Another excellent day of talks and comment at #swfsummit24. It's great to see a recognition that space sustainability encompasses a much broader universe than we might have thought at first, spanning dimensions not just related to the Earth orbital environment, but also other Earth systems and reaching into and beyond cislunar space (thanks to Pam Melroy and Richard DalBello, amongst others). However, we must not forget another important dimension - that of time. Whilst I am always encouraged when I hear speakers refer to "future generations" when they talk about space sustainability, I also worry that its meaning is not truly or fully appreciated within our community. We often refer to our children or grandchildren to offer some context and, perhaps, an important personal aspect but is it really helpful to do this? By way of an answer, I wanted to share an example that changed my perspective. A spacecraft with an area-to-mass ratio of 0.01 sq.m/kg abandoned in a circular orbit in LEO at 1800 km altitude could have a residual orbital lifetime of 50,000 years thanks to the extremely low atmospheric density there. In his book "The Good Ancestor: How to Think Long-Term in a Short-Term World" the social philosopher Roman Krznaric shows the scale of the future generations over this timeframe compared with the scale of all those who live now. The graphic, prepared by Nigel Hawtin for the book, is quite humbling. The living can almost be seen as insignificant compared with future generations, yet the choices we - the living - make now in orbit, on the Moon, and on our home planet could easily affect all who will come after us. Roman Krznaric articulated this clearly in a recent post on X: "Humanity has colonised the future, dumping ecological and tech risk on future generations who have no... voice." This also brings to mind a quote that I refer to often when talking about space sustainability, a quote that was made in the context of a fictional future that showcases the wonders of space exploration. Such a future could be available to humanity if we were to truly understand how to grasp it: "The needs of the many outweigh the needs of the few."
Alan Fromberg
1mo
Of course, it is important to think about the longer term, philosophical, implications of the presence of space debris. However, isn't it more pressing to focus upon the open questions as to how that debris may impact upon the use of LEO for the benefit of human kind in the coming decades and whether the preferred solution of some in the space community to remove that debris via demise in the earth's atmosphere will have negative impacts upon the earth's climate? NASA has just let a contract to de-orbit the ISS on the (unproven) assumption that this will not have adverse impact on the chemistry of polar stratospheric cirrus clouds. Operational satellites are having to spend an increasing proportion of their delta V budget on avoiding debris, some of which should never have been licensed to launch in the first place. So, Hugh Lewis, it is indeed of value to not lose sight of the wider context. However there is an urgency that the space community quickly answers the questions as to whether the demise of satellites in the atmosphere is adversely impacting the earth's climate and how we license future launch to make sure that LEO continues to sustain viable services for humanity without adding to the climate emergency.
Michael Turner
1mo
Global population is expected to start declining later in the century. Space development may have a big role in making life on Earth at a decent level of comfort for all, but it's not needed to contain some hypothetical ever-growing population that's not going to be growing much more anyway.
Red Boumghar
1mo
Ok wait... we are not going to be 6.75T human beings in 50000 years. That is only the number of birth. It just grows with the number years we project it unto. With a life span of 100 years (fingers crossed) and 135 Million births every year, that means that in 100 years we are going to be 13.5 Million people on Earth that can all be fed with bio Food. The grey circle will grow too. So this graph underlies that we are going to be a stable human population of 13.5 Million for a 100 year human being lifespan.
Philip Pauley
1mo
With this context and timeframe in mind, the demographers estimate that 109 billion people have lived and died over the course of 192,000 years. If we add the number of people alive today, we get 117 billion humans that have ever lived. The rest is optimistic at best
Maksym Kloka
1mo
I would be surprised if the planet survives past 2050, but entertaining nonetheless.
Torsten Kriening
1mo
Thanks for sharing your thoughts. Very inspiring
Nick Shave FRAeS
1mo
An incredible post! Thanks Hugh for bringing this view into context for space sustainability.
Science Communicator, Chemist and Meteorite Merchant
1moWhile the diagram does look interesting, predicting the population 50,000 years into the future seems impossible given the rapid pace of technological advancement. Additionally, assuming that space debris will remain an issue over such a long timescale is incredibly naive. If technology continues to advance at its current rate, space debris will likely be a short-term problem. In 50,000 years, assuming humanity hasn't wiped itself out, our technology would be unimaginably advanced and unlikely to be troubled by a bit of orbital debris. Consider how much AI could transform the world in just a few decades, let alone all other tech to come over 50,000 years.