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#100 by Robotbeat on 13 Jan, 2022 04:20
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That’s not really true. You can use Oberth burns at Jupiter or the Sun to get to 15AU/year with chemical propulsion.
Staging helps by reducing dry mass. You can include the effect of arbitrary number of staging by just assuming the empty stage is massless but reducing the Isp (or exhaust velocity if you will) by the dry mass to wet mass ratio of a stage. So if you had 100 stages for a rocket with 500s or 5km/s exhaust velocity and a dry to wet mass ratio of 0.05, then you treat it as 475s Isp, etc. with lower number of stages, it’s worse than that, but it’s a good limit. -
#101 by InterestedEngineer on 14 Jan, 2022 03:25
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Going to the outer solar system puts you way out on the very tiny edge of the rocket equation where things are really hard to change.
Some thought experiments to show how little even a huge change in launch mass changes the result:
Assume you start in Earth orbit, and take full advantage of Earth's orbit around the sun and the rocket's orbit around the Earth. Next, assume a hydrogen/oxygen rocket with ISP = 460. Assume the 860 kg probe from the report.
If you need 5 AU/year, something Centaur-ish will do. 50K kg launch mass, 2500 kg dry mass. This is already at the practical limit of stage performance.
If you need 10 AU/year, you need a stage with half the mass of the Saturn V, but no more dry mass than Centaur. Maybe tanks with flawless graphene skins, assembled in space, or some other wild technology. Definitely beyond the state of the art.
If you need 15 AU/year, give up. You'd need a massless stage with 10x the fuel of the Saturn V.
Staging does not help these number, as staging profits from getting rid of dead weight as soon as possible. These designs have no dead weight.
These limitations apply to any design that uses chemical combustion for energy and carries its own fuel. For thousand AU missions within a human lifetime, we need designs where supplies (power, mass, or both) are sent to the ship. It's the only way around the rocket equation.
You are only correct if you are thinking old fashioned staging where the fuel you have is what you lift off with. That's so 20th century. Err, rather, the Air Force completely changed air power with refueling, so the concept isn't new.
Refueling, especially with a HEEO refuel, changes everything. You can get a 5 ton payload going to > 100km/sec after Jupiter with old fashioned multiple Oberth burns and gravity assists. Turns the JHUAPL mission into a 5 year mission with far more payload mass for the probe. For about $150M in launch costs.
All sorts of gory details in this thread, which is where you should take any replies, since this thread is the thread to handle "how Starship can do extra-solar missions"
https://forum.nasaspaceflight.com/index.php?topic=55550.0 -
#102 by AegeanBlue on 17 Jan, 2022 05:12
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The random dude in the AGU press conference is far from random, it is Leo Enright (sp?) from Irish Television, which I assume is RTE or their equivalent of PBS. If you watch enough NASA science press conferences about planetary science you will hear him, he regularly participates. Since Ireland is part of the Ariane consortium I would guess, since I have never met the guy, that he is trying to understand if a new megaproject and the jobs it entails is coming for the European space sector.
Now Scientific American has an article on the mission which contains more information than the AGU press conference. It also talks about the Chinese Interstellar mission, also in the proposed stage, called Interstellar Express. Now per that article, which I wish I could link but I read it a few weeks ago, the main instrument that will give the JHUAPL probe a major advantage over Voyager is the Electric Neutral Atoms imager. Which gets for me the question, did ENA imagers exist back in 1977? -
#103 by AegeanBlue on 20 Apr, 2022 22:09
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NASA Interstellar Probe: Overview and Prospects
https://www.centauri-dreams.org/2022/04/15/nasa-interstellar-probe-overview-and-prospects/
It is a Centauri Dreams articles over the mission proposal -
#104 by Blackstar on 02 Jun, 2022 17:16
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#105 by vjkane on 03 Jun, 2022 00:18
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https://www.leonarddavid.com/destination-universe-the-interstellar-probe/
It appears that the paper Leonard David summarizes isn't behind a paywall and can be accessed at:
https://www.sciencedirect.com/science/article/pii/S0094576522001503
I can't be sure it's not behind a paywall because I work at a university and my computer may have access not available to everyone. -
#106 by Redclaws on 03 Jun, 2022 00:35
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https://www.leonarddavid.com/destination-universe-the-interstellar-probe/
It appears that the paper Leonard David summarizes isn't behind a paywall and can be accessed at:
https://www.sciencedirect.com/science/article/pii/S0094576522001503
I can't be sure it's not behind a paywall because I work at a university and my computer may have access not available to everyone.
Paper is open access, available to anyone at that link. -
#107 by Blackstar on 22 Apr, 2023 17:14
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#108 by Robotbeat on 22 Apr, 2023 17:33
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That’s awesome.
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#109 by deadman1204 on 23 Apr, 2023 19:17
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This would be great.
Doubly so if they say they're doing it because the US is to scared too
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#110 by Don2 on 25 Apr, 2023 19:11
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In the graphic from China, the folded umbrella on a boom looks like a nuclear reactor.
https://en.wikipedia.org/wiki/SNAP-10A
Looks like the Chinese are developing a nuclear-electric propulsion system. An interstellar probe would be a good way to demonstrate it.
Developing a pair of nuclear powered probes indicates a very well funded program. I wonder why they have decided to go for nuclear reactors rather than RTGs. Maybe they are developing both? -
#111 by VSECOTSPE on 26 Apr, 2023 00:43
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The China mission is Interstellar Express or Interstellar Heliosphere Probe and was just a concept study as of January last year. It probably still is.
The plan is a couple, 200kg, RTG-powered spacecraft to the head and tail of the heliosphere. Supposed to launch in 2024 and reach their destinations by 2049 for the PRC’s centennial. How the mission was going to launch in 2024 when it was still a concept study in 2022 makes the schedule highly suspect. They now claim launch delays to 2025 or 2026 due to Covid, which is still a wildly unrealistic timeline. I would not take this mission seriously unless/until it wins funding in a five-year plan or similar, formal CCP announcement/document. Given the stepwise progress of China’s civil space exploration efforts, that presumably won’t happen until after Tianwen-4/Gan De (last notionally scheduled for launch in 2029) or a similar outer planets mission is undertaken first.
Just like everywhere else, China has business executives, program managers, and researchers floating trial balloons, making presentations, and undertaking studies. Doesn’t mean that everything they’re discussing is government approved and budgeted. Just like everywhere else, a lot/most of it will never enter development.
A third, reactor-powered spacecraft to launch in 2030 to the “north” heliopause is also part of the plan. That’s probably the image in the presentation snapshot upthread.
More here:
https://en.m.wikipedia.org/wiki/Interstellar_Express
https://www.scientificamerican.com/article/u-s-and-chinese-scientists-propose-bold-new-missions-beyond-the-solar-system/
https://spacenews.com/china-to-launch-a-pair-of-spacecraft-towards-the-edge-of-the-solar-system/
https://www.planetary.org/articles/china-voyager-like-interstellar-mission
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#112 by Bob Shaw on 26 Apr, 2023 00:59
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They should really build SIX spacecraft rather than two and send them off on all six faces of a cube, providing a holistic view of our local environment!
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#113 by vjkane on 26 Apr, 2023 18:45
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The China mission is Interstellar Express or Interstellar Heliosphere Probe and was just a concept study as of January last year. It probably still is.
With NASA, ESA, and probably JAXA, there are public steps to a concept going from that to a project. That is less clear (at least for me) with China, where formal decision making is more closed.
Based on my knowledge, China's lunar program and Mars sample return missions seem to be formally approved. I'm not as certain with the asteroid mission. The interstellar mission still seems to be in the concept stage.
Anyone have better knowledge? -
#114 by Blackstar on 26 Apr, 2023 20:12
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The China mission is Interstellar Express or Interstellar Heliosphere Probe and was just a concept study as of January last year. It probably still is.
With NASA, ESA, and probably JAXA, there are public steps to a concept going from that to a project. That is less clear (at least for me) with China, where formal decision making is more closed.
Based on my knowledge, China's lunar program and Mars sample return missions seem to be formally approved. I'm not as certain with the asteroid mission. The interstellar mission still seems to be in the concept stage.
Anyone have better knowledge?
I don't have an answer to your question about China. I will provide a bit more information about how the United States works in taking a concept to an officially approved project. (vjkane already knows all this stuff)
For NASA, planetary, astrophysics, Earth science, and heliophysics all have generally similar structures and processes. Smaller mission concepts, generally on the order from $100 million to ~$1 billion, can compete for selection for an approved mission line and don't have to be on a pre-approved list of missions that can compete. They have to justify the science that they will do as worthy of funding. Missions that cost more (depending on the science area, but let's say it is $500 million to $2 billion) have to be on a pre-approved list of acceptable missions. If they're not on that list, they don't have a chance of being selected. The biggest missions, often referred to as flagships or strategic missions, cost $2+ billion, and they have to be endorsed by a science decadal survey. The planetary decadal survey came out in 2022, the astro one in 2021, and so on. If a mission concept is highly prioritized in a decadal survey, then generally it is going to be funded eventually, although being endorsed in the decadal survey is a necessary but not sufficient condition. If a mission concept is not endorsed by a decadal survey, then it is extremely difficult (maybe impossible) for it to get funded.
So bringing this back to the original topic of the Johns Hopkins University Applied Physics Laboratory Interstellar Probe, right now that is simply a mission concept. It is being pitched by its proponents to the currently ongoing heliophysics decadal survey. Maybe it will be highly prioritized by them, maybe not. So that's how it works for NASA.
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#115 by VSECOTSPE on 27 Apr, 2023 03:47
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That is less clear (at least for me) with China, where formal decision making is more closed.
AFAIK, decisions on what major space science missions China undertakes next are made through the CCP’s five-year planning process:
https://en.m.wikipedia.org/wiki/Five-year_plans_of_China
These include R&D and space priorities, at least in recent cycles:
https://www.space.com/china-five-year-plan-space-exploration-2022
In the arena of space science, there appear to be two tracks within each five-year planning cycle.
One track is through the China National Space Administration (CNSA), which supports a top-down, stepwise, capabilities-driven program in lunar and planetary exploration. The lunar side is the China Lunar Exploration Program (CLEP), also known as the Chang’e (lunar goddess) Program, which has given us Chang’e 1 thru 5. The planetary side is the Planetary Exploration of China (PEC) Program, also known as the Tianwen (questions to heaven) Program, which has given us Tianwen-1 to Mars so far. Although they obviously conduct space science, these CNSA missions are driven more by proving out new spacecraft capabilities (especially in advance of human missions in the case of CLEP) than scientific curiosity. They progress step-wise — orbit then land then sample return, or Mars then asteroids then Jupiter. The process by which these missions are formulated is pretty opaque and seems to reside with the CNSA bureaucracy. But presumably CNSA sends a proposal (or maybe a set of options), probably within certain CCP-provided budget guidelines, to the CCP as part of each five-year planning process, and then there is some back-and-forth or downselect to get to the missions that will be undertaken in the next five-year plan.
https://en.m.wikipedia.org/wiki/Chinese_Lunar_Exploration_Program
https://en.m.wikipedia.org/wiki/Planetary_Exploration_of_China
A second track is through the Chinese Academy of Sciences and is a bottoms-up, curiosity-driven process more similar to the US decadal planning process. A list of candidate missions are drawn up by the Chinese Academy of Sciences (CAS) from university, government research institute, and industry proposals, and then studied under the current five-year plan for development starts in the next five-year plan. For example, Interstellar Express is one of 13 concepts currently under study for starts in the 2025-2030 Plan (which made me highly skeptical of claims about launching Interstellar Express in 2022 or 2024-2025):
https://www.inverse.com/science/china-space-missions-selection-process
CAS makes the recommendation on which mission candidates enter development, although I’m sure there are opaque government decisions on funding after that. The upcoming downselect will become “Strategic Priority Program III” for space science. This paper (in Mandarin, I think) reviews Strategic Priority Program I and II:
https://bulletinofcas.researchcommons.org/journal/vol37/iss8/1/
“Strategic” implies big missions. I do not know if there is a separate track or process for smaller CAS missions, like NASA’s Discovery/Explorer or suborbital programs. Also unclear to me is how, all other things being equal, CAS decides between missions in disparate disciplines, like astrophysics versus planetary (although I’ve wondered the same about ESA’s selection process).
Lastly, there’s the large but oddball China Space Station Telescope, also known as Xúntiān or “surveying the sky”, which is a Hubble-sized survey scope that is supposed to co-orbit with the Tiangong manned space station. The Tiangong co-orbit would imply CNSA leadership, but Xúntiān seems to be led by the National Astronomical Observatories of CAS, which runs China’s ground telescopes. I’m not sure which track, CAS or CNSA, Xúntiān went through or future major observatories will go through. Just to add to the confusion on major space observatories, the China Aerospace Science and Technology Corporation (CASC) is studying a SIM/TPF clone for exoplanet hunting:
https://spacenews.com/china-to-hunt-for-earth-like-planets-with-formation-flying-telescopes/Based on my knowledge, China's lunar program and Mars sample return missions seem to be formally approved. I'm not as certain with the asteroid mission.
CLEP is funded thru the end of Chang’e 8 operations. Chang’e 6 was was a copy of Chang’e 5, and will launch in 2024. Chang’e 6 also starts China’s well-advertised International Lunar Robotic Station (ILRS), which includes Chang’e 7 and 8 that are supposed to launch in 2026 and 2028, respectively. After that, there is planning and technology work towards a human lunar effort, but mission funding is TBD for the 2026+ planning cycle. There are Long March presentations on how to use their rockets in various human lunar architectures that catch the eye of the Western press every few months, but no missions are approved beyond Chang’e 8.
Tianwen 2, the asteroid mission, was approved in the last five-year plan. It’s under development to be launched in 2025. Tianwen 3, the Mars sample return, and Tianwen 4, the Jupiter mission, are funded for technology work. But mission funding won’t be approved until the 2026+ cycle. The architectures for each are still be up in the air, and Tianwen 3 really couldn’t start until Chang’e 5 (lunar sample return in 2020) and Tianwen 1 (Mars landing in 2021) had proven out, anyway. Although they have notional launch dates of 2028 and 2029, I would guess that the launch dates for Tianwen 3 and 4 will be later when the missions are actually funded.
What’s funded thru what (technology versus mission) in the Chang’e and Tianwen programs can be gleaned from the current five-year CNSA plan:
http://www.cnsa.gov.cn/english/n6465652/n6465653/c6813088/content.html
I’m an armchair Sinophile at best, so anyone with better knowledge or insights should correct or add to the above.
FWIW...
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#116 by JulesVerneATV on 02 Nov, 2023 14:30
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Tiny Swarming Spacecraft Could Establish Communications with Proxima Centauri
https://www.universetoday.com/163132/tiny-swarming-spacecraft-could-establish-communications-with-proxima-centauri/
Not exactly a Solar-Sail but Breakthrough Starshot the project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail interstellar probes named Starchip.
https://breakthroughinitiatives.org/Initiative/3
