Crossing a Sand Sea Is an Arithmetic Problem

Deserts are the most predictable of the hostile environments. The weather is knowable, the terrain does not change quickly, and there is almost nothing that can surprise a prepared party. What makes them dangerous is that the margins are consumed silently. You do not notice the extra fuel burned in soft sand until the gauge is lower than the plan, and by then the plan is behind you.

Fuel: the number people get wrong

Consumption in soft sand at low tyre pressures with a heavy vehicle runs 40 to 80 percent above the same vehicle's road figure, and occasionally double it. A truck that returns 11 litres per 100 kilometres on tarmac will use 18 to 22 in dunes. Calculate the crossing on the higher figure, then add a reserve of at least 25 percent on top, and treat that reserve as untouchable rather than as part of the range.

Carry fuel low and outside the living space where possible, in proper containers, secured so they cannot move. Note that jerrycans on a roof rack are the worst option available: high weight, heat, and a fire risk if the vehicle rolls. Plan refuelling points on the assumption that at least one will be out of stock, which in remote regions is normal rather than exceptional.

Water: more than you think

In 40 degrees with physical activity, an adult loses six to ten litres a day. Plan six litres per person per day for drinking alone, plus two for cooking and minimal washing, plus a fixed emergency reserve of twenty litres per vehicle that never enters the daily calculation. For four people on a five day crossing that is 160 litres of working water plus the reserve, which is 160 kilograms of payload and a real constraint on the build.

Carry it in at least two separate tanks or containers, so that one failure does not empty the trip. Treat and filter what you take on along the way rather than trusting the source.

The desert does not care how good your vehicle is. It cares how honest you were with your fuel calculation.

Heat, for people and for machines

Work in the cool hours. In serious summer heat, that means driving from first light until eleven and again from four until dusk, and resting in shade in between. This is not a comfort preference; it halves water consumption and removes most of the risk of heat exhaustion in the party.

Machines need the same discipline. Radiators pack with fine dust, which you clear daily. Automatic transmissions overheat in prolonged low-range sand work, which is why an auxiliary cooler earns its place. Tyres run hot at low pressure, so speeds stay down. Batteries fail earlier in heat than in cold, and a failed battery in a group of one is a serious situation.

Navigation and the discipline of a track log

Sand seas move and tracks disappear. Carry a satellite navigation device with topographic mapping, a phone with offline maps as a backup, a compass, and paper at a scale that shows the escape routes rather than the detail. Record your track continuously. The single most valuable navigational asset in a desert emergency is the log of exactly where you came from, because your own tracks are compacted, known and lead to fuel.

Agree a turnaround rule in advance and write it down: the point at which remaining fuel, water or days requires the party to reverse, regardless of how close the objective is. Discussing this at the table, before the trip, removes the worst decision-making conditions in travel, which are tiredness, sunk cost and an audience.

Convoy discipline

Two vehicles minimum for a genuine crossing. Keep visual contact and radio contact, agree fixed intervals for regrouping, and never let a vehicle out of sight of the group in dune country, where a rollover on a slip face can happen in seconds and be invisible from two hundred metres away. The lead vehicle carries the responsibility for the line; the last vehicle carries the responsibility for nobody being left behind.

Communication and the plan at home

A satellite messenger with a scheduled daily check-in, plus somebody at home holding the route, the vehicle details, the party list and the date at which they should raise an alarm. This costs nothing and is the difference between a search that starts on the right day in the right place and one that starts a week late across a hundred thousand square kilometres.

Questions we get asked

How much fuel range do I need for a crossing?

Enough for the planned distance at sand consumption, plus 25 percent, plus the distance back to the last known fuel from the halfway point. If those three do not fit in the vehicle, the route needs a depot or a different plan.

Can a solo vehicle cross a desert?

Experienced parties do it on established routes with satellite communication, full recovery equipment and conservative margins. For anything off a known track, a second vehicle is the difference between a breakdown and an emergency.

What about sandstorms?

Stop, park with the rear to the wind, close everything, cover intakes and wait. They are usually a matter of hours. Driving in one causes collisions, and the fine dust that gets into an engine while it is running is what does the lasting damage.