Successful Starship SN5 Fueling Test

Have a look at the solar storm shelter on Starship Deck D

Welcome space friends!

SpaceX, Starship and Mars Mission Update

Starship SN5 successfully completed its planned fueling test. Venting is visible in the photo below:

There may be one more day of fueling tests; it's unclear at the moment. After that should be the static fire test, using a single Raptor engine. On Twitter, @Ppathole recently asked "Elon, what's the update on SN5?" He responded "Will attempt to fly later this week". However, since then Tropical Storm Hanna has been strengthening in the Gulf, and is headed toward the area north of Boca Chica.

SpaceX successfully launched a South Korean military satellite called ANASIS-II into a geostationary transfer orbit, on a Falcon 9. In addition to the now-standard booster recovery (the 57th for Falcon 9), SpaceX also successfully recovered both halves of the fairing for the first time. The booster used for this launch was the same one previously used to launch Doug and Bob with Crew Dragon to the ISS.

In other Mars-related news, China successfully launched Tianwen-1, their rover mission, on a Long March 5. It's due to arrive on Mars in Feb 2021. Good article about it at the link:

https://www.nasaspaceflight.com/2020/07/china-ambitious-tianwen1-mars/

The last mission to go to Mars during the current launch window will be NASA's Perseverance rover and Ingenuity helicopter, together known as Mars 2020. It just had its radioisotope generator (RTG) installed, which will provide nuclear power for the entire mission. The last launch readiness review is scheduled for July 27, followed by launch on July 30.

Getting There

Deck D is next up, shown in the image below:

This deck is surrounded on all sides by containers full of water and cargo. There is a bathroom at the top of the sketch, and openings to Deck C near the center.

You will be exposed to a higher level of radiation than is present on Earth for the entire duration of the trip. However, during a solar storm, radiation exposure is much higher, to the point where it can damage human health. The solution is to have an area like Deck D on the ship, with some moderate shielding.

Fortunately, solar storms can be detected before the damaging radiation arrives, using data from a satellite that’s positioned between Earth and the Sun. When Starship receives notification of an upcoming storm, everyone on the ship will need to gather on this Deck, in order to be appropriately shielded. Solar storms can last from a few minutes to 6 to 12 hours.

The effectiveness of a radiation shield depends on two things: total mass, and the atomic number of the atoms that make up the mass (called “Z” for short). Low-Z materials are desirable. Water is nice in that way, since it contains two hydrogen atoms.

There are about 400 cargo boxes in this area, 0.5 x 0.5 x 0.6m in size (0.15 m3). Toward the interior of the deck from the boxes, there are 24 relatively thin flexible plastic water bags. Each bag measures 1.2 x 2.3 x 0.125m (0.345 m3), so that’s about 8,300 kg of water total. Deck C below will have space in the ceiling for you to store your carry-on luggage, which adds a little extra mass to the radiation shield in that direction.

I’m expecting Starship to spend most of the flight with its engines facing the Sun. That should help improve the solar incidence angle for the ship’s solar array, while also putting the mass of the fuel tanks and other ship structures between passengers and the Sun. Unfortunately, simply pointing the ship in that direction won’t be enough on its own, though, since radiation from solar storms swirls around, and can actually hit the ship from all directions.

The bags of water can be removed and plugged into the ship’s water distribution system. ISS uses a similar approach. The empty space left when bags of fresh water are removed can be filled with bags of waste water before it’s recycled, or fresh water after recycling.

The cargo boxes will contain food or luggage. One or two would be moved to the galley (ship’s kitchen) every day. To access a cargo box, you simply remove the water bag first to access the area behind it. Similarly, if you ever need to access the hull for some reason, such as to repair a leak (unlikely, but not impossible), simply remove the luggage.

Living There

One cool thing about Mars is that although it’s very much the “red planet,” the color of the sky during the day and at sunrise and sunset are reversed from Earth. On Mars, the daytime sky is red, but sunrises and sunsets are blue.

Here’s a view from Curiosity rover of some hills in the distance. It’s interesting to think that at least in the relatively low, flat zones, frozen water may be available as little as one meter below ground.

When you’re outside on Mars, in your spacesuit, the only audio you will hear is from yourself and your suit, and your radio. External sound waves won’t carry very well or very far in Mars’ thin atmosphere. I think many people may end up preferring to have their radios on all the time, with an “open mike.” One reason for that is that if you fall or otherwise injure yourself, you may end up in a position where you can’t activate your microphone. On Earth, sound often alerts us to situations like that, but on Mars there’s no distant sound without your radio, and it may be that no one happened to be looking in your direction at the time.

It’s worth noting that a compass won’t work, since Mars doesn’t have a magnetic field. We will need to use dead reckoning and similar navigation techniques instead. In fact, the art and science of navigating without a compass would be an excellent thing to study on Earth before you leave.