Staged combustion engines such as the Russian RD-180 and American SSME are regarded as the utmost in efficiency because they achieve high vacuum Isp while being able to achieve high thrust at sea level. They achieve this by operating at high chamber combustion pressure.
SpaceX is developing the Raptor engine also as a staged combustion engine. However, a surprising fact is a medium performance, mid-level pressure and cheaper engine such as the Ariane 5’s Vulcain engine or Delta IV’s RS-68 can get higher performance than a staged combustion engine by using altitude compensation.
See the graphic of the Isp of the Vulcain engine with an altitude compensating nozzle:
The vacuum Isp of the SSME is 452.3 seconds (4,436 m/s), and the sea level, 366 seconds (3,590 m/s). You see from the graphic with altitude compensation the Vulcain sea level Isp would be ca. 3,850 m/s. And already at ca. 20,000 m, its altitude compensating Isp would match that of the SSME. An thereafter the the Isp would exceed the maximum vacuum Isp of the SSME. Indeed its Isp could reach 4,850 m/s, and above
That the Isp with adaptive nozzles can be this high is supported by calculations for hydrogen/oxygen engines at ultra large expansion ratios. This report concludes at a 600 to 1 expansion ratio we can get ca. 480 s vacuum Isp:
ORBITAL TRANSFER VEHICLE (OTV) ENGINE STUDY, PHASE A - EXTENSION CONTRACT NO. NAS8-32996
The method to get the altitude compensation does not have to be the aerospike nozzle. Better actually would be to add an altitude compensation nozzle extension to an existing engine such as the Vulcain or RS-68. Redesigning such an engine to use an annular combustion chamber for an aerospike nozzle would be expensive. Far cheaper would be to use an altitude compensating nozzle attachment to the already existing engine.
Such nozzle extensions already have been in existence for decades on upper stage engines, such as the extendable nozzles on for example the RL-10B2 engine.
But in actually the increase in efficiency would be higher for a first stage engine. For instance the vacuum Isp for the Vulcain or RS-68 could be increased from 432s or 412s to 480+ s and above.
The nozzle extension is just a well-known, simple way to accomplish it but there may be simpler or more lightweight methods of accomplishing it.
A puzzle in solar science that has existed for 150 years is the corona heating problem:
Why is the sun’s corona 200 times hotter than its surface? The paradox has astronomers scratching their heads over magnetic waves, nanoflares, and the now-debunked element coronium. BY BRILEY LEWIS | PUBLISHED APR 12, 2023 6:00 AM EDT https://www.popsci.com/science/how-hot-is-the-suns-surface-corona/
The Sun's surface is at about 10,000 F, 5,500 C. But the solar corona reaches millions of degrees. How is it possible to get so much hotter hundreds of thousands kilometers away from the Suns surface?
Noted solar astronomer Eugene Parker for whom the Parker Solar probe was named suggested it was due to nanoflares small flares emanating from the solar surface much smaller than the usual solar flares:
ScienceCasts: The Mystery of Nanoflares.
But what causes the nanoflares? Could it be asteroidal impacts? The argument could be made they are too small to cause any visible reaction on the Sun. But the question is of the local impact. The Sun’s escape velocity at its surface is 600 km/s. That is a tremendous amount of energy for a body impacting it at that speed. When material is thrown up after the impact the high temperature could be maintained far above the surface.
Nanoflares and coronal heating.
Micro-flare observed on 4 September 2016 with NASA SDO/AIA and the Swedish 1-m Solar Telescope.
The image shows a micro-flare observed on 4 September 2016. Magnetic reconnection in the corona as sketched in the cartoon in the lower left produces a hot loop of more than 7 million degrees. This hot loop is visible as the bright area in the green background image taken with the Solar Dynamics Observatory (AIA 94 Å). The active region with bright magnetic loops is shown in more detail in the yellow inset, corresponding to plasma of less than 1 million degrees (AIA 171 Å). The reconnection event in the corona produces fast electrons that hit the lower atmosphere with high energy. The impact region is very small and is shown at high resolution in the image taken with the Swedish 1-m Solar Telescope on La Palma. With the European Solar Telescope, we will be able to study the magnetic environment of the impact region in even finer detail.
But the major, key reason for suspecting it is this: there is a type of nuclear fusion called impact fusion. It arises when bodies are made to collide at hundreds of kilometers per second relative impact speed.
Proceedings of the Impact Fusion Workshop ~ National Security and Resources Study Center LOS Alamos Scientific Laboratory Los Alamos, New Mexico LOSALAMOS SCIENTI LABORATORY PostOfficeBox 1663 LosAlamos,New Mexico87545 July 10—12, 1979
There are private fusion research concerns now investigating this to bring about controlled nuclear fusion.
Recent observations of nanoflares have observed million degree temperatures locally around the nanoflares origin point on the Sun’s surface, while the surrounding area is at the normal 5,500 C temperature.
So why don’t we see the asteroids during imaging of the nanoflares? It could be their small size. The Sun is so bright it completely washes out the asteroids that may be only a few kilometers across.
Recent observations and theoretical modeling suggest the million degree temperatures seen in the vicinity of the nanoflare origin point on the Sun’s surface should be able to be communicated to the corona-sphere thousands of kilometers above the Suns surface:
This May Be the First Complete Observation of a Nanoflare. Heating the corona. So far, these bright loops appeared to be tiny flares – but did their heat actually reach the corona?Bahauddin looked to NASA’s Solar Dynamics Observatory, which carries telescopes tuned to see the extremely hot plasma only found in the corona. Bahauddin located the regions right above the brightenings shortly after they appeared. “And there it was, just a 20-second delay,” Bahauddin said. “We saw the brightening, and then we suddenly saw the corona got super-heated to multi-million degree temperatures,” Bahauddin said. “SDO gave us this important information: Yes, this is indeed increasing the temperature, transferring energy to the corona.” Bahauddin documented 10 instances of bright loops with similar effects on the corona. Still, he hesitates to call them nanoflares. “Nobody actually knows because nobody has seen it before,” Bahauddin said. “It’s an educated guess, let’s say.”From the perspective of the theory that says nanoflares heat the corona, the only thing left to do is to show that these brightenings occur often enough, all over the Sun, to account for the corona’s extreme heat. That’s still work in progress. But observing these tiny bursts as they heat solar atmosphere is a compelling start. https://www.nasa.gov/solar-system/this-may-be-the-first-complete-observation-of-a-nanoflare/
Additionally I was startled see to what would be the kinetic energy of an asteroid impacting the Sun at the 600 km/s escape velocity. Asteroids have been estimated to have densities in the range of 2,000 kg/m3 to 5,000 kg/m3 . The iron-nickel asteroids would have the higher density. This is important because they could also maintain their cohesiveness as they impacted the Sun.
Searches of a population of asteroids inside the orbit of Mercury, called vulcanoids, have been unsuccessful. This is because you have to look at the bright solar disk to detect them. But such searches put a size limit of 6 km wide on them. So assume the asteroid has size, say, 5 km across, with density, say, 4,000 kg/m3 . At that density the mass would be 4,000 kg/m^3 * (6,000 m)^3 = 8.64 * 10^14 kg. Now suppose this impacted the Sun at 600 km/s. Then the kinetic energy of that pact would be:
(1/2) * 8.64 * 10^14 * (600,000 m)^2 = 1.55*10^26 Joules. That is a tremendous amount of energy! To put in perspective the energy the Sun puts out each second is 3.86 * 10^26 watts. So if the asteroid deposited that energy in, say, 1 second, it would be a significant percentage of the total energy the Sun puts out in a second!
However, asteroids of kilometers size impacting the Sun must be quite rare, judging from this graph of asteroid impacts to Earth by size:
One meter and below must be more common. If the meteor impacting the Sun was 1 meter wide, then the kinetic energy would be (1/2)*4,000*(1)^3*(600000)^2 = 7.2*10^14 joules, nearly a quadrillion joules of energy.
About the likelihood of asteroids impacting the Sun in accordance to the change needed in their established orbital velocity, if they started further out in the Solar System, much less velocity change (delta-v) would be needed to direct them to impact the Sun.
Key confirmation required is to confirm the existence of these small solar impactors. Observations in the visual light spectrum have not succeeded. This is the solar irradiance spectrum showing the range of intensity’s according to wavelength:
You see it is vanishingly small at extreme ultraviolet wavelengths and at radio wavelengths around 10,000 nm, 10 microns, and above. The problem with observations at the extreme ultraviolet is that not large enough telescopes have been launched to observe them at less than 6 km diameters (the extreme UV is absorbed by the Earth’s atmosphere.)
Then the suggestion is to use large radio telescopes at the micron and above wavelengths to detect the close in asteroids.
One radio telescope that might manage it is the ALMA radio telescope array:
The Band-to-band (B2B) method demonstrated this time to achieve the highest resolution with ALMA. In the B2B method, atmospheric fluctuations are compensated for by observing a nearby calibrator in low frequency radio waves, while the target is observed with high frequency radio waves. The top right inset image shows the ALMA image of R Leporis that achieved the highest resolution of 5 milli-arcsec. Submillimeter-wave emissions from the stellar surface are shown in orange and hydrogen cyanide maser emissions at 891 GHz are shown in blue. The top left inset image shows a previous observation of the same star using a different array configuration with less distance between the antennas and without the B2B method, resulting in a resolution of 75 milli-arcsec. The previous resolution is too coarse to specify the positions of each of the two emission components. (Credit: ALMA (ESO/NAOJ/NRAO), Y. Asaki et al.) Download image (1.3MB)
At a max resolution of 5 milli-arc it should be able to detect kilometer wide asteroids at the distance of the Sun. The detection sensitivity should also be improved for iron-nickel meteorites for radio astronomy.
Note the importance of this is that if it is confirmed then we know impact fusion does indeed work.
James Webb was promised to provide revolutionary results in cosmology and has not disappointed. Several observations have shown well-developed galaxies that stem from the earliest time after the Big Bang, which current theories suggest should not be possible.
JWST finds very early galaxies that should not exist.
The observations have led some scientists to question the accuracy of the current models for the beginning of the universe. Further, the cosmological microwave background(CMB) had been regarded as strong confirmation of the Big Bang theory for the origin of the universe. But there is a discrepancy between the rate of expansion of the universe based on the CMB and measurements of galactic motion.
This discrepancy has existed for several years now, but it was hoped with better instruments the discrepancy would be found due to measurement error. Instead, the JWST has provided further evidence the discrepancy is real. Then either the CMB estimate or the interpretation of the redshift measurements or both are wrong.
Here I'll discuss the possibility there is a problem with the interpretation of the origin of the CMB.It seems to me there should be some contribution to the CMB due to highly red shifted infrared and optical radiation from galaxies at high red shifts, but I never see this mentioned. The CMB is only described by relic radiation of the intense heat at the beginning of time that gradually cooled as the universe expanded.
An argument can be made that the CMB is seen in all directions but there are blank areas in some part of the sky. This does not support the idea of the CMB deriving from redshifted light from primordial galaxies.
But the Hubble Deep Field showed abundant galaxies in areas previous thought to be devoid of galaxies.It was a revolutionary advance in our knowledge of the extent of the universe. Hubble deep field images integration times ranged from 10 days to 23 days. But the JWST deep field image only went for a day:
In view of the startling find of fully formed galaxies going back to near the time of the Big Bang by the JWST, such long integration times as for the Hubble must also be done for the JWST.
The estimate of the number of galaxies in the universe from the Hubble deep field was 170 billion. But numerical simulations put it at perhaps one hundred times more at 6 to 20 trillion galaxies:
STARTS WITH A BANG — JUNE 22, 2022 There are more galaxies in the Universe than even Carl Sagan ever imagined Forget billions and billions. When it comes to the number of galaxies in the Universe, both theorists' and observers' estimates are too low. https://bigthink.com/starts-with-a-bang/galaxies-in-universe/
By doing the longer integration times JWST may be able to confirm this larger number of galaxies. Such a large number of galaxies going back to near the time of the Big Bang may allow the CMB to be equally well explained by highly redshifted light, infrared and optical, from these earliest galaxies.
However, there may be another even greater contributor to the observed CMB. A little known fact is that for most of the galaxies in the universe they are receding from us faster than the speed of light(!)
97% of Galaxies Are Moving Faster Than Light, HOW IS THIS POSSIBLE?
This is explained as not being in conflict with relativity by the virtue of the fact that space itself is expanding. It is not the case that objects are moving through space as these superluminal speeds.
Nevertheless, this raises an interesting possibility. If it is the case that these galaxies are moving away from us at these apparent superluminal speeds, would we observe a luminal "boom" from these galaxies when they appear to cross the light-speed barrier relative to us?
The luminal boom is a concept that is analogous to the sonic boom for sound waves. This is actually seen for some subatomic particles traveling though matter, where the speed of light is reduced below that of the vacuum speed. In cases where the particles exceed that materials light speed, a phenomenon known as Cerenkov radiation is observed. Note that the particles are still not traveling faster than the vacuum speed of light, only the speed of light in the material. So relativity is still upheld.
An analogous phenomenon is seen in cosmic ultra high energy gamma ray bursts, GRB's:
Faster-Than-Light Speeds Could Be Why Gamma-Ray Bursts Seem to Go Backwards in Time. SPACE 30 September 2019 By MICHELLE STARR
This blog post contained the discussion of an alternative explanation for the CMB. Follow up posts will discuss alternative explanations for universe expansion and dark matter.
