The merits of strategic decision deferral

Li-ion battery
Turbofan engine
Hydrogen fuel cell

The attainment of zero-CO2 emissions from aviation is an environmental necessity. Whilst the urgency of this is unquestionable, timely deliverability is the issue. The two principal hurdles are:

  • Self-evidently, aircraft require energy dense, or more accurately high specific energy, storage and related propulsion solutions for the source of energy that is carried onboard. Fossil-based aviation fuels, unsurprisingly, achieve this by packing, in the case of Jet A-1 fuel, a very considerable 43.15 MJ of energy into every kilogram (equivalent to 11.99 kWh / kg). Much R&D effort is underway to improve figures for electrically powered storage, the two more developed front-runners for general aviation being batteries (presently offering a few hundred Wh / kg at best), and the hydrogen fuel cell (offering c. 1,500 Wh / kg at best).
  • Aviation certification / regulatory authorities have at their core, entirely reasonably, a focus on safe operation of aircraft. The development of regulations and certification standards has historically been incremental rather than involving sudden step-changes, let alone complete changes to energy storage, control & management systems, and propulsive units. The culture of regulatory authorities is evolving, albeit slowly, as they become more responsive to the requirements of an aviation industry in a state of flux transitioning to new energy sources, management systems and standards. Their focus critically needs to remain on safety whilst being responsive to demands from newly applied technologies.

At Cormorant, we do not see ourselves as being leaders in the development of management thought. However, being vested in e-aviation we briefly write here regarding strategic decision deferral, which we summarize as:

A management decision-making approach, particularly relevant in times of dynamic technological and / or regulatory development, which seeks to consciously defer making key choices until the latest point practicable without affecting a project’s critical path, such that knowledge development and /or the evolution of the regulatory environment may proceed to the most advanced extent possible so that the likelihood of a correct decision is increased.

To illustrate this approach, we look at a question that we are often asked:

Which battery system are you going to use? – This is, obviously, a leading question that significantly presupposes the outcome. Given ongoing developments in potential CO2-zero energy storage solutions for aviation applications such as Cormorant, our position is best described as one of agnosticism whilst keeping a watching brief on developments in battery and other energy storage solutions. Deliberately Cormorant’s airframe can accommodate several energy storage possibilities. Obviously, we must select the optimal solution to progress initial certification with the regulatory authorities – the time to decide is not yet and will be addressed when such a decision lies on the critical path for Cormorant’s development. Beyond this it is entirely possible that more than one energy source and propulsion solution may be incorporated in different certified configurations of the aircraft.

Energy storage agnosticism

Cormorant’s design has within its airframe some 550 dm3 of volume (550 kg of mass) allocated for energy storage. There is also space forward of the fan, in the thrust line, to accommodate power generating and / or energy management systems. Historically this would have been occupied for CO2-generating, aviation fossil fuel.

At the present phase in Cormorant’s development, as the aircraft has many other attractive selling points, we are deliberately ‘energy storage solution agnostic.’ That is, we are consciously deferring selection of the preferred energy storage solution until such time as this decision is critical to the progress of the aircraft. This is a benefit of our SEA design values that avoids us becoming wedded to a particular solution too early in what is a rapidly evolving area of technological progress; the risk of doing so is to expose us to a “fake it until you can make it” scenario where the pitfalls of too early a choice of a subsequently realized, suboptimal solution leads to a downward spiral of overpromising and under-delivering.

Here we briefly summarize where we are at with the two front-runners for ‘green’ energy storage in general aviation: batteries; and, the hydrogen fuel cell.

The current green energy storage alternatives

Within the short-term, there appear to be two principal routes to the storage of energy for smaller, zero CO2-emission at point-of-use, electrically powered aircraft. Here we briefly review some of the considerations for each.

Rechargeable batteries

  • Rechargeable batteries use electrochemical reactions (that consume the electrodes) to generate a current when discharging or require a current when being charged (when electrodes are substantially regenerated). The ideal, or ‘holy grail,’ is to maximize the total energy that can be stored in the electrodes per unit mass and volume whilst also facilitating the reversible transfer of ions between the electrodes through an electrolyte to generate current and to recharge. Whilst the chemistry is simple in principle, the devil is in the detail – choreographing the match between (and finding) high specific energy electrodes and an efficient electrolyte to transfer charge to maximize performance whilst delivering a commercial viable product at acceptable cost that: degrades minimally for long product lifetime; delivers multiple (ideally fast) recharging; is safe, lightweight, and certifiable (for aviation use); and, is sustainably sourced and produced – is anything but.
  • Traditional Li-ion technology enables charge transfer using lithium ions between a cathode often containing heavy metals and a graphite anode via a liquid electrolyte.
    • Commercially developed by Sony over 30 years ago, much research is ongoing into maximizing the potential of Li-ion cells. As rechargeable or single-use derivatives, they now power just about everything not connected to the mains, from TV remote controls via mobile smart devices to cars and aircraft, they have become ubiquitous.
    • Issues remain regarding maximum possible specific energy and dangers from overheating or overcharging, Li-ion batteries can suffer thermal runaway and, ultimately, cell rupture – in extreme cases this can lead to leakage, explosion, or fire. Flammable, liquid electrolytes have generated bad press for Li-ion technology on several occasions, be that for example in mobile smart devices,[1] cars,[2] and, for larger batteries, in fossil-fueled large aircraft.[3]
    • The specific energy for these traditional Li-ion batteries lies currently in a range up to c 265 Wh / kg,[4] with a likely practical limit proposed of some 435 Wh / kg.[5]
  • A considerable number of alternatives to traditional Li-ion battery formats are at various stages of development that seek to improve specific energy, specific power, cycle life, and safety. Still focused on the transfer of lithium ions between electrodes, much effort is under way:
    • At the cathode – where environmentally unacceptable heavy metals are often used in current configurations. Recycling of such material is highly desirable – in fact necessary,[6] though we believe total avoidance of their use is preferable. Early promise was indicated by the likes of IBM in 2019,[7] though at the time of writing there has been little further news regarding its .
    • Regarding the electrolyte (the medium that allows the transfer of charge between the battery’s electrodes) – solid electrolytes[8] offer interesting possibilities and improved safety characteristics.
    • At the anode – historically comprised of graphite in a traditional Li-ion unit (and limited to a capacity of 372 mAh/g),[9] electro-chemistries other than for graphitic carbon, such as sulfur[10] and silicon[11] offer promising possibilities and the prospect of significantly higher energy densities, theoretically up to a fivefold increase in the case of a sulfur anode.
  • Some alternatives to traditional Li-ion batteries (with may reach 435 Wh / kg with continual improvement)[12] include Li-Metal with a 400 Wh / kg product recently announced[13] (and potential up to 677 Wh / kg),[14] Li-Sulfur (with a theoretical gravimetric specific energy of 2,567 Wh / Kg – a fivefold increase above traditional Li-ion).[15]
  • In addition to all the above considerations there are also regulatory authorities’ concerns regarding the development of accurate methods and standards for monitoring energy storage in battery systems such that those operating aircraft are aware of how much usable energy is available to them. This is a work in progress. Simply put, if systems do not provide an operator of an electric aircraft with an accurate indication of how much energy is available to them – they will be flying in an uncertified (for commercial use), likely experimental, aircraft.
  • Irrespective of specific energy performance, as per the above point, battery energy systems for aircraft have basic safety and operational certification standards to be passed and, in some cases, devised.[16]

Hydrogen – specifically the hydrogen fuel cell

  • Here we focus on the hydrogen fuel cell as a means of converting stored hydrogen as a compressed gas or liquid in the role of a ‘consumable electrolyte’ in a fuel cell to produce electrical energy rather than being combusted directly to yield mechanical energy. Regarding sustainably produced, ‘green,’ hydrogen, many multinationals (e.g., Siemens Electric) [17] are vested in its development as are certain communities with a focus on sustainability.[18]
  • A fuel cell, like a battery, is an electrochemical cell. It has an anode and a cathode at which oxidation and reduction reactions take place, however the electrodes act as catalysts, and are not consumed in these reactions as in a battery (these reactions are reversed in a rechargeable battery, though it does degrade over several charging cycles). Instead, the reactions take place within a “fuel” – hydrogen in this case, which provides the source of electrons to generate current. The anticipated specific energy for an efficient aviation hydrogen fuel cell system (inclusive of hydrogen tanks) is forecast to be 2,000 – 3,000 W / kg over the period 2022 – 2025.[19]
  • As with batteries, significant R&D is underway, including the retrofitting of solutions into existing airframes, such as with Project Fresson[20] using a Britten-Norman Islander aircraft.
  • Development of a ‘hydrogen infrastructure’ to facilitate the replenishment of hydrogen in aircraft is obviously a concern, though interesting modular, ‘swappable,’ capsule-based solutions[21] offer a potentially rapid roll-out of locations where hydrogen can be made safely available. However, loading and on-board storage of hydrogen is not trivial, either as a gas at very high pressures up to 700 bar, or as a liquid at very low temperatures (minus 253°C).
  • As with batteries for energy storage in aircraft applications, there is a time consuming ‘regulatory process’ regarding the development of agreed standards for the use of hydrogen fuel cells in aviation applications, where industry needs to come up with viable solutions. Though, back in 2017, in a final report to the FAA’s Energy Supply Device Aviation Rulemaking Committee concluded “As certain technological, logistical, and regulatory hurdles are overcome, the use of fuel cells in both manned and unmanned aviation will become more prevalent”,[22] and “The main new risks identified have to do with the introduction of Hydrogen. Other possible introduced fuel cell system hazards are known, or are similar to them.”[23]

Minimizing the number of ‘known unknowns’

As the above illustrates, there are many considerations and intangibles regarding the two front runners for potential green energy storage in aviation applications. We do not envy those projects that have made or are having to make such choices now. As Donald Rumsfeld when Secretary of Defense under George W Bush notably remarked in 2002:[24] “…there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don’t know we don’t know.”

Based on publicly available knowledge and the number of current ‘known unknowns’ (let alone any ‘unknown unknowns’) impacting leading potential green energy storage solutions for e-aircraft,  it is not unreasonable to suggest that firmly committing to one solution at present is akin to a game of roulette, The stakes for individual projects, appropriately for aviation, are sky high.

Avoid accumulator bets

Some projects take the betting analogy to a rarefied level.

These ‘exotic’ projects play roulette sequentially with all their winnings, betting on the success of all known unknown outcomes. They may thus be proposing, for example, a specific green energy storage / power system; a novel propulsion system; autonomous flight in areas of dense population; and more – all innovative, having to satisfy the reasonable demands of regulators devising new standards as necessary, let alone relying on multiple applications of new technologies to deliver promised outcomes, whilst satisfying the expectations of investors who may have provided many hundreds of millions of € or $ in funding.

It may not be unreasonable to suggest that, for some of these highly marketed, ‘exotic’ projects that a real objective might be to serve as knowledge / expertise magnets such that they can function as e-aviation centers of excellence to survive and develop beyond any current project abandonment. They may then perhaps use their expertise, IP etc. to take advantage of and exploit other opportunities developing in the e-aviation sphere.

The original question, reworded – and answered

For readers good enough to have read this far, we might now answer the original question, somewhat reworded, hypothetically. Let us assume that we have today (February 16, 2022) successfully demonstrated an electrically powered Cormorant flying proof-of-concept prototype to the satisfaction of all stakeholders; the question as we contemplate ‘freezing’ the design such that it may progress through the regulatory certification process is – Which energy storage system is to be used?

The three proactive options in no particular order are:

  1. Go Green
    1. Select the preferred electric power system partner and most suitable electrochemistry for a battery system.
    2. Select the hydrogen fuel cell system partner(s)
  2. Stay Grey, then Go Green – use standard aviation fuel in an existing propulsion format, deliver a proof of concept or even a certified initial Entry Into Service of a versatile, robust and efficient aircraft, then proceed to option 1 in a certified e-version of the aircraft when the developmental and regulatory environment has crystallized around a certifiable green solution with acceptable performance characteristics.

The risks of pursuing either option 1.1. or 1.2. at the time of writing would present too many ‘known unknowns’ that can all too easily enter us into a terminally expensive regulatory or technological cul-de-sac, proving fatal for the project. The certification process would thus commence as the ‘grey’ option, likely using a turbofan propulsive unit. Those customers intending to buy this configuration would be offered retrofit options such that their ‘grey powered’ aircraft could be reconfigured to ‘green powered’ at a future point. Which green route to be selected would depend on having a satisfactory level of certainty for the strategic decision to be made to proceed that option to certification.

To conclude

Wherever practical, key strategic decisions should result in outcomes that are themselves adaptable and flexible. From a safety perspective, the electrification of aviation requires regulatory catch-up in most innovators’ opinions. For these original projects, management of this uncertainty whilst also incorporating technological progress in specific energy storage are crucial risk management challenges. Adding layers of to-be-regulated complexity is an invitation to delay and more likely failure. Embedding the required, currently subject to regulatory development, electric propulsion technology is therefore a sufficient goal for most projects with incremental improvements in design being useful add-ins.  History is littered with visionary projects that have failed due to being overly innovative, complex, or ‘ahead of their time’; technical innovation can prove to be a blind alley for many ‘exotic’ projects.

Vanity projects, or at least projects ahead of their time, are nothing new. A relatively unknown example of an advanced transportation system being from 1903: the ‘Zossen’ high-speed electric train.[25] Running on a 23 km section of specially adapted track with three-phase AC overhead energy supply, it held the world rail speed record of 210 km / h for half a century – and provided an expensive glimpse of the future but was at a dead-end at the time. Its technology had to wait for both AC electricity technology to mature, and associated infrastructure to be built and standardized  over subsequent decades. To be kind, maybe ‘Zossen’ was genuinely conceived of as a project to demonstrate what the future could hold and increase knowledge. The message for entrepreneurial companies in a highly regulated sector such as aviation is germane: do not build something that is undeliverable – too many projects bypass the market and end up in museums.

When made, most strategic decisions require the commitment of significant resources. In a dynamically developing environment, using the most up-to-date relevant information available is critical to enhancing success. Where decision outcomes depend on those developments, deferring decision-making to the latest practical point within a project is vital – this allows the minimization of uncertainty at the time by, to use Donald Rumsfeld’s terminology, allowing the most known unknowns to mature into known knowns.

Decisions can still of course be wrong, but they are less likely to be so.

‘Strategic decision deferral’ is not an excuse for inaction, rather it is taking key actions at the right time. The right time is when the making of such a decision enters the project’s critical path and technological, regulatory (and market – more on this in a later post) knowledge evolution has been allowed to develop to the maximum.

As previously mentioned, the ability to pursue such a ‘safe’ (or ‘safer’) route to market is borne out of the flexibility that our SEA design values gives Cormorant. Not only does it allow us to offer an aircraft with a large, adaptable, readily reconfigurable cabin volume to undertake a variety of mission types across market segments, but also, critically in the context of this post, it enables deferment of strategic decisions affected by technological developments and their regulation, positive procrastination if you will, such that the greatest amount of current information is available before irreversible or costly choices are made. It has resulted in an aircraft design that has flexibility and adaptability at its core; including in its energy storage and power system – permitting reconfiguration if necessary. Strategic decision deferral, used proportionately, is embedded within and is therefore an important integral part of our SEA design values.


[1] BBC (2017, January 23), Samsung confirms battery faults as cause of Note 7 fires, BBC News, https://www.bbc.co.uk/news/business-38714461 – accessed 14/02/2022

[2] Siddiqui, Faiz (2021, August 4), While they were asleep, their Teslas burned in the garage. It’s a risk many automakers are taking seriously., The Washington Post, https://www.washingtonpost.com/technology/2021/08/04/tesla-fire/  – accessed 14/02/2022

[3] Irfan, Umair (2014, December 18), How Lithium Ion Batteries Grounded the Dreamliner, Scientific American, https://www.scientificamerican.com/article/how-lithium-ion-batteries-grounded-the-dreamliner/  – accessed 14/02/2022

[4] As at What is a lithium-ion battery and how does it work?, Clean Energy Institute, University of Washington, https://www.cei.washington.edu/education/science-of-solar/battery-technology/ – accessed 15/02/2022

[5] See footnote 12

[6] Summarized at “WHAT HAPPENS TO YOUR WASTE Batteries – Wet and dry cell, rechargeable and single-use” https://erp-recycling.org/learning-centre/what-happens-to-your-waste/batteries/#:~:text=Most%20types%20of%20batteries%20contain,be%20recovered%20and%20re%2Dused

[7] As at “IBM announces battery technology breakthrough” – https://www.techrepublic.com/article/ibm-announces-battery-technology-breakthrough/

[8] As under development by e.g., NEI Corporation – https://www.neicorporation.com/products/batteries/solid-state-electrolyte/

[9] Shao, Gaofeng et al (2020, September 24), Polymer-Derived SiOC Integrated with a Graphene Aerogel As a Highly Stable Li-Ion Battery Anode, ACS Appl. Mater. Interfaces 2020, 12, 41, 46045–46056, https://pubs.acs.org/doi/full/10.1021/acsami.0c12376 – accessed 14/02/2022

[10] As under development by e.g., Li-S Energy – https://www.lis.energy/site/li-s-energy-applications/li-s-energy-battery

[11] As developed by e.g., Amprius Technologies – https://www.amprius.com/technology

[12] Karabelli, D.; Birke, K.P (2021 November) Feasible Energy Density Pushes of Li-Metal vs. Li-Ion Cells, Appl. Sci. 2021, 11, 7592, https://doi.org/10.3390/app11167592 – accessed 15/02/2022

[13] As at Sion Power (2021, August 4), Sion Power Introduces a Full-Scale Rechargeable Battery Targeting the Electric Vehicle Industry, Over 400 Wh/kg and 810 WHO/L  https://sionpower.com/2021/sion-power-introduces-a-full-scale-rechargeable-battery-targeting-the-electric-vehicle-industry-over-400-wh-kg-and-810-wh-l/ – accessed 15/02/2022

[14] Ibid.

[15] As at Li-S Energy Here are the key advantages of Lithium-sulphur battery technology   https://www.lis.energy/site/li-s-energy-applications/lithium-sulphur-key-advantages#Greater-Energy-Capacity – accessed 15/02/2022

[16] Early concerns regarding lithium batteries were, for example, summarized by the EASA in 2017 – EASA (2017, March 27) SPECIAL CONDITION LSA Propulsion Lithium Batteries https://www.easa.europa.eu/sites/default/files/dfu/SC-LSA-Fx2480_LSA-Propulsion-battery-id1_19052017%20Final.pdf

[17] Siemens Energy LLC (2021), Green Hydrogen: Cornerstone of a sustainable energy future [White Paper]. Retrieved from and downloadable at https://www.siemens-energy.com/mea/siemens-energy-in-middle-east/company/megaprojects/dewa-green-hydrogen-project.html#Download

[18] E.g., the Scottish Orkney Islands as at https://www.orkney.com/life/energy/hydrogen

[19] As at HyPoint, Inc (November 2021), Technical White Paper (Appendix 2) – retrieved from and downloadable at https://docsend.com/view/t9aw2mk

[20] As at Project Fresson – https://projectfresson.uk/

[21] As developed by Universal Hydrogen Co, https://hydrogen.aero/product/

[22] Quote from Section 6 ‘Conclusion’ of Final Report [re Hydrogen Fuel Cells] of Energy Supply Device Aviation Rulemaking Committee to Federal Aviation Administration Executive Director, Aircraft Certification Service and Executive Director, Office of Rulemaking (08/12/2017) p 35 – https://www.faa.gov/regulations_policies/rulemaking/committees/documents/media/Energy%20Supply%20Device%20ARC%20Recommendation%20Report.pdf

[23] Quote from Section 6.3 ‘What is the highest priority for the airworthiness authorities so they can facilitate certification of fuel cell systems?’ of Final Report [re Hydrogen Fuel Cells] of Energy Supply Device Aviation Rulemaking Committee to Federal Aviation Administration Executive Director, Aircraft Certification Service and Executive Director, Office of Rulemaking (08/12/2017) p 38 – https://www.faa.gov/regulations_policies/rulemaking/committees/documents/media/Energy%20Supply%20Device%20ARC%20Recommendation%20Report.pdf

[24] Quote as at https://en.wikipedia.org/wiki/There_are_known_knowns#:~:text=Rumsfeld%20stated%3A,things%20we%20do%20not%20know

[25] See “Test runs at world-record speed – The Zossen high-speed railcar reaches 210 kilometers per hour”, Siemens https://new.siemens.com/global/en/company/about/history/stories/speed-world-record-1903.html – accessed 15/02/2022

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