Which Will Be First to Space – the SpaceX Starship or the SLS?

SpaceX is talking with three companies about the first commercial launch of the fully reusable Super Heavy Starship with a 2021 target date.

United Launch Alliance and NASA have been working on the Space Launch System since 2011. There was also the Constellation rocket program from 2005 to 2011. SLS and Constellation were trying to re-use Space Shuttle booster technology. However, despite spending over $20 billion (not including another $10 billion for the Orion capsule) there has not been a successful test or a live mission with SLS. NASA is still talking about a first mission with SLS in 2020 but the government Accountability Office has report which indicates that we would be lucky if SLS can launch in 2021.

The first flight test of the SLS will feature a configuration for a 70-metric-ton (77-ton) lift capacity and carry an uncrewed Orion spacecraft beyond low-Earth orbit to test the performance of the integrated system.

The SpaceX Falcon Heavy can carry 63.8 metric tons (70-tons) to low earth orbit. The Falcon Heavy has flow three times and has 90% of the lift capacity of the version of the SLS.

The development of the BFR (previous name for the Super Heavy Starship) started in 2012, when SpaceX started Raptor upper-stage engine development. By September 2017, Raptor engines had been tested for a combined total of 1200 seconds of test firing time over 42 main engine tests. The longest test was 100 seconds, which is limited by the size of the propellant tanks at the SpaceX ground test facility. The test engine operates at 20 MPa (200 bar; 2,900 psi) pressure. The flight engine is aimed for 25 MPa (250 bar; 3,600 psi), and SpaceX expects to achieve 30 MPa (300 bar; 4,400 psi) in later iterations.

In December 2018, nine months after starting construction of some parts of the first test article carbon composite Starship low-altitude test vehicle, SpaceX CEO Musk announced a “counterintuitive new design approach” would be taken by the company. SpaceX switched to a stainless steel alloy which is very heat resistant.

A Starhopper has been built from a 300-series stainless steel. The high melting point of 300-series still would mean the leeward side of Starship would need no insulation during reentry, while the much hotter windward side would be cooled by allowing fuel or water to bleed through micropores in a double-wall stainless steel skin, removing heat by evaporation.

There are now two orbital versions of the Starship being built. One is in Texas and another in Florida.

As of May 2019, SpaceX says construction of the first SuperHeavy would not start before August.

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