Lunar flyby achieved!

[1953 January 3.,  Illyrien Space Center]

News conference

Greetings all, please take your seats. We are happy to announce today, that a probe launched from Florida, arrived at Moon SOI and bypassed our companion in the heavens. After approaching at higher than 40.000km, it has left the Moon on cause back towards Earth, where it will impact in the Pacific.

The rocket, a T12 – Orbiter IIId, launched at 3 in the morning on December 31. 1952, heading north east to an irregular lunar planar orbit. From this orbit, roughly in plane with the Moon, a flight path was set up and towards the Moon and a 3000+ dV burn was performed. After that, we just waited for 3 days, only to be interrupted by 4 high space science experiments

Right, that was the quick intro, any questions?

Any pictures?

The Moon, at the closest point

What is this T12 – Orbiter IIId?

Ah, right, its the 12th type of rocket, its part of the Orbiter series. The III indicates that its the third alteration of the basic design. Which in this case, involved increasing the size of all fuel tanks and adding 4 heavy boosters. As well as more avionics. The original Orbiter Ic was 39,999t, while this launch weight it at 262,204t. A substantially larger launch. It carries an impressive 13.467 dV and a supply of nitrogen for RCS. The “d” indicates the level of the number of minor alterations, usually due to simulations.


But why launch at night?

The Earth has an axial tilt of about 23,5%, this is the cause of the seasons, but it also means that Earth’s equator does not align with the rest of the solar system.  So we can’t just aim for an equatorial orbit, we need an orbit in plane with the Moon. At 3 in the night, on that day, we where in the that plane, at that exact time, which greatly eased launch or pre-boost orbit.

Rendition of Earth showing Orbiter I satellite and Lunar Plane. Note that the ISP is right on the line.

What did the stages do

The booster and mainstage where sufficient to lift the launch apoapsis out of the atmosphere, and to do so with a large margin. The second stage, with a strong vacuum engine, the LR105 series, accelerated the craft almost to orbital velocity. The final stage finished the orbital circulation and lunar burn.


Any problems?

Plenty. To start with the last, we had miscalculated the energy required and ran out of electricity just before Moon SOI. For future launches, we are really going to have to add some solar panels, or a much larger battery.

From start, our launch angle was off, and we had to adjust it continually, to get it close to the lunar plane. This took a lot of attention, and did cost some fuel. Also, when space was reached, our accent was wrong and the apoapsis was far too high.

Our upper stage, was also spinning, which disrupted RCS alignment. We could not stop the spinning, therefore we where unable to use the RCS to align the probe on the navigation node.

We had some problems with engine restart, but not a new challenge. The upper stage engine cannot handle free floating fuel, so, to fully restart, we have 4 RCS thrusters at the engine level, pointing rearwards. Once fired, they push the fuel to the rear, allowing the engine to fire.

Later we lost communications and drifted completely. It was not until the lunar burn was initiated that the craft could be turned almost 150 degrees to the right direction.

The vehicle is also structurally weak at the intersection between the mainstage and the second stage. This is due to the set of avionics. Its incredible dangerous, and despite 16 struts, that point is really really weak. Several rockets where lost in simulations due to this.

What did these simulations show?

That failures can always happen… Just look at this:


How sure where you that this mission would successfully reach Moon SOI?

Oh, the common bets here at ISP where in the 50-66% range. It must be understood though, that even a failure to reach the Moon would still gain us a huge amount of knowledge, and increase the success chance for future launches.

The Moon Flyby Contact stated 5000km above the Moon, doesnt that mean its a failure?

No, that just mean that we did not full-fill the requirement for that specific contract. We are, however, going to have to full-fill it at some point during 1953.

So what is next?

Well, we have to finish the contact, so we will be launching more rockets at the Moon. However, this mission did reveal weaknesses in the design, and those we are going to have to take a close look at. Especially the power issue. Secondarily, we are going to have to take a look at the restart problem.

Any other questions?






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