Space and Science BS Thread

What's the highest a starship can get without needing a refill? I think it is limited to LEO. If the big transport ship is too high you're going to need a refill tanker for the refill tanker to reach it. Plus all the cargo starships would need refills to reach it and transfer cargo. Or bring it into a leo orbit and need a 100 refills to get the big transport ship out of leo. Its the same problem, getting mass out of orbit costs energy.

And all fuel is expendable. Even nuclear rockets use expendable fuel that would need to be brought up from Earth's surface, and Elon has talked about adding those to starship. If we see anything I think we'll see fuel depots with chillers to prevent boil off.

 

Most rockets pre-F9 with solids used them as 'dial a rocket' systems. The main core is sized to orbiting the minimum mass payload and the and additional performance comes from the (variable number/size) strap ons. The cost optimization really comes to the fact that the center cores used to be quite expensive (a single main engine or two) compared to the 'cheap' solids. With F9, the core cost went way down since instead of a single expensive engine, they're using a cluster of 9, mass manufactured cheaper engines. But those add up - speculated cost per GEM63XL (vulcan) is 7m a pop, while a F9 first stage is ~30m a pop. 4x solids will basically end up being the cost of one of the liquid boosters, and those you can't reuse.

Exceptions - Shuttle, which literally can't go anywhere without the solids (the SMEs are sized basically as a stage 2 amount of thrust, burning all the way until orbital insertion. And the SRBs are about 300m a pop. SLS ones are ending up about 600m (1.2bn per pair)

 

So would there be a substantial savings to using SRB’s for expendable FH missions? It sounds like it might be about 1/4 the cost (14m vs 60m) if 2 SRB’s could match the thrust of 2 F9 1st stages.

 

Starship will get used. I just don’t happen to think it’s ideal for every use and you seem to think nothing else could possibly be better in any scenario. Orbital altitude is always a trade off with mass to orbit. Starship could go higher with less payload or in expended configuration. It’s no different from any other lift vehicle in that respect. If it takes ten launches to refuel a similar capacity transfer ship then it’s not an upgrade but I’m assuming such a drive upgrade is inevitable since it’s necessary to completing the task.Transfer ships might be bigger, I would assume so but they won’t be affected by any atmospheric concerns so shape, configuration, spin modules, etc can be optimized for what it will need to do rather than crammed into the bullet shape whose sole purpose is to navigate the first 100 miles of a 35 million mile trip. A constellation of LIFE modules and a propulsion module would serve better with far less dry mass. Drop them in orbit for ferrying to the surface and return with preloaded cargo cells or LIFE modules to be reused. Or the modules can be separated as needed for orbital stations or deflated and brought down for surface use with only the propulsion module returning to earth. Everything will have to get used and be made to be easily modified, the easier the better and those modules will be far more valuable there than the cost of sending more up here.

 

I have been following this argument about the usefulness of Starship to go to Mars, refuelling, etc.

My take on it is, Starship might be used for the first couple of trips, sure. But with the recent leaps in tokamak fusion energy production, I can see where larger, built-in-orbit, interplanetary ships will be built with fusion drives. Then you will have Starship as the taxi up to those larger ships, and then you will have Starships in LMO for taxiing on Mars.

But ultimately, I see chemical rockets going the way of dinosaurs. Once fusion drives become smaller and more economical, we'll see SSTOs with fusion drives as taxis taking us uphill.

 

I think it will be more than the first few but the environmental cost of using the equivalent of a supertanker’s cargo of fossil fuels for each one of them will become readily apparent. Multiplanet is the goal, not wrecking the better one to get to a second one. I don’t know if it’s possible but a much more sustainable and palatable option would be a hydrolox fueled Starship for use on earth ASAP and transitioning the fleet to that as methalox ships age out elsewhere. I couldn’t predict how long if ever it might take to transition off of chemical lift rockets but the science for interplanetary drives is already ahead in terms of efficiency and has a much higher ceiling so I agree it should happen much sooner. It would be easy to imagine such drives being fitted into Starships as an interim stage since the hulls would be readily available but I believe once all the advantages of purpose built ships become apparent Starships will be used where they serve the need best and not because they’re the only thing available. We’re still early in the infancy of the whole notion and things could change radically but that’s how I see it playing out. Spacex will play the lead role but it’s critical that they not follow the examples of previous powerful corporations that stagnated instead of being aggressively proactive.

 

It'd 1) have to be designed for it, 2) A F9 S1 puts out 7.6 MN of thrust for 162 seconds (~1200 MNs), while a single gem63xl puts out 2MN for 84 seconds, (so 160MNs) so to replace each booster would require 7.5 GEM63 XLs costing 52m. So a F9 with 15 SRBs is gonna be kinda kerbal lol.

It's still the first steps, and the problem with fusion-electric is you gotta cool the darned things, or use fusion rockets, which are still a ways off. You'll also want some sort of chemical taxi until you get space elevators built, at least for places with atmospheres.

 

Anyone know anything about GRX810 and how it compares to and differs from GRCop42? It seems to be a high strength high temp alloy as opposed to the higher thermal conductivity but lower strength GRCop42. Both utilize additive manufacturing so I’m thinking the first might be used as moving parts in turbo pumps and the second in combustion chambers, casings and bell nozzles with cooling channels designed in.

 

https://x.com/aj_fi/status/1807339807640518690?s=46

 

https://x.com/sciguyspace/status/1806762777333076064?s=46

 

surprised they weren't dusting the XL plans.. instead you just get some junk in the trunk?

Wish.com hold down clamps.

 

Ooops.

 

https://x.com/djsnm/status/1807436543696720110?s=46
Kinda looks that way…

 

Do any space companies install the fts for static fires?

 

Most of the time the hardware holding down the rocket keeps it from going anywhere, plus some tests are done horizontally. Also automatic shutdown if the thing starts moving.

Ex:



(F9 using launch holddowns)

https://www.youtube.com/watch?v=SZQY902xQcw

F9 full duration, top holddown cables



SRB test stand, horizontal.

 

My initial reaction differs from Scott Manley’s in that while something blew up the rocket definetly launched with some engines still working. I’m guessing the failure was external to the rocket which then broke free but was not unscathed and suffered progressive failures.

 

Here's a cool short I saw of Nasa testing heat shields.

https://www.youtube.com/shorts/Cam3drnEomY?feature=share

 

They both seem to be the same high-heat, low creep, low cycle fatigue, but GRX810 is nickel based and GRCop42 is copper based.

As with most space related things, Scott Manley has a long form video.

https://youtu.be/HxmuxlKh4UQ?si=m30fTwJeUPuFcFp_

 

Last time it was Ida threatening KSC, now we get to watch as Beryl slides towards the Yucatán and possibly Brownsville. I hope they get things buttoned down or put away. It’s not so much the big stuff but all the smaller equipment, pieces under construction at Sanchez, the launch and factory sites, and materials that could get messed up, contaminated, swept away or piled in heaps.

 

Wild stuff:
https://x.com/astromaterials/status/1808257889754095865?s=46