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41 votes

Will the James Webb Space Telescope be insured against launch failure?

NASA tends not to insure its missions, nor do any government missions. These missions are one-of-a-kind, and so expensive that the satellite insurance market would have a hard time making it work. ...
PearsonArtPhoto's user avatar
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28 votes
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What does the Ariane 5 rocket use to turn?

Like most large modern launchers, Ariane uses gimbaled engines for attitude control during ascent. Both the Vulcain liquid-hydrogen engine and the nozzles of the solid rocket boosters on the Ariane ...
Russell Borogove's user avatar
21 votes
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How can the 6.5 m primary mirror of the JWST fit inside the 5.4 m fairing of Ariane 5?

The JWST is made to fold up, to fit inside the standard fairing. You can sort of see this in your image, 3 mirror segments are visible (the hexagons in the middle), other segments are viewed side-on ...
Hobbes's user avatar
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19 votes
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What are these circular spots on these Ariane V SRB nozzles?

Meet the Ariane EAP (Étage d'Accélération à Poudre, "Solid Booster Stage"): what are the (presumably eight) circular spots on the external nozzle-like protrusions at the bottom of each of ...
Russell Borogove's user avatar
18 votes
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What's the shiny silver turnip on the bottom of this Ariane 5 launcher?

It's an Helium tank; nicknamed LHESS This website capcomespace.net have a very good article on the subject (in french) Extract (roughly translated): The tanks pressurisation system preserve the ...
Antzi's user avatar
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18 votes
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Why does the core stage of the Ariane 5 produce more thrust in vacuum?

It's because the ambient atmospheric pressure affects the thrust generated by the engine. (Image source) An engine nozzle has a "design altitude" at which the pressure of the exhaust at the exit ...
Organic Marble's user avatar
18 votes

Why are Europe’s Air & Space Academy and DLR urging ESA and CNES to reconsider the use of solid fuels for the proposed Ariane 6?

This is a pretty interesting question in retrospect now. When it was asked in 2013, booster re-usablity was just a gleam in SpaceX's eye. The first Falcon 9 attempt to land a booster wasn't until ...
SafeFastExpressive's user avatar
16 votes

Will the James Webb Space Telescope be insured against launch failure?

Insurance is done when losing a mission would mean an unacceptable financial loss, e.g. when a launch failure would bankrupt your company. The government is large enough to absorb such losses, so no ...
Hobbes's user avatar
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12 votes
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Are all payload fairings this floppy?

That ULA video was great. I googled for "fairing vibrational modes after jettison" and came up with a lot of interesting links. The prize is probably this paper "Simulation of the behavior of a ...
Organic Marble's user avatar
11 votes
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Why aren't the Ariane 5's SRBs reused?

The shuttle SRBs weren't really cost-effective to reuse. The nozzles and nozzle boots were replaced completely, as were many other components; the segment casings were deformed by the force of ...
Russell Borogove's user avatar
11 votes
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Why do Ariane rockets not have ice break off on liftoff?

Ariane 5 does not shed ice at liftoff. The first stage is covered in foam insulation that prevents ice buildup. In this image, the insulation is the brown stuff. Later Ariane 5 versions switched to ...
Hobbes's user avatar
  • 128k
10 votes

What does the Ariane 5 rocket use to turn?

The first stage of Ariane V has in fact RCS thrusters, but only for roll control. While the solid boosters are burning, roll control of the whole stack is exercised by differential gimbaling of the ...
Peter Lichtenberger's user avatar
9 votes
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Ariane 6 upper stage schematic showing integration of APU

I found a doctoral dissertation that discusses the possibility of increasing the thrust of the two nozzles (TAPUs) of the APU on Ariane 6's upper stage. The drawings in the dissertation when combined ...
ymb1's user avatar
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8 votes
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Is the Ariane 5 rolled out or is the hangar moved away?

The Ariane 5 is moved from the BAF (FR: Bâtiment d’Assemblage Final, EN: Final Assembly Building) to the launch pad: There is no encapsulation facility at the launch pad, which is "approximately ...
BrendanLuke15's user avatar
7 votes
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Does Arianespace have a modified Soyuz launch vehicle?

Soyuz launch vehicles have been launched from Arianespace's launch facility in French Guiana since 2011. OneWeb has already used the French Guiana Soyuz in 2019 (Flight VS21) "ownership" is ...
SE - stop firing the good guys's user avatar
6 votes
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What is this flying debris during Ariane 5 liftoff

That is a cover plate at the top of the Etage d'Acceleration à Poudre (EAP) – solid rocket booster at the nose cone that at the time of launch comes off exposing the separation rockets. Video of ...
gwally's user avatar
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6 votes
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Why is ESA developing the Vinci engine rather than buying RL10Bs?

The RL10 is a terribly expensive engine to produce (I've seen estimates of US$25 million per unit), mainly due to its welded-tube nozzle construction. I expect Vinci will be substantially cheaper to ...
Russell Borogove's user avatar
6 votes

What are these circular spots on these Ariane V SRB nozzles?

Is there a lock down mechanism somewhere? There doesn't seem to be. Detail of the aft skirt: Note the lack of attachment hardware. The page on the launch table says: A la nuance près que si Ariane ...
Hobbes's user avatar
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6 votes
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Is vertical assembly worth the cost (Ariane 6)

Ariane 6 had one goal: to reduce cost compared to Ariane 5. To achieve this, they took several steps: replace vertical integration with horizontal integration. All components of Ariane 5 are ...
Hobbes's user avatar
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6 votes
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How long does it take for Ariane 5 to roll to the launch pad?

For the upcoming JWST launch - which is presumably representative - the rollout will take a couple of hours: Ground crews at the jungle spaceport in French Guiana planned to transfer the European ...
Andrew is gone's user avatar
5 votes

How to identify loads for a Payload Adapter System during Rocket Launch?

The loads (acceleration, vibration) that occur during launch are specified in the Ariane 5 user manual. The payload is attached to the top of the PAF via the ring at the top.
Hobbes's user avatar
  • 128k
5 votes
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Will Ariane 5 ECA have LES for the launch of JWST?

There is no* safe condition used by Ariane 5. It is not common to use Launch Escape Systems for UNmanned flights. Actually the hardware of a spacecraft is not as costly as you may think, the ...
CallMeTom's user avatar
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5 votes
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Why doesn't Ariane-5 lift off at T=0 seconds?

Liftoff at T-0 is common, but not universal. For Ariane 5, T-0 is the moment of ignition of the Vulcain engine. In a nominal countdown, checkout takes 6 seconds, and the solids are ignited when ...
Hobbes's user avatar
  • 128k
5 votes

Why is Ariane-5's upper stage appear to vent exhaust post engine cut off?

ESA's space debris mitigation guidelines are aimed towards reducing the generation of space debris by following two approach The most effective short­term means of reducing the space debris growth ...
karthikeyan's user avatar
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4 votes

Could we easily build a "super-heavy" Ariane 6?

Adding liquid rocket engines to a stage that is otherwise unchanged (i.e. without increasing fuel tankage) could increase the rocket's acceleration, but, because of the added engine mass, actually ...
Russell Borogove's user avatar
4 votes

Why do Ariane rockets not have ice break off on liftoff?

They do. Ariane 5 uses Liquid Oxygen/Liquid Hydrogen for its main stage engine, so ice accumulation on the body also occurs. See this video for a very clear example of it falling away, but on most ...
Jack's user avatar
  • 9,966
4 votes

How much fuel did JWST save due to an accurate launch, and how much will remain after L2 orbit?

The three MCC course correction burns, which are listed In this NASA blog and and this NASA blog have totaled 24.4$\frac{m}{s}$ fuel used so far, in burns totaling 79.5 minutes. Dec 25th, 20$\frac{m}{...
Sheldon's user avatar
  • 555
4 votes

Why is the Ariane 5 shorter than the Ariane 4?

Fuel changes. Ariane 5 core burns LOX and Liquid Hydrogen. This needs larger tanks and thus is wider. Ariane 4 uses hypergolics that are much denser. (Nitrogen Tetroxide, UMDH). Thus the tanks are ...
geoffc's user avatar
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3 votes
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Which of these configurations is preferred and why?

There are lots of tradeoffs at work here: cryogenic stages are more difficult to design than storable liquid stages, so space agencies tend to start building storable liquid stages, then move on to ...
Hobbes's user avatar
  • 128k
3 votes
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Has foam loss been observed in Ariane 5 launches?

Yes, at least once, for the Rosetta launch. The damage was discovered before the launch: A fallen chunk of foam insulation from the rocket’s fuel tank scuppered the latest launch attempt. During a ...
Hobbes's user avatar
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