Star Tracker
The Earth from orbit, half in daylight and half at night with city lights, and the path of the International Space Station drawn around it.

Space jobs, and the engineering to get them.

A free weekly email of internships and graduate roles at space companies and agencies in the UK and Europe, sorted by closing date. Plus worked orbital mechanics problems where every number is checked by a script.

Join the free weekly email Try a problem first

Work the problem.
Then move the numbers.

This is the free orbital mechanics course, running in the page. Read what is given, ask for a hint, open the working, then change the altitude and watch the orbit answer back. The other tabs hold chapter 1 of the thermal, power and attitude control courses.

Orbital mechanics 0 of 6 done

Problem 1 of 6

How fast is the ISS going?

Given

Circular orbit at h = 420 km altitude. RE = 6378.137 km, μ = 398600.4418 km3/s2. Find the orbital speed and the period.

To scaleAt 420 km the orbit is only 6.6% wider than the Earth. One lap takes 92.97 min.

These six are from the free course. Open the full orbital mechanics course

Jobs

The space roles worth applying for, one email a week.

Internships and graduate roles at space companies and agencies in the UK and Europe, sorted by closing date so nothing expires unseen. Every role links to the employer's own posting. Free, and it stays free.

Get the weekly email Jobs archive

Learn

Worked problems, with the working left in.

Each course shows every step and keeps a Python script behind every answer. The full orbital mechanics course is free: 19 chapters, 57 graded problems and runnable Python. Thermal, power and attitude control are full courses in the founding membership, and chapter 1 of each is free to read.

  • Orbital mechanicsFree full course, 19 chaptersOpen
  • Thermal control16 chapters, chapter 1 freePreview
  • Power systems17 chapters, chapter 1 freePreview
  • Attitude determination and control18 chapters, chapter 1 freePreview

Build

Calculators for the budgets a student satellite team argues about.

Mass, power, link and thermal, in the browser, each checked against a worked example before it goes live. Power is first: the same models as the Power systems course, and a script checks that it reproduces the course's 6U mission case. Mass, link and thermal follow, and the list hears first.

Budgets Teaching calculator

Power budget

A 6U CubeSat at 550 km, Sun-synchronous

Preloaded with the Power course's 6U mission case. Change any unit, duty or margin and the results follow.

UnitPower WDuty %Cont. %Sun onlyRemove

Orbit

Array and battery

Regulation

Depth of discharge follows the cycle-life limit until you type your own.

Fixed: aphelion sunlight 1316.6 W/m²; losses 0.96 × 0.98 × 0.98 and −0.23 %/K above 28 °C; radiation fitted to the 3G30 cell datasheet; panel 210 × 340 mm holding 24 cells of 26.6 cm² (packing factor 0.894); 4S strings of 2.6 Ah, 3.65 V cells plus one spare; battery to load 0.90; cycle life 20 000 (0.2/DoD)1.7.

The engineering behind it

How space things work, with the calculation on screen.

r₁ r₂ Δt
Lambert's problem: given two positions and the time between them, find the orbit that joins them.

Short video explainers, each with the numbers worked out on screen. Videos coming soon.

  • How fast the ISS movesand why it never falls down.
  • Why geostationary orbit sits at 35,786 kmand nowhere else.
  • The Hohmann transferthe cheapest way to reach geostationary orbit.
  • Sun-synchronous orbitsand why many Earth-observation satellites orbit at about 98 degrees.
  • The cost of a plane changeand why you do it where the satellite is slowest.
  • Lambert's problemfinding the orbit that joins two points in a given time.

Built by engineers, for engineers.

The writing and the code are made with AI tools. Every number in a pack or an explainer is computed by a script and checked against a textbook value before it is published.

Everything is written from scratch. It is not copied course material and not assignment answers; it is for understanding the method.

Who it is for

Made for three moments.

  • 01Revising for a space engineering exam, and wanting the method, not just the answer.
  • 02A CubeSat team preparing a design review, checking its budgets line by line.
  • 03Preparing for a space-industry interview, and wanting to talk through the numbers.

What you get

Start free. Go the whole way for £29.

Free

£0

  • The full orbital mechanics course: 19 chapters, 57 graded problems
  • The CubeSat power budget calculator
  • The weekly space jobs email
  • Chapter 1 of each paid course
Join the free weekly email

Founding member

£29 for the first year

  • The thermal, power and ADCS full courses: 51 chapters, 153 graded problems
  • Every new course we publish in your 12 months
  • All calculators as they are built
  • Renews at £29 a year; cancel in one click
  • 14-day refund, no questions

Founding price. The full membership is planned at about £49 a year.

Founding membership opens soon. Get notified

In the founding membership

Spacecraft thermal control16 chapters · 48 graded problems · 81 Python programs · 2,894 script checks · 20 references
  1. 1Heat transfer in space30 min
  2. 2Radiation basics: α, ε and the two bands30 min
  3. 3The orbital thermal environment35 min
  4. 4Beta angle and eclipse30 min
  5. 5View factors35 min
  6. 6Single-node equilibrium30 min
  7. 7Hot and cold cases with margins40 min
  8. 8Multi-node thermal networks45 min
  9. 9Transients and eclipse cool-down40 min
  10. 10Passive control I: coatings, MLI and radiators40 min
  11. 11Passive control II: heat pipes, louvres, doublers and straps40 min
  12. 12Active control: heaters, thermostats and pumped loops35 min
  13. 13Component limits and design margins30 min
  14. 14The thermal analysis workflow and tools30 min
  15. 15Testing: thermal vacuum and thermal balance30 min
  16. 16Worked mission case: a 6U CubeSat end to end60 min
Read chapter 1 free
Spacecraft power systems17 chapters · 51 graded problems · 86 Python programs · 2,089 script checks · 27 references
  1. 1The power subsystem and the power budget30 min
  2. 2Sunlight, orbits and eclipse30 min
  3. 3How a solar cell works35 min
  4. 4Cell types, efficiency and temperature30 min
  5. 5Array geometry: pointing, cosine losses and layout35 min
  6. 6Sizing the array: beginning and end of life40 min
  7. 7Batteries: how Li-ion cells behave35 min
  8. 8Sizing the battery: eclipse, cycle life and recharge40 min
  9. 9Regulating power: DET, MPPT and the bus40 min
  10. 10Distribution, harness and protection35 min
  11. 11Margins, worst cases and end of life30 min
  12. 12Power modes, energy balance and contingency35 min
  13. 13CubeSat power systems30 min
  14. 14RTGs, fuel cells and other sources25 min
  15. 15Testing and verifying the power system30 min
  16. 16Mission case: a 6U CubeSat in Sun-synchronous orbit50 min
  17. 17Contrast case: a GEO communications satellite40 min
Read chapter 1 free
Attitude determination and control18 chapters · 54 graded problems · 93 Python programs · 2,079 script checks · 18 references
  1. 1Frames and direction cosine matrices30 min
  2. 2Euler angles and gimbal lock30 min
  3. 3Quaternions40 min
  4. 4Attitude kinematics30 min
  5. 5The inertia tensor and principal axes35 min
  6. 6Euler's equations and spin stability40 min
  7. 7Disturbance torques40 min
  8. 8Sun sensors, Earth sensors and magnetometers35 min
  9. 9Star trackers and gyros40 min
  10. 10Attitude determination: TRIAD, Wahba, QUEST45 min
  11. 11Kalman filtering for attitude45 min
  12. 12Actuators: wheels, CMGs, magnetorquers, thrusters40 min
  13. 13Feedback control: PD, bandwidth and settling40 min
  14. 14Detumbling, momentum management and slews45 min
  15. 15Stabilisation modes: spin, gravity gradient, three-axis40 min
  16. 16Pointing budgets: knowledge versus control35 min
  17. 17CubeSat ADCS and testing on the ground35 min
  18. 18Worked mission case: a 6U imager end to end50 min
Read chapter 1 free

How the numbers are checked

script checks
9,319
Python programs, each run and checked against its answer
351
references across the 4 courses
94
of them from NASA; 8 ESA or ECSS
44

Every number in a course is computed and checked by a script before it is published. Constants and inputs come from NASA, ESA and ECSS documents and peer-reviewed papers, such as Kopp and Lean (2011) on the solar constant and Izzo (2015) on Lambert's problem, each cited where it is used. See the orbital course's references

Questions

Before you start.

What format is a course?

An interactive file that opens in your browser, with hints, answers, full solutions, quizzes and runnable Python, plus a printable PDF of the same course. The PDF works fully offline. The interactive file opens offline too, but it needs an internet connection to show the equations at their best and the first time you run a Python program, because Python loads into the page.

Do I need to install anything?

No. A current browser is enough. The Python runs inside the page, so there is nothing to set up.

What if it is not useful to me?

Email within 14 days of buying and we refund the full amount, for any reason. Reply to your receipt or write to [email protected]. Details in the terms.

How does renewal work?

The founding membership runs for 12 months and renews at £29 a year, the founding price, for as long as you stay a member. We email you before each renewal. You can switch renewal off in one click in your Whop account, and you keep access to the end of the year you paid for.

Is this course material or assignment answers?

Neither. Every chapter, problem and number is original work written from scratch. It is for learning the method; it is not copied university material and not answers to anyone's assignment.

Who writes it?

Built by engineers, for engineers. The writing and the code are made with AI tools, and every number is computed and checked by a script against a textbook value or a cited source before it is published.

How do I get in touch?

Email [email protected].

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