ptfrd

joined 8 months ago
[–] ptfrd@sh.itjust.works 1 points 5 days ago

Earth-Sun L4 and L5 Lagrange points

I understand these are at 60 degrees ahead of, and behind, Earth (respectively). Does anyone know how much harder it is to keep satellites at other 'offsets' from Earth? Could we realistically also have one at 30 degrees, one at 90 degrees, one at 120 degrees, and one at 150 degrees?

And could it be beneficial to send data via that route? Could they play a role analogous to something like this?:
https://en.m.wikipedia.org/wiki/Optical_communications_repeater
Or would it just be a pointless increase in latency for no benefit?

[–] ptfrd@sh.itjust.works 2 points 5 days ago (2 children)

My uneducated guesses:

  1. Starlink's existing provision for Earth could be achieved for Mars too, using a very similar system
  2. In some ways, Mars will be easier.
    1. Much thinner atmosphere
    2. Far fewer of the constraints needed to 'play nice' with an existing high-tech civilization, like minimizing reflections of sunlight to the ground, or avoiding radio interference.
  3. But the first generation system for Mars will be different in an important way: significantly higher altitude
    1. Thus higher ping times
    2. And fewer satellites than would otherwise be needed for continuous coverage, which in turn means lower total bandwidth capability, and less redundancy, but much cheaper & quicker to set up and maintain.
  4. None of the above covers the actual NASA requirement/aspiration for new interplanetary comms (which seems to be referred to as "DRM 4").
    1. For one thing, an in-space laser link that can cover 100s of miles efficiently, is qualitatively different from one that can cover 100s of millions of miles.
    2. But as NASA has already achieved over 6 Mbps across 240 million miles, SpaceX will also be able to create a usable interplanetary link
  5. SpaceX will equip some of their Earth-orbiting Starlink satellites, and all of their Marslink satellites, with this qualitatively different, and outward-facing, laser comms tech.
    1. Having, as your endpoints, devices that are orbiting around planets, is disadvantageous in some ways, such as the fact they spend about half the time on the wrong side.
    2. But SpaceX will find a way to make it into an advantage. (Multiple simultaneous connections?)

Any thoughts?

Also, you need a relay capability when the sun is in the way. But are such relays expected to be beneficial even at other times? Will SpaceX find a way to make them beneficial?

P.S. It's interesting that Spaceflight Now did a tweet thread on this NASA presentation, but didn't consider it worth an article. Yet PC Mag made a whole article primarily out of 1/3 of a slide from one of those tweets by Spaceflight Now! (And I'm glad they did!)

[–] ptfrd@sh.itjust.works 1 points 1 week ago* (last edited 1 week ago)

Elon may have given them the info

No need. Spaceflight fans (like me!) are supporting and funding what may be the biggest aerospace espionage operation in history by a factor of 10, down in South Texas. With crowdsourced tracking and analysis. Must be beyond the CPC's wildest dreams!

E.g.:
https://www.youtube.com/live/mhJRzQsLZGg
https://ringwatchers.com/
https://sh.itjust.works/post/27492397

And we ain't gonna stop!

starlink availability in Russia

I remember a story coming out about Russians using Starlink but it seemed a bit vague to me. Has anyone reliable actually asserted that SpaceX are significantly underperforming in the job of blocking captured terminals (once notified), or other aspects of the day-to-day operations that the Ukrainians would do if they controlled it themselves?

FWIW, SpaceX seems to deny it. https://x.com/SpaceX/status/1849956344691912873

" … As has been repeatedly confirmed by the Department of Defense, SpaceX has worked (and continues to work) in close partnership with the U.S. Government regarding Ukraine and denial of service to bad actors. …"

[–] ptfrd@sh.itjust.works 5 points 1 week ago* (last edited 1 week ago) (1 children)

Also onboard is the ARTEMOSS experiment, which is pronounced similarly to “Artemis” in a nod to NASA’s Moon-bound program. The acronym stands for “From Antarctica to Space: Molecular Response and Physiological Adaptation of Moss to Simulated Deep Space Cosmic Ionizing Radiation and Spaceflight Microgravity.”

Shouldn't that be FATS:MRPAMSDSCIRSM?

Nestled inside the trunk of the Dragon is a device called CODEX (COronal Diagnostic EXperiment), ... the device will be unpacked and installed using the Canadarm-2 robotic arm.

I've been wondering why this mission couldn't just dock to the zenith port. Could this be why? Is there better access for the arm at the forward facing port? (For those who didn't know, Crew-9 had to relocate Dragon Freedom to the zenith port a couple of days ago, to free up the forward port for CRS-31.)

[–] ptfrd@sh.itjust.works 1 points 2 weeks ago

Just saw this https://x.com/SpaceX/status/1849956344691912873

... As has been repeatedly confirmed by the Department of Defense, SpaceX has worked (and continues to work) in close partnership with the U.S. Government regarding Ukraine and denial of service to bad actors. ...

[–] ptfrd@sh.itjust.works 1 points 3 weeks ago

Yeah. One possibility is that SpaceX were indeed underperforming, and the story was placed to put public pressure on them to improve. (A bit like the 2019-09-27 Bridenstine tweet.)

[–] ptfrd@sh.itjust.works -5 points 3 weeks ago

(And just to be clear, I have many problems and potential concerns about Musk. I'm just saying I'd choose him over, say, a Maoist, or a Stalinist, and over "Burn_The_Right".)

[–] ptfrd@sh.itjust.works 3 points 3 weeks ago (3 children)

I’m sure he could block the Starlink terminals Russian army is using, if he wanted to try, for example.

I remember a story coming out about Russians using Starlink but it seemed a bit vague to me. Has anyone reliable actually asserted that SpaceX are significantly underperforming in the job of blocking captured terminals (once notified), or other aspects of the day-to-day operations that the Ukrainians would do if they controlled it themselves?

[–] ptfrd@sh.itjust.works 2 points 3 weeks ago (1 children)

Though at least they've already proved they can relight during a belly flop.

[–] ptfrd@sh.itjust.works 2 points 3 weeks ago* (last edited 3 weeks ago)

I would not have thought it could float in a different orientation

Me either. But they call that orientation "Stable 1", possibly implying they've accounted for other stable orientations, and some non-stable situations.

Here was the first time I heard that term (with Bob & Doug): https://www.youtube.com/live/tSJIQftoxeU?t=6h29m34s

The commentator then gives some explanation.

[–] ptfrd@sh.itjust.works 3 points 3 weeks ago

Post-splashdown news conference: https://youtu.be/gOUoI-UYi2Y

They mentioned that Cargo Dragon sometimes reuses parachutes, which I didn't know.

 

Steve Stich states at today's Crew-9 news conference that Dragon has a new contingency capability if all 4 parachutes fail; the SuperDracos will ignite prior to splashdown.

The Crew-8 return to Earth will also have this capability.

(He said this about 20 minutes after the start of the stream.)

 

A Youtuber called Ellie in Space claims that a NASA source sent her the following message. It was in response to a question about when NASA knew that the Boe-CFT mission's Starliner vehicle would not be able to undock and return to Earth autonomously without being reconfigured.

So if you want to know when??? Well always, but it wasn't a reasonable consideration to retain the unmanned Starliner capsule software to work in the manned version of the capsule as a contingency. Would you call that a mistake?? Maybe, but let's think about the need to really ever plan to send folks up to space and leave them there with no way to fly home... they would always chose to risk the ride vs having no way home.

No one really considered this very unique and dynamic situation would happen.

Background

I believe this issue was first brought to light by Eric Berger.

Regardless, sources described the process to update the software on Starliner as "non-trivial" and "significant," and that it could take up to four weeks. This is what is driving the delay to launch Crew 9 later next month.

A couple of days later, NASA held a press teleconference in which they emphasized that what was needed was merely a "data load", not a software change. But they indicated timelines that do seem consistent with the "up to four weeks" claim by Berger's source.

My questions

Aren't there several realistic scenarios where you'd want to undock a crew vehicle, without its crew (or at least without them being in a fit state to operate the vehicle), in less than 4 weeeks?

Can Crew Dragon do it? Soyuz?

 

Relevant portion of the video is 18:06 - 22:22.

Key quote: "We'll move a Dragon recovery vessel to the Pacific some time next year, and we'll use SpaceX facilities in the Port of Long Beach for initial post-flight processing".

Although this was revealed in a Crew-9 briefing, it doesn't actually apply to Crew-9.

The announcement has just now been posted to the SpaceX website.

Key excerpts:

During Dragon’s first 21 missions, the trunk remained attached to the vehicle’s pressurized section until after the deorbit burn was completed. Shortly before the spacecraft began reentering the atmosphere, the trunk was jettisoned to ensure it safely splashed down in unpopulated areas in the Pacific Ocean.

After seven years of successful recovery operations on the U.S. West Coast, Dragon recovery operations moved to the East Coast in 2019, enabling teams to unpack and deliver critical cargo to NASA teams in Florida more efficiently and transport crews more quickly to Kennedy Space Center. Additionally, the proximity of the new splashdown locations to SpaceX’s Dragon processing facility at Cape Canaveral Space Force Base in Florida allowed SpaceX teams to recover and refurbish Dragon spacecraft at a faster rate [...]

This shift required SpaceX to develop what has become our current Dragon recovery operations, first implemented during the Demo-1 and CRS-21 missions. Today, Dragon’s trunk is jettisoned prior to the vehicle’s deorbit burn while still in orbit, passively reentering and breaking up in the Earth’s atmosphere in the days to months that follow. [...]

When developing Dragon’s current reentry operations, SpaceX and NASA engineering teams used industry-standard models to understand the trunk’s breakup characteristics. These models predicted that the trunk would fully burn up due to the high temperatures created by air resistance during high-speed reentries into Earth’s atmosphere, leaving no debris. The results of these models was a determining factor in our decision to passively deorbit the trunk and enable Dragon splashdowns off the coast of Florida.

In 2022, however, trunk debris from NASA’s Crew-1 mission to the International Space Station was discovered in Australia, indicating the industry models were not fully accurate with regards to large, composite structures such as Dragon’s trunk. [...]

After careful review and consideration of all potential solutions – coupled with the new knowledge about the standard industry models and that Dragon trunks do not fully burn-up during reentry – SpaceX teams concluded the most effective path forward is to return to West Coast recovery operations.

To accomplish this, SpaceX will implement a software change that will have Dragon execute its deorbit burn before jettisoning the trunk, similar to our first 21 Dragon recoveries. Moving trunk separation after the deorbit burn places the trunk on a known reentry trajectory, with the trunk safely splashing down uprange of the Dragon spacecraft off the coast of California.

 

That's 27 hours from now.

SpaceX is targeting Saturday, July 27 for a Falcon 9 launch of 23 Starlink satellites to low-Earth orbit from Launch Complex 39A (LC-39A) at NASA’s Kennedy Space Center in Florida. Liftoff is targeted for 12:21 a.m. ET, with backup opportunities available until 4:21 a.m. ET.

And here is their blogpost, dated 2024-07-25, announcing that the mishap report has been submitted to the FAA, and discussing some of the details.

During the first burn of Falcon 9’s second stage engine, a liquid oxygen leak developed within the insulation around the upper stage engine. The cause of the leak was identified as a crack in a sense line for a pressure sensor attached to the vehicle’s oxygen system. This line cracked due to fatigue caused by high loading from engine vibration and looseness in the clamp that normally constrains the line.

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submitted 4 months ago* (last edited 4 months ago) by ptfrd@sh.itjust.works to c/spacex@sh.itjust.works
 

During tonight’s Falcon 9 launch of Starlink from Space Launch Complex 4 East at Vandenberg Space Force Base in California, the second stage engine did not complete its second burn. As a result, the Starlink satellites were deployed into a lower than intended orbit. SpaceX has made contact with five of the satellites so far and is attempting to have them raise orbit using their ion thrusters.

There's also a tweet saying the same thing in fewer words.

This is the affected mission: Starlink 9-3 launch bulletin

Let's hope it was due to SpaceX pushing the envelope on their in-house Starlink missions in some way, though I have no specific guesses along those lines. Perhaps a manufacturing defect or an operational mistake are more likely to be the leading candidates for the cause.

 

Quote from Bill Nelson:

... SpaceX, by having the return of the first stage, has brought the cost down significantly. That has affected the entire launch industry. We'll be seeing attempts at bringing the second stage down on some missions.

The key sentence is (currently) 52 minutes and 48 seconds into the video. Approximately 49 minutes after the event started.

No other mention is made of this. Should we assume he's specifically referring to the 2nd Stage of the Falcon 9? What is the likelihood that he is mistaken? Could he just be thinking of the existing deorbit procedure? Or could SpaceX be putting parachutes on some of their 2nd Stages in the near future?

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