Hot answers tagged

18

Reusability is the big factor. Kerosene engines have issues with "coking", where solid carbon is deposited throughout the engine's pipes. (See this dissertation and its supporting research for more details.) This isn't a major issue with expendable engines, but it drives up costs when trying to reuse the engines. The BO New Glenn's first stage is planned to ...


13

Yes, the pressure of the first stage exhaust is always at least slightly subatmospheric, because that gives the maximum average ISP over the whole burn time. Rockets with boosters attached (parallel staging) often operate at the lowest possible exhaust pressure that prevents the flow from detaching from the nozzle walls. Historically, the Summerfield ...


12

A planned hold adds flexibility to the schedule. The hold at T-4 was planned to be 10 minutes long if everything went without a hitch. If a problem had cropped up (e.g. weather suddenly deteriorates and goes outside the launch limits), the hold would have been longer. If there were delays earlier in the countdown, the T-4 hold might have been shorter. The ...


10

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 payload fairing during separation" which includes this graphic showing motion just like what's in the video. and this description The vertical jettison ...


10

That's a hydrogen vent fin disposing of GH2 (gaseous hydrogen) that can outgas into the payload fairing from the Centaur upper stage's LH2 (liquid hydrogen) tank that is stored in a balloon tank at the top of the upper stage. From History of the Titan Centaur Launch Vehicle (PDF):     This liquid hydrogen leakage caused explosion of the ...


8

One possibility is actually building two disparate launch vehicles in the same shared facility. The Delta 4 and Atlas 5 cores are pretty distinctive and different. Beyond that, he is blowing smoke. Atlas 5/Delta 4 are basically identical to before the ULA merger. They have managed to get launch cycle times down somewhat. but not enough to be considered an ...


8

The primary issue with SpaceX's horizontal integration approach is that the payload has to be able to be rotated. Horizontal Mating The primary costs of horizontal integration are the transitional equipment - essentially, a tilt-table the length of the assembled rocket. The rocket itself isn't designed for carrying the horizontal load itself, but is ...


8

Lucy has a fairly narrow launch window. NASA felt that ULA offered a better chance of being able to launch within this window than SpaceX. A key factor in the decision to award the contract to ULA was schedule certainty. Lucy has a complex mission profile with a series of flybys in order to visit several asteroid either leading or following Jupiter in its ...


7

Let's look at Wikipedia for possible liquid rocket fuels. The key item is the Exhaust Velocity. Let's remove any that could be toxic, so no Beryllium, Florine, or Boron, despite the fact that each could make a very efficient rocket. $H_2{\space}LOX$- 3816 $CH_4{\space}LOX$- 3034 $C_2H_6{\space}LOX$- 3006 $C_2H_4{\space}LOX$- 3053 $\textrm{RP1}{\space}LOX$- ...


5

The ACES stage is designed for a lifetime of weeks, not years. The tanks will be simply stacked on top of each other. There's no plan to place the LH tank inside the LOX tank. ACES design is optimized with long-duration cryogenic applications in mind. A number of passive-thermal management features are incorporated into the stage at the system level. ...


5

The main advantage of IVF is described by ULA as weight-saving measure (~1 ton) for longer-duration missions, compared to batteries / photovoltaics / fuel cells: An existing Centaur goes from a vehicle with nominal two main engine burns and 8 hour flight duration to one capable of 10+ burns and flight durations measured in multiple days. Burnout ...


5

Here's a list from Wikipedia: Atlas V In 2006, ULA offered an Atlas V HLV (Heavy Lift Vehicle) option that would use three Common Core Booster (CCB) stages strapped together to lift a 29,400 kg (64,816 lb) payload to low Earth orbit 541 configuration Some consideration of using the Delta tooling system to allow for a different engine. Delta IV *There's ...


4

Presumably the aerodynamic problems with the Starliner are specific to its use with the Atlas V launcher. The 4.6m diameter of the capsule has to "neck down" onto the 3m upper stage of the Atlas, and the shape of that transition has significant aerodynamic effects. Since Orion CEV is much too heavy for Atlas V, it will have a different set of problems. ...


4

The goals of Assured Access to Space are (PDF of a hearing by the House Committee on Armed Services, page 14): The existing policy, codified in federal law, requires that assured access policy and spending, at a minimum, achieve the following two objectives: the availability of at least two space launch vehicles (or families of space launch ...


4

ULA cannot really make it much cheaper because of the Solid Rocket Booster price. The Delta II-7920 (the most commonly used configuration) uses 9 GEM-40/46 boosters, \$2.5M (one) each, produced by an external manufacturer Orbital ATK (former Alliant Techsystems, former ATK Thiokol). This makes it total about \$22.5M for the boosters alone + at least $30M for ...


4

(Note: this is based on my current understanding of the technology, and it may not be complete.) I will focus here on your main question, which is "how [does IVF] make [a stage] reusable?". I should first refine the question to "how does IVF make a stage re-fuellable?". The critical points are that IVF eliminates the need to carry gaseous Helium, which is ...


4

With vertical integration, the payload force is absorbed in the same direction as the launch forces, so you only need to make the rocket strong enough to hold the payload in the vertical direction. With horizontal integration, that the rocket needs to be built to withstand the bending load of the payload when the rocket is horizontal. This generally means a ...


4

If it's a rocket launch, happens at around engine ignition, and it sounds like some variation of 'whooop', you can bet it's the sound of turbomachinery very rapidly spooling up. Consider those turbopumps go from zero to tens of thousands of RPMs in fractions of a second, they cover the whole range of audible frecuencies, fast. I actually ended here while ...


3

Rule 5 NASA rewarding ULA Lucy launch contract is a method governance use to maintain/increase the size of certain industries. This is an act for NASA to incentivise ULA in space program research. Also the price is deemed not too overpriced than what spacex asked for. Surely NASA want more expert in space industry than less.🙂


3

Since we know the Centaur on Atlas 5 uses RL10C engines, we can look that up. The current RL10C engine mixture ratio is 5.5.


3

The patent indicates they're aiming for exhaust pressures in the region of 10-20 psi (0.7-1.3 bar), which gives a thruster chamber pressure of 5-10 psi (0.35-0.7 bar), which generates 0.5-2 lbf of force (0.25-1 N). The patent claims is enough for settling the propellants during coast phases (where settling is only used to keep the propellants bunched up in ...


3

For missions that require more fuel than the standard ACES stage contains, they propose to launch 2 rockets, one with the ACES stage and payload, one with extra LOX en LH. They also propose using the ACES stage and XEUS lander as space tugs, keeping them in space for a long time instead of having to launch a new one for every mission. That's what the '...


3

One thing I thought of would be the need for an enclosure at the pad. Shuttle used the RSS (Rotating Servicing System) that was a monstrosity of a thing that covered the entire cargo bay, while on the pad, provided environmental control. As you can imagine, not a cheap structure, that had to survive being fairly close to 7 million lbs of thrust as the ...


2

No, it does not seem that the 3 different CBC's are interchangeable. The Common Booster Core employs separate spherical bulkheads on the LH2 and LOX tanks. The tanks employ internal stringers for additional stability and the LOX tanks use anti-slosh baffles. An external wiring tunnel runs down the length of the entire booster whereas some of these components ...


2

Per Spaceflight101, the Atlas 401 has a mass at launch of 334.5 tons (this likely varies with fuel load) and thrust is 3827kN. Cygnus is "just over 8 tons"; GPS IIF is 1.63 tons. So for the GPS IIF launch, we have $\frac{3827}{334.5+1.63} = 11.38 m/s^2$ acceleration, less Earth's gravity of $9.81 m/s^2$, gives acceleration off the pad of $1.57 m/s^2$. ...


2

I might give some answer to your five bullet points, although I don't have a number for the estimate cost (I doubt anyone has): 1) Cost of recovery: It should if anything be lower by capturing the engines in midair than having to soft land them on their own. Replacing the autonomous landing system and its fuel of the F9R with an ordinary helicopter sounds ...


2

Compliance is mandatory! Human Rating Requirements for Space Systems It's long, even with the rationale scraped out, but here you go. 3.2 System Safety Requirements 3.2.1 The space system shall provide the capability to sustain a safe, habitable environment for the crew (Requirement 58503). 3.2.2 The space system shall meet probabilistic ...


1

The ablator is more to protect the structure itself than the propellant quality/boil-off. Ablator was used in certain areas of the shuttle External Tank for this reason. This quote from "A Technical History of the External Tank" (not online) describes the initial design which didn't include the complete covering of the tank with the classic orange foam. ...


1

I asked, and Tory actually answered April 6, but Twitter didn't send notices, I wasn't paying close attention, and I wasn't really sure how it worked. Anyway, I found it today, and I don't think he really answered the specific question, but this is what he said. Tory Bruno Verified account @torybruno Apr 6 Replying to @GregHan21100390 Any ...


1

I believe the point is that the spacecraft itself only has to get out of Earth's gravity well once. Until ISRU propellant sources on the moon are up and running, propellant still needs to be brought up from Earth's surface, but regular bulk propellant-only launches to a fuel depot in LEO have different engineering requirements that may allow for cost ...


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