Summary of Musk's Talk on Twitter
SpaceXChat
• Well over 1000 changes in the vehicles since the last flight.
• Much higher chance of getting to orbit, "maybe like 60%" but depends on stage separation success.
• Late changes being made to stage separation where they will use hot staging to light the engines of the ship while the first stage is still on.
• Most booster engines will be shut down but not all before the Ship ignites.
• Adding extension to top of booster with extensive vents for the upper stage exhaust.
• Top of booster will need shielding.
• "Conservatively a 10% improvement in payload to orbit"
• "Never stop thrusting"
• Stage Separation is the "biggest risk right now".
• The launch pad upgrades and the vehicles will "probably" be ready in 6 weeks.
• Massive upgrade of launch site. Roughly 1000 m³ of steel reinforced concrete.
• Adding 2 thick plates of steel welded together with channels for water to cool and spray upwards below pad.
• "Gigantic upside-down showerhead"
• "The booster is the world's largest cutting torch"
• "We're going overkill on the steel sandwich and concrete"
• Aiming for a higher thrust-to-weight ratio at launch to spend less time on the pad.
• Fixed many engine issues.
• A number of improvements to the hot gas manifold which is arguably the riskiest part of the engine and subject to hot gas leakages.
• Higher torque on the bolts of the hot gas manifold to prevent leakages.
• Perhaps one of the single biggest improvements.