HOTOL: Britain’s Spaceplane 

by Dan Sharp

“Clearly, the Hotol project ended without the vehicle being built and an effort has been made, in the writing of this book, to avoid passing judgement on the decisions made by those involved in the Hotol story. It seems, where Hotol is concerned, that everyone familiar with the project has their own views on it one way or another. 

Would the Hotol project have resulted in a viable vehicle if fully funded and given the development time asked for by the aerospace companies? It cannot be said for certain that it would.” 

Wait—if more money and more time had been on the table, the project might still not have succeeded?? What other factors are there??

Mind you, Dan Sharp contrasts the British project with the American Space Shuttle that had launched just a year earlier “with vastly higher levels of funding” and rules it “not viable” either. It all depends on the criteria you apply. For the Brits those included winged / uncrewed / reusable, with quick turnaround / capable of operating in the airless environment of outer space but still be single-stage. If you remember your science lessons you know those last two items are not compatible: to be able to deal with the “unfortunate fact that the Earth’s gravitational field is about 10% too high to make a Single-Stage-to-Orbit rocket practical” a hybrid propulsion system was thought to be the only solution. (Which is why the NASA Shuttle launches with external tanks and lugs a lot of extra weight around.)

So secret was the project at the beginning (1982) that the chairman of Rolls-Royce didn’t know that his own company was bankrolling and developing HOTOLs propulsion system until in 1984 an evening news TV science editor blithely blew the cover after inadvertently catching a glimpse of the drawings at airframe maker British Aerospace during a pre-Farnborough airshow visit. While that was “information he should not have had access to,” apparently HOTOL had been slated for unveiling at the airshow anyway. Once the cat was out of the bag “hardly a week went by without publicity for Hotol appearing in the press,” which is the caption of this amusing photo:

An entire chapter is devoted to that unauthorized leak and it is the one chapter, of 12, that makes for relatively light reading. For everything else, copious amounts of grey matter are required. You probably won’t need your slide rule.

The book proceeds chronologically. To lay the groundwork, Sharp starts with fundamentals such as how an airbreathing engine achieves combustion, how a liquid hydrogen/liquid oxygen combo burns, and basic rocket architecture and fuselage configurations.

HOTOL was of course not the only idea the world’s rocket scientists investigated and so the book discusses (several) alternate approaches and of course most (all?) of the numerous HOTOL configurations/variants (none of which went past the paper/theoretical stage). If you are on familiar ground with this, know that cf. HOPE-X, Hyperplane, Star-H, DC-X are not included but, say, Hermes, NASP, Sänger, Skylon, LART are. This is, incidentally, the only book about Hotol. Work on it started in 2018, as a follow-up to Sharp’s 2016 book in Crécy’s “British Secret Projects” series (vol. 5) which dealt with the “British Space Shuttle” aka MUSTARD (Multi-Unit Space Transport and Recovery Device).

Research on that book brought Sharp into contact with Alan Bond, one of the founders of Reaction Engines Limited that created the HOTOL project, as well as deputy technical manager Gerald Wilson. Both of them made much material available that is new to the published record, hence the book is dedicated to them. Other HOTOL and Reaction Engines Ltd. people have contributed/commented as well, ergo this book can be considered properly vetted by principals, down to minutia as peripheral as BAe’s wind tunnel model naming convention. There are many bits from interviews, internal communications, and press notices. Thank goodness the book has an Index (albeit selective)!

Through much of 2024 prospective readers of this much-delayed book could see it taking final shape as the author posted frequent progress reports on the interweb, with the manuscript getting larger—and then smaller again. As ever, a really hard part of book-writing is to make peace with all that has to be left out in order to keep a book to a size a general-interest readership will find manageable.

After reading this book you will appreciate how vital, and technically complicated, heat exchanger technology is to cooling the 1000-degree air at hypersonic speeds before it melts the engine. That topic was in the news as recent as 2024, when Reaction Engines Ltd. in the UK/Reaction Engines Inc. in the US finally had to declare bankruptcy. Which sorta brings us back to the opening quote. What are the odds that after years in the making, this book came out just in time to sing a swan song?

Lest we forget: excellent, coated paper; very good image reproduction; easy-on-the-eyes layout; and, hey, a sky-blue book ribbon! And all these riches for such a small price!

Copyright 2025, Sabu Advani (speedreaders.info)

HOTOL: Britain’s Spaceplane 

by Dan Sharp 

Tempest, 2025    [In US: Casemate]

300 pages,450+ b/w & color images, hardcover

List Price: $65

ISBN-13: 978-1911704294

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