Lost in Space
The point is that there's a maximum change in velocity that a ship using any given propellant can practically obtain, which is related to its specific impulse, aka its exhaust velocity. That velocity is a limit as propellant mass fraction approaches 100% and propellant mass approaches infinity.
Edited by Fighteer on Apr 29th 2024 at 1:01:41 PM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
...at the risk of sounding dumb, how is something of that size supposed to include an antenna powerful enough for its signal to remain detectable, let alone comprehensible, at interstellar ranges?
Lost in Space
Good question. I am not personally aware of how the program intends to solve that problem, but I believe it involves lasers. We'd need enormous optical antennas to pick the signals up, of course.
ETA: The CRS-30 Dragon spacecraft splashed down at around 05:38 UTC today
, completing its mission. SpaceX no longer livestreams uncrewed splashdowns, but did keep us updated on X.
Edited by Fighteer on Apr 30th 2024 at 8:56:32 AM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Looked up on Wikipedia, they're indeed planning on using a laser bounced off of the probe's solar sail towards a 30-meter receiver antenna on Earth.
Lost in Space
Couple of tidbits for today as we get into May's launch activity...
European Starlink (IRIS²)
Ars Technica: Europe’s ambitious satellite Internet project appears to be running into trouble
When the Ukraine crisis blew up and Starlink proved to be such a decisive battlefield communication tool, Europe's leadership decided they wanted in on that. The Interconnectivity and Security by Satellite (IRIS²) project is the result of that conversation, and an independent committee is working to evaluate proposals from a consortium of companies.
Unfortunately, Europe doesn't have the domestic launch capability to get hundreds of satellites into orbit, nor does it have the ability to mass-produce them. Sure, Thales Alenia and Airbus are major manufacturers but they make bespoke, billion-dollar satellites. There's also drama between Germany and France that I don't completely understand.
The European Commission and European Space Agency are jointly investing in the project to develop these capabilities. However, the IRIS² constellation is intended to be a public-private partnership, with the space companies also investing in the project and subsequently profiting from selling communication services.
The problem is that the major players involved, such as Airbus and Arianespace, are not accustomed to operating in space projects in this way. Typically, they are given government contracts to provide services rather than investing significant amounts of their own capital.
The takeaway from all this is that there's no reasonable way a constellation could get up by 2027, as the project calls for. Europe decided not to invest in reusable launchers because there was "no demand". Now that there's demand, it doesn't have reusable launchers. Oops.
RFA One
We're getting very close to the maiden flight of Rocket Factory Augsburg's RFA One rocket. The company posted on Monday that the first stage has arrived at SaxaVord Spaceport in Scotland and been lifted onto the pad for its hot fire testing.
I'm a little confused because the maiden launch of RFA One is listed on Next Spaceflight as happening from Andøya Space Center in Norway. That could be old data. According to the site, SaxaVord's first launch will be the second flight of ABL Space Systems' RS1, also scheduled NET June.
There are a lot of newcomers with eyes on 2024 and I'll try to keep up to date on them.
Crew-8 Relocation
On Thursday, NASA will stream the relocation of SpaceX's Crew-8 Dragon spacecraft from the forward docking port to the zenith one. The zenith port was recently vacated by the CRS-30 Dragon, and will be where Starliner's Crewed Flight Test performs its docking.
Because of the hazards involved, it is NASA policy that the Crew-8 astronauts be aboard Dragon for the relocation. It's perfectly capable of performing the maneuver autonomously, but if something should go wrong such that it is unable to redock, the crew can't be left without a return vehicle.
NASA FY2025 Budget
Yesterday, the US House of Representatives Science, Space, and Technology Committee met to discuss NASA's FY25 budget request. The event was livestreamed on YouTube and live-posted by Spaceflight Now. Highlights:
- Bill Nelson downplayed reports of a potential change to the Artemis III mission. "The plan is to land."
- He pleaded with the committee to fund the de-orbit tug for the ISS, a project estimated to cost $1.5 billion over six years. It's crucial because "we don't know what the president of Russia is going to do".
- NASA is "not starting over with Mars Sample Return". They are trying to bring the cost down under $6 billion (from the OIG estimate of over $10B) by soliciting industry proposals.
- Nelson is concerned about China reaching the lunar south pole first and laying claim to it.
- ISS de-orbit would only occur once viable commercial stations exist.
- The Chandra X-ray Observatory is not sustainable at "the previous funding levels".
- Artemis II is delayed to Sep 2025 because of safety concerns with the heat shield. Artemis III is still booked for Sep 2026.
Launch Schedule
- SpaceX | Falcon 9 Block 5 | WorldView Legion 1 & 2 | May 2 18:30 UTC. This mission keeps being delayed - not sure why. It's rare for Vandenberg to go this long without a Falcon 9 launch. Hopefully it gets up as scheduled this time.
- SpaceX | Falcon 9 Block 5 | Starlink Group 6-55 | May 3 01:17 UTC
- CASC | Long March 5 | Chang'e 6 | May 3 09:30 UTC. This will be China's second lunar sample return mission and its first collaboration with France, whose instruments will be aboard the lander.
- SpaceX | Falcon 9 Block 5 | Starlink Group 8-2 | May 4 02:59 UTC
- SpaceX | Falcon 9 Block 5 | Starlink Group 6-56 | May 6 15:34 UTC
- ULA | Atlas V N22 | Starliner CFT | May 7 02:34 UTC. This is the big show for Boeing and ULA: Starliner's first crewed flight. I'll have a writeup ready soon.
- SpaceX | Falcon 9 Block 5 | Starlink Group 6-57 | May 7 22:09 UTC
Edited by Fighteer on May 1st 2024 at 9:25:16 AM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Lost in Space
Watch the Maxar 1 (aka WorldView Legion 1 & 2) mission here, with liftoff targeted at 18:36 UTC. SpaceX is contracted to launch six of these Earth-observation satellites in total, all of which will go into Sun-synchronous orbit.
Update: And that's another 20th launch and landing for a Falcon 9 booster. Plus the 300th successful Falcon mission in a row since the loss of AMOS-6.
Update: Deployments confirmed.
Edit: Apparently the Chang'e 6 mission was also successful this morning. Watch the VOD here.
Edited by Fighteer on May 3rd 2024 at 10:15:51 AM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Redmess
Well, that's certainly an intriguing idea. Maybe not right now, though.
But it does raise the prospect that other species may do the same thing. Perhaps our first contact won't be with another species, but a robotic craft carrying AI.
Optimism is a duty.
That assumes that the hardware survives the trip without being filleted by cosmic rays...
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman
Lost in Space
Let's be clear: it's much more likely that any first encounter we have with an extraterrestrial civilization will be through robotic probes than them parking on the lawn and saying Take Me to Your Leader. While the radiation argument is an important one, it's not something that should be completely unsolvable, and it applies to organic life just as much as it does to computers.
Take the Breakthrough Starshot program that we've talked about several times before. Those tiny little probes will need software that is capable of complex "understanding" of the things it is being asked to do so that they can send us back useful data. It is not unreasonable that we might try to incorporate a language model that attempts to study and communicate with anyone the probes happen to encounter, or at least analyze their transmissions.
Some of the Fermi Paradox solutions that we've discussed involve aliens sending out swarms of self-replicating probes to destroy life that they encounter and/or terraform planets into suitable locations for them to move into. Without some form of AI, these probes are unlikely to succeed.
In summary, if it is possible/feasible to travel interstellar distances at all, it is far more likely that robots will make the journey before people. If it is impossible for robots, it's definitely impossible for people.
Speaking of humans in space, SpaceX just revealed (official site, X thread) its new extravehicular activity suit that will debut on the Polaris Dawn mission this year. It'll be the first time that a private company, on a private spacecraft, with private astronauts performs an EVA.
A Spaces broadcast will be held at 3 PM EDT (19:00 UTC) today to provide more comprehensive information.
Edit: Looking at the information that has been provided, it should be clear that this is not a suit for long-duration, independent spacewalks. It is not equipped with its own life support, but relies on tethering to the spacecraft. It will take a lot more development to have the equivalent of the EMU suits used on the ISS and that will be used on the Moon.
Edited by Fighteer on May 4th 2024 at 10:56:31 AM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Y'know, since Liebig's law of the minimum applies to such a question, it's probably fair to ask if computer chips handle cosmic rays better, worse or the same as neurons. Because from what I know, the answer might very well be "much worse", which would imply that robots cannot remain operative in other stellar systems no matter what.
Lost in Space
If that were true, then the spacecraft that we've had out there for dozens of years, like Voyager, could not possibly remain working. Since they do, it's obviously not that disastrous a problem. Engineers have been working on radiation hardening for decades. We have probes like New Horizons studying the environment beyond the heliopause in part to inform the designs of future interstellar spacecraft.
Edited by Fighteer on May 4th 2024 at 1:14:37 PM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
In any case, using "chips" is not the only method of building computers.
![[up]](https://static.tvtropes.org/pmwiki/pub/smiles/arrow_up.png "[up]"){kind=icon}
Such as ?
Lost in Space
I'm hardly an expert, but radiation hardening for spacecraft, including satellites, can take a number of forms. These include, but are not limited to: redundant hardware, fault-tolerant software, physically larger components so that individual electrons getting bumped around don't have as much impact, and external shielding.
Anyway, the idea that people could fare better than computers on interstellar journeys misses a fundamental point: the people need the computers to survive. You're not gonna be much use arriving at your target in an dead ship.
The idea that the radiation environment in deep space is unavoidably deadly to people and/or computers is a favorite "gotcha" of the anti-space crowd, but it's provably false because we have sent computers (and people) into deep space. The Apollo and Gemini astronauts went well beyond the protection of Earth's magnetosphere, feats that the Artemis and Polaris astronauts are about to repeat.
Edited by Fighteer on May 4th 2024 at 1:29:59 PM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Such as vacuum tubes, relays, gears, etc...
Sure, but there are good reasons why these are not in use any more. For one, such a computer does not last long before it break down. So it does not make sense to use on a spacecraft that is going to spend decades in space. So it is not relevant to the discussion.
Vacuum tubes in particular are/were less reliable than transistors (in low-radiation enviroment, at least), yes. My point is that you can make a computer from anything if you realy need to.
Edited by Smeagol17 on May 4th 2024 at 8:49:18 PM
Lost in Space
Geostationary satellites operate for decades outside the protection of the Earth's magnetosphere. We have sent spacecraft through the heliopause and they're similarly durable. This is a mostly solved problem.
Making them last all the way to other stars is a significant engineering challenge for a number of reasons, not least of which that we can't accelerate them to a suitable velocity with current propulsion methods. Before we worry about a probe lasting hundreds of years in interstellar space, we need to get it to travel hundreds to thousands of times faster than anything we've ever achieved before.
Also, they can't effectively use solar power, radioisotope thermal-electric generators don't last hundreds of years, we still don't have a complete picture of how much dust and other particles are out there, communication becomes extraordinarily difficult... there are a lot of problems to solve.
Edited by Fighteer on May 4th 2024 at 2:57:55 PM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
I wonder... what are the chances of a non-RTG nuclear-powered probe suffering a reactor meltdown from electronic failure caused by space radiation?
Lost in Space
Probably zero, if only because any fission reactor put onto a spacecraft would by necessity have negative stability: that is, any deviation from normal operation would tend to shut it down, not make it run away into a meltdown. Of course, the electronic systems on such a reactor would be multiply redundant and heavily shielded.
We know how to design fission reactors with negative stability coefficients; there's no need to be concerned about a Chernobyl or Fukushima in space.
A bigger problem would be fueling it, since you can't exactly resupply uranium in deep space. Related is heat dissipation, because while I'm not sure what the minimum power setting of a fission reactor is, it's probably at least a few kilowatts, and that's a lot of power to have always on in a spacecraft.
We've launched fission reactors to space in the past, but never for long-duration missions. Nuclear-thermal propulsion is something that NASA is studying for transportation to Mars, but we aren't anywhere near trying to build one for interstellar travel.
Edited by Fighteer on May 4th 2024 at 3:42:06 PM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Redmess
A glory is basically a rainbow seen from space. Except this planet has an honest-to-god iron cycle instead of a water cycle, it's that hot.
I'm surprised that actually works, too. I thought the drops would need to be transparent to form rainbows, which liquid iron isn't.
Optimism is a duty.
Lost in Space
Waiting for the "extraterrestrial life doesn't have to look like us" crowd to come up with some way for biochemistry to work on a planet whose oceans are made of liquid iron. (Only slightly joking.)
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Redmess
Can't really imagine any coherent biochemistry surviving at those temperatures. Water is one factor for life, but the other is things being cool enough that chemistry can happen in a controllable way. And not much stuff is going to be solid at those temperatures, either.
Optimism is a duty.
Lost in Space
It's launch time! I figure I'll get this posted now, far enough in advance that I'm not having conflicts with work or chores later.
First up today, another Starlink mission. Whoo. Liftoff is scheduled from SLC-40 at Cape Canaveral at 18:14 UTC, although that keeps slipping sideways. Watch here (X) or here (YouTube). The booster for this one is B1069, making a mere 15th flight.
But the big story of the day is...
Boeing Starliner Crewed Flight Test
What we're really here to see is the first crewed flight of Boeing's CST-100 Starliner spacecraft as it takes two astronauts on a test mission to the International Space Station. Veteran NASA astronauts Barry Wilmore and Sunita Williams will ride the fire to space, and if all goes well will spend about a month on station as they put the capsule through its paces.
Liftoff is scheduled to take place at 02:34 UTC (10:34 PM EDT) from SLC-41 at Cape Canaveral, Florida. The launch vehicle is a United Launch Alliance Atlas V N22 rocket, and the Starliner capsule, serial number SC3, has been dubbed Calypso. It's making its second flight after performing the first (and partially failed) orbital flight test in 2019. Weather is currently 90% favorable.
The official NASA livestream is here. Fan coverage includes NASA Spaceflight and Everyday Astronaut. Official coverage will begin about four hours prior to launch.
If all goes to plan, Calypso and its crew will dock with the ISS on May 8 at 00:48 UTC (12:48 AM EDT).
A little history
We're used to seeing Crew Dragons launch, but for a while back in 2020 it looked as if Boeing was neck-and-neck with SpaceX to carry the first humans from US soil since the retirement of Space Shuttle in 2011. Indeed, I remember a lot of arguing over which was safer and more reliable. Boeing was the industry veteran with all the experience and SpaceX was the brash newcomer with something to prove.
How the tables have turned. Now the comments I'm seeing on news reports about Starliner's launch are filled with snarks like, "I hope the doors don't fall off." In all seriousness, I expect Starliner to succeed. It's had enough time to get things right and Boeing can't afford another highly visible disaster. Seven years late is better than never, after all.
NASA's Commercial Crew Program started back in 2011 and awarded fixed-price contracts to Boeing and SpaceX in 2014. Service was originally expected to begin in 2017 but budget cuts from Congress pushed that back several years. SpaceX flew its first crew on May 30, 2020, while Boeing had to go back to the drawing board after its uncrewed flight test revealed multiple flaws in the spacecraft's software.
Additional setbacks occurred after the second flight test in May 2022 as safety reviews found issues with Starliner's parachutes and wiring harnesses. Boeing has reportedly taken nearly $1.5 billion in losses on the program, leading its management to consider rejecting future fixed-price contracts.
The vehicle
Starliner is a crew capsule meant for low Earth orbit transport, owing a great deal of its design heritage to Apollo and Orion. It is closer to those vehicles in formfactor than Dragon. Like Dragon, it can carry four crew members at a time, giving them a much roomier ride than Apollo or Soyuz. Also, like Dragon, it features an integrated launch escape system with four high-power hypergolic thrusters mounted at the rear of its service module. These will fire to carry the capsule away from a failing rocket in the event of an emergency.
Once on orbit, it can autonomously rendezvous with and dock at the International Space Station's IDA ports on the Harmony module. It's able to remain docked for up to seven months. Unlike Dragon, after it departs it will land on land rather than on water, with its primary site being the White Sands missile range in New Mexico.
The rocket
The launcher for this mission is the venerable Atlas V, built and operated by United Launch Alliance. It is a two-stage, liquid-fueled rocket with multiple configurations. Its first stage is powered by kerosene and liquid oxygen, while its second, the equally venerable Centaur III, is powered by liquid hydrogen and liquid oxygen.
In the "N22" configuration, it has two strap-on solid rocket boosters for extra thrust at liftoff. The Centaur upper stage will also use two RL-10 engines instead of the typical one. The "N" refers to the lack of a payload fairing, since Starliner acts as its own fairing.
Atlas V is scheduled for retirement in favor of the Vulcan rocket. In addition to the cost reduction and potential for future reusability that Vulcan offers, ULA can no longer obtain the RD-180 engines used on the Atlas first stage since the termination of US relations with Russia.
Edited by Fighteer on May 6th 2024 at 1:33:22 PM
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Personally, I don't find specific impulse intuitive at all. Effective exhaust velocity is thrust divided by fuel flow, which makes it exactly clear what it's about: how much momentum you get for a certain amount of fuel expended. In vacuum, it equals the actual exhaust velocity, and you cannot get more intuitive than that. In contrast, specific impulse measures... what now? You divide the effective exhaust velocity by an arbitrary number that only makes sense on launch and is completely useless for calculations most of the time. And it's not even intuitive what it's supposed to mean.
The universe is under no obligation to make sense to us.