# Tag Info

29

It is an access hatch used during construction and maintenance. Credit: NASA-KSC Credit: NASA This part got at least some media coverage during the scrubbing of STS-121, when a Engine Cutoff (ECO) sensor, a fuel gauge, mounted behind that cover, inside the Liquid Hydrogen (LH2) tank, malfunctioned, causing that launch to be delayed, while the sensors were ...

27

I did a crude spreadsheet sim using the Rogers Commission report to get throttle times, to wit: Throttle down to 94% at 24 seconds Throttle down to 65% at 42 seconds Throttle up to 104% at 65 seconds I neglected startup propellant consumption and assumed step function throttling. I took liftoff O2 load to be 1,387,457 lb and H2 load to be 234,265 lb. I ...

25

That's the intertank - the cylinder that connected the bottom of the LO2 tank to the top of the LH2 tank. It didn't contain propellant, but did contain the forward interface with the Solid Rocket Boosters, and was built for lightness and strength, with skin-stringer construction. The ribs you see were the stringers. The intertank is a steel / aluminum ...

24

The breakup of Challenger occurred about 73 seconds into flight. Main engine cutoff normally occurs about 510 seconds into flight, implying that about 86% of the fuel would be remaining. (Many sources give 480 seconds, but I suspect that's a simple division of the tankage mass by the full-throttle consumption rate; looking at actual mission reports supports ...

22

The shuttle external tank held the propellants for the shuttle main engines. It was filled from spherical tanks positioned at the perimeter of the launch pad. Insulated lines ran from the spheres, through the Mobile Launcher, and into the Orbiter through two tombstone-shaped Tail Service Masts. Then through the Orbiter Main Propulsion System plumbing into ...

21

No, the previously used External Tanks (ETs) disintegrated in the atmosphere before they fell into the sea. Notably, Buzz Aldrin and others proposed different ideas for reuse of the tank in orbit, and allegedly NASA said that they would be willing to take external tanks to orbit if a private company would use them. No private effort ever stepped up to the ...

20

This part of the External Tank is called the "LH2 Tank aft dome". There are really two large circular penetrations on it. They are the ones offset from the center of the tank. One is the access hatch/manhole. (this description is from the LO2 tank part of the linked document. Further down it says the LH2 "manhole fitting was similar to those on both the ...

17

Based on this description of the Space Shuttle flight profile, no external tank would ever have completed so much as a single orbit. An external tank would achieve essentially the same orbital apogee as the orbiter itself, but that is all. The shuttle fired its OMS engines to achieve an actual orbit AFTER tank separation. This means that the tank remained on ...

13

I don't have a great reference for this, but it was to reduce cost on the throw-away External Tank. By using the same interface into the Orbiter used to supply propellants to the main engines, the cost and complexity of adding a dedicated loading interface to the tank was avoided. It was not a tremendous complexity hit to the Orbiter Main Propulsion system ...

13

No reuse, but... NASA did not at any point actually reuse an external tank in any way. However... They made plans to allow reuse in orbit. NASA did have tentative plans for utilization of the tanks in orbit. These plans were scrapped, however. The primary factors being (1) decreased payload capacity to stable orbit †, (2) risk of insulating foam falling ...

12

tl;dr - the parts at the rear of ET-94 where the foam was removed were painted orange for display. The foam was not dyed but started out a light cream color. It slowly turned orange when exposed to light. Here is a picture of foam that was trimmed off during the stringer crack problem on STS-133. You can see the internal foam is lighter, and the metal is ...

10

This was when planning safe disposal of the External Tank on certain types of launch abort. Source: Space Shuttle Abort Evolution page 9-10 A major design activity was conducted preparing for Shuttle launches on the West coast from Vandenberg AEB. Though not flown due to new program directions following the Challenger accident, a lot of design work and ...

8

As a design decision, if you throw away the External Tank and it has engines attached, you are throwing away the engines. Since the Orbiter was returning for sure anyway, the decision was to leave the engines on the orbiter. Once the ET is done its job, the engines are not needed to make orbit. The OMS pods provide enough punch for the needed orbital ...

8

Setting aside the political/managerial issues this is about mass. The final version of the tank had a "dry" (empty tanks) mass of about 26.5 tons and a fuelled mass of about 760 tons. The surface area is a roughly 2600 $m^2$ and the total mass of the thermal protection system is just over 2 tons (all masses and dimensions from wikipedia). So any replacement ...

7

The original External Tank nose cone design was indeed blunt - almost like a fireplug, as seen in this 1975 concept art. [Image source - lost in the mists of time to me, but NASA somewhere] However, wind tunnel testing at the Arnold Engineering Development Center revealed that this configuration caused unsteady aerodynamic buffeting at some conditions. A ...

7

A few facts: SRB Burn Time is 127 seconds Start of Challenger Incident- 64 s Vehicle breakup- 72 s Nominal time to orbit- 510 s. So the SRBs were about half-way done with their burn time before the vehicle started to break up. The Space Shuttle Main Engine actually produced less than 1 g thrust until about the time of SRB separation. If the SRBs could have ...

7

A big issue with boosting the tank to orbit, would be the foam insulation. It was believed it would come off in chunks, like popcorn, causing immense amounts of orbital debris, potentially in the orbit you wished to store it at. Which could be really bad news.

6

Reusability. The whole idea of the shuttle was to discard all the parts that are simple, cheap and easy to replace and recover everything expensive, complex and hard to replace. Of course the reality, involving meddling by parties other than NASA, never mind failures in the process the shuttle was designed (not so much the design itself as the process of ...

5

Safety distances are decided by modelling the worst-case scenario (an explosion of the rocket right on the launch pad). An explosion results in an overpressure which drops off as distance increases, the safe distance is one where the overpressure is limited to a survivable level. The same goes for structures: you can calculate how much overpressure a ...

5

There were three attach points. The forward bipod that you show in your answer, and two aft attach points. At each attach point a large explosive bolt held the tank and Orbiter together. Large umbilical door openings in the aft of the Orbiter let the aft bolts pass through and also had all the fluid and electrical connections. After separation tile-covered ...

5

There are generally speaking 2 conops to get into orbit with the Space Shuttle. The first one, and most commonly used, requires two thrusts post Main Engine CutOff (MECO) to achieve orbit. This one drops the ET in the Indian Ocean. The "Direct Insert" requires only one OMS maneuver, and the tank landed in the Pacific Ocean. So the External tank might ...

4

What the equations I used completely ignore is initial thrust to gross launch mass which'd surely affect gravity drag? ... What is the assumption behind the 9.7 km/s delta-v on the Wikipedia page as to gravity drag fraction and initial launch acceleration? 9.7km/s is towards the high end of delta-v to orbit requirements. It varies with both the aerodynamics ...

3

Launch vehicles don't stage to get the earlier stages out of the way, they stage to get rid of excess mass so they can actually reach orbit with a useful payload. The Shuttle ET was a bit of an exception due to various compromises in its design, and a poor design in that it hauled 27 metric tons of mass up to just short of a circular orbit that could ...

3

Your question is based on a misunderstanding- the External Tank propellant tanks did in fact have relief valves. The 02 valve relieved at 24 psid and the H2 valve relieved at 36 psid. From the 1982 Press Manual, pages 92-95 GremlinWrangler's comment about the inadvisability of venting hydrogen is well founded - see Flight Rule A5-154 whose rationale ...

2

I believe you are right, it is the External Tank. Why does it have problems? The external tanks were deposited in either the Indian or Pacific Oceans, clear across the world. So, what would that do for a low southward inclination launch from Vandenburg? It would cut across South America, then over Africa, the Middle East, and Russia, with only a brief stay ...

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