Racescort666

No, same engine, it's just the new Porkjet version.

Mass/dV. What I meant by that comment is that if you took something like the New Horizons mission, ditched the Star 48, and stretched the Centaur a little bit, you'd have a lighter upper stage and more dV. They didn't do that because they couldn't make changes to the upper stage. If you were to replace the Star 48 with a liquid stage, there isn't a huge advantage in mass/dV so you're right, go with the simpler solution.

There is some advantage to denser propellants when it comes to very large mass fractions and SRMs have good mass fractions. I’ve really only looked into it on upper stages but I suspect that a better designed liquid stage would still be superior. As for boosters, I haven’t ran any numbers on pure performance but it seems that liquid is the best because you have the option to propulsively recover.

Ha, fair enough, Cosmo for wannabe nerds. After learning to play KSP and spending a good amount of time on this forum, decent websites who write about spaceflight have been pretty hard to come by. It's kind of funny too, the people I know on social media have no idea that what they share is crap. Here, the expectation is that claims must be backed up with evidence and technical issues must be addressed for something to be feasible. On social media, you get insulted if you even point out that there are technical problems.

My problem with the article is that it is manufacturing drama when there is none. As you pointed out, for specific circumstances one is objectively better than another and as a result we have converging design philosophies for rockets depending on their purpose. When it makes sense to use SRMs, do so and no engineer will argue with you. The same can not be said for politicians and journalists. Also “ISP per pound” was a direct quote from the article. I had a hard time finishing the article after that.

But “ISP per pound”... wait, that is completely ridiculous.

So I came across this article: https://www.popularmechanics.com/space/rockets/a19724715/liquid-solid-rocket-fuel-spacex-orbital-atk-blue-origin/ That claims there is a debate between solid rockets vs liquid rockets. It reads an awful lot like an Orbital ATK sales pitch if you ask me but I will leave that to the reader.

Was this a scientific paper dedicated to describing mansplaining? jk, I found this passage from the article interesting because I helped my gf proofread a paper on getting specific demographics of students more involved.

@RealKerbal3x to build on what @DerekL1963 has said, they use TEA-TEB injected into the engine which automatically combusts with oxygen (even liquid oxygen) to start the engine. You can even see when they inject it during engine starts because it’s burns green. They also used it to start the engines in the SR-71 and A-12. Think of it like starting fluid for your lawnmower/snowblower/whateverelse is hard to start. (Now that I think of it, it’s probably closer to ether start on a diesel but nobody deals with that much anymore so let’s not go there.) During the landing, the center cluster engine did fire (as can be seen in the video) but one or both of the side engines were not lit. If the announcement is taken at face value, one or both of these engines was either completely out or didn’t have enough starting compound to ignite. Speculation on which case or other causes we will leave to the fan forum.

Assuming your knowns are F, x, E, A and you're trying to find L_i, L_i = (E*A*x)/F

This deserves a like. There are certainly smart people at ULA and their "tribal knowledge" is unrivaled but they suffer from the same problem as every big company, bureaucracy. They can't see past their own shortcomings and the people who have the ability to let the smart people loose on the big problems can't see past the next fiscal year or even the next month. Startups don't have this problem but they don't have the same ability to foresee technical problems that allows them to be 100% successful. Take what you can get I guess.

ULA is considering the BE-3 for ACES. Frankly, it’s probably the best choice of upper stage engine as far as I see. With ACES and IVF, ULA does appear to be the most serious about long duration missions with cryogenic propellants. Now all I need is to figure out how much hydrogen you need to start with to perform a braking burn at Uranus...

I have been using 99.2 kN since most of my comparisons have been to Centaur which uses RL10A-4-2. I believe the DCSS has slightly more thrust at 110 kN with the RL10B-2. I assume this is because RL10B has the extendable engine bell, weighs more, and has better ISP. As for BE-3U, it appears to be a really solid choice. At 600 kN (I really wish I had a better mass estimate), the new payload is still around 60t (59 922 kg, GTO is 19 844 kg) and the engine mass jumps 160 kg since it's based on TWR. Second Stage TWR is LEO: 0.35:1 and GTO 0.39:1 both are pretty reasonable while a 3 or 4 engine version gets you back in the neighborhood of the original TWR.

Here is my estimate for payload increase by switching to 2 BE-3U engines instead of a single BE-4: LEO: Metholox BE-4: 45 000 kg Hydrolox BE-3: 60 243 kg GTO: Metholox BE-4: 13 000 kg Hydrolox BE-3: 20 165 kg There was some discussion about TWR with switching to 2 BE-3 engines but based on my estimates, it seems reasonable considering other launch vehicles. LEO TWR: Metholox BE-4: 0.71:1 Hydrolox BE-3: 0.29:1 GTO TWR: Metholox BE-4: 0.78:1 Hydrolox BE-3: 0.32:1 For reference, F9 is around 0.70:1 while Atlas V is around 0.30:1. Obviously this varies with payload but Centaur has very low thrust and Atlas V has a pretty big payload capacity. Methodology and some discussion in the spoiler:

I know the RL10 is labor intensive to build but where are you getting the cost for this? I thought we estimated the cost of a F9 booster to be $40m which is what the RS-25 was quoted to cost. I'm curious because I looked for the cost of the RL10 at one time and was unable to find good numbers.

Sounds like a used Ferrari.

That's certainly bold.

I couldn't for the life of me figure out why they were launching from Vandenberg until here: I assume they plan on making a dogleg flight path? Is this one going directly into an Earth escape trajectory? I assume that ULA doesn't want to make it all the way to space with the first stage still attached like I did before I really got the hang of KSP.

Maybe insurance is less because they have better launch history? Is there another cost I'm unaware of that affects how expensive it is to put something into space? SX is catching up quick and BO is still the wild card. Also, yes, I agree, I would like that job. It sounds like KSP in real life with real rockets.

From the article: “We should be able to offer them a better deal,” he said. “We’re not trying to do this to make higher profits. We’re trying to do this to be more competitive by offering them a better solution.” Tory seems to be aware that they cost too much and they’re in the process of doing something about it.

I work in the auto industry and believe me, benchmarking is serious business. We are currently in the process of building test equipment to reverse engineer competitor vehicles and being on this forum and seeing people beat the scientific method drum gives me a warm fuzzy because I get to do it for my job too.

My vote is Alan Mulally he's kinda old at 72 but the dude jumped from Boeing to Ford and turned the place around. According to the "word around town" people actually cheered when the Ford signs went back up on the corporate buildings. It seems like he's got a good management style and despite being a government agency, Mulally could probably make something awesome of NASA.

Space nerds have hypothetical missions to calculate!! Seriously though, when you put it that way, it makes a lot of sense.

@Bill Phil @sevenperforceI ran the numbers for New Horizons if Centaur were replaced with a Metholox stage: Payload: New Horizons + Star 48B: 2615 kg Stage Mass: 25 692 kg (same for both stages) Engine ISP: RL10: 451 Metholox: 380 Engine Mass: RL10: 168 kg Metholox: 51 kg Tank Mass: Centaur: 2079 kg Metholox: 739.6 kg Fuel Mass: Centaur: 20 830 kg Metholox: 22 286 kg Delta V: Centaur: 7358 m/s Metholox: 7525 m/s So, maybe I was wrong, a 2% increase in performance isn't exactly great. 167 m/s improvement on an Earth departure stage probably doesn't gain you much but I suppose it's better than nothing. Anyway, I shall find some seasoning for my hat...