Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Starship's Third Flight Test [video]

spacex.com

Post reply on HN
Print view View original

181–190 of 413 posts

Re: Starship's Third Flight Test [video]

#181

Post by ortusdux »

throwuwu wrote: post #170
DarmokJalad1701 wrote: post #151

Earlier quoted context omitted.

They can launch payloads that bring in revenue while working on that problem. There is a good chance they put a bunch of Starlinks on the next flight.

Exactly, they’ve reached feature parity with large expendable launch systems so they can piggyback paying customers with a high risk threshold (starlink) on flights they’d be doing anyways. Given their cadence this phase won’t last long, they’ll likely achieve at least one successful landing next flight.

They have also been eager to launch version 2.0 starlink satellites, but they don't fit in the falcon fairing. The first couple batches of those would be test articles as well, so I'd be surprised if the next starship launch doesn't a few on board.

Re: Starship's Third Flight Test [video]

#182

Post by trollied »

jfoster wrote: post #13
namaria wrote: post #9

I was just watching Spacex official stream and at ignition they switched to Musk hawking cryptocurrency. What just happened?? edit: wild I just realized take off is 50 minutes from now... what had I been watching?? they did a countdown and there was ignition... was that a time wrap? Am I going insane? edit2: @spacex034 is not @spacex... today I learned...

There's a fake SpaceX YouTube account that looks official because they included videos from the real channel in playlists to get verification ticks & have managed to harvest thousands of subscribers. YT's interface is a bit dumb for including the verification ticks in that use-case.

> looks official because they included videos from the real channel in playlists to get verification ticks

That is not how it happens. The account is verified because it is a stolen account that had lots of subscribers & views. They hide/delete the existing videos & rebrand the channel. It famously happened to Linus Tech Tips last year after a staff member fell for a spear phishing attempt.

Re: Starship's Third Flight Test [video]

#183

Post by Laremere »

DarmokJalad1701 wrote: post #167
Laremere wrote: post #148

Earlier quoted context omitted.

Parent's (correct) point is that it isn't a matter of the ascent trajectory. They can't leave the Starship up in orbit, and where it reenters needs to be controlled.

> They can't leave the Starship up in orbit, and where it reenters needs to be controlled. Why? Plenty of boosters re-enter uncontrolled and burn up all the time.

Afaik, when talking about objects large enough that some debris will actually hit the ground, only China intentionally lets their final stage re-enter uncontrolled. Everyone else at least has a plan for controlling re-entry. SpaceX has lost control of some of their Falcon 9 second stages before, but that's the exception not the rule.

Re: Starship's Third Flight Test [video]

#184

Post by golol »

DarmokJalad1701 wrote: post #80

The test is essentially a success at this point. Starship can take payload to orbit and open/close the payload doors. The remaining things are icing on the cake. They can refine re-usability while flying payloads.

One technical modification: They need engine relight in orbit to work to deliver payloads, otherwise Starship will stay in orbit and they can not test reentry.

Re: Starship's Third Flight Test [video]

#185

Post by dotnet00 »

perihelions wrote: post #159
dotnet00 wrote: post #125

Earlier quoted context omitted.

Technically it's a transatmospheric orbit. That is, an orbit such that it'd stay up there if the atmosphere were not present. The difference between this and full orbit is just a few seconds longer burn, so it's a difference with little meaning in terms of proving out the ability to reach orbit.

I don't believe that's the case—see the math in my sibling comment.

The number going around from people who typically do this kind of thing is a ~55x235km orbit: https://twitter.com/planet4589/status/1768270310199935299

I'm not really in a place to judge your math right now to really add anything on that.

Re: Starship's Third Flight Test [video]

#187

Post by perihelions »

grecy wrote: post #163
perihelions wrote: post #94

Earlier quoted context omitted.

I did the math. So, the minimal orbit at 180 km, the one that grazes the earth's surface at its perigee, is about 7.75 km/s or 27,900 kph. The other commenters are right: it was never technically orbital. edit: (let* ((μ 398600.0) ;; km^3/s^2 (r 6371.0) ;; km (peri (+ r 0.0)) (apo (+ r 180.0)) (a (* 0.5 (+ peri apo)))) (sqrt (* μ (- (/ 2.0 apo) (/ 1.0 a))))) ;; 7.745844595118488

That is really cool. For those of us that are space nerds but don't have the depth of understanding, do you mind walking us through the calculation above?

I apologize I don't have a good explanation of it at hand! It's a form of the vis-viva equation [0] that's basically a restatement of conservation of energy. It derives the (scalar) speed of an object in a 2-body orbit, at any position within that orbit, as a simple function of their separation distance.

In the form I'm using, I'm using standard parameters of an elliptical orbit: the periapsis (the closest approach to the center of mass of the massive body (which is a focal point of the ellipse which the orbit traces)), apoapsis (farthest distance), and semimajor axis (their arithmetic mean [1]). I'm evaluating the orbital velocity at the highest point, the apoapsis. μ is a short form for the product G*M, the standard gravitational parameter [2] of Earth (which is known to much higher precision than either the universal gravitational constant G, or the mass of the earth M, individually).

The particular orbit I'm applying it to is one whose periapsis is equal to the Earth's radius—an orbit that touches the surface of the Earth. This is the dividing line for orbital / suborbital: a suborbital trajectory is one that (mathematically) goes beneath the Earth's surface.

[0] https://en.wikipedia.org/wiki/Vis-viva_equation#Equation

[1] https://en.wikipedia.org/wiki/Semi-major_and_semi-minor_axes...

[2] https://en.wikipedia.org/wiki/Standard_gravitational_paramet...

Re: Starship's Third Flight Test [video]

#188

Post by [deleted] »

namaria wrote: post #9

I was just watching Spacex official stream and at ignition they switched to Musk hawking cryptocurrency. What just happened?? edit: wild I just realized take off is 50 minutes from now... what had I been watching?? they did a countdown and there was ignition... was that a time wrap? Am I going insane? edit2: @spacex034 is not @spacex... today I learned...

[deleted]

Re: Starship's Third Flight Test [video]

#189

Post by golol »

DarmokJalad1701 wrote: post #167
Laremere wrote: post #148

Earlier quoted context omitted.

Parent's (correct) point is that it isn't a matter of the ascent trajectory. They can't leave the Starship up in orbit, and where it reenters needs to be controlled.

> They can't leave the Starship up in orbit, and where it reenters needs to be controlled. Why? Plenty of boosters re-enter uncontrolled and burn up all the time.

Ok so they could leave Starship in orbit and launch payloads like that. The idea however is to launch payloads WHILE testing reentry and landing. This requires an engine relight in orbit.

Re: Starship's Third Flight Test [video]

#190

Post by golol »

dotnet00 wrote: post #171
iwontberude wrote: post #147

Earlier quoted context omitted.

Nevermind

The latest Soyuz revision is ~$50m per launch, it has a payload less than half of a Falcon 9 that lands on a droneship, and ~2/3rd of a Falcon 9 that returns to launch site. Making it twice the cost per kg. The highest flight rate it has ever achieved has been 2/month. It has a 96% success rate. The latest Falcon 9 revision is ~$67m per launch. Lately it flies every ~3 days. Over the past year it has flown ~100 times…

>The latest Falcon 9 revision is ~$67m per launch

And that is the price, the cost is unknown but likely lower.

Post reply on HN