Elon Musk @elonmusk
@SciGuySpace Densifying hydrogen is difficult, as its liquid temp is close to absolute zero. Much easier with CH4, which is an underappreciated advantage. Cooling O2 is good too, but becomes operationally difficult at N2 liquid temp, as air is ~78% N2. Entire system wants to drip air! — PolitiTweet.org
