NoUFO From Germany, joined Apr 2001, 7798 posts, RR: 13 Posted (1 year 3 months 1 week 5 days 4 hours ago) and read 2821 times:
Vega, basically the (much) smaller sibling of Ariane V, has made its first qualification launch, carrying nine small satellites into orbit.
While there is a strong tendency for satellites to become larger, there is still a need for a small launcher to place 300 kg to 2.000 kg satellites, ESA says.
Vega consists of three solid-propellant stages and has an additional liquid-propellant upper module for attitude and orbit control, and satellite release. Unlike most small launchers, Vega is able to carry multiple payloads into orbit.
boacvc10 From United States of America, joined Jul 2006, 516 posts, RR: 0 Reply 2, posted (1 year 3 months 1 week 5 days 4 hours ago) and read 2794 times:
Quoting NoUFO (Thread starter): Vega consists of three solid-propellant stages and has an additional liquid-propellant upper module for attitude and orbit control, and satellite release. Unlike most small launchers, Vega is able to carry multiple payloads into orbit.
2012 and 2013 will be an exciting time for private space companies as several are getting their systems ready to go towards LEO. Do you have any status update of the cubesat missions that were carried onboard? Which ones made the final manifest?
jollo From Italy, joined Aug 2011, 180 posts, RR: 0 Reply 3, posted (1 year 3 months 1 week 5 days 3 hours ago) and read 2783 times:
Quoting NoUFO (Thread starter): Vega, basically the (much) smaller sibling of Ariane V, has made its first qualification launch, carrying nine small satellites into orbit.
Well, not really a sibling... Vega's first three stages are solid-propellant powered (no strap-on boosters) and are the first all-composite (graphite epoxy filament) single-barrel launcher stages in history.
And at 137 tons liftoff mass and over 3MN max thrust, Vega litterally leaps out of the pad!
redflyer From United States of America, joined Feb 2005, 4181 posts, RR: 30 Reply 6, posted (1 year 3 months 1 week 4 days 23 hours ago) and read 2720 times:
Quoting NoUFO (Reply 5): Nice video. Lifts off like a ... well: rocket!
Holy....!!!!! Look at that thing go! What kind of G's is that thing pulling? I would assume the payload has to be built to a more robust specification to endure launch forces than a typical payload taking a leisurely ride on an Ariane 5 or something comparable from Boeing/Lockheed.
rwessel From United States of America, joined Jan 2007, 1991 posts, RR: 2 Reply 7, posted (1 year 3 months 1 week 4 days 19 hours ago) and read 2689 times:
Quoting redflyer (Reply 6): Holy....!!!!! Look at that thing go! What kind of G's is that thing pulling? I would assume the payload has to be built to a more robust specification to endure launch forces than a typical payload taking a leisurely ride on an Ariane 5 or something comparable from Boeing/Lockheed.
3040kN at 137,000kg works out to 2.47G at takeoff. That's well within the ranges of accelerations developed during the flights of most orbital launchers. The need for structural improvements occurs if later portions of the flight start to exceed 5 or 6G. I'd assume that they'd avoid that, since the extra structure comes at a weight penalty. That's often worse on a solid, because the inherent vibration levels are higher. Many vehicles throttle down as stages empty to keep maximum accelerations down. For example, on the S-V, both the S-IC and S-II center engines shut down before the nominal burnout. While liquids are easy to throttle, solids can have their burn patterns shaped to produce varying thrust during the flight, although there are limits to what you can do, but a 2 or 3:1 thrust ranges are possible (although it’s usually easier to stage at the high end of that range). In the case of the Vega, they also have three (solid) boost stages, with relatively short burns, which will also help in maintaining reasonable accelerations.
On the flip side, higher accelerations reduce fuel needs to orbit.
And the actual accelerations are dependent on payload mass as well, although that's usually a fairly small effect (if the payload is exceptionally large, you're probably not getting to orbit without a bigger launch vehicle, and if it's exceptionally small, you'd use a smaller launcher).
But if anyone has access to any publically available payload integration documents for the Vega, the accelerations profiles should be well documented.
Quote: The peak longitudinal acceleration does not exceed 5.5 g for a payload
above 300 kg.
The highest lateral static acceleration is less than 0.9 g at maximum dynamic pressure
and takes into account the effect of wind and gust encountered in this phase.
That's not much more than Ariane V (4.55 g at the end of the solid rocket boost phase), that looks comparatively a sluggard at liftoff. Anyway, well within typical payload tolerances (would be ok for a human too... but Vega will never be human-rated: too little payload).
jollo From Italy, joined Aug 2011, 180 posts, RR: 0 Reply 9, posted (1 year 3 months 1 week 3 days 11 hours ago) and read 2408 times:
Quoting NoUFO (Reply 5): True, it's not really a sibling other than that Vega is part of the ESA launcher family.
Yes, I was just trying to say that Vega's common technical ground and "ancestry" with Ariane (and Soyuz) is very limited (basically to the current "family name"). Yet another example: Vega is the first launcher to use electricallly powered actuators for nozzle steering (à la 787).
I looked it up and found that the correct word for the concept is "stepsibling", as in stepbrother or stepsister (from Wikipedia: "the child of one's stepparent from a previous or subsequent relationship. Not blood related"), but still a "sibling". So you were right. Sorry!
rwessel From United States of America, joined Jan 2007, 1991 posts, RR: 2 Reply 10, posted (1 year 3 months 1 week 2 days 23 hours ago) and read 2315 times:
Quoting jollo (Reply 8): Quoting rwessel (Reply 7):
the accelerations profiles should be well documented.
The graph on 3-2 is interesting as well. It clearly shows the effects of the fuel geometry in the first stage, with high initial thrust tapering off significantly in a short time, while vehicle accelerations (except for the one big drop) mostly keeps increasing as the vehicle mass decreases. Ballparking from the graph (hard because of the difficulty of estimating remaining vehicle mass), it's about a 1.6:1 thrust falloff from maximum.
It also shows acceleration hitting about 2.25g a few seconds off the pad, so my back-of-the-envelope calculation was not too far off.
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