Masten Space Systems was an aerospace manufacturer startup company in Mojave, California (formerly in Santa Clara, California) that was developing a line of vertical takeoff, vertical landing (VTVL) rockets, initially for uncrewed research sub-orbital spaceflights and eventually intended to support robotic orbital spaceflight launches.

[6][7] On 2 November 2009, it was announced that Masten Space Systems had won first place in the level two category, with Armadillo Aerospace coming in second.

[10] Masten was accepted to make a bid for NASA's Commercial Lunar Payload Services (CLPS) program on 29 November 2018.

[3][12] Masten's Xombie (model XA-0.1B) won the US$150,000 second prize in the Level One competition of the Lunar Lander Challenge on 7 October 2009 with an average landing accuracy of 16 centimetres (6.3 in).

[5] The primary goal of these two airframes was to demonstrate stable, controlled flight using a GN&C system developed in-house at Masten.

[13] By October 2009, the regeneratively cooled isopropyl alcohol and liquid oxygen rocket engine was running at around 900 pounds-force (4 kN).

[14] XA-0.1B, nicknamed "Xombie", first flew free of tether 19 September 2009,[15] and qualified for the Lunar Lander Challenge Level One second prize of $150,000 on 7 October 2009.

It was proposed to NASA as a potential suborbital reusable launch vehicle (sRLV) for carrying research payloads under NASA's Flight Opportunities Program (initially known as the Commercial Reusable Suborbital Research/CRuSR program), projecting 30 kilometres (19 mi) altitude in initial flights of five to six minutes duration, while carrying a 10 kilograms (22 lb) research payload.

As the sixth VTVL testbed developed at Masten, Xogdor would have improved upon the work done with Xodiac and tested descent and landing technologies at speeds up to 447 mph (719 km/h).

Xeus consisted of a Centaur upper stage (from United Launch Alliance) with RL-10 main engine to which four Katana vertical thrusters have been added.

United Launch Alliance, supplier of the Centaur, referred to Xeus as an abbreviation for eXperimental Enhanced Upper Stage.

Further details of the proposed design were given in the paper "Experimental Enhanced Upper Stage (XEUS): An affordable large lander system".

[35] On 30 April 2014, the NASA announced that Masten Space Systems was one of the three companies selected for the Lunar CATALYST initiative.

The SAA lasts until August 2017, has 22 milestones and calls for "End-to-end demonstration of hardware and software that enables a commercial lander on the Moon.

[47][42] On 11 October 2016, Masten Space Tweeted a video showing the test firing of its new bi-propellant combination, internally called MXP-351.

As of March 2017[update], a 1,000 pounds-force (4.4 kN) thrust version of Machete for the terrestrial testbed of the lander, dubbed XL-1T, was being manufactured.

[51] On 29 November 2018, it was announced that Masten was eligible to bid at a Commercial Lunar Payload Services (CLPS) contract by NASA.

[52] On 8 April 2020, NASA selected Masten to deliver eight payloads – with nine science and technology instruments – to the South Pole of the Moon in 2022 with the XL-1 lander.

Masten would also operate the payloads, helping to lay the foundation for human expeditions to the lunar surface beginning in 2024.

A terrestrial flying test-bed was being used since lack of vehicle access to lunar landers after launch would make Masten's incremental design and test development methodology difficult and very expensive.

These included multi-engine architecture, avionics, software, fuel, movement of inertia, slosh management, and mission design tools.

[56] In addition to its line of vehicles, Masten Space Systems was offering its internally developed igniters and engines commercially to interested and qualified parties.

Broadsword was a 25,000 pounds-force (110 kN) methane/liquid oxygen rocket engine Masten Space Systems was developing for the US government.

[61][needs update] Cutlass was a 25,000 pounds-force (110 kN) methane/liquid oxygen rocket engine Masten Space Systems was developing for the US government.

[66] Machete was the name for a family of throttleable rocket engine designs Masten Space Systems was developing to permit their XL-1 lunar lander to land on the Moon.

[46] MXP-351 was Masten Space's internal name for a self-igniting bipropellant combination invented to fuel its small lunar landers.