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India's first privately-developed rocket reaches orbit on debut launch

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Re: India's first privately-developed rocket reaches orbit on debut launch

#121

Post by pfdietz »

OneDonOne wrote: post #116
pfdietz wrote: post #103

Earlier quoted context omitted.

Ok, there are at least two bad assumptions there. First, it assumes the radiator is at the same temperature as the GPU. But radiators become dramatically more effective as temperature increases, with radiated power increasing as the fourth power of absolute temperature. So a heat pump that drives the radiator at higher temperature could make the radiator far smaller. More power would be required (and the radiator wou…

> Ok, there are at least two bad assumptions there. > First, it assumes the radiator is at the same temperature as the GPU. But radiators become dramatically more effective as temperature increases, with radiated power increasing as the fourth power of absolute temperature. So a heat pump that drives the radiator at higher temperature could make the radiator far smaller. Carnot's theorem and refridgeration cycles rea…

> Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C.

Sorry, that's all nonsense. Yes, the extra power needs to be radiated. But the advantage of operating at high temperature is so extreme that the more effective radiation will overwhelm that unless the heat pump is extraordinarily inefficient. If the heat pump would be perfect, operating at the Carnot limit, then if it doubled the absolute radiator temperature it would double the amount of energy to be radiated, but the area of the radiator would decrease by a factor of (2^4)/(2) = 8.

As for the second point, no, this does not require the GPU to operate at higher temperature. What made you conclude it would?

> Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?

I don't need to; I'm just debunking a bad argument. What you are doing there is called "moving the goalposts". But satellites normally have means of orienting PV toward the Sun. So, maybe have the radiator perpendicular to those? Those claiming the idea violates the laws of physics and using solar absoption on the radiator as part of the argument need to show no such scheme can work, even in principle.

Re: India's first privately-developed rocket reaches orbit on debut launch

#122

Post by Imustaskforhelp »

notahacker wrote: post #114
Imustaskforhelp wrote: post #44

Earlier quoted context omitted.

My cousin is an aerospace engineer and works in ISRO (Indian space research organization), its impressive what they are doing but I'd like to chime in on a few things. I am unsure about private salaries but in govt. jobs, because it follows a rigid structure, the salary is still lower than what you might expect and is around the mark of 20-25 thousand dollars per year. It's similar to administrative services or depen…

I suspect a lot of the value from the job comes from the engineers being people who drew up dreaming of rockets and playing Kerbal Space Program (as in many other countries where working for space companies is relatively speaking even less lucrative). Average engineer quality might also be higher filtering for that rather than people who chose their engineering subfield based on salary and emigration prospects and pa…

> I suspect a lot of the value from the job comes from the engineers being people who drew up dreaming of rockets and playing Kerbal Space Program as in other countries

I think so, but I can only say it about my cousin to whom this field of line was suggested by one of my uncles was that the most major prospect of a government job.

Within India, there is a very strong prestige surrounding govt. jobs, like a lot.

The cousin whom I am referring to actually even studied and gave some exams after becoming a rocket scientist to get into a sub part of civil services just on the side (to get even better salary), I am unsure if this is an Indian specific phenomenon or not, but the prospect of the govt job for most people is the combination of comfort,prestige etc.

The prestige of the govt job is so much to many people that another person I know has spent 7 years solely dedicated towards getting to a govt. job and they still sadly don't have it but they are close to getting it :-( and they denied one of the most prestigious private institutions just for the effort to study solely for govt. job (though they are from civil engineering background), they would've completed their degree by now and atleast gotten a package close to the cousin working in rocket science itself.

My cousin actually wanted to go into computer science, I was in 4th or 5th grade back then and little me was already arguing that he should go rather to the CS college because of my love to computers ;) ,but my cousins really happy now so its all fair and in all fairness he and everyone thinks it was a decent decision.

Back during the process of his college and eventually going to ISRO, it wasn't that well known, but then two missions made it really have a spotlight it was before there were movies and the national fame and recognition that it got, before that nobody knew too much of ISRO but then suddenly literally everyone knew what ISRO :)

Also, the papers regarding ISRO if going through the college route is the JEE Mains/Advanced exam. Based on my personal observation, it is like the gakao exam and its a really really soul-sucking exam :-(

Most people who actually top that exam leave the nation anyway and the most focus is on the IIT or rather on prestige rather than passion. It sucks a little because Computer science is treated as prestige rather than passion which hurts people like me who are passionate getting grinded into dust :-(

Indian society and gatherings really feel very prestige/respect focused in many areas to me, though I am not sure if its an Indian phenomenon or not. Respect/comfort/stability seems to mean a lot more in my opinion

Re: India's first privately-developed rocket reaches orbit on debut launch

#123

Post by OneDonOne »

rayiner wrote: post #104
OneDonOne wrote: post #95

Earlier quoted context omitted.

If the "physics" tells you that your satellite cannot radiate heat away from your nVidia GPU cluster because each H100 needs 1.1 meter square of radiator, then opinions do not matter. The same applies to power supply and bandwidth.

The radiator is much more efficient than the solar panels (for obvious reasons), so that’s not the limiting factor. As to power, Caltech is already at 2-3 pounds per square meter: https://magazine.caltech.edu/post/sspp-space-solar-power-pro... > Another way to think about it: An SSPP spacecraft with a 60-meter-by-60-meter surface area made using today’s space PV-cell technology would cost $36 million and weigh nearly…

The Caltech Concept is just that — a concept. No prototype, no tests, no manufacturing, no results. When they achieve this order of magnitude improvement on a prototype scale, that's when we should take them seriously.

Re: India's first privately-developed rocket reaches orbit on debut launch

#125

Post by WalterBright »

alephnerd wrote: post #48
mayama wrote: post #46

Regarding Indian private space sector, In addition to skyroot solid rocket, following are noteworthy Agnikul is planning to launch semi-cryo kerosene rocket pretty soon. Their engine is 3d printed and use electric pump fed 25kN small engine. Planning to launch 4 clustered engines as first stage and already did suborbital test, with some parachute splash down reusability claims. Astrobase is recent entrant. With decen…

Also, Pixxel, Skyroot, and Agnikul are targeting orbital data center launches this year for defense applications (which is what the entire ODC story is about). The US NRO already uses India's Pixxel [0] along with Finland's ICEYE (which is now co-manufacturing synthetic aperture sats in India with Agnikul [1]) for hyperspectral scanning. Edit: can't reply > But.. why? Missile Defense and C4ISR [2]. Seconds matter, so…

> targeting orbital data center launches

I am regularly assured by HN denizens that orbiting data centers will never work.

Re: India's first privately-developed rocket reaches orbit on debut launch

#126

Post by alephnerd »

WalterBright wrote: post #125
alephnerd wrote: post #48

Earlier quoted context omitted.

Also, Pixxel, Skyroot, and Agnikul are targeting orbital data center launches this year for defense applications (which is what the entire ODC story is about). The US NRO already uses India's Pixxel [0] along with Finland's ICEYE (which is now co-manufacturing synthetic aperture sats in India with Agnikul [1]) for hyperspectral scanning. Edit: can't reply > But.. why? Missile Defense and C4ISR [2]. Seconds matter, so…

> targeting orbital data center launches I am regularly assured by HN denizens that orbiting data centers will never work.

Because they won't for commercial usecases (which was never the point of an ODC).

For C4ISR usecases they solve the latency problem and are worth the spend needed.

Everyone on HN is talking about a commercial usecase that isn't under serious consideration.

Re: India's first privately-developed rocket reaches orbit on debut launch

#127

Post by OneDonOne »

rayiner wrote: post #84
TeMPOraL wrote: post #82

Earlier quoted context omitted.

> Is my borderline childish understanding of basic physics THAT off because I cannot see the value or utility (beyond a small smear of niche edge cases) of space-based compute? Don't worry, most of the people online didn't get the memo on this. One of the major selling points of orbital compute is power supply - more specifically, it turns out that, compared to beaming power from space, it's projected to be cheaper t…

Could we have giant nuclear reactors in space? What's the power loss from beaming down power?

See:

SNAP-10A

BES-5 (oops, sorry 'bout that Canada!)

TOPAZ-I

Kiwi, Phoebus, and NRX (Mars here we come!)

RD-0410 (Dossvidanya Solar System!)

SP-100

TOPAZ-II

Kilopower

Re: India's first privately-developed rocket reaches orbit on debut launch

#128

Post by notahacker »

TeMPOraL wrote: post #82
detritus wrote: post #77

Earlier quoted context omitted.

Mein Gott, you're not just making this up ( https://www.datacenterdynamics.com/en/news/neevcloud-and-agn... ). But.. why? Musk bandwagon-hopping? Investor bamboozlery? (Same diff?) Is my borderline childish understanding of basic physics THAT off because I cannot see the value or utility (beyond a small smear of niche edge cases) of space-based compute? - ed, disclosure: You seem to have edited your response whilst I…

> Is my borderline childish understanding of basic physics THAT off because I cannot see the value or utility (beyond a small smear of niche edge cases) of space-based compute? Don't worry, most of the people online didn't get the memo on this. One of the major selling points of orbital compute is power supply - more specifically, it turns out that, compared to beaming power from space, it's projected to be cheaper t…

The unit economic tradeoffs aren't quite that straightforward (beamed power is lossy enough to require more panels[1], but solar cells and satellite structures have longer useful lives than inference chips so over longer time periods you likely end up launching more stuff into space with disposable datacentres anyway[2], particularly given the datacentres also need bigger radiators. Other issues which favour power being beamed to the ground are not exposing those expensive chips to radiation, and being able to replace them on cycles dictated by inference chip innovation or end-of-life rather than fixed cycles depending on a satellite propellant budget...

The other comparison point is of course plain old terrestrial power sources, including energy storage in the mix if it relies heavily on solar power without a sufficiently global grid. Not having to launch into space buys a lot of power.

C2 RTT times and edge computation of large datasets collected in space make much more sense since unit economics aren't the driving factor, but are unlikely to need datacentres on the same scale as inference compute for the general population (another reason why this use case makes more sense)

[1]but I think the underrated problem with beamed power isn't just the low maturity of the technology, but that as soon as you start talking about sending power to earth via RF or laser you're going to encounter political opposition that makes objections to terrestrial datacentres seem tame.... [2]chips can in theory be replaced on orbit, but the "million satellite" filings are disposable. Replenishing propellant for a few large power stations, potentially on longer cycles, is a simpler task.

Re: India's first privately-developed rocket reaches orbit on debut launch

#130

Post by rayiner »

OneDonOne wrote: post #123
rayiner wrote: post #104

Earlier quoted context omitted.

The radiator is much more efficient than the solar panels (for obvious reasons), so that’s not the limiting factor. As to power, Caltech is already at 2-3 pounds per square meter: https://magazine.caltech.edu/post/sspp-space-solar-power-pro... > Another way to think about it: An SSPP spacecraft with a 60-meter-by-60-meter surface area made using today’s space PV-cell technology would cost $36 million and weigh nearly…

The Caltech Concept is just that — a concept. No prototype, no tests, no manufacturing, no results. When they achieve this order of magnitude improvement on a prototype scale, that's when we should take them seriously.

I'm referring to the description of "today’s space PV-cell technology" (I believe the lightweight panels used to upgrade the ISS in 2021).

SSPP has already sent prototypes to space: https://www.caltech.edu/about/news/space-solar-power-project....

There's a ton of work being done on lightweight solar panels for space. E.g. https://ascentsolar.com/asti-technology-and-unique-advantage...

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