Galactic cosmic ray simulation at the NASA space radiation laboratory – Progress, challenges and recommendations on mixed-field effects

•A virtual workshop on galactic cosmic ray simulation at the NASA Space Radiation Lab was held in 2020.•The GCR simulator (GCRsim) represents the radiation field encountered by humans in deep space behind shielding.•Automated delivery of the 33-ion sequential GCR simulator field takes approximately 75 minutes.•The GCR simulator and delivery approach are considered scientifically sound and state of the art.