(HABITATION EXTENSION MODULE)
What is HEM?
The Habitation Extension Module (HEM) is a study to explore what Britain could do to become a full partner in the International Space Station (ISS). This goal is captured in the HEM objective, which is to:
“make a contribution to the International Space Station that both creates and demonstrates a UK capability to contribute to human space flight that is comparable to other ESA nations”.
The study is intended to contribute to the current debate about what the UK should be doing in human space flight and in particular whether the UK should undertake late involvement in the International Space Station. There have been two reports that have examine the minimum Britain could do to get an astronaut onto the ISS from the British Interplanetary Society and the Science and Exploration Working Group (set up by the Science, Technology and Facilities Council) The HEM study explores the implication of a fuller UK role in human spaceflight.
There would be two HEM modules that attach to two berthing ports on the Node 3 module of the ISS, which contains the habitation equipment that enables a permanent crew of six people to live at the station. The HEM modules would add many of the habitation features that were originally intended for the ISS but are not in the current design.
What Does HEM Do?
Together the two modules would add 100 m3 to the habitation volume of the ISS (doubling Node 3 volume) providing:
- a communal area for eating, meeting and socialising.
- 6 crewrooms with enhanced radiation protection (100 kg / m2).
- a habitation store for 82 ISS Cargo Transfer Bags – (around 2 tonnes)
The two HEMs would also deliver over 3 tonnes of supplies and experiments, which would support British science activity and be Britain’s contribution to the running of the ISS.
HEM Design
The basic HEM module is a cylinder 3.8m in diameter and 5.7m long. At its launch on a Soyuz/Fregat rocket the HEM weighs 7 tonnes. Once in orbit it flies to the ISS using its own propulsion system. When it reaches the space station the robotic arm catches the HEM and berths it to Node 3.
Each HEM has a internal volume of 50 cubic meters. One module called HEM-C uses this space as a common room and the second HEM-D has the space divided up into six crew cabins.
Isometric view of HEM C
What Would HEM Cost?
The development programme for the basic HEM would cost around £300 million and then each module would cost around £90 million to build. The complete cost for two modules including the two Soyuz/Fregat launches and a complimentary science programme to use the ISS facilities would be £600 million.
This would be spent over 6 or 7 years so the average would be below £100 million a year but the spend cannot be uniform and in the most expensive years the spending would peak around £170 million. This would mean in the peak year that the UK civil space budget would need to increase by 80% but this would still leave the UK the lowest GDP spending nation in ESA.
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READ ABOUT HEM IN SPACEFLIGHT The Feb 2008 issue of Spaceflight has a feature article about HEM To download article click here To download cover artwork click here |
WEB QUESTIONS AND ANSWERS
I have been following the Web discussions on HEM and some issues they raise merit responses, so here they are.
Isn’t the UK, as an ESA member, already involved in the ISS/Columbus; after all there is a Union Jack among the flags in the Destiny Module?
The answer is an unequivocal no. Columbus is an optional programme and the UK opted out and has made no contribution to it or any other part of the International Space Station. It is because the UK has made no contribution to the ISS that it cannot as a matter of right utilise it.
The Union Jack is in the Destiny Module flag display, this because the UK did sign the international treaty that established the ISS, but that treaty did not commit the UK to support the programme in anyway and I doubt if we even paid for the ink in the pen used to sign it.
The HEM cannot be launched until after Node 3 is attached in 2010 and
the current plans are to end the ISS in 2015 so is the HEM worth it?
The earliest the HEM could be launched is 2011, and although it quite likely the ISS life will be extended beyond 2015 any decision on the proposal would have to assume the operational would be around 4 years. It would however allow UK scientists to use the space station before the HEM’s arrival, so they would end up with pretty much the same access as the scientists from other partner nations.
Getting HEM ready for launch by 2011 would possible but tight (communications satellites with higher levels of complexity meet this sort of timescale). Even if one assumes 2012 as more realistic it still leaves a reasonable useful life. The key point here is that this sort of system does not require decades for completion.
I think also the much of value of HEM would be in the technology demonstration of things such as plastic composite structures, radiation shelters, and generic avionic approaches and a 4 year life is quite adequate to do that. It also would demonstrate that the UK can contribute to major human space flight activities and thus getting our feet under the table with an effective voice as the next round of programmes are negotiated.
Would it not be cheaper to launch just one module?
Yes, it would save about £120 million but it would mean losing the radiation protection in the HEM-D (maybe the most valuable new thing it offers) and the total logistic load carried drops below a single Progress supply mission and starts to look a bit thin. It should be remembered that HEM study is a contribution to the overall debate concerning UK involvement in human space flight. It shows that the UK can still make a technical contribution to the ISS and, while there are of course other options, HEM represents an upper bound when the UK involvement would become comparable to the other European partners.
Why should the UK fund this rather than more astronomy and space physics where we already have a strong capability?
The space activities of British astronomers and space physicists are funded on a GDP basis the same as in all other European countries (enforced by the ESA treaty). Britain has a very large GDP so they get a lot of money (about a third of the total UK civil spend that also includes Earth observation and ventures like the Gailleo Navigation system). There is no doubt they do an excellent job with this money and I for one would not begrudge them a little more.
However the campaign for UK Human Spaceflight addresses the needs of all the other UK scientist and engineers who also need access to space for their research and who have, no facilities, no government money whatsoever, and no body to look after their interests. Ironically given the constant emphasis by the UK government on the importance of getting a tangible return from the UK space budget, the science being excluded includes medicine, pharmaceuticals, materials, micro-physics, engineering that is all the sciences that actually produce results the general public will really notice impact on their everyday lives.
The Habitation Extension Module is the most ambitious of a range of options the UK Human Campaign has put forward highlighting this iniquity, and if this were the one selected, it, and a corresponding science programme, would need annual expenditure at a similar level to that currently enjoyed by the UK’s astronomers and still leave the UK the lowest spending by GDP nation in ESA by a very considerable margin.
Britain should not get involved in human space flight because it is
much more expensive and less cost effective than robotic spacecraft.
It is an urban myth that human space flight is less cost effective than robotic spacecraft, in fact the costs are about the same (an average around £20 million per experiment). The HEM programme and a complimentary science programme would be a total of £600 million and this would enable around 100 UK experiments to be flown over 6 or 7 years. This would be £6 million per experiment well below the average – and by current space standards very cost effective.
It may also be worth pointing out the HEM is considerably cheaper than the British led Envisat – the most expensive unmanned satellite ever launched into earth orbit and it was made in Britain! And also cheaper than some UK military space projects.
If Britain was to get involved in human space flight it should by-pass
the space station and go straight to the new Moon Mars initiatives.
This approach would not help UK scientist who would like to use the experimental facilities on the ISS. Also the ISS is an important precursor development to long duration space flight, especially for human flights to Mars. And the HEM feasibility design would develop radiation protection, plastic structures and a generic avionic suite, all of which would be valuable contributions to missions to Moon and Mars not currently on the ISS.
The other key issue if the UK did want to do Moon / Mars we would have to cooperate with some or all the partners on the ISS. The HEM is a politic way to demonstrate the UK can be a partners in such enterprises and make real contributions. If we can demonstrate this early (which means this year) then we will be able to have some influence the direction these new initiatives.
In short if the UK
wants involvement in Moon/Mars then HEM is actually a pretty good starting point.
Mark Hempsell
DOWNLOADS
Dimensioned Drawings (Issue 1) -pdf
Drawing of HEMs attached to ISS Node 3 - jpeg
Mass Budget Report (Issue 3) - pdf
Propulsion
Schematic (Issue 1) -pdf
Isometric View of HEM C - jpeg
