sevenperforce

Right, GTO is not what Starship was designed for. Given that Starship can take over 100 tonnes to LEO, we are probably likely to see rideshares and kick stages for sending satellites to GTO. Refilling is obviously way more useful than sequential staging. Even starting in LEO with 100 tonnes, you need more than half of your payload to be propellant to get to GTO on something like hydrazine. So if your notional supersized comsat is 10 tonnes, you could deliver two with a single Starship GTO launch or up to four with a single Starship LEO launch and a commercial kick stage. I wonder how many propellant refill runs it takes to get Starship's full GTO/GEO delivery.....

21 tonnes to GTO on a single launch...less than expendable Falcon Heavy.

Crush cores will be used on all, most likely -- they are reusable as long as they aren't used.

So do they still drop straight down? Those looks like crush cores.

I wonder if it would be possible to do a lithostaged Munar touch-and-go using a twin boar and the internal RCS on the MEM capsule.

The jet intakes all have suction at zero forward airspeed. On the other hand it becomes a "whose computer can handle the highest part count" challenge, which is not as interesting. To make it more interesting you could do a "no parallel staging and no engine more than once" rule which would be very interesting.

Wholly practical. They are already used, in fact. The X-43 has one half of a linear shock cone forming its entire forebody.

Or leaving the interior empty and manifesting a 5 tonne module externally.

I don't think it will be though. I think it will. Single payload adapter/docking ring/propulsion unit.

We don't know whether that 5-tonne payload is limited by injection dV (FHUS) or insertion dV (vehicle). Let's start with the assumption that the 5-tonne payload is limited by the insertion dV. It takes 430 m/s to go from TLI to the gateway...let's pump that up to 500 m/s for margin, rendezvous, docking, and so forth. Dracos develop 300 s of specific impulse. The Dragon XL would need to burn 15.6% of its mass as propellant to generate 500 m/s, and the Dragon 2's propulsion package has 1388 kg of propellant, so that's a total vehicle wet mass of 8.9 tonnes. With 5 tonnes being payload and 1.38 tonnes being propellant, that leaves a vehicle dry mass of 2.51 tonnes. Dragon 2 has a dry mass of 9.53 tonnes. Does that mean ECLSS+heat shield+aeroshell+ballistic sled+parachutes total a whopping 7 tonnes? Or are we looking at a vehicle with higher propellant capacity?

Looks like the depiction has the same docking port (with four Draco RCS thrusters) as Dragon 2. There's probably a 75% chance this has the same exact propellant tanks as Dragon 2, just with the aeroshell and heat shield and chutes removed. Might be useful for estimates.....

We spend too much time close to Kerbin -- it's time to think beyond! I was building a Sepratron-powered orbiter for this excellent challenge: When I used my crewed rocket with just a probe core instead, I discovered that I was very nearly interstellar. Adding two extra stages and a few more tweaks got me out of Kerbol's SOI on a Sepratron-only rocket massing just over 16.2 tonnes. It made me think...what are the limits of going interstellar? Who can go interstellar with the lowest liftoff mass? Who can get interstellar the fastest? Who can go interstellar with the fewest parts? Who can get onto an interstellar trajectory as low as possible within Kerbin's atmosphere? Is it possible to take an SSTO to Kerbin's atmosphere without staging? What is the lowest mass-to-interstellar without using nukes or ions? Rather than doing a leaderboard with this challenge, I was thinking of doing a challenge-within-a-challenge. Each entrant should post an interstellar vehicle optimized for whatever they are good at and challenge other entrants to beat them. I'll kick it off -- go interstellar in under 16 tonnes!

Just put Jeb into orbit with a 6.997 tonne rocket but getting him back to Kerbin is tricky. Six stages, like @qzgy, but distributed a little differently. All motors are inside one of the two fairings.

With MHD you are still limited by intake area. It's always going to be better to just use an initial propellant dump to get up to speed. Either that or a rolling start.

The upper limit on pusher-plate specific impulse is somewhere around 12,000 s. The upper limit on the specific impulse of an antimatter rocket is somewhere around 15,000,000 s.

Yeah, 2-3 million dead in the U.S. alone. 7 billion infections worldwide.

In order to "suck in" air, you need to lower pressure at your inlet. You can do that with a big-ass turbofan/turbocompressor, or you can use the Coanda effect or laminar flow. The important thing is that you only need that high mass flow for a very brief period of time. Once you have velocity, the ram effect will do compression for you. So if you have an engine design that can vastly boost thrust for a short period of time without increased dry mass (maybe with lower specific impulse), you just boost hard during the first 30-60 seconds of flight and then you're good. You need the entire forebody of the spaceship to act as a shock cone intake for forebody compression.

Propulsion system alone.

The 1959 Interplanetary Orion had a planned specific impulse of 4,000 s and a propulsion system TWR of 4.8 or thereabouts. That is NOT a high TWR; it's barely higher than the lowly NERVA and it's nowhere near conventional chemical rocket engines that routinely reach TWR of 60-100 or more. What Project Rho doesn't account for is inert propellant injection into the propellant stream of a plasma-core antimatter rocket.

Yeah,, there is a very good possibility that in order to make it work, you'd need to basically make your entire ship the intake. Consider Bucknell's NTTR SSTO, where the entire forebody provides compression: Also the old LACES (liquid air cycle) design: Or the X-30 Aerospaceplane: Here's one where the conical forebody compression is really obvious: There's another airbreathing SSTO design that used a concave conical forebody and slush hydrogen with payload bay at the rear but I can't find a picture. One thing for you to keep in mind is that if you're using antimatter, your available dry mass is much higher than these designs, and so you can afford to play around with the physical structure a little -- so you could have a saucer shape with the intakes on the sides, for example.

Exactly. That is not correct. Pusher plates need reaction mass too: a tamper made of tungsten powder that is vaporized into plasma at detonation. In terms of total impulse, an antimatter rocket would use many many times less reaction mass than a pusher-plate rocket. Also less dry mass. It will not. If you want the antimatter rocket to have more thrust, just make it bigger. You can make it as big as you want. It would have thrust equivalent to a pusher-plate design at a fraction of the total weight. That is a bug, not a feature.

Yep. Slosh baffles and rings in the first stage RP-1 tank:

Flu's seasonality means that it is always flu season somewhere, which is why it never hits zero. You could wipe out flu completely in the US and still import it. Agreed on serological testing.

Intake design is nontrivial. Unlike in KSP, you can't just slap an intake on the front and expect the air to get through to the back. The air needs a flow-through path. Moreover, at high-supersonic speeds, you need forebody compression. Finally, you can't balance the engines in the middle of the craft like Skylon or the exhaust will torch the back end of your ship. The intake is going to need to be integrated into the shape of the overall ship. Well yes. Even cruising around will require propellant. You need a way to add energy to the air -- more energy than it already has, mind you, which is A LOT at hypersonic speeds. Your best bet, presuming total antimatter confinement, is to use a dense cryogenic propellant that does double duty as open-cycle coolant and working mass. Pump the propellant around the combustion chamber, warming it, and then pump it into the chamber along with a small amount of antimatter. It annihilates and does what rocket exhaust does. Make sure it's throttleable. Then you can use this engine on the low-throttle setting to spray superheated exhaust into the airstream, which will heat it up and give you tons of thrust. Once out of the atmosphere, throttle up and use it in pure-rocket mode.

Nope. It's now endemic. If you think this is true, then you presumably think that after a full lockdown the common cold will also cease to exist (multiple different viruses, but all will similarly go away with zero contact to new patients and even brief conferred immunity). Asymptomatic or very mild cases ("colds") will continue forever. Viral load tests only show people shedding virus, so even testing everyone with a cold with an instant test, you only know if they are shedding NOW. They can test negative this afternoon, and positive by bedtime. Which is why I said this works only if asymptomatic carriers never beat it. Seems to be, but we don't have good data on that yet. In reality, immunity is a function of a lot of variables, including the mutation rate of the virus and the types of antibodies produced.