 people team and 4 years to build the satellite, like many of the missions of the European Space Agency (ESA) then you would easily run into 40 ton CO2e for the personnel alone.

Example Calculation

Materials

Satellites are made from goods all the across the spectrum complexity. From simple raw materials like aluminum to very complicated integrated integrated circuits. All these products produce CO2 while being produced and should therefore be accounted for.

• Solar Cells (~70g/kWh per lifetime over 30 years -> 262800h & 0.173kW) -> 3200kg CO2e
• Electronics (~25kg @ 100kg CO2e / kg -> value from Microsoft Surface Laptop ;) ) -> 2500kg CO2e
• 30-60kg Structure Mass (Aluminium?13kg CO2e /kg?* 2-3x material losses & machining) ~ 2350kg CO2e
• Battery (500 kg CO2e /kWh -> 175Wh) ~ 175kg CO2e

==> 8.2 ton CO2e per 100kg satellite

Personnel

Not surprisingly your own personnel which designs and builds the satellite has a CO2 footprint, too. More precisely the labs that you need to make them work in. You might overlook this but considering how long some projects take it is fair to assume that this will be a significant factor to the carbon footprint.

If you assume a classical ESA mission you have 25 people (FTE) working on your satellite for four years. As a result you get up to 40 ton CO2e per 100kg class satellite. A serial built satellite made in a factory can have a CO2e footprint factor 100 lower.

note: a typical ESA small satellite has a cost of 20MEUR and it usually takes 4 years to build it. At lets say 150kEUR per person per year. Let's assume 75% of that is labor cost then that's around 100 person years (~25 FTE for 4 years).

note: BST for 2019 and 2020 has ~1000kWh/person-year.

note: Germany hat a 0.42kg CO2e / kWh -> 25,000kWh * 0.42 * 4 ~?40t

Note: For a serial satellite build in a factory the labor time is actually much lower - when compared to the traditional single satellite approach. For example the Indian factory of Berlin Space Technologies produces a satellite with roughly 1-2 person years per satellite. Therefore, 0.5-1 ton CO2e. Building something recurrent and in series helps to drastically reduce the carbon footprint of a satellite.

Note: much of the effort in satellites is in the QA/PA. Instead of reducing the quality it is a good choice to automate. BST has automated a great deal of the test including test report writing (see BST TV episode 1). There is great innovation potential in the automation of tests. Unfortunately, "Innovation does not pay" and therefore with the current payment structure (cost plus in all but the name) does not incentivize being more efficient (using less persons to do the job) and consequently CO2 footprint stays big (same as costs).?

Recommendations

To my surprise the numbers speak a clear language: the long development cycles of our satellites and not the rocket launch contribute about 70% of the total carbon footprint of a satellite. To be more environmentally friendly we need to lower our NRE and automate testing which consumes much of the manufacturing efforts.

How can you help:

This text is part of a?series?of articles in which the author sets the framework to start a discussion about the wrongs of the space industry. If you have experienced similar things, leave a comment. Other views and opinions are very welcome, too, as they may present a way forward. Please be kind to each other.

Disclaimer

The author’s views are his own do not represent the views of Berlin Space Technologies.