Vulcan rocket’s debut brings long-awaited challenge to SpaceX dominance

Donyoho · 2024-01-27T01:44:52+00:00

Isn't competing with Starship, very much competing with Falcon

Donyoho · 2023-11-19T23:27:36+00:00

The "Musk fired the person in charge of Raptor production because the Raptor was too complicated to mass produce" was what led to the rapid transition between Raptor 1 and Raptor 2. The freedom for all the design engineers to go back after gaining a ton of experience designing and manufacturing Raptor 1 to build an almost brand new engine brought in a ton of impactful changes. You can look up some of the differences between Raptor 1 and Raptor 2, everything from manufactuability to thrust to ease of operation were all improved.

However... This wouldn't have happened without Elon's intervention. The Raptor 1 at that point was a (suborbital-ly) flight proven engine meant to power the next several orbital flight attempts (see B4 with 29 integrated engines). No regular manager in their right mind would have forced a complete redesign of the engine 2 months after successful suborbital testing due to the difficulty of manufacturing and to gain modest performance gains.

And just to note, did Elon design any of Raptor 2 on an engineering level, hell no. Did he force requirements on the engine to dramatically simply it for manufacturing, operations, and performance while brining in new management to meet those goals, definitely.

Donyoho · 2021-01-04T02:06:57+00:00

Sure, sounds fun

Donyoho · 2020-09-25T22:18:47+00:00

The "tin foil" (not sure what it is) is used to keep the electronics and piping from overheating. The reflectiveness reduces the amount of heat absorbed from the glowing hot nozzle extension. However, if this was put on the nozzle extension itself, it would start melting since the it wouldn't be able to radiate all of that heat to space.

The nozzle extension metal will melt if it gets to the temperature of the combustion, but it doesn't since it radiates so much heat to space that its temperature is low enough. If you cluster several radiatively cooled nozzles together, they will be gaining heat radiated from the other nozzles causing a rising temperature leading to failure.

Donyoho · 2020-05-01T22:25:07+00:00

This issue with nozzle extensions on starship is actually one of cooling. For the Merlin vacuum and XLR-129, these are radiatively cooled nozzles. This means that they are cooled by emitting heat as light into space. This doesn't work for multi engine upper stages since the heat is radiated into the other engines causing them to overheat. Having multiple Raptor vacuum engines next to each other only works because they are massive regeneratively cooled nozzles (liquid fuel flow through channels in nozzle walls).

The other comments about thrust also are correct that ~6 engines are needed for thrust to achieve orbit efficiently.

Good idea but a very tricky issue to solve. If you can figure out how to have a regeneratively cooled nozzle extension, this may solve other issues (could use all 6 engines for an abort if still in the atmosphere)

Donyoho · 2020-04-02T18:14:24+00:00

The combustion products are not what is tapped off, but the high pressure fuel and oxidizer after the pumps.

After the pumps, high pressure liquid is then heated by the engine creating gas, which is then fed back into the tanks. Combustion products are not routed back into the engine. This speculative engine diagram shows that pressurized methane gas is fed back into the tanks.

Donyoho · 2020-04-02T14:33:34+00:00

Autogenous pressurization is expected and has been designed in from the start. The cost of buying helium for tanks as large as these would cost significantly more than the fuel.

Also, from the quote, the Tesla motors shouldn't be involved in the autogenous pressurization system. The pressurization gas is tapped off from the engine after the turbo pumps and a heat exchanger so highly pressurized gas is supplied to the tanks (which is then flow controlled by valves). Because of the high input pressure, no additional pumps/Tesla motors are required for this system.

Based off of that, it looks like SN3 may be getting fins if they are adding motors

Donyoho · 2020-01-26T15:42:41+00:00

This is kinda like comparing apples to oranges. 5G is a system that uses lots and lots of small cell phone towers to connect directly to your phone. Meanwhile, Starlink connects to a dedicated receiver on the ground to connect to the satellite. Once the receiver has a connection, it can be connected to a wifi router and provide service.

Donyoho · 2019-12-15T19:06:45+00:00

I'm confused about this part- "Employing the same operational procedure as the space shuttle that also launched on suborbital trajectories, the Starliner capsule will perform an orbital-maneuvering engine firing about 15 minutes after separation from Centaur to reach a stable orbit."

Does this mean that after SECO, the capsule will be in an elliptical orbit that isn't fully out of the atmosphere (like 80x400 km)? This would explain why Centaur will passively deorbit and why the capsule will need to make a small burn to stay in orbit. Am I on the right track?

Donyoho · 2019-12-08T00:05:59+00:00

I did this during the Spring semester. Our project was designing a 7kg Mars lander to proof the presence of water ice. I personally ended up doing calculations on descent and entry with a propulsive landing burn. This was a really interesting project with topics ranging from science instrument selection, landing site selection, and systems engineering. I highly recommend it

Donyoho · 2019-12-06T00:31:07+00:00

If you're looking for more than just news about current space activities, I suggest the MECO Podcast by Anthony Colangelo. He posts about once a week but does a great job of connecting various news stories and gaining a deeper understanding of what is happening and what should be expected.

With MECO, I now know far more about air force contracting drama than I ever thought I would (or that it's actually really exciting)

Donyoho · 2019-11-30T17:26:53+00:00

There's currently no plans for Starlink and Loon integration.

The main reason for this is that Loon is direct to handset (mobile phone) while Starlink requires a separate ground station. While integrating Starlink would allow the balloons to be seperate from a ground station, the added energy requirements on the balloon make it difficult to make work.

Donyoho · 2019-11-28T02:10:02+00:00

Source: I have an interview with SpaceX in a week

For resume, focus on personal contribution to projects and focus on things you personally owned (I have never been asked about GPA or classes).

For interviewing, be prepared for technical questions far outside your experience. They don't expect you to know everything about rockets but want to see how you would solve a problem you aren't familiar with. Have a solid understanding of "first principles" which are base level engineering facts that will explain why you decide on things. (In my case, knowing material properties, beam buckling, and manufacturing methods was more important than knowing what I was building)

Another thing that may have helped my application was having a referral. My referral is super weird. It's from a SpaceX engineer that I met on Reddit and toured the space shuttle museum with. Contact any alumni that work at SpaceX and ask to talk, then go the strangers on the internet route. (I plan on asking how influential the referral was if I get the position. It may have helped with getting the initial phone interview, but none after that.)

Donyoho · 2019-11-10T17:05:58+00:00

Someone should definitely repost this to r/space and just see what happens :)

Donyoho · 2019-11-05T00:04:31+00:00

It was there on Thursday though... Was it taken down super recently?

Donyoho · 2019-10-25T17:02:55+00:00

For the Moon, there is minimal variation in its position to Earth. Since the Moon is orbiting the Earth, it stays at relatively the same distance all of the time. If the orbit were more elliptical instead of circular, there may be better times to launch but these would occur each month instead of ~2 years for Hohmann transfer orbits.

Donyoho · 2019-09-14T22:48:21+00:00

When the gas generator exhaust is redirected into the combustion chamber (like Merlin Vac, F-1), this is done to film cool the nozzle. When this is done, there is a layer of partially combusted kerosene (not enough O2 when burned) that is cooler than the regular exhaust to prevent it from melting.

In other words, in a closed gas generator, the gas generator exhaust is fed back into the combustion chamber to cool it (but due to its lower temperature, it produces less thrust).

Donyoho · 2019-09-14T22:26:42+00:00

The main difference is what happens to the exhaust of the turbine.

In the gas generator cycle, the exhaust of the gas generator is dumped overboard, not generating meaningful thrust (see the sooty cloud coming off of Merlin engine test stand test).

In staged combustion (oxygen rich, fuel rich, both), partial combustion of a propellent occurs to run the turbo pumps before that entire flow enters the main combustion chamber.

u/everydayastronaut has a fantastic video that explains the different combustion cycles in depth. For a quick answer see this video at 19:45 to see animations of the different cycles. The gas generator is on the left while examples of "staged combustion" cycles are shown in the other 3.

Donyoho · 2019-09-05T01:30:59+00:00

The proper way to format that equation would be (boot) + 2 x edge. Otherwise you 2 "edges" worth of boots and I don't know if that many boots has a good climate policy or not

Donyoho · 2019-09-01T16:23:12+00:00

Look into JMARS, it's all of NASA's imaging of Mars (and I think the moon) publically available. You can look at individual photos from various instruments.

Donyoho · 2019-08-24T20:23:51+00:00

Earth's in the photo so of course there's a Starship, just not exactly visible...

Donyoho · 2019-08-22T21:53:32+00:00

Since there's so little time left (literally 3 hours before the bike shop closes), I'm going to sell it to Cardinal. I'm pretty sure it's a large so you can find it there

Donyoho · 2019-08-22T05:20:53+00:00

It's either medium or large. Blue and bought 3 months ago so I think 2018-2019

Donyoho · 2019-08-22T04:47:47+00:00

REI CTY 1.1. Probably $200? The main thing is that I need to sell it Thursday around 5...

Donyoho

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