sevenperforce

Hey, looks like I was wrong (and I'm very happy about it):

Here's some lineart of my proposed crewed-version upper stage:

Eye candy:

This sort of thing could easily be a drop-in replacement for something like an upgraded/reworked Dragon 2 or the New Glenn equivalent. Having LES is a huge deal. Really huge. There were SO many failure modes for the Shuttle which resulted in LOCV.

Yeah, exactly. This sort of system could have enabled the Hubble servicing missions readily enough.

I think (I hope) that happens to all of us. Oh, it does.

Yes, exactly. The ISS could have been built without the Shuttle, for sure. Unpressed downmass was never used apart from ISS missions, I don't think. But if manned presence in space had been far, far greater than it was, then the Shuttle's capabilities would have been much more useful, and building a better version of it would have been a good idea.

My original post was more of a what-if, namely: what if the expectations in play when the Shuttle system was designed and funded (rapid launch cadence, need for frequent on-orbit servicing of payloads, and the need for downmass) had actually been accurate? Obviously they weren't, but if they had been, what systems could have performed the same tasks better than the Shuttle? Answers could be something as simple as "use liquid boosters with crossfeed on the Shuttle" or "fly with multiple booster configurations depending on payload".

There are so many tradeoffs. The idea of ISRU is really attractive, on the surface. You can give Tsiolkovsky the middle finger and use local resources. But actual utilization is challenging. In theory, the most straightforward ISRU approach is to land an empty MAV with the ISRU unit already attached and plumbed in, and let it collect its own propellant. For simplicity, you can just let it collect LOX in-situ and let it bring its (less massive) fuel along with it. But there are a lot of reasons why it's sub-optimal. The concept of having the crew leave their descent vehicle and head to a separate ascent vehicle is not attractive at all. You'll probably need a very sturdy rover as a primary mission survival requirement, just to allow the crew to get to the ascent vehicle, so that drives up mass. You have to have a separate airlock, cabin, and ECLSS in the ascent vehicle, and all its systems need to be able to be landed long in advance and remain perfectly ready for at least 2 years without maintenance or checkups. Are crew members in IVA suits or EVA suits? EVA suits take up much more space, but you need to bring at least one along in case there is some mission-critical problem that needs to be correct in order to allow ascent. Most disturbingly: no landing abort mode. None. From the moment you start entry, you're committed, and your survival depends not only on successful EDL, but landing in a site that will allow egress, and allow you to unload your rover, and allow you to make it to your MAV safely. Imagine how much riskier Apollo would have been if Buzz and Neil had been forced to head off to a separate ascent vehicle! Now, since the lander needs descent engines, you can size them a bit bigger and use your lander for ascent as well. Just go the ITS route and transfer propellant from a pre-launched ISRU unit to your sole crewed vehicle. But that requires an even greater landing precision, and I don't think anyone is comfortable with the idea of hooking up hoses for propellant transfer in an EVA on another planet for the first time. The only other option for ISRU (other than bringing the ISRU unit on the lander, which is a non-starter because of the time it takes to collect propellant even if dry mass wasn't an issue) is to have the ISRU vehicle autonomously land, collect propellant, and then return to Martian orbit on its own, to transfer prop to the manned vehicle prior to crew EDL. This is the lowest-risk option, because the manned vehicle has all the propellant it needs for ascent before committing to entry. It's also promising from a dry mass point of view; if your lander can drop up enough payload on Mars with a single direct ascent (projected mass to TMI from a fully-reusable Falcon Heavy with my mini-ITS upper stage is 4.5 tonnes plus the entire dry mass of the vehicle), then you can end up with about 35-40 tonnes of propellant available for transfer in low Martian orbit. Of course, you've wasted more than half of your fuel getting that fuel up into orbit, but you don't have to worry about finding a way to transfer propellant on the ground. And it would take much more than a single reusable Falcon Heavy launch to put 35 tonnes of propellant into a TMI; 35-40 tonnes of propellant is what the Falcon Heavy + mini-ITS tanker combination can manage for LEO. The biggest advantage of the last option is that your EDL and ascent double as tests for the parallel manned mission.

I stand corrected.

Best collection of views yet, including some alternate tracking camera footage not included in the webcast:

THE PIXELS THE PIXELS I CAN TELL BY THE PIXELS

My gut is no, due to the classified payload issues, but you never know.

Falcon is a 2 stage lifter... Wow, that was dumb. Fixed it. Bingo.

Congrats, this post is the reason I got the dreaded "You are only allowed to give 25 likes per day. You cannot give any more likes today." message.

Yeah, I saw that. Shocked they didn't scrub again.

The empty solid booster is heavier than a liquid-propellant tank of equivalent volume, but it is lighter than the entire liquid rocket assembly would be.

Tail-first video of the entry burn confirms that the first stage central engine ignites first, followed by the other two stages engines. Rewatching...from the ground, it appears that the bottom half of the rocket is already pretty sooty at the conclusion of the boostback burn. I didn't expect that.

Going back and watching the launch, since I tuned in about a minute before MECO... Was it just me, or did she feel pretty sluggish coming off the pad? Checking...looks like 100 m/s at T+0:27 in this flight. Quickly compared to CRS-10 and it was identical. SES-10 reached 100 m/s about two seconds later, at T+0.29. Guess that's the difference between an LEO launch and a GTO launch.

Bezos's mom? Okay that might have been wrong.

Yeah, he said "over 200 feet tall, 12 meters in diameter" so that's probably right. Funny thing is, he made the same mistake yesterday.

He definitely said meters. Check T-8:07.

Whoa!! This is intense, really intense.

Why did he say it is "12 meters in diameter"? It's 3.66 meters wide. Maybe he meant 12 feet? Or maybe he meant that the TEL assembly is 12 meters in order to support Falcon Heavy....

Now that's how to start a Monday! (I work an 8-to-5 so that's where I am with days like this...) Gotta conserve likes, for sure. You might be a nerd if your biggest thrill of the day was that SpaceX provided telemetry for the first stage recovery! Federstein keeps tripping over his words this morning, but not so badly as yesterday. Anyone know if they are attempting fairing recovery?