The 'just enough booster to make things work' line has me thinking about Mars ascents. Musk said a while back that a Starship could SSTO from the Martian surface and this looks even more reasonable now

@EagerSpace

9 ай бұрын

It's *so* much easier to get from the Martian surface to orbit. It's only 3600 m/s of delta v, where getting to earth orbit is around 9000 m/s. You can get from the surface of Mars back to earth for 5700 m/s. My model says that you can do that with the current model of starship with 150 tons of payload.

@judet2992

Ай бұрын

So orbiting Kerbin is about the same DV as orbiting Mars? Huh.

@judet2992

Ай бұрын

@@EagerSpaceso it’s like orbiting Kerbin? Huh.

Hear my plea, o algorithm: bestow upon this channel more views! Lots of people want humanity to live in space someday. Eric's videos are part of what those folks need: accessible technical details.

@sCWasP

9 ай бұрын

Content is to high quality for the algorithm is my guess, gotta appeal to the tiktok crowd to get boosted

@arnslyff6859

2 ай бұрын

Ive been binge watching his whole channel today

@chimpychimp4921

Ай бұрын

Amen!

Ends up like they will choose another change, stretch booster AND stretch starship.

@EagerSpace

Ай бұрын

Which makes more sense but doesn't align with what Elon says in the past.

This channel is unlimited nuggets of rocket knowledge and I’m here for it 💯

YESSSSSSS NEW EAGER SPACE VIDEO AND ITS ON STARSHIP OMG

Another nice one ... great tech with some historical context ... thanks.

@EagerSpace

9 ай бұрын

Thanks.

It is going to be interesting to see what payloads will be when approaching 100t.

@goldenfloof5469

9 ай бұрын

My best guess is that they'll probably be starlink launches, or refueling missions. Any mission far past low earth orbit will most likely need several refueling missions after all.

So what's the conclusion? We just need more information about therefore we wait, then? I'm thinking the whole starship system will get significantly more massive if the Raptor 3, staging timing and mass to thrust ratio is to make sense; something closer to the 6000T mark.

@EagerSpace

9 ай бұрын

I don't expect it to change much in the near term - the Boca Chica infrastructure is sized for the current design and it would be time consuming to change it. I suspect that for Raptor 3 they are going to dial back the engine a bit and accept a lower chamber pressure and specific impulse to be able to push more thrust and reduce the engine count. For a first stage thrust matters more than specific impulse, especially with very early staging.

@davidhenry5128

7 ай бұрын

I love this reply, almost everyone else implies ISP is king in all situations. Thanks.

Ok here to watch it

I suspect hot staging also offers improvement in abort modes for the ship.

@EagerSpace

9 ай бұрын

It probably does as it would allow you to spin up the second stage engines right away rather than trying to stage from a dying booster.

@TheNheg66

8 ай бұрын

That could totally be a feasable abort mode for the booster portion of the flight with a landing droneship, or maybe even RTLS. In any case, with bellyflop>powered landing your survival chances are pretty good regardless of where you land. But, all that is only true if there is an issue with the booster. If there's an issue with the ship... well, you better hope that it's not the centre raptors.

@davidhenry5128

8 ай бұрын

The abort options for the space shuttle were much worse. Consider solid rocket boosters, or the need to get the shuttle to an altitude and speed that allows for landing on a runway. Also the early implementation of ejection seats, and the later implementation of a pipe that the whole crew could slide down are to say at the least, limited. Stership has the potential to do much better than that.

@armandomercado2248

6 ай бұрын

It looks like there wasn't much left of the Titan 2 first stage after hot staging. True, the Titan was never meant to be reusable, but the stress on SuperHeavy is nontrivial. EM's explanation on why the second SH was lost after separation (an LO2 dump) escapes me.

@TheNheg66

6 ай бұрын

@@armandomercado2248 only way EM's explanation makes sense to me is if there are some methane leaks on the raptors. They solved these on SH with CO2 and my guess is they deemed that mitigaton unnecesarry on the SS due to SS only firing it's raptors in thin atmosphere where there's not enough oxygen. And then they forgot about that part and dumped that oxygen there themsekves. But this is purely my ad-hoc attempt at explaining Elon's explanation, i have no idea whether any of this is correct.

Starship: as close to SSTO as you can get while still making sense. On a more serious note, my amateur calculations suggest that shifting propellant capacities from 3400 + 1200 to 3000 + 1500 could increase payload by 5 tons, decrease propellant by 100 tons, _and_ allow earlier staging.

I think Elon said in EA that 6 mins return time for booster launch to landing. That maybe another variable

@EagerSpace

9 ай бұрын

He did say something like that, and a quick return requires earlier/closer staging.

There's another advantage to early staging. Most of the atmosphere is down low, meaning that the booster can capitalize on compact, low expansion nozzles while the starship can run vacuum optimized engines along it's entire ascent where the improved Isp is most needed. I believe KSP exaggerates the effect of nozzle expansion and I quite successfully exploited this for highly cost effective almost-ssto vehicles.

@EagerSpace

2 ай бұрын

In boosters you generally care more about thrust than you do about specific impulse, as the amount of rocket you can lift depends on how many engines you can stack under it. The exit diameter of both Merlin and Raptor are roughly the size of the rest of the engine so they can be packed tightly.

@ARandomTroll

2 ай бұрын

@@EagerSpace Exactly what I meant.

The stretched version would use nine raptor engines(sixth vacuum and three sea level)according to Musk (and have an initial mass of 6 000 tonnes),, so probably your estimation for upper stage is too low, we are speaking about a 2100 tonnes upper stage!, if we ignore the payload !, reusablilty isn't included in those calculation, but for booster wouldn't be that hard, and for upper stage penalty would be so huge that is better to consider only expandable upper stages!

@EagerSpace

9 ай бұрын

I do expect the stretch starship to use 9 engines... Do you mean 2100 tons total for starship or 2100 tons propellant? 2100 tons total would be around 1800 tons of prop with payload of 150 tons. About 1.9 to 1. I'm taking "trending towards 2:1" as meaning "coming down towards 2 to 1" as they were considerably higher than that. To get to 2 to 1 requires more prop on the booster and it's hard enough to get to 100 seconds for staging with the current prop load; more prop make that harder. It also might require changes to the launch tower and that would likely be slow.

@theOrionsarms

9 ай бұрын

@@EagerSpace I mean 2100 tonnes (2000 tonnes propellant) for a expandable upper stage that needs to deliver 300 tons of payload into LEO, that is the only way you can deliver such huge payload without modifications to the booster, also probably that 300 tons payload would be propellant for refueling HLS(so no fairing for payload but a ship made from tanks, or a fuel depot ) , because that is the priority that needs to be achieved in less launches, like four in this case. Well actually total mass for upper stage would be 2400 tonnes with the propellant that would be delivered into LEO, so actually 65%from the booster mass, but would be only with five meters taller than current vehicles , those speculation are on Musk claims that future version would weigh 6000 tons and delivers 300 tons of payload into LEO(I find kinda vague that " roughly 2 by 1 ratio" ) , like I said only way that would be achieved even on the paper is with a expandable upper stage and that need to have a dry mass of 80 tonnes , and nine engines(those would be more powerful than current ones and delivers 25 MN of thrust, which will take from the beginning to a thrust to weigh ratio higher than 1/1), in this case the booster will contribute with 2700 m/s deltaV and upper stage with 6600 m/s deltaV. Maybe the booster can be reused but the upper stage not, with the exception propellant depot usage .

Honestly I was kinda hoping that they'd just slap a cheese wheel on SN26 and get it to orbit by itself. Just so the could say they had the first SSTO flight even if it wouldn't accomplish anything useful.

Dang I wish I found this channel sooner. Any chance you could do a video based on the latest starship test? In relation to all of this and whatever else you can think of

@EagerSpace

Ай бұрын

I don't generally do flight reviews because so many other people do them and I think do them better. This video is sort of a post-flight review because there was a specific topic that came up that I wanted to talk about. I can tell you that my views have changed on this video, based on my realization that second stage reuse is much, much harder than I realized. There will be a video on that relatively soon.

wait and see ;)

Excellent, of the people out here trying to represent themselves as understanding rocket dynamics only you and Scott Manley are worth listening too (and occasionally an engineer or similar from NASA will float by)I once worked for JPL and once for NASA and I hate to say it but unless you are willing to give it the effort do not try to understand what space flight takes, its going to take some numbers..

@EagerSpace

9 ай бұрын

Thanks.

with the risk to embarrass myself, how much of a problem is the hot staging for superheavy? that titan separation looked pretty violent ...

@ryanrising2237

9 ай бұрын

It can be assumed they’ll want to build that ring so it doesn’t explode like Titan II, but as SpaceX has found out in other situations, point blank rocket exhaust is not good for the surface being subjected to it. The hot staging shield will need to have significant mass to survive that repeatedly, which makes hot staging not a pure win. In some situations it’s still worth it, and maybe starship is one of those.

@TheEvilmooseofdoom

9 ай бұрын

@@ryanrising2237 Steel does give them some wiggle room. It can take a lot of abuse and heating and stay strong. I suspect the ring and shield will be a WIP for a while. :)

@EagerSpace

9 ай бұрын

My take is that the current design is a "what is the minimal thing we can do to test this?" approach since they aren't planning on getting this booster back anyway. I think a real design probably needs a taller vent area, probably two rings high. The titan staging is violent because the shroud around the second stage engine is part of the first stage - that is what you see explode as the first stage pulls away. In Starship the shroud is part of starship, so as soon as there is separation between the stages the exhaust will be much less problematic.

Did they ever consider hot-staging for the falcon 9?

@EagerSpace

Ай бұрын

I have an upcoming video that explains why, but I'll give you the preview. Hot staging makes little sense for falcon 9 because the savings in Delta v didn't have much effect on payload. It's critical for starship because it's much more sensitive to Delta v savings and therefore there's a much bigger payload effect.

Falcon 9 uses ~113t of propellant to do an RTLS landing. With an avg Isp of 296.5s, that's ~5250 m/s of required delta-v. Thats ~750t of propellant for a 200t Super-Heavy with the same trajectory. Adjusting for it's higher terminal velocity and more energetic staging point, Su-He could need up to ~1000t. I also calculated independently that RTLS landing F9 would require ~1465 m/s, but real fuel usage is wayyy higher. Maybe it's some massive cosine and gravity losses.

@EagerSpace

3 ай бұрын

The new starship configurations are especially designed to stage earlier and lower and push more of the delta-v requirement onto the second stage.

@kolbyking2315

3 ай бұрын

@@EagerSpace Could that get the delta-v requirements below an ASDS Falcon 9? That requires ~55.5t of fuel for a 22.2t F9 1st stage, ~3640 m/s of Δv. That's ~390t of propellant for a 200t Super-Heavy. Idk if I believe Elon on that 200t dry mass anyway. Edit: I used a specific impulse halfway between sea-level and vacuum. F9 = 296.5s (282s 311s) Su-He = 345 (327s 363s)

Have you considered that at sea level the ISP isn't the same as in the vacuum?

@EagerSpace

9 ай бұрын

I'm assuming you're referring to the mass flow rate. Engines get higher exhaust velocity in vacuum because of the lack of atmospheric pressure. That pushes the thrust up but doesn't *generally* affect the mass flow rate.

@AlbertoGirardi747

9 ай бұрын

​@@EagerSpaceexactly, the mass flow rate should not change. But you calculate it using the ISP. That changes. So which ISP should be used? The sea level one or the vacuum one?

@SpaceAdvocate

4 ай бұрын

@@AlbertoGirardi747 The thrust also changes, you should use the sea level thrust and the sea level Isp, or the vacuum thrust and the vacuum Isp.

Unrelated to the video itself, I haven't even watched a minute in, but seeing the photos at the start and then seeing a thread on the SpaceXLounge about (possible) updated HLS renders, god, it makes me wanna play KSP and do an updated recreation mission of the HLS and SLS (I did two missions last year in-game) buuuuut I'm gonna be busy here soon so I guess this video will have to help satisfy my space/rocketry cravings until later tonight when I can fire up KSP lol

Do an analysis now, after the test flight

@EagerSpace

3 ай бұрын

*Everybody* does analysis after the flights and I don't think I have much to add. I may, however, do something based on the SpaceX update on Starship that Elon recently gave.

@lorisperfetto6021

3 ай бұрын

Sounds ok!

Would ditching return-to-launch-site for Super Heavy - and instead landing them somewhere around Africa - allow for any significant gains? I assume the biggest roadblock would be getting the boosters back, but that could be achieved with either a second, booster-only hop or by then launching more Starships from a few different places around the globe, forming a cycle. Assuming that the west coast of Africa is the right distance, the next spots would be around central Asia (Kazakhstan | Mongolia | China) and in the middle of Pacific. Besides that, such a change would require major redesign to fit the new constraints (tho if thousands of Starships are the goal maybe it would be worth it once everything else is perfected).

@EagerSpace

7 ай бұрын

Super Heavy wouldn't be able to make it transatlantic, and the problem is that the direction that you launch changes depending on your target inclination. Shuttle had that issue for transatlantic aborts; you can see the details in my shuttle abort mode video: kzread.info/dash/bejne/iYWA07OEeNuwebw.html You're stuck with barges or other maritime vessels if you want to land downrange. And those are expensive and subject to weather, and the you need to wait for them to come back. If you want to hop back, you need a full fueling system on the landing barge, which means regular deliveries of propellants. And you need multiple ones to get to different inclinations. *way* easier to just plan on coming back to the launch site every time.

Heads up, that video you showed at the beginning shows staging on a Saturn IB vehicle. This is observable from the cylindrical interstage - though that might be hard to tell from the wide field of view - and the triple ullage motors on the S-IVB, of which there were two in its Saturn V configuration. That video clip is commonly misattributed to a Saturn V, as you did here, but in reality it comes from the AS-202 mission testing out the Apollo CSM.

@EagerSpace

9 ай бұрын

Thanks. I should have keyed on it being Apollo 4...

@WilliamDye-willdye

9 ай бұрын

Tech channels have the best comment sections. :-)

What dry mass numbers and payload did you use in the thrust-to-weight calculation? Assuming 170t for the booster, 100t for the ship and 100t for payload, witch seems optimistic, the total mass for the streched stack would be 5470t. Thrust would be 33*234,5t=7,740t for Raptor 2. The thrust-to-weight then would be 1,41, which sounds about right and we would get to 1,3-1,4 if the dry mass or payload is heavier.

I don’t think hot staging is as pure a win as you make it seem here. It’s a tradeoff, and the things it trades off for the advantages are significant even in this context. While it does reduce boostback range and save you some gravity losses, those gravity losses are quite small by my figuring. The procedure itself is violent - this was shown excellently by the clip of the Titan II blowing out its interstage. While SpaceX’s interstage would be built to survive this, to do so repeatedly requires a heavy blast shield and grating, which will increase dry mass, in turn reducing or possibly even negating the performance benefits relative to a more conventional staging procedure. While hot staging is what SpaceX have chosen for starship, it’s not necessarily the optimal choice for a reusable rocket, even one of similar configuration and flight profile.

@albhem_eh

9 ай бұрын

For you maybe...

@EagerSpace

9 ай бұрын

The staging losses are in the range of 100 m/s for the second stage, 200 m/s for the first stage. You also save an additional cost on the first stage by not coasting downrange during staging, that's maybe another 100 m/s. So 100 m/s second stage, 300 m/s first stage. It's not huge but it's not nothing. I'd love to know what the change in mass is, but it suspect that it's not going to be enough to overcome the savings in delta v on the first stage. The other big win for the first stage is that with your engine(s) still running, you can gimbal your way around to head back where you came from. That's another savings - if you compare how quickly starship flips to land versus how long it takes Falcon 9 to do a 180. WRT the violence, that's an outgrowth of the Titan approach. The part that fragments is an interstage shroud that covers the second stage engine, but on Starship that shroud is integral to Starship, so there's nothing to fragment. Having said that, I don't think the current design is a reusable design - I think it's just the simplest way they could test things. I'd expect to see something two rings high with some protection on the tank top. I also suspect that they might go for a staged ignition - just light the three sea level engines to get starship away from the booster and then light the others soon afterwards.

@ryanrising2237

9 ай бұрын

@@EagerSpace I believe you’re significantly overestimating the gravity losses there. That 200 m/s you quote for the booster isn’t actually something that needs to be made up. The booster’s job pushing upwards and outwards to fling the upper stage away from Earth is done, and so it doesn’t need to carry extra fuel to do those things. The gravity losses on the upper stage are those that need to be made up. The range savings for the booster are real and do need to be considered, however, and is why flipping over quickly is desirable. If we take your 100 m/s as gospel, that may or may not be outweighed by the extra mass of the shielding. The Titan approach did fragment the interstage, but it’s not necessarily because the the second stage engine bell was contained within it. You’ll note that the fragmentation happens only *after* the bell clears the interstage, which puts it near where the booster’s hot stage venting would be when the orbiter’s Raptors have to pull it away. There’s something there to fragment indeed, even though it can be built not to. Finally, based on what we have seen of the hot staging hardware for Starship, your staged ignition idea is likely nearly correct. The shielding only provides clearance on the sloped part where the Vactors’ exhaust would impinge on, and very little near the sea level engines, where there’s a flat plate. This would indicate only the outer engines would be firing during the initial part of the maneuver. It’s still not going to be a light piece of material that withstands their exhaust point-blank.

@kiwigurn

9 ай бұрын

Elon mentioned 10% improvement when HSing comments at the time I think said ulage of propellant was a significant benefit.

@ryanrising2237

9 ай бұрын

@@kiwigurn Yeah. I don't put much stock in numbers Musk says in a tweet, but it's true that the previous "twig snap" could have caused some problems with the ullage gas.