Have You Ever Taken Apart a Lighter?

You may never have built a rocket, but there is a good chance you have held a lighter in your hand, or perhaps even taken one apart out of curiosity.

Inside, the mechanism is surprisingly simple. A small spark is created, fuel is released, and the spark ignites the fuel to produce a flame. The lighter is not fascinating because of the flame itself. It is fascinating because such a small object can store energy and release it in a controlled way whenever we need it.

At first glance, a lighter seems to have little connection with spacecraft. One creates a small flame on Earth; the other travels through the vacuum of space. Yet the engineering idea behind both is surprisingly similar: storing limited resources and releasing energy in a controlled way to accomplish useful work.

Now imagine replacing that flame with motion. Not the motion of a car or an airplane, but the carefully controlled movement of a spacecraft. And not a spacecraft the size of a building or even a satellite the size of a car. A spacecraft small enough to fit in your pocket.

Welcome to the world of PocketQubes.

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A Satellite Small Enough to Fit in Your Pocket

A standard 1P PocketQube measures only 5 × 5 × 5 centimeters. Compared with the satellites most people imagine, it is incredibly small.

But the surprising part is not simply its size. Despite having a volume smaller than a coffee cup, a PocketQube can still carry cameras, radios, onboard computers, solar panels, and—on some missions—even its own propulsion system.

That immediately raises a question: How can something so small move itself in space?

Most people imagine spacecraft propulsion through the image of a rocket launch: powerful engines, enormous flames, and tremendous force.

A PocketQube works very differently. In fact, if you watched one operating in space, you probably would not see anything at all.

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Why Fire Does Not Move a Spacecraft

Our everyday experience teaches us that engines create movement by burning something.

Cars burn fuel. Jet engines burn fuel. Rocket launches produce spectacular flames.

So it is natural to ask: why not simply build a tiny rocket engine for a tiny satellite?

The answer is that the flame itself is not what moves the spacecraft.

The important part is what leaves the spacecraft.

A spacecraft moves because it throws mass in one direction, causing itself to move in the opposite direction. This is Newton’s third law of motion: every action produces an equal and opposite reaction.

Imagine standing on a skateboard while holding a heavy ball. If you throw the ball backward, the skateboard moves forward. The harder you throw, the more your position changes.

The same principle works in space. A spacecraft does not push against air or the ground. It pushes against physics itself by ejecting something away from its own body.

That “something” is called propellant.

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What Does a PocketQube Throw Away?

Large rockets carry enormous amounts of chemical propellant because they need tremendous thrust to escape Earth’s gravity.

A PocketQube cannot do that. There simply is not enough room.

Instead, some miniature spacecraft use a very different approach. Rather than burning large quantities of fuel, they use electrical energy to accelerate very small amounts of propellant to extremely high speeds.

Some electric propulsion systems use solid materials, such as metals or polymers, as their propellant. When an electrical pulse is applied, a small amount of material is vaporized. Some atoms and molecules lose electrons and become electrically charged, creating plasma.

Unlike the bright flame of a rocket engine, plasma propulsion is not designed mainly to create heat or visible light. Its purpose is to create charged particles that can be controlled and accelerated by electric fields.

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From Thrust to Mission Capability: Why Delta-V Matters

Creating thrust is only the beginning of spacecraft design.

A propulsion system may be able to push a spacecraft, but that does not yet tell us whether the spacecraft can complete its mission.

The more important question is: How much can the spacecraft change its motion during its lifetime?

For spacecraft engineers and builders, this question leads to one of the most important concepts in astronautics: Delta-V.

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Delta-V Is a Spacecraft’s Maneuvering Budget

Delta-V is often misunderstood. It is not the speed of a spacecraft. A satellite orbiting Earth is already traveling at tremendous velocity. Delta-V does not describe how fast the spacecraft is moving around Earth. Instead, it describes how much additional change in velocity the spacecraft can create using its available resources.

The symbol itself provides a clue. The Greek letter Δ (delta) means “change,” so Delta-V literally means “change in velocity.” A useful way to think about Delta-V is as a spacecraft’s maneuvering budget.

Just as a battery has a limited amount of stored energy, a spacecraft has a limited amount of ability to change its motion.

Every maneuver spends part of that budget.

Changing orbit requires Delta-V. Correcting the spacecraft’s position requires Delta-V. Maintaining a formation with other satellites requires Delta-V. Avoiding potential collisions requires Delta-V. Even safely ending a mission through controlled deorbiting requires Delta-V.

Once that capability has been used, the spacecraft may continue operating, but its ability to adapt becomes increasingly limited. For a spacecraft builder, Delta-V is not simply a number. It represents the choices that remain available after launch.

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Why Two Similar PocketQubes Can Have Very Different Capabilities

Delta-V becomes easier to understand through a simple example.

Imagine two PocketQubes with the same size, the same mission goal, and similar miniature propulsion systems. From the outside, they may look almost identical. Both can produce thrust. Both can communicate. Both can collect data. But one spacecraft has a total Delta-V capability of 20 meters per second (20 m/s), while the other has 100 meters per second (100 m/s).

These numbers do not tell us how fast either satellite is orbiting Earth.

Instead, they tell us how much additional change in motion each spacecraft can create during its mission. The PocketQube with 100 m/s of Delta-V has a much larger maneuvering budget. It may be able to perform more orbit corrections, maintain its position within a constellation for longer, respond to unexpected changes, and still have enough capability remaining for end-of-life operations. The spacecraft with only 20 m/s may need to make much harder choices. A few necessary maneuvers could consume a large portion of its available capability. This is why two spacecraft with similar engines can have very different mission outcomes.

The difference is not always visible from the outside. It is hidden inside the design calculations.

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Estimating Delta-V Before Launch

A spacecraft builder cannot wait until a satellite reaches orbit to discover how much Delta-V it has. That capability must be estimated during the design process. One of the most important tools engineers use is the Tsiolkovsky Rocket Equation:

Δv = Isp × g₀ × ln(m₀/mf)

At first glance, the equation may look complicated. But its meaning is surprisingly intuitive.

Delta-V increases when a spacecraft:

• carries more propellant;
• uses that propellant more efficiently;
• reduces the amount of mass it needs to accelerate.

These three factors influence almost every spacecraft design decision. The equation reveals one of the fundamental challenges of spacecraft engineering: Every improvement comes with a trade-off.

Adding more propellant can increase Delta-V, but propellant also adds mass.

A larger battery or solar panel may provide more power for propulsion, but it also consumes valuable space and weight.

A more efficient propulsion system may improve performance, but it may introduce additional complexity, cost, or development challenges.

A spacecraft is therefore not designed by choosing the most powerful individual component.

It is designed by finding the best balance between limited resources and mission goals.

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Why Efficiency Matters More Than Force for Small Spacecraft

This is why electric and plasma propulsion are so interesting for PocketQubes.

Small spacecraft cannot simply carry large amounts of propellant. They must achieve more with less.

Many electric propulsion systems work by accelerating propellant to extremely high exhaust velocities. Although the resulting thrust is very small compared with chemical rockets, the propellant can be used much more efficiently over long periods of time.

For a PocketQube, this trade-off can be extremely valuable. The goal is not to create the biggest push. The goal is to create the largest amount of useful mission capability from every gram of propellant, every watt of electricity, and every cubic centimeter of space.

This is the engineering mindset behind modern miniature spacecraft.

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