Hot answers tagged

34

In the defense of NASA, SpaceX does not per se have an operational vehicle for the purposes they want to use SLS. (Yet, Starship is coming) However, missions to the moon using Falcon Heavy vehicles have been proposed by Bob Zubrin. Once SpaceX has an actual flying Starship/Super Heavy I think the situation will change. Ultimately the SLS program is ...


29

Yes. (Image source) Some configurations of the Delta II used nine solid boosters. In launches from both the ER and WR, the first-stage RS-27A main engine and six of the nine strap-on solid-rocket motors are ignited on the ground at liftoff. Following burnout of these six SRMs, the remaining three are ignited. Delta II ...


29

For Shuttle EVA, the Space Shuttle Flight Rules show that the safe distance for a suited crewmember was 27 feet for the main jets, 3 feet for the vernier jets, and 3 feet for the APU exhaust. It's rule A-15-22 in the document. This rule is probably a simplified version of what would actually be managed to; I remember seeing "Keep Out Zones" (KOZ) ...


26

Starship is a 9 meter wide vehicle. The first stage (Super Heavy) will be mounting 35 or 38 or some other number in that range of sea level engines. As you can imagine that will take at least three separate rings of engines. 6 in the center, then two more rings with the rest. The Starship is the same diameter as Super Heavy, and the inner ring will be ...


24

Because there are no super heavy-lift launch vehicles flying right now. In fact, simply by existing, SLS will be the most up-to-date and the most efficient super heavy-lift launch vehicle since the Saturn V (Shuttle is debatable). Super heavy-lift launch vehicle, Proposed designs When looking at current SpaceX rockets, the Falcon Heavy are human certified. ...


21

In addition to the foreshortening illustrated by Organic Marble, the appearance of rocket plumes changes significantly with altitude. At higher altitudes, the pressure of the surrounding air is lower, the plume expands and dissipates faster, and less free oxygen is available for combustion with the fuel rich exhaust (which is the source of the bright yellow ...


16

The rocket equation is solved based on the principles of momentum. The differential form that is true in any reference frame (relativistic, classical, etc) is $$dp_{e} = dp_{rocket}$$ The form you presented uses Newton's laws in a classical frame of reference: $$dm\cdot v_e = m\cdot dv_{rocket}$$ which solves into the familiar form $$\frac{dm}{m} = \frac{...


14

A space ship may need some protection against the heat of its own RCS thrusters. The Apollo Lunar Module was covered with multiple layers of thermal insulation foil. Close to the RCS thrusters the top layers were made from from nickel and the high temperature alloy inconel. The thermal blanket consists of multiple-layered (at least 25 layers) of ...


12

Partial answer: the ammonium perchlorate is manufactured in the western United States. The two perchlorate manufacturing facilities located in Henderson, the Kerr-McGee and the PEPCON plants, supplied the entire perchlorate demand for the United States until 1988, when the PEPCON plant was destroyed by an explosion. (note: Henderson is in Nevada) ...


12

SLS has been in development for a long time, although it suffers from political winds quite a bit. It started in its current form in 2011, when there was no other system in existence that even was close. Falcon Heavy was a concept then, but it would have only been slightly better than Delta IV Heavy, still nothing compared to SLS. They considered other ...


11

The 1976 NASA monograph Liquid Rocket Disconnects, Couplings, Fittings, Fixed Joints, and Seals defines "couplings" as Couplings are manually actuated separable connectors that require more than a few seconds for engagement or disengagement. and lists the following types: Flanged Threaded: Dynamic swivel couplings Shape memory alloy is not ...


11

Besides the Delta II and PSLV-G/PSLV-XL, there are a few proposed/in-development stages that would fire 7 engines at once. Blue Origin’s New Glenn booster is designed with 7 BE-4 engines powering its first stage. ULA has put forth a paper design for a “Delta Super Heavy”, 6 boosters surrounding the central first stage core of the Delta IV. I don’t know if ...


9

@russell-borogove explains that the plume changes during flight. We don't know the precise height when the two photographs were taken (both are labelled "climbing after lift-off" in the NASA archive). For a better comparison, I combined the two images and adjusted size and contrast to be roughly the same: My impression: There is a slight difference in the ...


8

You'll be definitely better off with thrusters on individual cubesats, when taking the total mass: last stage + payload, into consideration. To create the distance needed, with a single launch, you'll need to put the satellites into an elliptical orbit tangent to the target one, but of period longer or shorter by 1/8 or an integer fraction multiple of 1/8. ...


7

For the shuttle program, the water was not recovered. The water that was not vaporized ran through concrete channels and was collected in two holding ponds. (NASA photo, annotations mine). The water was later pumped out and allowed to soak into the sandy soil. The discharge of deluge and firex water (during the launch of each Space Shuttle) resulted ...


6

To those who want more specificity. Pictures are borrowed from post from geoffc. Elon Musk: There’s a puck at the base that takes the engine thrust load. In the photo below the three engines are mounted at the green circles. The thrust puck distributes the thrust from the engines to the larger structure. The entire structure circled in red is the "...


6

Ruling out nuclear propulsion in the comments pretty much rules out electric thrusters of all flavours as well since the Juno mission is notable for pushing the limits of solar power, and only needs enough to operate sensors and radio link and is still 1/5 solar panels by dry weight (340 kg making 486 W, where electric demands for thrusters are in kW). For ...


6

NASA has priority over almost any customer from SpaceX, so if a Dragon capsule was available, it could be done on short notice. Assuming that it would be something that fits in to a dragon capsule, it could potentially be done in a matter of a few weeks. If the hardware isn't available, it would be a few months. But realistically, this isn't very likely to ...


5

I don't know the exact details of the Gemini suit, but here are some contemporaneous patents that describe similar joints. The different parts are in red and blue, bearings in green and o-rings yellow. Omni-directional high altitude helmet, US3030626A by Leonard F Shepard, filed 1958: It's basically a large ball bearing with an o-ring, both in such an ...


4

To calculate the x-axis location of the center of mass of a group of objects, calculate the sum of the products of the object's masses and their individual x-center-of-mass locations, and divide by the sum of the masses. $$X_{cm} = \frac{(m_1*X_{cm1} + m_2*X_{cm2} +...)}{(m_1+m_2+...)} $$ Referring to the left side of this figure, you can see the x-center-...


4

Yes, part of NASA's function is public outreach. As such they will use units such as "Aircraft Carriers$^1$" "School Buses$^2$" and "horsepower$^3$" While not precise, expressing thrust in terms of horsepower notionally allows people to understand it more. 1: [...] horsepower [...] 2: [...] horsepower [...] 3: [...] horsepower [...]


4

Substances equivalent in hazard to the hydrocarbon are available at any gas station. It's the oxidizer that's an issue. Gaseous nitrous oxide is used as a propellant in some aerosol cans with rather low pressures. However, there's a variety of hazards that appear at higher pressures, or when using the liquid form. Under certain conditions, the gas can ...


3

Yes. It is the oxidizer of choice of more advanced hobbyist rocket builders, like the Copenhagen Suborbitals. It's not entirely safe, but it's way safer than most alternatives. Its performance is deal-breaker in professional rocketry - 1 oxygen per 2 inert nitrogens, vs 4 for N2O4, and it gives you most of the headaches of liquid propellant (proper mixing in ...


3

I'm going to interpret your question as being: "What factors drive the choice between bipropellant and monopropellant thruster systems for spacecraft maneuvering systems?" If that's wrong, advise in a comment, and I'll delete this. This answer is a summary of the paper Performance Evaluation of Spacecraft Propulsion Systems in Relation to Mission Impulse ...


2

You want your rocket to have the least aerodynamic drag (other term for "dynamic pressure" in this context) and as a result fluid dynamics give you an ogive shape as the optimal shape, as seen here: https://www.jvejournals.com/article/16142


2

You will need to know the impulse you will need. To derive this, you need to know the mass of your probe, and the required delta-v. To know the delta-v you need to know the route you're going to take. Your route will also guide you as to the required thrust to weight ratio you will need at the different points of your flight, which will inform your ...


2

Possible answer: Another answer not yet explicitly listed could be: to limit the loss of-/build/maintain/expand their independence on other parties when it comes to launch technology (usage). For example, an agency might account for uncertainties in the availability of the technology provided by other parties, or contracts might be such that it becomes ...


2

Composite Parts for Moments of Inertia and the Parallel Axis Theorem by Jacob Moore, Majid Chatsaz, Agnes d'Entremont, Joan Kowalski, and Douglas Miller is licensed under Creative Commons Attribution-ShareAlike 4.0 International License (CC BY-SA 4.0). It is reproduced here from the Open Textbook Project's Mechanics Map Digital Textbook under these terms. ...


1

This difference was tracked by the Space Shuttle Program. Each flight had a Propellant Inventory prepared for it. Here is an example. The major prelaunch times tracked are LOADED (blue arrow) ENGINE START COMMAND (green arrow) SRB IGNITION COMMAND (red arrow) The mass at SRB IGNITION COMMAND is the mass that was important for ascent performance. (Note: ...


1

I was looking for a constellations of smallsats (they are not cubesats) that were able to space themselves out using only drag. I hypothesized it was TROPICS but that hasn't been launched yet. But I finally found it, and it turns out to be CYGNSS and is discussed in How can the CYGNSS spacecrafts (actually) measure ocean roughness?. The technique is called ...


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