Hakuto‑R (iSpace Resilience) Low‑Energy Transfer to the Moon:
Resilience lifted on a Falcon 9 on January 15 alongside Firefly's Blue Ghost.
Instead of a direct Hohmann transfer, iSpace chose a low-energy (weak stability boundary) trajectory.
This trajectory trades propellant mass for time by exploiting three-body dynamics (Earth-Moon-Sun) to gradually “fall” into lunar capture with minimal Δv. The downside is, that this process can take months instead of days.
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But firstly, what is the Hohmann transfer in the first place? It uses two burns and is the most commonly used maneuver when you want to move a spacecraft between two circular orbits using the least amount of fuel.
If you are in Earth's orbit, for example, and you want to move to a bigger orbit, like the Moon. Instead of aiming directly for the Moon, you give yourself a little push (a prograde burn) that stretches your orbit into an ellipse that just touches the Moon's orbit. When you are at the farthest point of your orbit (the apogee), you give yourself another push to make the ellipse into a circle again.
The first burn speeds the spacecraft up to a lower orbit and puts it into an elliptical transfer orbit.
The second burn speeds it up again at the top of the ellipse, making the new higher circular orbit.
Animation of Hohmann transfer from Earth to Mars
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And now what is the Weak Stability Boundary trajectory? It takes much longer, but it uses way less fuel in doing so.
It works by launching the spacecraft into a very elliptical orbit around with a high apogee - often reaching or exceeding 1 million km (far beyond the Moon's orbit.
The fact that its orbit is further than the Moon's might lead you to think that it should use MORE fuel, but it does not, because the goal is to barely escape Earth's gravitational dominance, whilst with the Hohmann transfer, you need to escape the Earth's gravity completely and speed up to “catch” the Moon.
With this orbit, the spacecraft drifts into a chaotic region near the Earth-Moon-Sun Lagrange points. In this region, the Earth and the Moon's gravity balance out. Here the Sun's gravity plays a crucial role, tugging on the spacecraft to alter its path slowly. The spacecraft remains in this state, slowly shifting its orbit, sometimes looping multiple times.
Eventually, the trajectory aligns with the Moon's orbital path. The spacecraft is weakly captured by the Moon's gravity and the Moon slowly pulls it towards it without needing a large breaking burn.
Animation of the WSB trajectory (Blue=Earth; Green=Moon)
Going back to the Hakuro iSpace Resilience, this trajectory was efficient for this mission, due to the lander being quite small with limited onboard fuel. The mission demonstrated propellant-efficient navigation techniques vital for tasks like these.
It is important to say that Resilience has not landed yet. It completed 6 of 10 planned deep space maneuvers; next is Lunar Orbit Insertion on May 7, then approximately one month of coasting in NRHO* before landing in the Mare Marginis region on June 5.
*NRHO - Near-rectilinear halo orbit: It is a very stretched elliptical orbit around the Moon. Centered around the Moon's Lagrange Point 2 - a spot where gravity from Earth and the Moon balance in a helpful way. The spacecraft swings far away from the Moon on one side, then gets very close on the other.
NASA's upcoming Lunar Gateway space station will use NRHO.
Animation of the Lunar Gateway´s upcoming NRHO orbit
SPACEX´s STARSHIP STATIC FIRES:
The Starship underwent a single-engine 6-second burn simulating in-space relight and a six-engine 30-second full stack fire.
The post‑shutdown “flame show” was more intense than prior ships—possible transient Raptor shutdown flow separation or hot‑gas reingestion.
This test validates the Raptor's relight capability and full-duration sea-level operation ahead of IFT-9.
THAT´S IT FOR THIS WEEK, NEXT WEEK WE ARE EXPECTING THESE LAUNCHES:
- A Starlink launch on Saturday *
- Another Starlink launch on Sunday *
- Another Starlink launch on Tuesday
- Another Starlink launch on Friday
Well, just Starlink launches for this week...
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