Relativity Space: General Thread

[playadelmars]

They updated the engine from 17,000 pound thrust to 23,000 and at the same time added a gas generator to run the turbines. This was when they increased the payload fairing dimensions to be much larger and needed to lift more.

[Davidthefat]

They updated the engine from 17,000 pound thrust to 23,000 and at the same time added a gas generator to run the turbines. This was when they increased the payload fairing dimensions to be much larger and needed to lift more.

Ah, did not notice that. I figured the chamber needed to be A LOT longer for the expander cycle to work, especially for a non vacuum engine and using a nickel based alloy for the chamber liner material. May be the mass was just too big for the chamber for when the engine cycle balances, and they might had to look into bimetal AM as well to get a material with a higher conductivity as the liner (like chromium zirconium copper)

[ChrisWilson68]

Or alternatively: Relativity see potential for their large-volume metal fab technology (and potentially more important, QC-as-you-fab technology) outside of rocket bodies and engines, and intend to spin out that arm as a separate company, with one founder taking over operations of the spinoff. Though I'd expect that to be announced all at the same time if so.

To me, that theory seems entirely inconsistent with an announcement that someone is transitioning out of their role at a company.  A company would never make a big announcement that makes it sound like someone is leaving if they're secretly going to be staying with a spin-off of the company.  It just wouldn't happen.

[JEF_300]

They updated the engine from 17,000 pound thrust to 23,000 and at the same time added a gas generator to run the turbines. This was when they increased the payload fairing dimensions to be much larger and needed to lift more.

I actually hadn't noticed that. Honestly it's not even a change to the engine, it's just a new engine. That's a pretty drastic change to make this far into development.

Let's take a moment and put this into context with their two most obvious competitors, Firefly Aerospace and ABL Space Systems.

Firefly's design hasn't changed in years now, and they are planning to launch in the next few months.

Despite being founded two years after Relativity, ABL is also planning for a launch next year, and avoided this problem altogether by going with the simplest possible design from the beginning.

Relativity recently changed the most fundamental aspect of their engine design, after thousands of hours of testing of the old engine design over years, and (last I saw) still claim they will be launching next year.

Hey, maybe this'll prove that 3D printing your engine decreases iteration time so much that it's possible to design and thoroughly test a new one in only a year. I'm skeptical though.

[ringsider]

I actually hadn't noticed that. Honestly it's not even a change to the engine, it's just a new engine. That's a pretty drastic change to make this far into development.

Indeed. As I said, a reset. It was first mooted in the big interview with Eric Berger earlier this year:

https://arstechnica.com/science/2020/03/relativity-space-has-big-dreams-is-the-company-for-real/

Relativity recently changed the most fundamental aspect of their engine design, after thousands of hours of testing of the old engine design over years, and (last I saw) still claim they will be launching next year.

Precisely.

I think that slipped by most observers.

There are other symptoms if you look closely and read carefully. Just look at the number of days it takes to print a Stage 2 tank....

If you are the CTO and these things have to be corrected by experienced new hires it has to lead to... discussions.

But the real issue might be one deck higher.

[JEF_300]

If you are the CTO and these things have to be corrected by experienced new hires it has to lead to... discussions.

But the real issue might be one deck higher.

I mean alternatively, maybe the switch to gas generator and increase in performance is something the SpaceX new hires with experience on the Merlin were pushing for, and if Noone had stuck to his guns they'd still be using the old design and he'd still be CTO.

I could come up with 10 more possibilities, but my actual point is that it's hard to judge any personnel problems an organization might have from the outside. I think we're better off acknowledging the personnel changes, and only reading into the technical problems.

[playadelmars]

At least worth pointing out, from the time they announced upgrading the engine (shortly after a $140m funding round) they signed a contract for a half dozen Iridium launches, announced a launch site at Vandenberg, and hired a very impressive top engineer in Zach Dunn and US Govt leader from spacex too. I imagine all of these people have more insight to where the tech is really at

[edzieba]

It may have just been changing tradeoffs: from "we don't have the funds or experience to develop a GG engine as our first engine, and we're targeting a smaller launcher" to "we have cash, we have a bunch of new hires with experience with GG engines, and the launch market appears to be aiming for larger payloads, so we can start developing now. Do we even need the old design now?".

[novak]

It may have just been changing tradeoffs: from "we don't have the funds or experience to develop a GG engine as our first engine, and we're targeting a smaller launcher" to "we have cash, we have a bunch of new hires with experience with GG engines, and the launch market appears to be aiming for larger payloads, so we can start developing now. Do we even need the old design now?".

A GG engine is much simpler than an autogenous press expander cycle mathematically, it's the difference between open and closed cycle.  So I think it's the opposite: realism sinking in instead of early optimization, and building a better, simpler, engine to get the job done.  Maybe a setback, but a rational engineering decision, corresponding to the talent they've attracted.

[playadelmars]

Initially they were doing open cycle expander not closed, but still true GG likely easier especially as thrust increases.

[novak]

Initially they were doing open cycle expander not closed, but still true GG likely easier especially as thrust increases.

Open expander cycle with autogenous press still has the difficulty of a closed cycle engine in many ways.  Depends on the valves but any cycle based on the integrated heat into the rocket nozzle is highly complex.

[TrevorMonty]

Initially they were doing open cycle expander not closed, but still true GG likely easier especially as thrust increases.

Open expander cycle with autogenous press still has the difficulty of a closed cycle engine in many ways.  Depends on the valves but any cycle based on the integrated heat into the rocket nozzle is highly complex.

Keep it simple and start with He tank pressure system, upgrade to autogenous in future when flying regularly.

[ParabolicSnark]

https://twitter.com/relativityspace/status/1311347723426246656?s=20

Relativity published a new video today. Some closeup shots of the turbopump and chamber, and then a lot of shots of the same hotfires from different angles.

[Davidthefat]

https://twitter.com/relativityspace/status/1311347723426246656?s=20

Relativity published a new video today. Some closeup shots of the turbopump and chamber, and then a lot of shots of the same hotfires from different angles.

LOL at the spinning fitting at 8 sec.

Looks like they might only have a LOX turbopump on those hot fires. The fuel is coming from way out of the way.

[ParabolicSnark]

New article on Relativity from CNBC: https://www.cnbc.com/2020/10/07/inside-relativity-space-hq-3d-printer-rocket-factory-of-the-future.html

Overall the text seems large common with everything else we've seen before. The only thing that stuck out to me is an updated photo of the enclosures they're putting each printer inside and a nice glamor shot of their new lobby.

[edzieba]

Question for the Relativity guys: how many pieces of furniture in that lobby were self-printed?

[jongoff]

I was going to ask if they were moving in right next door to Virgin Orbit, Spin Launch, and Rocket Lab (all of which are now almost next-door neighbors on Conant Street, just north of the Long Beach airport). The architecture and size seemed similar. But apparently Relativity's new facility is on the south side of the airport. Still pretty cool. Last time I visited them, they were spread out across a bunch of smaller buildings over by LAX. This should be a lot more convenient for them.

~Jon

[john smith 19]

A GG engine is much simpler than an autogenous press expander cycle mathematically, it's the difference between open and closed cycle.  So I think it's the opposite: realism sinking in instead of early optimization, and building a better, simpler, engine to get the job done.  Maybe a setback, but a rational engineering decision, corresponding to the talent they've attracted.

Yes, you wonder how ever did P&W manage to do it in the early 60's.

6 decades later I'd guess things have gotten a bit easier.

I'd say when it comes to complexity staged flow combustion, were everything is tightly coupled  would be the hardest challenge. The SSME retrospective series offers a rich set of object lessons in some of the pitfalls you can expect.

[novak]

A GG engine is much simpler than an autogenous press expander cycle mathematically, it's the difference between open and closed cycle.  So I think it's the opposite: realism sinking in instead of early optimization, and building a better, simpler, engine to get the job done.  Maybe a setback, but a rational engineering decision, corresponding to the talent they've attracted.

Yes, you wonder how ever did P&W manage to do it in the early 60's.

6 decades later I'd guess things have gotten a bit easier.

I'd say when it comes to complexity staged flow combustion, were everything is tightly coupled  would be the hardest challenge. The SSME retrospective series offers a rich set of object lessons in some of the pitfalls you can expect.

I'd surely grant that staged combustion is harder than an expander cycle, but while on the subject of the SSME...  It took the SSME 35 weeks and 13 turbopump replacements before they managed to hit their minimum power level for an instant.  A bunch of these small, lean companies can't and shouldn't try to afford that type of thing.

Whether it's easier these days- it should be, for sure.  But I don't think Relativity's problem is biting more off, it's chewing.

[FutureSpaceTourist]

https://twitter.com/thesheetztweetz/status/1317102747490058246

Lockheed Martin's in-space cyrogenic fluid management demonstration (which won a $89.7 million NASA Tipping Point award) will launch on a Relativity Space Terran 1 rocket in Oct. 2023 and with support from a Momentus Vigoride vehicle: lockheedmartin.com/content/lockhe…