astronomy

Nuna 3

Nuna 3 is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Nuna 3 rather than just read about it. In short: The Nuna 3 is a solar car developed by Nuon Solar Team form the Delft University of Technology in 2004-2005 for the 2005 World Solar Challenge. It succeeded the Nuna2, the solar car that scored a second consecutive win for this solar team by winning the World Solar Challenge for the third time in a row.

Key takeaways

Nuna 3 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Nuna 3 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Nuna 3 from memory before moving on to harder problems.

Reference excerpt

The Nuna 3 is a solar car developed by Nuon Solar Team form the Delft University of Technology in 2004-2005 for the 2005 World Solar Challenge. It succeeded the Nuna2, the solar car that scored a second consecutive win for this solar team by winning the World Solar Challenge for the third time in a row. Nuna 3 was one of the favourites for the 2005 edition of the World Solar Challenge with a pre-race test-drive recorded top speed of 130 km/h. The final result was that the 3021 kilometers between Darwin and Adelaide were covered in a record 29 hours and 11 minutes, averaging about 103 km/h. It has very efficient solar cells of a type normally used to power orbital satellites (as had the previous Nunas), and it has better aerodynamics and is lighter than its predecessors. It was designed and built by 11 students from different disciplines of the Delft University of Technology, who have partly put their studies on hold for this. They used the high-tech labs and workshops of the University and, as with the Nuna 2, they received advice from Wubbo Ockels, the first Dutch astronaut and professor at the University.

Main specifications

Design criteria To have a good chance to win, the car has to:

collect as much solar energy as possible use as little energy as possible to drive at a certain speed. This means special attention to: the efficiency of transferring electrical energy to the wheels, and minimizing friction, constituted by: air friction (air resistance), and rolling friction, which in turn is affected by the weight, among other things

Solar cells The solar cells are made of gallium arsenide (GaAs) and consist of three layers. Sunlight that penetrates the upper layer is used in the lower layers, resulting in an efficiency of over 26%. This type of solar cell is among the best available currently. Apart from efficiency, size also matters, so the entire upper surface of the Nuna 3 is covered with them, except for the cockpit. Efficiency is optimal when the cells are hit by the solar rays perpendicularly. If not, output is reduced by roughly the cosine of the angle with the perpendicular. Because the 2005 race was held in September (as opposed to October or November in previous years) the sun was lower in the sky (it is earlier in spring). To compensate for this, as many cells as possible were placed at the sides, most notably on the wheel caps.

A solar cell gives a certain amount of current for a certain amount of sunlight. The voltage depends on the load (more precisely the resistance of the load). The power is the product of voltage and current and therefore also depends on the load. Over a certain voltage the current of the solar cell quickly drops to zero, as the graph illustrates. However, the batteries have a fairly constant voltage, which also has a rather different value than that of the solar cells. So a voltage transformation is needed. A special type of DC-DC converter is used to ensure the load resistance presented to the solar cells is such that the solar cells give maximum power, so also at the top of the green line in the graph. This is called a Maximum power point tracker (MPPT). Here too, the goal is to have this conversion achieve maximum efficiency (>97%).

Aerodynamic design

The aerodynamic drag is an important part of the total resistance. Important are the frontal surface and the streamline. Any deviation from the ideal streamline will cause turbulence, which costs energy. The ideal streamline is achieved in various stages:

Through computer simulations of the design Through testing of a scale model in a wind tunnel. For example, liquid paints can be applied to see the flow of air over the surface. The photo shows is taken during one of those tests in the Low Speed Laboratory of the TU Delft. Through testing of the full scale car in a wind tunnel. For this a German-Dutch wind tunnel in Emmeloord will be used. From meteorological data from the area where the contest is to take place, it can be concluded that there will likely be a strong side-wind. The wheel caps of the Nuna 3 are designed such that a sidewind will have a propulsory effect.

Motor

The electromotor is totally encased in the rear wheel to minimise loss through mechanical transmission from motor to wheel (such as in a normal car in the gear box and cardan). The motor is an improved version of the original 1993 Motor of the Spirit of Biel III by the Engineering School of Biel, Switzerland (now: Berner Fachhochschule Technik und Informatik). The improvements are due to completely redeveloped digital power electronics and control, realized 1999. They allowed for 50% more power (over 2400 W) and a 45% higher torque compared to the 1993 Spirit of Biel II. The efficiency of the total drive system (including the power electronics losses) is also improved and is now over 98%. But as the graph shows this depends somewhat on the speed and increases with speed. The design was initially made to reach its maximum performance at the normal cruising speed of the solar car at around 100 km/h.

Test drive During one of the test drives in the Netherlands the Nuna 3 achieved a speed of 130 km/h. On the first day of the race the car achieved a top speed of 140 km/h. For comparison, the Sunraycer (the first winner of the Solar Challenge race) attained a top speed of 109 km/h in 1987.

Important opponents The winner of the North American Solar Challenge from the University of Michigan (USA) was considered to be one of the most important opponents. Other important contestants were the MIT (also USA) and the Japanese Ashiya University team. In 2005 there were also two other European contestants, the Dutch Raedthuys Solar Team from the University of Twente and the Belgian Umicore Solar Team from Leuven.

… excerpt ends here. Continue reading the full article.

Illustrations

Nuna 3: VI characteristic of a solar cell — VI characteristic of a solar cell

Nuna 3: Efficiency of the Biel engine — Efficiency of the Biel engine

Worked examples

Example 1 — a first encounter with Nuna 3

Start with the simplest possible case. Write down what Nuna 3 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Nuna 3 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Nuna 3 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Nuna 3

In research: Nuna 3 appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Nuna 3 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Nuna 3 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Delft University of Technology, Dutch inventions, Electric vehicles, so understanding it makes those chapters shorter.
In everyday life: Look for Nuna 3 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Nuna 3 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Nuna 3 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Nuna 3 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Nuna 3 in simple terms?

Why does Nuna 3 matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Nuna 3?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Nuna 3.