# Santa’s sleigh flies with the power of the Apollo mission rocket

Santa’s sleigh would need an engine with the thrust of the Saturn V rocket developed for the Apollo space program to fly, according to Physics students at the University of Leicester.

That is, as long as he attaches a pair of wings to his sleigh!

The study was inspired by a scene in the 2003 movie Elf, in which Santa replaces the waning Christmas spirit with a jet engine. The students calculated the thrust required for Santa’s sleigh to remain in flight during his Christmas Eve travels, and how powerful that jet engine would have to be.

Their conclusions have been published in the University’s Journal of Physics Special Topics, which enables undergraduate Physics students to learn about the process of peer review by writing and reviewing papers by applying theoretical concepts to light-hearted ideas.

The paper was written by University of Leicester Physics students and aimed to create a simple model that applied some basic physics concepts to the problem of keeping a sleigh in flight.

For Santa’s sleigh to remain in level flight, the weight of the sleigh must be balanced by the lift, which is when air flows over a wing at lower pressure than the air flowing under it. Assuming the sleigh has a pair of wings attached, and accounting for the weight of all the presents for the children of the world, they calculated that the sleigh must move at 5500m/s, around 10 times the speed of sound, in order to generate enough lift.

An engine powering the sleigh at that speed would need to provide enough thrust to not only stay at that speed, but also balance the effect of air resistance, which would be greater at high speed. They worked out that this would require 38 million newtons of thrust – roughly equivalent to 150 Boeing 747-400 engines or the Saturn V rocket used for the Apollo missions during the 1960s and 1970s.

Ryan Rowe, one of the student authors of the paper, said: “We have concluded that Santa’s jet engine must be extremely powerful and as a result he and the elves must have access to advanced technologies.

“We have found this module to be a fun and valuable experience as we were able to experience the process of submitting a paper to a journal. As well as experiencing how journals are run from an editorial perspective.”

Professor Mervyn Roy, Director of Education for the School of Physics and Astronomy, said: “In the Physics Special Topics module, we ask students to formulate new problems that can be explored using some of the simple physics that they know – and they often choose fun, imaginative topics! Although some of the scenarios may be from fictional universes or myths, the students learn some key skills around choosing relevant simple models, making appropriate approximations to explore these problems, and communicating their results. The basic physics should, of course, be correct - and this is checked by the student reviewers of each article, in a process overseen by a student Editorial Board.

“The process that the students go through mimics that of real research physicists working on exciting topics from black holes to cancer treatment. We have to investigate new problems and approach their solution in a creative way, we have to clearly communicate our findings, and these results are checked by fellow scientists as part of the peer-review process.”

Over the years, University of Leicester students have suggested several theories to account for Santa’s festive feats, from calculating the speed required to deliver all his presents in one night, how much energy is required to power his sleigh to the Christmas spirit required to lift his sleigh into the air

However, no single theory has managed to explain how Santa accomplishes the incredible feat of delivering presents to all the world’s children on Christmas Eve, so research is expected to continue in future.