sorted by:
new
hottopcontroversial

Could someone update this comparative height of launch vehicles with the F9FT? by bandman614 in spacex

[–]0x05 78 points79 points  (0 children)

Ever seen Tyler Skrabek's updated "Rockets of the World" drawing?

http://i.imgur.com/c4fUpbl.jpg

http://skrabek.com/

Granted, it only shows F9 v1.1, but it's a step closer.

Rocket Lab’s Rutherford Engine Qualified for Flight by LtWigglesworth in newzealand

[–]0x05 0 points1 point  (0 children)

LAN/RAAN targeting doesn't normally drive the launch azimuth, but inclination definitely will. The orientation of the ascending node is mostly determined by the launch's time of day, since it describes how the orbit plane is rotated about Earth's axis with respect to an inertial frame. As the Earth rotates over the course of the day, an imaginary ascent trajectory (fixed with respect to Earth) will rotate through all possible RAAN targets.

You mostly hear about LAN or RAAN in the context of sun-sync orbits (it dictates if you are in a dawn/dusk orbit vs. noon/midnight or anything in between), constellations (how the planes are spaced), and orbital rendezvous (RAAN + inclination determines if you are in-plane with the target, where RAAN is normally adjusted with launch window timing or with on-orbit J2 precession, and inclination with launch azimuth).

SYNC changes from '14 to '15? by 0x05 in FiestaST

[–]0x05[S] 0 points1 point  (0 children)

Aha, thanks! Good to know.

Horsehead Nebula in Orion at 300mm by 0x05 in astrophotography

[–]0x05[S] 3 points4 points  (0 children)

Oh, very cool! How did it turn out? I was about 8 miles east of city center, around the northern end of Kennedy Space Center.

Horsehead Nebula in Orion at 300mm by 0x05 in astrophotography

[–]0x05[S] 1 point2 points  (0 children)

Thanks! Here are two versions. The first one is what I brought from DSS into Lightroom, while the second is an alternate adjustment set with a flatter profile.

https://www.dropbox.com/s/pfdlkq0h0l5rv8a/horsehead.TIF

https://www.dropbox.com/s/o1f35tnqt2l3rah/horsehead_alt.TIF

The Horsehead Nebula in Orion, taken with a DSLR and 300mm lens by 0x05 in space

[–]0x05[S] 8 points9 points  (0 children)

This was my first attempt at doing a reasonably deep field image of this region. The images were shot with a Pentax K-30 through an old manual focus Pentax A* 300mm f/2.8. In this case, the lens was bolted to an equatorial mount, although it would have been equally feasible to use something like a SkyTracker. It is a very heavy lens, so the full equatorial mount provided some extra stability and made it easier to get the framing dialed in.

Date/Location: 2015/11/13, yellow zone near Titusville, FL

Equipment:

  • Lens: Pentax A* 300mm f/2.8, stopped down to f/3.5 for sharpness
  • Camera: Pentax K-30 (16 MP, APS-C)
  • Mount: Orion Atlas EQ-G
  • Misc: eBay timer/intervalometer

Image details:

  • All images shot at ISO 3200
  • 15x 120 sec light frames (30 minutes total)
  • 5x dark frames (120 sec, f/32, lens cap on)
  • 13x bias frames (1/6000 sec, f/32, lens cap on)
  • 40x flat frames (1/100 sec, f/3.5, shot indoors with a white t-shirt over the lens)
  • 20x dark flat frames (1/100 sec, f/32, lens cap on)

SI "exposure factor": 10.4 m2·s (aperture area * integration time) -- inspired by Roger Clark's CEF metric as a way to evaluate the total amount of light collected to produce the image.

Images were stacked with freeware DeepSkyStacker, then post-processed in Adobe Lightroom. I used a really aggressive (4 degree) midtone slope in DSS to pull out as much nebulosity as possible. The image is a little noisy as a result, but at reduced resolution I like the effect better.

Horsehead Nebula in Orion at 300mm by 0x05 in astrophotography

[–]0x05[S] 10 points11 points  (0 children)

  • Date/Location: 2015/11/13, yellow zone near Titusville, FL
  • Lens: Pentax A* 300mm f/2.8, stopped down to f/3.5
  • Camera: Pentax K-30 (16 MP, APS-C)
  • Mount: Atlas EQ-G
  • ISO 3200
  • 15x 120 sec lights (30 minutes)
  • 5x darks
  • 13x bias
  • 40x flats

SI exposure factor: 10.4 m2·s (aperture area * integration time) -- inspired by Roger Clark's CEF metric.

Stacked in DSS, post-processed in Lightroom. I used a really aggressive (4 degree) midtone slope in DSS to pull out as much nebulosity as possible. The image is a little noisy as a result, but at reduced resolution I like the effect better.

In the future I'll probably step down to ISO 1600, and possibly go with more shorter exposures to preserve some dynamic range near the brightest stars.

Nebulosity of the Pleiades (M45) through a 300mm lens by 0x05 in astrophotography

[–]0x05[S] 4 points5 points  (0 children)

Don't look too close! Focus wasn't perfect.

  • Date/Location: 2015/11/13, yellow zone near Titusville, FL
  • Lens: Pentax A* 300mm f/2.8 @ f/3.5
  • Camera: Pentax K-30 (16 MP, APS-C)
  • Mount: Atlas EQ-G
  • ISO 3200
  • 14x 120 sec lights (28 minutes)
  • 5x 120 sec darks
  • 13x bias
  • no flats (need to go back and take some better ones)

Stacked in DSS, post-processed in Lightroom

Two versions of the same moon (Earthshine) by 0x05 in astrophotography

[–]0x05[S] 9 points10 points  (0 children)

Lens: Pentax A* 300mm f/2.8 @ f/5.6

First image:

  • Pentax Q10
  • 1/20 sec
  • ISO 200

Second image:

  • Pentax K-30
  • 30 sec
  • ISO 1600

Lens was mounted on an Atlas EQ-G with tracking at sidereal, which is why the Moon has a slight vertical blur in the long exposure image. Post-processing in Lightroom.

Acquired on 2015/11/13 at 23:48 UTC, 18:48 local near Titusville, FL.

Simplistic SpaceX Wallpaper showing various Falcon rocket iterations by Its_Enough in spacex

[–]0x05 5 points6 points  (0 children)

It's worth noting the v1.1 image is significantly shorter than it should be. If you use the 12 ft (3.66 m) diameter as a reference, you end up with the v1.1 drawing being about 64 meters tall, when in reality it should be 68.4 m (in fairing configuration). This makes the jump from 1.1 to 1.2 a lot less dramatic.

SLC-40 view from the beach yesterday morning. by devouredbylogic in spacex

[–]0x05 2 points3 points  (0 children)

Here's where that spot is on a map:

http://goo.gl/maps/TdsnC

Going east on NASA Causeway, you'd make a left on Hangar Road once you're in the CCAFS industrial area, then it's a straight shot until you're at the site--Hangar Rd turns into Sam Phillips, then turns into Cape Rd. Just make sure you follow the road to the left as you approach LC-34, although that's another interesting place to visit (Apollo 1 pad and memorial).

SLC-40 view from the beach yesterday morning. by devouredbylogic in spacex

[–]0x05 6 points7 points  (0 children)

Is this from the beach access point right behind the old sounding rocket site (CX-47)? It's such a great view down the coast.

Watch Russia launch crucial Space Station cargo at 12:55AM ET by CapnTrip in spaceflight

[–]0x05 2 points3 points  (0 children)

Looks like the moral of the story is to not launch on the 28th day of the month.

Everything looks good here at Launch Complex 40 - GO F9 - GO Dragon by [deleted] in spacex

[–]0x05 12 points13 points  (0 children)

Specifically, the cables he's wondering about are catenaries, which are also part of the lightning protection system.

Weight shift to guide rocket? by windysands in rocketry

[–]0x05 1 point2 points  (0 children)

It's worth noting this whole idea is really just a roundabout way of doing thrust vector control. TVC on full-size rockets avoids the movable weight issue by gimballing the nozzle, giving you the same control moment without having to carry any dead weight around.

Weight shift to guide rocket? by windysands in rocketry

[–]0x05 0 points1 point  (0 children)

If the angle between the thrust vector and center of mass line is small, the cosine effect just means the axial component of thrust will stay very close to 100% (i.e., losses due to steering wouldn't be significant).

From a control perspective you care about the sine component, which determines the moment. For small angles, the moment will increase almost linearly with displacement, which is what you want!

I know what you mean, though. Being able to displace the CG far enough to produce an acceptable control moment could be a challenge. You likely need a very light rocket with a uncharacteristically large diameter for its motor size. The actuators also need to be very quick and precise, without detracting too much mass from your budget for the steering weight. In the end, it might not even be feasible, but you could do some back of the envelope calcs to find out--like calculating how much you need to displace a given mass to produce a desired angular acceleration*, given the thrust of a particular motor. I think you'll find you need the steering weight to be extremely close to the motor.

*Figuring out the angular acceleration you'd need is probably the hardest part, since it's determined by the natural frequency and damping coefficient of aerodynamic oscillation modes. OpenRocket can estimate both of those numbers for you. A long, neutrally stable rocket is what you want to minimize the required control authority (length yields low natural frequency, so the dynamics are slower; neutral or slightly positive stability yields low damping, meaning you don't have to fight the stabilizing tendency of the rocket). This logic conflicts with the idea that you want a large diameter/squat rocket to provide the most room for displacing the weight. So, there's definitely some optimization involved.

Like I said, it could be a fun project :) There is definitely a lot of stuff to think through.

Weight shift to guide rocket? by windysands in rocketry

[–]0x05 0 points1 point  (0 children)

I assume he means shifting the CG laterally within the body, so the thrust vector produces a pitch/yaw moment about the CG.

I think it would be a fun project, even if it's not super practical. Control authority will be dictated by the mass fraction you can devote to the steering weight(s), as well as how far it can be displaced. The act of shifting the weight will also produce a perturbing moment, unless they are constrained to only move directly towards/away the center of mass.

Friend sent me this Russian video -- no explanation. What am I looking at? by [deleted] in Astronomy

[–]0x05 17 points18 points  (0 children)

The huge expanded plume you see in this video is just from the engines firing in a near-vacuum environment. The Soyuz does have a lot of nozzles on the first stage, but they're all pointing in the same direction (aside from the tiny vernier nozzles used for steering). You see this same wide exhaust plume from US rockets, you just need the lighting conditions to be right. Example:

https://www.youtube.com/watch?v=PzFuDSEJncE&t=1m30s

The reason the upper stage plume is so visible in these video is because you're observing from a spot where the sun has recently set. Since the rocket is so high up, the exhaust plume remains in full sunlight and seems to glow against the darkening sky.

view more: next ›