They previously stated that they would start booster testing after SN11. However Elon tweeted that SN15 will be rolled out in a few days.
Interesting side note. Firstly Elon said they were going to try for suborbital in July. He must have meant July 2022. LOL
Also the down select for HLS happens next month. If you don't know NASA selected three vendors last year to do preliminary work. And then that was suppose to be pruned down to two in Feb but they extended it to April. Of the three vendors (SpaceX, BO, Dynetics) the SpaceX proposal has always been considered by NASA the most risky. SpaceX would have been well served to demonstrate a landing prior to that down select. There is some concern that due to budget constraints they will only down select to one.
In review:
1) Blue Origin National Team: By far the worst option. BO uses an Apollo style Lunar Lander.
It has three parts;
a) The Transfer Element - The TE just gets the HLS in the proper orbit to land and then it is thrown away.
b) The Descent Element - Exactly like Apollo the DE has the engines and landing gear. It is also thrown away.
c) The Ascent Element - Again exactly like Apollo it is the living quarters and ride back to lunar orbit.
The BO HLS is a six decade old concept. It's the least reusable. It provides no new capabilities. Also the ladder to get in and out is three times as tall as the Apollo Lunar Lander making for troublesome ingress/egress. However it is led by the team with the most powerful lobbyists. It's a shoe-in to be selected. Undoubtedly it will be the most expensive solution.
2) Dynetics: Hands down the best solution. Their HLS system "The Alpaca" is innovative, reusable and versatile.
- The crew compartment is slung under the landing bed. Among other things that makes ingress/egress very easy. Also because of the configuration they can land different modules and leave them on the surface. They can sling whatever they want under the lander; habitats, labs, ISRU's supply containers, rovers, etc. (up to 15 tons).
- The lander only discards fuel tanks and the rest is reusable.
- Unlike Apollo ( and BO?) it will have an airlock.
- Reusability: Because it only loses it's drop tanks it can be refitted for landing with only one additional launch. BO would require at least two much heavier payloads.
3) SpaceX: SpaceX plans to modify a Starship for Lunar operation. Many hurdles to overcome.
- Of course they are still in rocket development.
- They have to master orbital refueling which has never been done before.
- They have to demonstrate landing on unprepared ground and as such can't use the Raptor engines under the skirt.
- They have to use an elevator to get astronauts and cargo to the surface.
Lots of challenges. It does have the ability to deliver 100 tons to the surface though which is 7x what anyone else can do. Even if NASA does not select SpaceX it would behoove them to continue development. If they are able to deliver 100 tons to the Lunar Surface they will not lack for customers.
All options have a similar problem and that is refueling. Long term it is hoped that they can make hydrogen from Lunar ice. However Starship uses methane so they have a problem right there. Hydrogen is a difficult fuel to use for space travel. It boils off fast and has to be kept at cryogenic temperatures. Plus being a very small atom it leaks through everything. SpaceX has been given a contract by NASA to demonstrate hydrogen fuel transfer for use by anybody.