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As we know the launch of NASA SLS for the Artemis I mission was suspended due to a cryogenic hydrogen leak not possible to repair during the attempt on 3 September. At present, it has not yet been decided whether the large space rocket will return to the VAB (Vehicle Assembly Building) or it will be possible to operate directly at Launch Pad 39B.
The engineers and ground teams are checking the situation and the decision could already be announced later this week with several implications in terms of launch timing for the Space Launch System and the Orion capsule as well as for some additional operations (for example the new certification for the FTS). Another interesting question was related to Cubesat that are present in the top adapter of the space rocket. Their operation has some constraints and one of the people involved in two of these wanted to give some answers in this regard.
The Cubesats of NASA SLS and their operation after the postponement
THE Cubesat I am small satellites, relatively cheap, which are experiencing a period of great expansion precisely because of their (relative) simplicity of construction as well as for the low cost compared to larger and more expensive satellites. The US space agency has chosen to integrate ten of them into an adapter of the NASA SLS rocket (more precisely the Orion Stage Adapter).
TO write on Twitter was Craig Hardgroveresponsible of Cubesat LunaH-Map, which has provided some interesting answers. In particular, one of the major concerns concerns the operation of the batteries of the small satellites that are currently inside the adapter and that do not receive additional power from the system.
Hardgrove pointed out that all Cubesat integrated into NASA SLS for Artemis I they all use batteries with 18650 lithium ions in different numbers and at different charge levels based on the choices of individual manufacturers / agencies / companies which in turn depend on the type of mission and hardware. Charged batteries are necessary for the first start-up of the system and to start operations and then switch to the power supply given by the solar panels.
While there are some unit-to-unit differences, in general the batteries are discharging at a rate of around 2% / month (once integrated in October 2021, they were no longer uploaded). Of course, there are some variables and therefore that percentage could undergo some variations over time and the more you wait, the more the unknowns increase.
According to Hardgrove, in the case of LunaH-Map, the batteries will have a sufficient charge up to 30 months after integration. Obviously, if we went from 2% / month to 5% / month, the time available would be reduced to about 12 months. To recharge the batteries it would be necessary to remove the Orion capsule from the adapter, which would require returning to the VAB and adding additional time beyond repairs to the hydrogen leak. In addition, five of the ten units present cannot recharge their batteries due to their design.
However, there is an additional resource for some models. For instance CuSP (CubeSat for Solar Particles) e LunaH-Map they can recharge if the batteries are also discharged. The only caution is that when NASA SLS will be launched and the adapter will be separated as sunlight hits the solar panels. However, this is not a characteristic common to all Cubesat.
That’s not all. Depending on the mission profile, the operations that these satellites will have to perform will be different. Always taking it as an example CuSP And LunaH-Mapthe first will transmit the first message after some time while the second will have to perform some corrective maneuvers immediately after the release and therefore will have to contact the Deep Space Network first.
There are therefore differences from unit to unit and in general the sooner the rocket is launched, the lower the risks for the additional missions of the Cubesat. Hardgrove wrote that the postponement of the launch does not mean these missions “are dead”.
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