Space General Space News, Image and Discussion Thread

[Skallagrim]

Fundamentally it was a "steam" rocket -- the business end uses the thermal power of the nuclear reactor to flash a liquid into exhaust gas.

I think you also could use something like that to create nuclear-powered steam-jet aeroplanes. Which is obviously a dangerous idea, but -- hear me out -- should be done anyway, because it's really cool.

Nuclear-powered submarines and carriers already exist, and they're awesome. High time we add nuclear aeroplanes and spacecraft to the mix!

 

[Bacle]

I think you also could use something like that to create nuclear-powered steam-jet aeroplanes. Which is obviously a dangerous idea, but -- hear me out -- should be done anyway, because it's really cool.

Nuclear-powered submarines and carriers already exist, and they're awesome. High time we add nuclear aeroplanes and spacecraft to the mix!

Ships and subs don't crash as often as planes; nuclear powered planes are effectively flying dirty bombs if they crash.

 

[Skallagrim]

Ships and subs don't crash as often as planes; nuclear powered planes are effectively flying dirty bombs if they crash.

I know, and I recognise this.

But it's cool, so I want it anyway.

 

[ATP]

I know, and I recognise this.

But it's cool, so I want it anyway.

Excellent idea,only weakling fear some small crashing.Everything,especially walking super heavy tanks,should be nuclear -powered !

 

[Bacle]

Livestream of the SLS moving out; has not moved as of this post, but doors are open.

 

[Urabrask Revealed]

has not moved as of this post, but doors are open.

Must be having stage-fright.

 

[Robovski]

Nasa's giant new SLS Moon rocket makes its debut

The Space Launch System vehicle rolls out for a practice countdown ahead of a flight this summer.

www.bbc.com

 

[bintananth]

Nasa's giant new SLS Moon rocket makes its debut

The Space Launch System vehicle rolls out for a practice countdown ahead of a flight this summer.

www.bbc.com

I'm not confident NASA got this right.

The RS-25 has a mixture ratio of about 6:1 and a specific impulse of about 453s with a chamber pressure of 2,740psi. It's wasting enormous amounts of liquid oxygen because that specific impulse is doable at 4.83:1 and 1,000psi before even getting into the "Why the fuck are you using Liquid Hydrogen in a first stage?" questions.

EDIT: for max performance a little less than 80% of what's sitting on the launch pad at T-0 will be first stage oxidixer and fuel regardless of what's in the tanks and that isn't enough to get something into orbit.

 

[Doomsought]

I'm not confident NASA got this right.

It is a monstrosity designed by comity to some truly bad requirements.

 

[bintananth]

It is a monstrosity designed by comity to some truly bad requirements.

You will get no arguments from me in response to that statement.

EDIT: The heaviest thing in a rocket is the oxidizer and LOX is one of the lightest and most energetic ones you can get. Fluorine is somewhat more energetic, but you need 2.25lbs of F2 for 1lb of O2 and I'm pretty sure everyone would rather not deal with clouds of hot hydrofluoric acid.

 

[Doomsought]

The thing you need to understand is that to cut costs, the SLS was requried to use spare rocket parts that were gathering dust in a warehouse.

 

[JagerIV]

A very, very long article on the SLS, bashing basically every element of it.

SLS: Is cancellation too good?

The SLS axiomatically cannot provide good value to the US taxpayer. In that regard it has already failed, regardless of whether it eventually manages to limp to orbit with a Falcon Heavy payload or…

caseyhandmer.wordpress.com

[Update March 2022: During a House Science Committee hearing NASA OIG Paul Martin revealed that the marginal launch cost for each of the first four Artemis SLS launches was $4.1b. This doesn’t include any development costs, which will total $93b by 2025. Incredible!]

Can you imagine showing up for your day job and telling your boss that your salary is now a secret, but at least 3x higher than the day before, and that your work product was going to be a decade late? Even the people whose only job is to know exactly how much the SLS costs apparently do not know.

The only metrics that matter for big rockets and humans in space is $/T and T/year. By an unbelievably huge margin, the SLS has mismanaged itself into the wrong end of the field on both these axes, with a rocket that costs maybe 20x more per tonne and, due to its appallingly low flight rate, delivers less mass to orbit in a year than SpaceX can in a fortnight, in 2021.

The SpaceX Starship is designed to deliver on order a million tonnes to orbit a year, for about $100/kg. That’s 15,000 times the stuff for 1/500th the cost. I have no doubt that the Starship development program will have its surprises and setbacks but they’ve already flown to 12.5km – roughly as high as the stack of $100 bills already spent on SLS would reach. Even if Starship comes in at 10x the design cost it will still be 50x cheaper than the competition. Would you spend $20k on a car, or $1m on the same car? It’s hard to even make meaningful comparisons here.

 

[bintananth]

The thing you need to understand is that to cut costs, the SLS was requried to use spare rocket parts that were gathering dust in a warehouse.

To paraphrase John D. Clark: the Soviets did it right.

Need more thrust? Build a bigger rocket.
Need more Δ-v? Add more stages.

The first stage of a modern Soyuz is an improved version of the 20-nozzle monster used to get Sputnik-1 into space.

 

[Undertone]

Well, SLS *is* the bigger rocket. It's the Space Shuttle, with two extra engines, and the flying brick on the side removed.

SLS doesn't buck the modern trend of two stages plus the odd SRB. Staging may have some benefits, but it comes with costs to consider beyond the launch pad. Add a stage and you also add a supply chain leg, a point of failure, and a blob of space debris in orbit.

I'm amazed by what SLS can do, but deeply disappointed that it has taken so long to deliver even a test article. I also already mourn how it is certain to be ended before its time by Congressional caprice. If you could put everything wrong with "Old NASA" in a bottle, well, it'd look just like this entire program.

 

[bintananth]

If you could put everything wrong with "Old NASA" in a bottle, well, it'd look just like this entire program.

The Soviets were highly critical of the Space Shuttle. They didn't think it was actually a civilian project and their "copy" was a) much more thoroughly tested, b) didn't need a crew for the orbital test flight, and c) had an autopilot capable of handling re-entry and safely landing at a pre-designated runway (which occured when there was a 40kt crosswind, BTW).

 

[Morphic Tide]

and a blob of space debris in orbit.

*laughs in SpaceX*

No, really, they figured out how to get the stages to come back to ground.

 

[Flintsteel]

The SLS program is Congressional Graft. That we actually got a (theoretically) functional rocket out of it is a miracle. At 4 billion each and vendors associated with it in every single state, plus stuff in Europe, it's doing exactly what it is designed to do.

...which is not launching things, in case anyone needed that cleared up.

 

[ATP]

The SLS program is Congressional Graft. That we actually got a (theoretically) functional rocket out of it is a miracle. At 4 billion each and vendors associated with it in every single state, plus stuff in Europe, it's doing exactly what it is designed to do.

...which is not launching things, in case anyone needed that cleared up.

Of course,any state agency is doing exactly the same - not their job.
There is joke in Poland - what is camel? horse designed by state comitee.

 

[bintananth]

There is joke in Poland - what is camel? horse designed by state comitee.

I'll need to use or pass that joke on to someone some day.

 

[JagerIV]

New post from ToughSF, Fusion without Fissile.

Fusion without Fissiles: Superbombs and Wilderness Orion

A blog dedicated to helping Science Fiction authors create and discuss worlds where a realistic setting can still serve the fiction.

toughsf.blogspot.com

Nice picture's still.