The SLS: too expensive for exploration?

Tom Kalbfus · 2016-06-09 07:42:26

I think the rocket plume causes the air ahead of the rocket to expand out of the way, it is sort of like a standing explosion. the rocket also slows the rocket relative to the atmosphere so there is less frictional and compressive heating after the rocket burn.

GW Johnson · 2016-06-09 10:01:21

The first burn takes the stage upward and starts killing some of downrange velocity, which is around 3 to 3.5 km/s (Mach 10-ish if there were any sensible air). From there it accelerates downward under gravity toward the sensible air. This event takes place at orbital altitude (160+ km).

The second burn reduces vertical speed downward that was gained by falling under acceleration of gravity from orbital altitude, or even more, depending upon how high up the first burn took it. At these speeds, the sensible air interface is somewhere in the vicinity of 150,000 feet. It's moving well above the nominal shown Mach 3 at the grid fin deployment point, which would be somewhere around 100,000 feet. They call it "hypersonic", which for blunt objects is at least Mach 3-ish, and for not-blunt objects (like this) is at or above Mach 5-ish.

The third burn is the landing burn, which takes them from supersonic to nothing at touchdown. Don't forget, it accelerates downward under gravity between burns. But apparently they don't want it over Mach 3-ish with the grid fins deployed. It has to be a whole lot slower than that to deploy the landing legs, or the wind pressure will rip them right off.

What I'm showing from compressible flow calculations is that the ideal gas model works well enough up to about 1.8 km/s speeds (about Mach 6 at 100,000 feet), and above that, the old reentry rule-of-thumb ("effective temperature in K is numerically equal to speed in m/s") gives you a better estimate of effective gas temperature. That's because there is increasing dissociation above that speed. The energy that would have raised total and recovery temperatures (and those two are not much different, really) goes into ionization instead.

At 100,000 feet, the ambient static air temperature is 227 K. At the 1.8 km/s / Mach 6 point, total/recovery temperatures are about 1830 K. Engine chamber gas temperatures are about 3000 K, which is the stagnation temperature in the engine gas stream. At 3 km/s (Mach 10) speeds, the rule-of-thumb oncoming air effective temperature is also about 3000 K.

The retropropulsion plume from the engine shocks down subsonic just behind the vehicle bow shock wave, so it can turn downstream alongside the stage. It reverts to pretty near its chamber temperature once subsonic like that, and its recovery temperature still drives heat transfer rates, even after it reaccelerates to supersonic alongside the stage tankage.

Shocks are compression events, not expansion events, by the way. Post shock turns back streamwise are expansion events, but these are localized. That is what reaccelerates it supersonic alongside the tankage.

The oncoming air stream shocks down subsonic at the bow shock wave. It goes to its effective temperature once subsonic, and that temperature drives its heat transfer, even after it reaccelerates supersonic alongside the tankage.

So there are two very hot flows mixing alongside the tankage. The gas is largely rocket plume gas right adjacent to the tankage. Mixing is less than perfect, to be sure.

I don't see any cooling effects or low speed effects here. During the second burn, they're trying to decelerate down to Mach 3, so they can deploy the grid fins. That means they are moving somewhere well above Mach 3 when they start that burn. Mach 6? Mach 10? I don't know. But very fast. Both the local airstream and the plume gases are in the 3000 K class during this event, all around the engines and tankage.

I know these engines run slightly fuel rich at normal mixture, but that doesn't explain the heavy sooting seen all over the bottom and sides of the stage. As I said above, I'd hazard the guess they're running a little kerosene through the inactive engines to keep their bells from overheating. They look bad enough as it is, with all the soot all over them, but I don't see melt damage, which should be evident if those bells were not protected in some way. The meltpoint of carbon steel is only 1886 K, by the way, and stainless is a little lower than that, actually.

That kerosene flow would burn very inefficiently in the mixing slipstream, which would put gobs of sooting all over everything exposed to that shocked flow, but without adding much heat. Spontaneous ignition of that kerosene is extremely like in the localized zones where recovery temperatures are high, not so likely outside the boundary layers where things aren't so hot. Vaporization absorbs some heat, so there a localized cooling where that takes place.

High speed aerodynamics is a complicated bitch, ain't it? So is maneuvering flight dynamics. I did this crap for a living for over 20 years directly, and over 40 years indirectly. I might know just a little about the subject, after all.

GW

Last edited by GW Johnson (2016-06-09 18:29:28)

SpaceNut · 2017-02-18 20:01:25

We have heard the recent wishes to change the EM-1 and EM-2 mission timelines to being a crewed mission1 and an actual landing on 2 which on paper would save about 15 billion out of the Nasa budgets but is it realistic.

Do this change the view point that sls is to expensive by just changing the time line?
I would say no as the price really has not changed but only the goal posts.....

SpaceNut · 2017-03-06 21:01:42

https://www.nasa.gov/sites/default/file … s_mr_0.jpg

The propulsion system that will give the Orion spacecraft the in-space push needed to travel thousands of miles beyond the moon and back has completed major assembly at United Launch Alliance in Decatur, Alabama. The Boeing-designed interim cryogenic propulsion stage is a liquid oxygen/liquid hydrogen-based system that will give Orion an extra punch of power on the first, uncrewed flight of the spacecraft with NASA's new rocket, the Space Launch System, in late 2018.

But even once we test this we will be looking at a total redo of the EDS stage for use going anywhere else with this very expensive rocket....

SpaceNut · 2018-01-21 21:07:41

We know that the ship to what should be keeps sliding to the right as it gets farther down the line for making use of it for moon missions or more... But this will not help either

NASA estimates that nearly 17,500 employees will be furloughed during a government shutdown, according to a shutdown plan published by the agency in November 2017. That is nearly 85% of the agency's workforce. Those furloughed who are working on experiments will not be allowed to touch them until after the shutdown, and by that point, they might have to start all over again.

Post made for what will introduce more delays.....not politics

SpaceNut · 2018-04-14 08:40:20

EM-1 Update: Making progress, but still behind schedule
Exploration Mission-1 (EM-1) is currently expected to launch in 2020.
KSC is the final assembly and integration site where Orion prime contractor Lockheed Martin puts the whole spacecraft together for launch.

Sounds to me like a lot of feet dragging with each piece of the assembly.

update:
NASA’s realigning dual Mobile Launcher plan targets extra SLS Block 1 missions
written by Chris Bergin April 23, 2018

Originally, Exploration Mission -1 (EM-1) and Exploration Mission -2 (EM-2) were near-mirrors of each other, with an uncrewed Orion sent on a test flight “around” the Moon before the mission was repeated with a crewed Orion.

SpaceNut · 2018-05-13 14:51:27

The cost of a launch is directly tied to all of the heritage parts... so a switch over may not be a bad thing to help push Nasa...

SLS requires Advanced Boosters by flight nine due to lack of Shuttle heritage components

which means no more recovery....

NASA has issued a new Request For Information (RFI) that shows there is a deadline for the Space Launch System (SLS) to transition to “Advanced (Evolved) Boosters” no later than the ninth flight. This is due to a future obsolescence issue with the current booster design which relies on Shuttle heritage components of which there is only a limited amount of stock remaining. NASA intends to purchase another six SLS flight booster sets before the stock runs out, prior to moving to the Advanced Boosters.

It has always been in the planning for SLS to move to an Advanced Booster, partly in a requirement for its Block 2 rocket, that is required for Mars missions. The Block 2 is not expected to launch until the 2030s based on long-range NASA outlook manifests. Crewed missions to Mars with SLS have been projected internally as mid-to-late 2030s recently. Nearly six years ago, Dynetics, Inc. and Pratt & Whitney Rocketdyne (PWR) formed a team “to offer an affordable booster approach that meets the evolved capabilities of the SLS” – and presented their overview at the 63rd International Astronautical Congress, Naples, Italy in 2012.
Dynetics’ original proposal for liquid Advanced Boosters for SLS.
Their liquid booster approach – using the baseline of the famous Saturn V F-1 engines – claims they could advance SLS’ capability to launch payloads of 150mT to orbit.
Orbital ATK’s proposal – nicknamed the “Dark Knights” due to their black casings – builds on their booster legacy, with a motor that is “advanced” on several levels, by “provid(ing) NASA the capability for the SLS to achieve 130 mT capability – the baseline for SLS Block 2 – with significant margin, utilizing a booster that is 40 percent less expensive and 24 percent more reliable than the current SLS booster.

They are also looking at the dual launch as well...

NASA’s realigning dual Mobile Launcher plan targets extra SLS Block 1 missions

Block 1 performance capability for Europa Clipper may push the launch vehicle discussion into an uncomfortable debate, where SpaceX’s Falcon Heavy could force NASA’s hand based on the gulf of vehicle costs. A brand-new Falcon Heavy for a high priority science mission would cost just over $100 million, whereas the latest estimates for SLS put the per-mission cost anywhere between $500 million (from NASA in 2013) to a range between $1.5 – $2.5 billion (conservative industry estimates in December 2017). If Europa Clipper does indeed stay on an SLS, as is currently mandated by Congressional law, the third flight of SLS would again be a Block 1 variant carrying the first crewed mission Orion. A fourth Block 1 flight on the manifest may yet be needed before the EUS and ML-2 are ready.

plus possible other uses for such a large payload capability...

GW Johnson · 2018-05-14 13:31:18

I had always thought that it would be Falcon-Heavy that outcompeted SLS for large payloads. We built ISS from 15-ton payloads. Falcon-Heavy will fling something like 60-65 tons to LEO. SLS Block 1 is only about 70 tons to LEO. Even SLS Block 2 is only 150 tons, and from what you say, won't fly until the 2030's at the earliest. Per industry experts, the SLS price tag for Block 1 is $1.5-2.5 B per launch, from what you say.

Meanwhile, Spacex supposedly (we'll see) will start limited flight testing of BFR's by 2019 or 2020. If that goes well, the BFR/BFS system will be flinging 150 tons of payload to LEO before SLS Block 2 ever flies, and for a very tiny fraction of its cost. Looks to me like the handwriting is on the wall, although only a few letters of the first word, so far.

Not to mention Blue Origin and its plans for a similar heavy lifter. Not sure, but I think they're calling that concept "New Armstrong".

Amazing what can be done when Congress isn't dictating the show almost solely for pork barrel politics and favored-contractor corporate welfare. (THAT is why NASA cannot seem to do much any more. That and plain old bureaucratic bloat.)

GW

JMartin · 2020-10-14 07:01:19

Whew... that was a long read. Can't say I read every word of it, but I read a lot and skimmed over much of it... and I have to say after reading through much of the thread on this topic, I think it's noteworthy that I didn't see a single supporter of SLS in this thread. Apparently the only people who think the SLS is a good idea are SLS employees, corrupt politicians, and the contractors profiting from the program.

That said, I think the real problem with SLS is the way the contracts are handled. SLS is produced using something called "cost-plus" contracts, which basically means the government pays the contractor producing the rocket or rocket parts for the full cost of production, plus extra for the company's profit. When you think about the incentives involved in that type of business arrangement, it seems obvious that the company has little incentive to produce the rocket or rocket components efficiently. On the contrary, if the contractor drives up the cost and delays delivery of the product (which further drives up costs), the profit the contracting company gets may even grow if it is a percentage of the total cost of production.

To promote innovation, we need contracts where the government provides technical specifications for the rockets they want to several different rocket producing companies, then the companies bid to produce the product for the lowest cost in a competitive manner. And this way, if the company finds a way to build the rocket for a lower cost than what they're being paid by the government to produce it, the company keeps the extra money as profit... which encourages the company to innovate, lower costs, and increase efficiency.

Most importantly, for rocket launch services to orbit (and to the Moon, Mars, etc), we need to get rid of cost-plus contracts at NASA. The only time I can think of when cost-plus contracts can make sense is if the government is worried nobody in the private sector is capable of providing the government the product they need in the absence of cost-plus contracts, which obviously is not the case with the market for rocket launch services because we have companies like SpaceX now for that.

SpaceNut · 2020-10-14 17:19:08

JMartin, In so much that the program was hobbled from the start by the senates demands for a work fare program and then by contractors not wanting to do a clean sheet with advances by the commercial industry.
Its now over a decade late and twice its budget to get even the first ship to orbit let alone a crew to the moon.

Mars_B4_Moon · 2022-06-10 10:42:19

SLS rocket needs a second mobile launcher, at a $1 billion cost. NASA inspector general issues a scathing report on moon efforts & said it would take an additional 2½ years to build.

Co-chair Philip Christensen says the decadal is open to expanding CLPS (commercial lunar payload services) to other destinations once it’s successfully demonstrated on the Moon; Mars and asteroids come to mind.
https://twitter.com/jeff_foust/status/1 … 6748211204

NASA audit reveals massive overruns in SLS mobile launch platform
https://spacenews.com/nasa-audit-reveal … -platform/

NASA OIG Report On That SLS Transporter Thing
http://nasawatch.com/archives/2022/06/c … racti.html

The $93-billion plan to put astronauts back on the Moon
https://www.nature.com/articles/d41586-022-01253-6

SpaceNut · 2022-06-10 19:13:53

I think it was heading back to the vertical bay for more repairs but had gotten more testing done.

Nasa keeps doing what worked in the 60's, hoping to keep the same results and even Space x realized that it could not continue with some of these things.

The mobile launcher crawler is another of those things which should have not been continued with sls as bfr and starship has shown.

Mars_B4_Moon · 2022-07-27 05:00:37

NASA is proposing to transfer SLS production and associated testing, manufacturing, and transportation facilities from multiple existing hardware procurement contracts to a single launch service contract with Deep Space Transport LLC

https://twitter.com/nasaspaceflight/sta … 571pedbp8Q

Mars_B4_Moon · 2023-12-26 05:07:51

2026 Mid-Terms gone and a possible 2028 United States presidential election? Who would still be in politics and run Kamala Harris, Gavin Newsom, Gretchen Whitmer, Alexandria Ocasio-Cortez, Clinton's daughter, Obama's daughters, Rashida Tlaib, Rahm Emanuel, Brandon Johnson? Ted Cruz, the son's of Trump, Tucker Carlson, George Prescott Bush eldest child of the former governor of Florida, Jeb Bush; nephew of the 43rd president, George W. Bush; grandson of the 41st president, George H. W. Bush?

NASA’s Engineering Marvel: Preparing the Gateway to the Moon
https://scitechdaily.com/nasas-engineer … -the-moon/

2027 or …Later Again?

GAO Report
https://web.archive.org/web/20231220172 … -24-106256

As of September 2023, the Human Landing System program had delayed eight of 13 key events by at least 6 months. Two of these events have been delayed to 2025—the year the lander is planned to launch.

GAO found that the Artemis III crewed lunar landing is unlikely to occur in 2025.

An ambitious schedule: The Human Landing System program is aiming to complete its development—from project start to launch—in 79 months, which is 13 months shorter than the average for NASA major projects. The complexity of human spaceflight suggests that it is unrealistic to expect the program to complete development more than a year faster than the average for NASA major projects, the majority of which are not human spaceflight projects. GAO found that if development took as long as the average for NASA major projects, the Artemis III mission would likely occur in early 2027.

Last edited by Mars_B4_Moon (2023-12-26 05:17:30)

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#226 2016-06-09 07:42:26

Re: The SLS: too expensive for exploration?

#227 2016-06-09 10:01:21

Re: The SLS: too expensive for exploration?

#228 2017-02-18 20:01:25

Re: The SLS: too expensive for exploration?

#229 2017-03-06 21:01:42

Re: The SLS: too expensive for exploration?

#230 2018-01-21 21:07:41

Re: The SLS: too expensive for exploration?

#231 2018-04-14 08:40:20

Re: The SLS: too expensive for exploration?

#232 2018-05-13 14:51:27

Re: The SLS: too expensive for exploration?

#233 2018-05-14 13:31:18

Re: The SLS: too expensive for exploration?

#234 2020-10-14 07:01:19

Re: The SLS: too expensive for exploration?

#235 2020-10-14 17:19:08

Re: The SLS: too expensive for exploration?

#236 2022-06-10 10:42:19

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#237 2022-06-10 19:13:53

Re: The SLS: too expensive for exploration?

#238 2022-07-27 05:00:37

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#239 2023-12-26 05:07:51

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